Floral richness, phytogeography, and conservation on islandsin Bahia de Los Angeles, Baja California, Mexico
Item Type text; Thesis-Reproduction (electronic)
Authors West, Patricia A.
Publisher The University of Arizona.
Rights Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Download date 25/09/2021 21:46:57
Link to Item http://hdl.handle.net/10150/278789 INFORMATION TO USERS
This manuscript has l)een reproduced from the microfilm master. UMI films the text directly from the original or copy submitted. Thus, some thesis and dissertation copies are in typewriter face, while others may be from any type of computer printer.
The quality of this reproduction is dependent upon the quality of the copy submitted. Broken or indistinct print, colored or poor quality illustrations and photographs, print bleedthrough. substandard margins, and improper alignment can adversely affect reproduction.
In the unlikely event that the author dkl not send UMI a complete manuscript and there are missing pages, these will be noted. Also, if unauthorized copyright material had to be removed, a note will indrcate the deletion.
Oversize materials (e.g.. maps, drawings, charts) are reproduced by sectioning the original, beginning at the upper left-hand comer and continuing from left to right in equal sectk)ns with small overiaps.
Photographs included in the original manuscript have been reproduced xerographicaliy in this copy. Higher quality 6' x 9' black and white photographk; prints are available for any photographs or illustrations appearing in this copy for an additronal charge. Contact UMI directly to order.
ProGKjest Information and Learning 300 North Zeeb Road, Ann Arbor, Ml 48106-1346 USA 800-521-0600
FLORAL RICHNESS, PHYTOGEOGRAPHY, AND CONSERVATION ON ISLANDS
IN BAHIA DE LOS ANGELES, BAJA CALIFORNL\, MEXICO
by
Patricia A. West
A Thesis Submitted to the Faculty of the
SCHOOL OF RENEWABLE NATURAL RESOURCES
In Partial Fulfillment of the Requirements For the Degree of
MASTER OF SCIENCE WITH A MAJOR IN RENEWABLE NATURAL RESOURCES STUDIES
In the Graduate College
THE UNIVERSITY OF ARIZONA
2002 UMI Number; 1409490
(g> UMI
UMI Microform 1409490 Copyright 2002 by ProQuest Information and Learning Company. All rights reserved. This microform edition is protected against unauthorized copying under Title 17, United States Code.
ProQuest Information and Learning Company 300 North Zeeb Road P.O. 60x1346 Ann Arbor, Ml 48106-1346 2
STATEMENT BY AUTHOR
This thesis has been submitted in paitial fulfillment of requirements for an advanced degree at The University of Arizona and is deposited in the University Library to be made available to borrowers under rules of the Library.
Brief quotations from this thesis are allowable without special permission, provided that accurate acknowledgment of source is made. Requests for permission for extended quotation from or reproduction of this manuscript in whole or in part may be granted by the head of the major department or the Dean of the Graduate College when in his or her judgment the proposed use of the material is in the interests of scholarship. In all other instances, however, perm luthor.
SIGNED:
APPROVAL BY THESIS COMMITTEE
This thesis has been approved on the date shown below.
William L. Halvorson Date Professor of Renewable Natural Resources
^2 OZ William W. Shaw Date Professor of Renewable Natural Resources
o Steven Smii Date AssocialSProfessorAssociaSP of Renewable Natural Resources 3
ACKNOWLEDGEMENTS
It is my pleasure and privilege to thank the following people and organizations for their support encouragement, and assistance: Betty Armbruster, Tina Ayers, Xavier Basurto, Joe Seals, Drew Held, April Boulton, Codey Carter, Tiffany & Richard Cudney, Jose Delgadillo, Adam Duerr, Caroline Shepard Espinoza, Exequiel Ezcurra, Earthwatch Institute, Judy Gibson, Wolfgang Griinberg, Roy Hobbs, Gary Huxell, Christobal Jackson, Phil Jenkins, John Kupfer, Steve McLaughlin, Laurie Monti, Gary P. Nabhan, Paco Sanchez-Pifiero, Jon Rebman, Antonio & Beti Resendiz, Ben Rodriguez, Michael Rose, Mike Schroff, Cecil Schwalbe, SEMARNAT, Mary Soltero, Paul Stapp, Bob Steidl, Mark J. Spalding, Drew & Theresa Talley, Stuart Wolf, and the many field assistants and volunteers who helped me, especially Frances Gibson-Smith who provided late-night laughs and too many margaritas. I give special thanks to the fishermen and other residents of the town of Bahi'a de los Angeles, especially Martin de Cortes for his tireless smile and bottomless fiierba buena tea. I am indebted to Dave Humphrey and Amanda Subalusky for making preliminary lists of bay island plants, as well as for their friendship. There are not enough words to thank Gary Polis, my unofficial advisor and the inspiration and driving force behind this work. I will miss you. I am especially grateful to my advisor. Bill Halvorson, for his assistance and encouragement throughout my research and writing, and the other members of my committee. Bill Shaw (for the maps, too!) and Steve Smith, for their continued efforts and kindness. Thanks to the students, faculty and staff of the Department of Renewable Natural Resources for their family-like support. Richard Felger has been a mentor, friend and consultant and identified plants. Brooke Gebow graced this work with her writing expertise and inspired me with her courageous good cheer in the face of huge challenges. The generous support of the Arizona Federation of Garden Clubs, and the assistance of their scholarship directors Christie Bininger and Mary Jo Wall made my work and any resulting conservation possible. This project was also partially funded and supported through Vanderbilt University, University of California at Davis, the Arizona- Sonora Desert Museum, the National Science Foundation, and Laurie Shomo-Brown. Loving thanks to my friends, especially Caren Goldberg for late nights of work, fun and crying, Cristina Jones for early morning sanity and cookies, and Rebecca Prescott for excessive silliness. Thank you to Nancy Laney for adopting me into her beautiful home and vast heart. Thanks to my parents, Walter and Marie West, who gave me the sense, curiosity and restlessness to follow my heart, which has brought me many places, including the Gulf of California and these beautiful islands that they were not lucky enough to see. Thanks to my sisters, Bink and Jennifer West who gave me home and Yoo Hoo when I needed them most and to Gramma for fun money, caring, and updates on family news. Endless thanks to my Arizona family, the Gunns, for always giving me a place to land especially on holidays; and my California family, Laura and Billy Southworth and Geoff King, for showers, salads, and dancing after fieldwork. In spite of the efforts of all these people, mistakes are inevitable and they are all my own. 4
DEDICATION
I dedicate this thesis with love to Julian Archer, my nephew who loves flowers, in
the hope that when he is old enough to visit them, the flowers will still be on the islands,
and to the memories of my dear island-loving friends Michael Rose and Gary Polis.
"...those we love, those who love us, contribute to our work in ways too countless, too precious to explain."
-Rebecca Wells (1996; P. 2) 5
TABLE OF CONTENTS
1 LIST OF FIGURES 7 2 LIST OF TABLES 9 3 ABSTRACT 10 4 INTRODUCTION II 4.1 Phytogeography 12 4.1.1 Floristic Setting 12 4.1.2 Island Biogeography Theory 14 4.2 Human Occupation and Development in Baja California 15 4.3 Management of the Islands in the Gulf of California 18 4.4 Study Area - Islands in Bahfa de los Angeles 19 4.4.1 Location 19 4.4.2 Geography 20 4.4.3 Geology 21 4.4.4 Climate 22 4.4.5 Scientific Research 23 4.4.6 Phytogeography 24 4.4.7 Human Use 25 4.4.8 Management and Conservation of the Islands in Bahfa de los Angeles 26 4.5 Research Objectives 27 5 METHODS 29 5.1 Floristic Analysis 29 5.1.1 Floristic Inventory 29 5.1.2 Plant Community Characterization 31 5.1.3 Biogeographical Analysis 34 5.2 Human Impacts 37 5.3 Potential Threats 37 6 RESULTS 41 6.1 Floristic Analysis 41 6.1.1 Floristic Inventory 41 6.1.2 Plant Community Characterization 43 6.1.3 Biogeographical Analysis 47 6.2 Human Impacts 49 6.3 Potential Threats 53 7 DISCUSSION 56 7.1 Floristic Analysis 56 7.1.1 Native Species of Concern 58 7.1.2 Target Areas of Concern 64 7.2 Biogeographical Analysis 65 7.3 Human Impacts 69 7.4 Non-native Species 69 7.4.1 Plants 70 6
TABLE OF CONTENTS (CONTINUED)
7.4.2 Animals 74 7.4.3 Managing for Non-native Species 76 7.5 Future Analyses 77 8 APPENDIX A - LIST OF ACRONYMS AND TRANSLATIONS 79 9 APPENDIX B - MANAGEMENT AND CONSERVATION TIMELINE OF THE GULF OF CALIFORNIA 81 10 APPENDDC C - COMMON NAMES FOR PLANTS MENTIONED IN THE TEXT AND APPENDICES 87 11 APPENDDC D: GEOGRAPHICAL CHARACTERISTICS OF ISLANDS IN BAfflA DE LOS ANGELES 93 12 APPENDDC E - SPECIES RICHNESS, PRESENCE AND INFLUENCES FROM ANIMALS 94 13 APPENDIX F - PLANT SPECIES LIST FOR ISLANDS IN BAHIA DE LOS ANGELES 95 14 APPENDDC G - PHOTO-ESSAY OF BAHIA DE LOS ANGELES 107 14.1 The Town of Bahia de los Angeles 107 14.2 Coronado/Smith Island 109 14.3 Ventana Island 112 14.4 Cabeza de Caballo Island 117 14.5 Piojo Island 118 14.6 Mitlan Island 120 14.7 Pata Island 120 14.8 Flecha Island 122 14.9 Bota Island 122 14.10 Coronadito Island 123 14.11 Gemelito East Island 125 14.12 Jorobado Island 125 14.13 Cerraja Island 125 14.14 Llave Island 126 14.15 Gemelito West 127 15 APPENDIX H - NON-NATIVE PLANT SPECIES AND PREDICTED THREAT TO ISLANDS 129 16 REFERENCES 132 7
1 LIST OF FIGURES
Figure I. Gulf of California region (adapted from Case and Cody 1983) 11 Figure 2. Sonoran Desert subdivisions of vegetation (adapted from Shreve 1951) 13 Figure 3. Bahia de los Angeles and surrounding areas 16 Figure 4. Islands in Bahfa de los Angeles (adapted from Baja Almanac 1997) 20 Figure 5. Saltmarsh on Ventana Island 44 Figure 6. Coastal scrub on summit of Flecha Island with teddybear cholla, Bahfa de los Angeles barrel cactus, and carddn; Ventana Island in the background, July 2001. ..44 Figure 7. Xeroriparian wash on Ventana Island, in bowl 45 Figure 8. Coastal sand dune at the base of the Coronado/Smith volcano 45 Figure 9. Mangrove swamp on the south end of Coronado/Smith Island 46 Figure 10. Rock cliff on the south side of Coronadito Island with senita (Lophocereus schottii) 46 Figure 11. Species-area curve for islands in Bahfa de los Angeles 47 Figure 12. Uprooted Bahfa de los Angeles barrel cactus (Ferocactus gatesii) on Llave Island 59 Figure 13. A juvenile Bahfa de los Angeles barrel cactus, demonstrating reproductive recruitment 60 Figure 14. Mammillaria sp. on Fata Island 61 Figure 15. Fruiting Mammillaria sp. on Cerraja Island 61 Figure 16. Echinocereus ferreiriamis on Cerraja Island 62 Figure 17. Red mangrove (Rhizopliora mangle) with developing viviparous "fruit." 65 Figure 18. Calavera Island covered in guano deposits 67 Figure 19. Crystalline iceplant {Mesembryanthemiim crystallimun) 71 Figure 20. Monospecific stand of crystalline iceplant in abandoned comfield in San Quintin, Baja California 72 Figure 21. Three kilometers south of the town of Bahfa de los Angeles. Cabeza de Caballo Island (background), July 1999 107 Figure 22. Town of Bahfa de los Angeles looking north-northeast, prior to 1959 (photo by H. Aschmann [1959]) 108 Figure 23. Town of Bahfa de los Angeles from the water tank, approximately the same location as Figure 22, December 2000 108 Figure 24. Aerial view of Coronado/Smith Island (tall island in the lower center) and Coronadito (lower right) looking southwest, September 2000 109 Figure 25. Designated camping beach at the southwestern base of Coronado/Smith volcano, December 2000 110 Figure 26. Saltflat on Coronado/Smith Island with iodine bush, December 2000 110 Figure 27. Coronado/Smith volcano and beach at its base with moming fog, December 2000 111 Figure 28. A salt "lake" that is only exposed to the gulf during unusually high tides lies between the central beach and the mangrove swamp on the south end of Coronado/Smith Island, December 2000 111 8
LIST OF nCURES (CONTINUED)
Figure 29. Wind-trimmed littleleaf elephant-tree on Coronado/Smith Island, December 2000 112 Figure 30. Scientific expedition with April Boulton (foreground) camped on the beach at Ventana Island, July 1999 113 Figure 31. Magnificent Frigatebirds (Fragata magnificens) and western gulls {Lams occidentalis) scavenging the remains from fish processing on the main landing beach of Ventana Island, December 2000 113 Figure 32. Sign demonstrating regulations on main southern boat landing on Ventana Island, December 2000 114 Figure 33. The rock window for which Ventana Island is named, March 2(X)0 114 Figure 34. Rock-lined path from main boat landing to inner bowl of Ventana Island, December 2000 115 Figure 35. Wash leading from the main boat landing up to the bowl on Ventana Island, December 2(X)0 115 Figure 36. Juvenile Mammillaria sp. (with pen) on Ventana Island, July 2000 116 Figure 37. Cliffside overlooking main boat landing on Ventana Island, July 2001 116 Figure 38. Cabeza de Caballo Island, view from the lighthouse on Gemelito East Island, December 2001 117 Figure 39. Pitaya agria (Stenocereus gummosus) on rocky north point of Cabeza de Caballo Island, July 1999 118 Figure 40. Rocky wash on the southwest section of Piojo Island, July 2001 119 Figure 41. Chuckwaila {Sauromaliis hispidus) on Piojo Island, July 2001 119 Figure 42. Recreationists camped on the beach at Pata Island with iodine bush {Allenrolfea occidentalis) in the foreground, December 2000 120 Figure 43. Shoreline of Pata Island with bank of iodine bush, July 2001 121 Figure 44. Shrine of rusty metal on Pata Island, July 2001 121 Figure 45. Bahi'a de los Angeles barrel cactus (Ferocactus gatesii) on Flecha Island, July 2001 122 Figure 46. Bota Island's rocky cliffs in the background; Cardon (Pachycereits pringlei) on Pata Island in the foreground, July 2001 123 Figure 47. Rocky slope on the south side of Coronadito Island, Cardon {Pachycereus pringlei) (left) and senita (Lopfiocereiis schottii) (right), December 2000 124 Figure 48. Coronodito Island bowl above boat landing; the white areas in the foreground are remnants of dead crystalline iceplant {Mesembryanthemiim crystalliniim), December 2001 124 Figure 49. Northwest arm of Cerraja Island with Opuntia alcahes var. alcahes, July 2001. 126 Figure 50. Cerraja Island (foreground), Llave Island (middle) and Flecha Island (background) in a dry year, July 1999 127 Figure 51. Gemelito West Island looking westward from the lighthouse on Gemelito East Island, December 2000 128 9
2 LIST OF TABLES
Table 1. Ordinal rating system of abundance of plants on islands in Bahfa de los Angeles; N = number of plants on each island 32 Table 2. Representative plant species and characteristics of plant communities on Bahfa de los Angeles islands 33 Table 3. Correlations among characteristics on small islands in Bahia de los Angeles. Factors with >0.8 correlation with area were excluded from the multiple regression model analysis 36 Table 4. Plant collections made on the Bahia de los Angeles islands prior to this study. 42 Table 5. Plant communities on islands in Bahia de los Angeles 43 Table 6. Estimates of multiple regression coefficients and slopes for the associations between plant species richness with island area and seabird status, including the outlier 48 Table 7. Estimates of multiple regression coefficients and slopes for the associations between plant species richness with island area and seabird status, excluding the outlier 49 Table 8. Human uses and impacts on islands in Bahia de los Angeles 50 Table 9. Estimates of multiple regression coefficients and slopes for the associations between plant species richness with area, seabird status, and human impact index including the outlier 51 Table 10. Estimated percent of islands used by humans and areas most heavily used 52 Table 11. Non-native plant species cover on Bahia de los Angeles islands 54 Table 12. Threat status of non-native plant species near Bahia de los Angeles islands. ..55 10
3 ABSTRACT
Planners expect infrastructure development underway in Baja California to launch a wave of tourism. Managers will need information concerning the natural environment.
This study focuses on the floral richness of the islands of Bahia de los Angeles, Baja
California, Mexico. Results include a plant species inventory for each island; a
phytogeographic analysis evaluating the effects of island characteristics on plant species richness; a current human impact analysis, especially on floral richness; an evaluation of threats to floral richness and environmental health, including a non-native plant analysis; and management recommendations for preventing depletion of the native plant species richness on these islands from increased visitation. Floral richness ranges from 2 to 74 species per island. The best predictors of floral richness on the islands are the island area and the seabird presence or breeding. I recommend a combination of careful monitoring, dissemination of educational materials, and increased enforcement of current restrictions on island use to minimize human impacts. 4 INTRODUCTION
This study assesses floral richness, the number of vascular plant species, on the islands in Bahfa de los Angeles in the Gulf of California, and evaluates human disturbance and other factors as predictors of that richness. This chapter provides background on the history of development and human occupation in Baja California, information about the current use and management of islands in the Gulf of California
(Figure 1), and provides specific information concerning Bahia de los Angeles in the context of changes in human use and management.
United States of America 33
31 California I V Sonora
1. Bahia de los Angeles 29 2. Angel de la Guarda Island 3. Bahfa las Animas 4. Tiburon Island I 5. San Lorenzo Island Baja^ 6. Bahia Kino 27 7. Alcatraz Island Gulf or' Sur \.California ^ 8. Santa Rosaliliita 9. Guaymas/San Carlos 10. La Paz L 25 Q SD IB a a ttB 10 ^V 117 115 113 109 23
Figure I. Gulf of California region (adapted from Case and Cody 1983). 12
4.1 PHYTOGEOGRAPHY
4.1.1 Fioristic Setting
Shreve (1951) divided the Sonoran Desert into seven subdivisions, four of which occur on the peninsula of Baja California: Lower Colorado River, Vizcafno Region,
Central Gulf Coast, and the Magdalena Region (Figure 2). Sections in the south and north of the peninsula are not part of the Sonoran Desert. The entire 143,790-km" peninsula hosts approximately 3000 plant taxa (species and intraspecific taxa), 2705 of which are species of vascular plants (Shreve and Wiggins 1964, Wiggins 1980). Of these species,
23.2% are endemic to the peninsula and adjacent islands, and 124 species, or 4.6%, are non-native (Shreve 1951, Nabhan et al. in press). Found on the 898 islands in the Gulf of
California are more than 600 of the species in the peninsular region (Carabias-Lillo et al.
2000; see Appendix A for acronyms). The gulf islands also harbor many endemic species; the older, more isolated Pacific islands are especially rich in endemics. 13
Map of Sonoran Desert Subdivisions
fTTTI Lower Colorado Valley rm Arizona Upland Plains of Sonora Foothills of Sonora HI Central Gulf Coast I I Vizcaino Region uv.\i Magdalena Region
Ukf d ' ' " at ttP MKAttirf d" "s4 &
Figure 2. Sonoran Desert subdivisions of vegetation (adapted from Shreve 1951). 14
4.1.2 Island Biogeography Theory
At the core of the theory of island biogeography, as presented by MacArthur and
Wilson (1967) is the concept that species richness (the number of species in an area) is the result of a balance between immigration and extinction (Whittaker 1998). MacArthur and Wilson (1967) concluded that the relationship between the number of species (S) on an island of a certain area (A) was fairly simple and could be applied to many taxa:
S=CA'
Or
Ln (species richness) = z Ln (area) + C
In this formula, C is an empirically determined constant that represents biotic richness
(or the intercept in the equation), and z represents the slope of the diversity curve that refers to the rate at which species accumulate with increments of area. Whittaker (1998) interprets the z-value to be difficulty in reaching the island, while Holt et al. (1999) use the c-value to measure the strength of the relationship between size and species richness.
Endemism on islands is generally high because of different selection pressures on species, differences in colonization, and isolation as compared to mainland areas. Higher endemism is associated with oceanic islands that have generally been isolated much longer than continental shelf islands that may have been connected by land bridges to the 15
nearby mainland when sea levels were lower in the Pleistocene (1.8 to 0.01 mya;
Whittaker 1998).
4.2 HUMAN OCCUPATION AND DEVELOPMENTINBAJA CALIFORNIA
Humans have been part of the Baja California landscape since the peninsula was
occupied as early as 12,000 yr B. P. (years before present; Aschmann 1959, Bowen
2000). Although archeological evidence is scarce, researchers suggests that people were
present on the peninsula when the climate in the area was much wetter (Aschmann 1959),
and they have been using the Midriff islands for at least 10,000 years. As of the year
2000, many people still consider them "pristine" (Bowen 2000, Bahre and Bourillon in
press). Even before European settlement started In 1697 with the founding of a Jesuit
mission in Loreto (Aschmann 1997a), the population of Cochimi people in the Central
Desert region of Baja California was very high. It then declined sharply as a result of the
Introduction of new diseases from the Europeans (Aschmann 1997b). Many of the native people in the coastal areas of Baja California and Sonora, the Cochimi' and Comcaac
(Seri), were hunting animals, collecting plants and bird eggs, and camping on the islands in the Midriff region (Felger and Moser 1985, Bowen 2000). More intensive use by these people may have been limited to the larger islands, such as Tiburon and San Esteban
(Bowen 2000, Bahre and Bourillon in press). When Spanish missionaries arrived in the
1700's the population of the peninsula was an estimated 48,000 (Aschmann 1997b). San
Borja Mission is a traveling distance of 58 km from the supply station of Bahi'a de los
Angeles (now the town; Figure 3). In 1770 the mission had 1,538 Cochimi residents, but 16
by 1808 only 192 had survived introduced post-contact diseases, and only 12 people
remained at the mission in 1867 (Aschmann 1959, 1997b). The San Boija case
exemplifies the rapid decline in populations throughout the peninsula in the early 19"*
century (Aschmann 1959). By the late 1800s the last of the native people of the central
desert had died or disappeared (Aschmann 1959). Throughout the 1800s and early
1900s, the population of Baja California remained relatively small, but resource use continued in the form of hunting sea lions, guano and mineral mining, depletion of small
water sources, and fishing (Bahre and Bourillon in press).
Isia Angela de la Guarda
Coronado/Smith Island
Agua Amarga Punta la Gringa
Punta Arena
(Town oO . Bahia Isia el Pescador Bahfa ide los Angeles \ dellosi L^ngeles • La Mona
Bahia las Animas
Mission San Borja
Figure 3. Bahfa de los Angeles and surrounding areas. 17
Even through the mid-ZO"* century the peninsula remained isolated and sparsely
inhabited, especially in what Aschmann (1959) referred to as the Central Desert of Baja
California. Aschmann (1959) described the peninsula as growing more desolate as a
traveler moved south on the "rutted track." Krutch (1961) described traveling the
peninsula as rewarding and challenging, and suggested that if one were to drive down the
peninsula one would need to be self-sufficient and allow 10 days "of hard driving" to get
from San Diego to La Paz. Gerhard and Gulick (1962) recommended that only travelers
with at least a rudimentary knowledge of mechanics and essential spare parts should
attempt to drive the ungraded part of the transpeninsular highway. In 1964, ferry service
linked mainland Mexico with the peninsula, but only to La Paz. Central Baja California is approximately 450 km north of La Paz and an equal distance south of San Diego. In the
1960s, travel over land through the peninsula was uncommon, and visitors generally traveled by boat or small plane.
After highway 1 (the trans-peninsular highway) was paved in 1973, tourism and tourist facilities increased in all of Baja California (Bahre 1983). Travel guides from the
1970s encouraged exploring the peninsula in spite of the great challenges (Bates et al.
1971, Hunter 1977, Miller and Baxter 1977, Wheelock and Gulick 1975).
While central Baja California is still the least visited and least occupied sector of the peninsula, it is accessible by car, boat and small plane. Since the 1980s, travel by car has become common, especially with the increased use of high-clearance sports utility vehicles (SUVs). With the paved road, even the most remote locations in central Baja
Califomia can be accessible in a day from San Diego or La Paz. This access has 18
delivered more people to previously isolated places and it has also changed the way non-
native plants and animals move through the peninsula. Completion of the paved trans-
peninsular highway breached the isolation that previously had sheltered the ecosystems
of Baja California and their inhabitants from human impacts (Case and Cody 1983).
Along the shores in the Gulf of California (also called the Sea of Cortes, the Sea
of Cortez, Vermillion Sea, Mar Bermejo, and the Mar de Cortes), lack of fresh water has
kept development to a minimum. However, days of visitation by ecotourists increased on
islands in northwestern Mexico by at least 7% each year between 1986 and 1993; in that
time period, the total increased from <15,000 to about 47,000 visitor-days per year
(Tershy et al. 1999). Not only is tourism increasing, but the population in mainland
Mexico, adjacent to the Gulf of California, tripled from the 1950s to the 1980s (Reich
1984).
4.3 MANAGEMENT OF THE ISLANDS IN THE GULF OF CALIFORNL\
Mexico has passed much environmental legislation; some of it has been
progressive, such as the early listing of species to be protected. For the most part,
Mexico's environmental agencies' (see Appendix A for an explanation of agency
acronyms) abilities and willingness to enforce those regulations have been inconsistent
(Appendix B). One difficulty has been that the environmental agencies have no enforcement capabilities; enforcement is the job of Prociiradima Federal de Proteccion al Ambiente (PROFEPA; Office of the Attorney General for Environmental Protection).
Recent changes reflect a desire and willingness for lasting and effective environmental protection. In June 2000, the Mexican Government declared the islands in the Gulf of
California a reserve— Area de Proteccion de Flora y Fauna "Islas del Golfo de
California" (Protected Area of Flora and Fauna "Islands of the Gulf of California"). It is
the intent of this reserve to protect the flora and fauna on all of the 898 islands in the Gulf
(Carabias-Lillo et al. 2000). Over 600 plant species are found on these islands (Carabias-
Lillo et al. 2000). The smallest islands are unnamed and exposed only at low tide, and
the largest, as shown in Figure 1, is 1,208 icm~ Tiburon Island that has 298 species of
plants on its steep rocky slopes (Carabias-Lillo et al. 2000). The agencies that control the
use of the islands in the Gulf of California are SEMARNAT (formerly known as
SEMARNAP) and Secretaria de Gobemacion (the Secretary of Govemance [the
Mexican Federal Government]). These agencies need current resource information to
monitor effects of increasing visitation on island flora and to determine strategies that
minimize damage to these unique environments.
4.4 STUDY AREA - ISLANDS LV BAHIA DE LOS ANGELES
4.4.1 Location
Bahia de los Angeles is on the remote eastern side of the peninsula in the southern
part of the state of Baja Califomia (Figures I, 3, and 4). Along with 24 other islands in
the central section of the Gulf of Califomia, the islands in this bay (sometimes referred to as the Smith Island group; Figure 4) are considered Midriff islands. These islands lie
between 28° and 29° 45' N latitude and 112° and 114° W longitude (Bahre 1983), also 20
known as la Region de las Grandes Islas (the Region of the Great Islands) (SEMARNAP
1999).
Punta 113*30' 113*25' 113-20' Coronadito Island Canton 29"05'
Coronado/Smith Island
Miles Mitlan Island o 2 3 I J i_ (TTTTTT Calavera Island Kilometers Pata Island San Aremar Island N 29*00' Piojo Island Bota Island Jorobado Island Flectia Island (Borrego) Ventana Island Cenaja Island Llave Island Cabeza de Caballo Island Gemelito West Island 28"55' Gemelito East Island Punta Anna
Bahia de lo5 Angeles
Figure 4. Islands in Bahia de los Angeles (adapted from Baja Almanac 1997).
4.4.2 Geography
Figure 4 shows the 16 uninhabited islands, ranging in size from less than 0.02 km"
(Calavera Island) to 8.7 km" (Coronado/Smith Island), that make up the archipelago in
Bahfa de los Angeles. These islands are listed here from north to south: Coronadito,
Coronado/Smith, Mitlan, Calavera, Piojo, Pata, San Aremar, Jorobado, Bota, Flecha 21
(Borrego), Ventana, Cerraja, Llave, Cabeza de Caballo, Gemelito East, and Gemelito
West (Polis et al. 1997). The islands range in maximum elevation from 8 to 465 m (Polis et al. 1997), and in isolation from the mainland of the Baja California Peninsula from 0.8
to 6.3 km (Boulton and Ward in press).
4.4.3 Geology
The Gulf of California is a geologically and tectonically active area. A major spreading fault falls between Bahfa de los Angeles and Angel de la Guarda (see Figure
I). In the bay itself, 248 million year old Paleozoic metamorphic rocks uplifted, creating topography. In the Miocene (5-24 mya), volcanic activity layered that topography with
12 million year old basaltic and basaltic andesite flows and deposited Miocene pyroclastic and felsic rocks that formed from the remelting of the continental crust (Gastil et al. 1983, Delgado-Argote and Garcfa-Abdeslem 1999). The bay islands' rock material is similar in age to that of Angel de la Guarda, which also primarily consists of Miocene pyroclastic and felsic rocks.
The uplifted areas were connected to the adjacent peninsular mainland when sea levels were low during the Pleistocene (1.8 mya to 15,000 years ago; Phillips 1964,
Gastil et al. 1983, Delgado-Argote and Garcfa-Abdeslem 1999). The Bahia de los
Angeles islands became isolated from the adjacent peninsula when icecap melting produced higher sea levels at the end of the last glaciation (15,000 to 10,000 years ago;
Anderson 1950, Gastil et al. 1983). Phillips (1964) dates the formation of the islands to the Pleistocene. Seafloor spreading and rising sea levels isolated Angel de la Guarda in the same time period (Anderson 1950, Gastil et al. 1983). The Midriff islands are typical continental islands and are much younger than oceanic islands such as the Hawaiian chain (1 to 5 million years old) and the Galapagos Islands (3.3 to 5 million years old;
Whittaker 1998).
4.4.4 Climate
Reliable weather data are not available for individual islands. Weather stations are difficult to maintain on the islands because of high unpredictable winds and access problems, but there has been an operable weather station in the town of Bahfa de los
Angeles, located approximately 15.5 km from the most distant bay island, since 1953.
The Comision Nacional de Agua (National Water Commission of Mexico) has reported the rainfall, minimum and maximum temperature in a 24-hour period, median daily temperature, maximum precipitation in 24 hours, days of rainfall greater than or equal to
O.l mm, and snowfall - although there has been no snowfall since 1953 (Comision
Nacional del Agua 2001). Maritime dew may be a factor, but has not been recorded for this area.
The town of Bahia de los Angeles is one of the most arid localities on the Central
Gulf Coast of the Baja California Peninsula, averaging 71.3 mm of annual rainfall
(Turner and Brown 1994). Some years (including 1999), the weather station recorded 0 mm {Comision Nacional del Agua 2001). Because of this low rainfall, the vegetation on all the islands is sparse and is restricted to arid-adapted and salt-tolerant species. In the years of this study and just prior to this study, the rainfall was variable: 24.0 mm (1996), 23
111.0 mm (1997), 49.0 mm (1998), 0.0 mm (1999), and 38.5 mm (20(X)), (Comision
Nacional del Agua 2001). Because of "El Nino" years like 1997, there is a seedbank of ephemerals that are winter-rain-dependent. The timing of the winter rains is as important as the amounts of rain at Bahia de los Angeles (Shreve 1951, Wiggins 1980). Although in 1997 the winter rains were heavy, Bahia de los Angeles has seen much wetter years. In
1966, the annual rainfall was 272.5 mm with 181.0 mm falling in the month of
September, most of which fell in five days. The pattern of long drought periods with intermittent torrential rainstorms is typical of most of the Baja California peninsula
(Shreve 1951). Between 1997 and 2001, the highest and lowest temperatures recorded for the area were a low in December of 1998 (3° C) and the high in July of 1997 (49 ° C).
The area is frost free.
4.4.5 Scientific Research
Case and Cody (1983) suggest that the flora of the islands in the bay had not been documented as of 1983 because the area is remote, hyper-arid, and the site had minimal facilities for visitation. However, Bahfa de los Angeles was already considered a tourist center in 1983 and was much more developed than surrounding areas (Bahre 1983).
Scientists did visit the area, and the San Diego Natural History Museum maintained a field station in the town of Bahfa de los Angeles from 1960 to 1969, but no research addressed the 16 bay islands (Case and Cody 1983). From 1980 to 2(K)0, improved tourist facilities and availability of supplies made the logistical aspects of scientific expeditions near Bahfa de los Angeles easier (G. A. Polis, pers. comm. March 5, 1998; Case and 24
Cody 1983), but the flora of these islands still had not been studied in a comprehensive manner.
Scientific research completed on and around the 16 bay islands includes studies of geology (Delgado-Argote and Garcia-Abdeslem 1999), food web interactions (Polis and
Hurd 1996), seabird nutrient input (Anderson and Polis 1999), coyotes (Rose and Polis
1998), human impacts on seabird nesting (Anderson and Keith 1980), diversity of scorpions (Due 1992), mollusks (Poorman and Poorman 1978), beetles (Sanchez-Pifiero and Aalbu in press), mammals (P. Stapp, unpublished data), ants (Boulton and Ward in press), sea turtles (Seminoff et al. 2000), and marine algae (Pacheco-Ruiz and Zertuche-
Gonzalez 1996). The endemic-rich floras of Angel de la Guarda and other larger Midriff islands (including Tiburdn, San Esteban, and San Lorenzo) attracted botanical researchers who collected plants and conducted floristic studies while based in Bahfa de los Angeles
(Case and Cody 1983). Before the present study the plant communities had not been described for any of the small islands.
4.4.6 Phytogeography
Despite the lack of collections for the bay islands, the area of Bahfa de los
Angeles is considered by Delgadillo (1998) to be among the 13 best-studied areas of the peninsula. Shreve (1951) and Wiggins (1980) characterized the flora of the islands as a sarcocaulescent desert, with dominant species being stem succulents, such as littleleaf elephant-tree (Bursera microphylla), cardon (Pachycereiis pringlei), and other large cacti
(see Appendix C for common and corresponding scientific names of plants in this text). 25
He characterized the adjacent area on the peninsula, starting just south of the bay and
extending north past the border with the U.S., as microphyllous desert with creosote bush
(Larrea tridentata) dominating, and associated species being ocotillo (Fouquieria
splendens ssp. splendens), bursage {Ambrosia spp.), littleleaf elephant-tree. Figure 2
shows the subdivisions of the Sonoran Desert; using Shreve's (1951) classification
system, Wiggins (1980) classified the Bahia de los Angeles islands in the Central Gulf
Coast subdivision, along with the large islands in the midriff region and the area to the
south of Bahi'a de los Angeles. Shreve (1951) and Wiggins (1980) both placed the shore
of the peninsula adjacent to the islands in the Lower Colorado Valley photogeographic
subdivision.
4.4.7 Human Use
Clavigero (1789) wrote that Spanish missionaries used Bahfa de los Angeles as a
port for obtaining supplies, but that very few people lived there. Modem human use of
the islands in Bahia de los Angeles began in the 1930s, when people from the town of
Bahfa de los Angeles visited to collect eggs (Krutch 1961). Travel guidebooks from the
1970s mention Bahi'a de los Angeles as a bleak but interesting place, known for sport
Fishing and good food, especially turtle steaks, that made it worth the 40 miles of dirt road that one had to travel to get there (Wheelock and Gulick 1975, Hunter 1977, Miller and Baxter 1977).
As with other factors, the types and intensity of current human use vary from island to island. Researchers, fisherman and recreationists visit the islands for camping. 26
recreation, scientific studies, fish processing, or marine emergencies. The area faces the
challenge of being a tourist destination, with a focus on ecotourism and adventure travel,
while maintaining the environmental integrity. The visitor population is environmentally
aware, but use is intense. Researchers and campers bring fleld equipment onto the
islands, from other islands and from the coast. The Mexican government is concerned
about I) damage to sensitive native vegetation, 2) decreases in plant species diversity,
and 3) the introduction of non-native species on these small islands (SEMARNAP 1999,
Tershy et al. 1999).
Meanwhile, the Fondo Nacional de Fomento al Turismo (National Fund for the
Promotion of Tourism) has also started development on the Nautical Steps (Escalera
Ndutica; FONATUR 2001). This $200 million project features a full-service port in
Bahfa de los Angeles (possibly at Punta Arena) and a new 13 m-wide paved road from
Santa Rosalillita (on the Pacific side of the Peninsula) to Bahia de los Angeles will be built to transport large boats (mostly American-owned) to the Gulf of California
(Spalding 2001). The project hopes to bring an additional 5.4 million tourists annually to the Gulf (Spalding 2001). The project is scheduled for completion by the year 2007
(Spalding 2001). Work on the road, waterline, and other improvements had already started by December 2000.
4.4.8 Management and Conservation of the Islands in Bahi'a de los Angeles
Because of increasing human visitation, managing agencies have established a permit system to limit access to the islands and placed signs on some islands explaining 27
regulations concerning the islands in Bahfa de los Angeles. Local fishermen and guides believe these signs are working (Paco Verdugo, personal comm., December 2000), but the actual effectiveness is not known. Local conservationists have initiated the establishment of a preserve of the intertidal zones of the islands that would decrease the use of waters surrounding the island areas and possibly protect coastal areas, but not the interior of the islands from increasing use.
The Mexican agencies that manage the islands in Bahfa de los Angeles need current inventory information so they can begin I) monitoring the effects of increased visitation on the island biota, and 2) determining strategies to minimize damage to these unique environments. To protect plant species richness effectively, managers will need
1) current and comprehensive floristic data, 2) an awareness of potential threats to these
16 islands, 3) knowledge of factors influencing plant species richness on the islands
(Jerez 1992, SEMARNAP 1999), and 4) information on the potential impacts of human visitors (Tershy et al. 1997).
4.5 RESEARCH OBJECTIVES
The goal of this research is to provide information that will help direct monitoring and managing the botanical resources of the islands in Bahfa de los Angeles. My specific research objectives were:
Objective 1: Describe the floral richness present on the islands, characterize plant communities, and analyze biogeographical associations; Objective 2: Document current human uses and impacts on the floral richness of the islands;
Objective 3: Identify, describe, and discuss potential threats to the floral richness and health on the islands; and
Objective 4: Recommend strategies for managing the natural resources and human uses of the islands to conserve their biodiversity, with an emphasis on conserving plant species richness. 29
5 METHODS
Accomplishing the objectives set forth in the last chapter required searching the
literature and herbarium collections for records. I then made eight plant-collecting trips,
identified specimens, and carried out analyses of abundance, biogeographical
relationships and human impacts. This chapter describes these steps in detail.
5.1 FLORISTIC ANALYSIS
The Bahfa de los Angeles floristic analysis for each bay island includes a plant species inventory, a biogeographical analysis, and an abundance rating for each perennial and non-native species. These analyses are designed to describe the plant species richness and characterize the vegetation of the islands.
5.1.1 Floristic Inventory
For each island, I searched for previous collections, lists, and publications. This information was sparse, covering only some perennial plants. Collections and documents at the San Diego Natural History Museum, especially the unpublished field journals of
Reid Moran, also indicate that researchers collected only minimally on the shore of the
Baja California Peninsula adjacent to Bahia de los Angeles; Moran made six collections on these islands.
Both L. D. Humphrey and A. Subalusky, as members of the University of
California at Davis research group of Gary Polis, started preliminary plant lists for some islands (unpublished field notes 1996 and 1997). Although valuable as a starting point. 30
these lists were not complete, had misidentifications, and lacked voucher specimens to
confirm identifications. I used my collecting trips to confirm the plant species on these
lists and added new records from my collections. I used the resulting comprehensive list
(Appendix F), including designations for non-native species and regional endemics, to
complete the biogeographical analysis.
My visits to each island lasted from 1 to 10 hrs, and I surveyed each one at least
once during eight collecting trips to the bay (from March 1998 to July 2001). Two trips
took place in each of the months of March, May, and July, one trip in October, and
another in December 2000.
Using standard processing and voucher procedures (Tuxill et al. 1998; San Diego
Natural History Museum 1991), I deposited primary vouchers at the San Diego Natural
History Museum herbarium (SD) and duplicates at Universidad Autonoma de Baja
California herbarium in Ensenada (BCMEX). I made collections under a collection
permit held by Gary A. Polis and Gary Huxell. Cacti were imported on a CITES
(Convention on International Trade in Endangered Species) permit through an agreement and exchange program between the San Diego Natural History Museum (SDNHM) and
Universidad Autonoma de Baja California (UABC) at Ensenada. Nomenclature follows
Rebman et al. (in press), because the list of plants from the Bahia de los Angeles islands is being published with Rebman's list of plants from larger gulf islands (Case et al. in press. West et al. in press). I identified plants using Wiggins (1980), Gould and Moran
(1981), Felger (2000), and reference collections in the herbaria at the University of
Arizona (ARIZ) and the San Diego Natural History Museum (SD). Because there is no 31
standard reference for common names of the Gulf region, I consulted the previously
mentioned botanical works and the following for these names: Standley (1922-26),
Martinez (1979), Roberts (1989), Turner et al. (1995), and Felger et al. (1997). See
Appendix C for a list of common names.
5.1.2 Plant Community Characterization
To evaluate the abundance of each perennial and non-native species on every
island, I used a standard ordinal abundance rating system (from rare to abundant)
modified from Junak and Philbrick (2000a; Table 1). I determined the class sizes based on the elevation, area, and the number of plant communities on the islands. I then estimated numbers of individual plants of each species on each island to determine the abundance rating. Using plant lists, abundance ratings of characteristic species on each island, photos, and field notes, I characterized the plant communities (Table 2), based on a modified classification system combining the systems of Shreve (1951), Wiggins
(1980), Jerez (1992), Costa and Davy (1992), and Delgadillo (1998). 32
Table 1. Ordinal rating system of abundance of plants on islands in Bahia de los Angeles; N = number of individual plants
Rating Definition for smaller Definition for larger island islands (< 0.08 km^) (> 0.09 km^)
Common (1) Many plants occurring on Many patches of plants a broad range of occurring on a broad range of topographical features topographical features
(N>21). (N>101).
Occasional (2) Plants scattered, but not Many patches, but not commonly encountered in commonly encountered in all all topographical areas topographical areas (11 Scarce (3) Few plants (6 Rare (4) One plant or a small group Few scattered plants of plants (I Table 2. Representative plant species and characteristics of plant communities on Bahia de IDS Angeles islands. Plant Representative species Characteristics Community Saltflat Iodine bush (Allenrolfea Tidal flats, flooded only during occidentalis), glasswort (Saliconiia extra-high tides, with perennial, siibterminalis), alkaliweed (Cressa evergreen halophytes. truxillensis), shoregrass {Monanthochloe littoralis), turtleweed (Batis maritima), shoreline purslane {Sesuvium portiilacastnim) Coastal scrub Choi la (Opiintia spp.), cardon. Inland with soil mixed with fishhook cactus (Mammillaria sp.) rocks that supports xeric shrubs, cacti, and small trees. Xeroriparian Littleleaf elephant-tree, white Wash areas between hills that wash brittlebush (Encelia farinosa), jojoba tend to hold ephemeral moisture (Simmondsia chinensis), agave better than exposed rocky slopes. (Agave cerulata ssp. cendata), Vegetation is more dense and whiiestem milkweed {Asclepias taller than on other inland areas. albicans) 34 Plant Representative species Characteristics Community Coastal sand California threeawn (Aristida Sandy dune areas near dune califomica var. califomica), Emory shorelines. indigo bush {Psorothamnus emoryi). Palmer's seaheath (Frankenia palmeri), crystalline iceplant (Mesembryanthemum crystallinum). desert saltbush (Atriplex polycarpa) Mangrove Red mangrove {Rhizophora mangle) Intertidal area with muddy substrate. Rock cliff Cardon, yellow nightshade Dry rocky areas exposed to high groundcherry (Pfiysalis crassifolia). winds with boulders as the main island ground vine (Vaseyanihus substrate. insiilaris) 5.1.3 Biogeographical Analysis The landmark work of R. MacArthur and E. O. Wilson (1967) brought home the notion that islands follow special species composition "rules." In order to account for variation in plant species richness across 16 islands, I considered important "island" factors and various representations of animal presence on the islands. I examined all available factors to build a model to predict plant species richness on bay islands. I examined correlations among all of the following potential variables to make sure that they were independent; island area (Polis et al. 1997), maximum elevation (Polis et al. 1997), island isolation (Boulton and Ward in press), mammal species richness (P. Stapp, unpublished data), ant species richness (Boulton and Ward in press), seabird status (whether seabirds are present, nesting or absent; Sanchez-Pifiero and Polis 2000), and percent of guano deposition (Sanchez-Pifiero and Polis 2000; Appendices D and E). Isolation is the measure of the shortest distance from the island to the nearest mainland area on the peninsula (Boulton and Ward in press). I log-transformed (natural log - Ln) plant species richness, area, isolation, and elevation to normalize the data (Ramsey and Schafer 1997). I excluded all factors that had a correlation of >0.80 with island area to avoid problems of multicolinearity that would give me erroneous results (Ramsey and Schafer 1997; Table 3). I then used stepwise multiple regression on the remaining variables to build a model of plant species richness among these islands (Ramsey and Schafer 1997). I determined the z-value for the archipelago, to compare the strength of the relationship between species richness and area of the islands with --values of islands in other areas. Table 3. Correlations among characteristics on small islands in Bahfa de los Angeles. Factors with >0.8 correlation with area were excluded from the multiple regression model analysis. Ln (area) Ln (elevation) Mammal Ant species Seabird status Ln (isolation) % Guano richness richness cover Ln (area)" 1.00 ------ Ln (elevation)'' 0.95 ------P<0.0001 Mammal richne.ss'' 0.68 0.66 — - - - - P<0.0001 P<0.0001 Am species richness*^ 0.85 0.85 0.50 — - - - P<0.0001 P = 0.0077 P = 0.0003 Seabird .status*' -0.51 -0.52 -0.68 -0.52 -- - - P<0.0001 P= 0.0009 P =0.0313 P =0.0030 Ln (isolation)' 0.3! 0.14 0.29 0.07 -0.24 " - P<0.000i P<0.0001 P = 0.970 P = 0.0005 P = 0.0055 Guano cover ** -0.56 -0.43 -0.58 -0..34 0.69 -0.56 -- P = 0.0171 P = 0.0937 P = 0.0378 P = 0.3146 P = 0.0421 P = 0.0364 Perimeter" 0.85 0.81 0.51 0,96 -0.38 0.07 -0.31 P = 0.0002 P = 0.6310 P = 0.0905 P<0.0001 P =0.3651 P =0.1109 P =0.0998 Polisetal. 1997, P. Stupp, unpublished data, Boulton and Ward in pres.s, Sanchez-Pincro and Polis 2000 0\ 37 5.2 HUMAN IMPACTS Because human activities on islands have been associated with ecological changes (Whittaker 1998), I hypothesized that intensive human use on the bay islands may affect plant life. Thus, I assessed current human impacts on the islands by documenting evidence of garbage deposition (in coastal areas and inland), path making, evidence of human-caused fire, erosion caused by humans (rocks and dirt being displaced in areas of high use), and camping. For each island, I added up the number of factors present to yield an impact index that ranged from zero (no impacts present) to six (all impacts present). As a final step, I computed this index, applied this index to the model by using it as an additional factor in a stepwise multiple regression, and evaluated whether human impacts accounted for any of the remaining variation in plant species richness. I also prepared a photo-essay demonstrating the types of visitation on each island (Appendix G). I obtained visitation data from personal observations, informal interviews with permanent residents of the town. 5.3 POTENTIAL THREATS Worldwide, invasions of non-native species threaten biodiversity and ecosystems, especially on islands (DiCastri 1989, Vitousek et al. 1996). Introduced non-native plants are capable of changing soil characteristics, altering fire regimes, and changing other ecological relationships (Heywood 1989, D'Antonio and Vitousek 1992, Mack and D'Antonio 1998). Non-native herbivores can selectively forage sensitive species and cause severe soil erosion; both herbivores and carnivores, especially feral cats, cause top- 38 down effects that change species compositions and abundances of plants through predation on island herbivores (Whittaker 1998, Donlan 2000). Jerez (1992) noted non- natives as she conducted surveys of perennial vegetation in five locations on the Baja California peninsula (Punta la Gringa, Punta Arena, La Mona, Las Animas mangrove esturary. Las Animas mudflat (See map - Figure 3 on page 16). Her study documented species in the desert scrub communities on peninsular shores near the Bahia de los Angeles islands, but specifically excluded grasses and annuals (Jerez 1992). In order to compile a list of non-native plant species that may threaten the islands, I combined information from Jerez's (1992) study, herbarium collections at SD and ARIZ, and literature on flora of islands of the gulf (Felger and Lowe 1976, Bourillon-Moreno 1996, ICEG 2002). I selected non-native plants found in studies and literature from the peninsula and other Midriff islands in the Gulf of California and recorded the distance of the nearest populations to Bahi'a de los Angeles. My surveys focused on the town of Bahi'a de los Angeles itself, and the road from town to Agua Amarga, 16 km to the west of town on the road that connects Bahi'a to Highway 1. I also conducted a survey of Agua Amarga (See map - Figure 3 on page 16), approximately 29 km west of the town, to identify non-native plants in that area. In the non-native plant evaluation, I documented some, but not all, stands of non- native plant species that might be transported to the town Bahi'a de los Angeles and the adjacent islands, and thereby pose a threat to the islands. I recorded factors that might make these species more of a threat to the islands: the distance to the closest population, amount of fertile seed production, dependence on fresh water, ability to reproduce 39 vegetatively, ability to self-pollinate or presence of apomixis, allelopathic properties, ability to cause changes in ecological disturbance regimes (such as fire), ability to thrive in xeric habitat, and affinity to disturbance (Noble 1989, Reichard 1997, Barbour et al. 1999; see Appendix H). I evaluated the threat from each species, based on a combination of these factors that may be important to increased invasive potential in the specific conditions on these islands. Higher fertile seed production resulted in higher threat ranking (Reichard 1997). I automatically gave the low threat status to any plant species dependent on year-round fresh water for survival, because there are no springs on these arid islands. For the other six criteria (reproduces vegetatively, self pollinates, produces allelopathic properties, causes changes in ecological disturbance regimes, lives in xeric habitats, thrives on disturbance), I considered a "yes" answer to indicate more threatening, while "no" indicates less threatening. The "yes" scores were added and used to form a range for different levels of threat: high (five to six), medium (two to four), and low (zero to one). For plants not needing year-round fresh water with other unknown factors (indicated by "?"), 1 calculated a range. For the lowest possible score I used "no" for the questionable factors, and for the highest possible score I used "yes" for the questionable factors. I estimated plant cover (m'), so that future increases in stand sizes within an island or new stands can be detected. These data will be useful to agencies monitoring the spread of non-natives to islands and within an island, and can also help gauge success of future eradication efforts. 40 The old-world mammals present on islands in northwest Mexico are house mice {Miis musciilus), black rats (Rattus rattus), Norway rats (JRattus norvegicus), European rabbits {Oryctolagus cmiculus), goats (Capra hired), donkeys (Equus asinus), dogs (Canis familiaris) and cats {Felis catus\ Donlan 2000). I discuss these mammals, describe their major impacts on other islands in northwestern Mexico, and predict their potential threat to the Bahia de los Angeles islands. To date, the bay islands remain free of non-native mammals. 41 6 RESULTS 6.1 FLORISTIC ANALYSIS 6.1.1 Floristic Inventory Searches in herbaria and the literature turned up a total of seven previous plant collections (five species) from the bay islands (Table 4). My own collecting efforts were more thorough; a two-week trip in March of 1998, after 1997's El Nino, yielded over 220 specimens representing 98 species. For the entire archipelago, I compiled a list of 101 species, 77 genera, and 35 families, including 2% non-native species, 10% Baja California Peninsula endemic species, 23% Sonoran Desert endemic species, and one archipelago endemic species (Appendix F). The number of species detected on the islands ranges from 2 species on the smallest (Calavera Island) to 74 species on the largest island in the archipelago (Coronado/Smith Island; Appendix F). On Calavera Island the terrain is extremely steep; on that island, I found only two individual plants, one of which (Lyciiirn sp.) appeared to be dead. Therefore, I excluded Calavera Island from the analyses. I also excluded San Aremar Island, an unvegetated rocky island only visible at low tide. For the detailed plant list for the Bahi'a de los Angeles islands, including abundance ratings, see Appendix F. Table 4. Plant collections made on the Bahia de los Angeles islands prior to this study. Plant species Location Collector; number; Date Notes References Agave ceruhta var. ccrulata Motherless Island, Los Angeles R. Moran; 4106; 10 May 1952 Gentry 1978, Bay SDNHM 1999 Agave cerulata var. cerulata Ventana Island, south end of I. L. Wiggins and D. Wiggins; Gentry 1978 island near beach 14882; 18 May 1959 Ecliiiwcereus ferreiriamis Piojo Island R, Moran; 7266; 26 March 1959 Topotype SDNHM 1999 Bahia de los Angcle.s barrel cactus Island in the Smith Island group. R. Moran; 4103; 10 May 1952 Type specimen Taylor 1984, (Ferocactiix gatesii) N. side of Bahia de los Angeles, Shreve and 28° 59.5'N, 113° 32.5'W Wiggins 1964, SDNHM 1999 Island fishhook cactus Lindsay Island R. Moran; 4104; 10 May 1952 Type specimen Gentry 1949 (Manimillaria inxularix) SDNHM 1999 Teddybear cholla Small island in Bahi'a de los R. Moran; 8186; 14 April 1960 SDNHM 1999 (Opuiitia higelovii ssp. higelovii) Angeles Teddybear cholla Lind.say Island R. Moran; 8187; 14 April 1960 SDNHM 1999 4^ «v) 43 6.1.2 Plant Community Characterization Using the system described in the methods section, I defmed six plant communities (Table 5): saltmarsh (s), coastal scrub (c), xeroriparian wash (x), coastal sand dune (d), mangrove (m), and rock cliff (r). Table 5. Plant communities on islands in Bahfa de los Angeles. Island Plant communities Number of plant communities Coronado/Smith s, c, X, d, m, r 6 Ventana s, c, X, d, r 5 Cabeza de Cabal lo c, X, r 3 Piojo c, X, r 3 Mitlan s, c, X, r 4 Pata s, c, X, r 4 Flecha c, X, r 3 Bota s, c, d, r 4 Coronadito c, r 2 Gemelito East c, r 2 Jorobado c, r 2 Cerraja c 1 Llave c 1 Gemelito West c, r 2 Figure 5. Saltmarsh on Ventana Island. Figure 6. Coastal scrub on summit of Flecha Island with teddybear cholla, Bahia de los Angeles barrel cactus, and cardon; Ventana Island in the background, July 2001. Figure 7. Xeroriparian wash on Ventana Island, in bowl. Figure 8. Coastal sand dune at the base of the Coronado/Smith volcano. 46 Figure 9. Mangrove swamp on the south end of Coronado/Smith Island Figure 10. Rock cliff on the south side of Coronadito Island with senita {Lophocereiis schottii). 47 6.1.3 Biogeographical Analysis The purpose of the biogeographical analyses was to find out what biological and geographic factors might best predict variation in plant species richness. Appendices D and E show the data from the literature as mentioned in section 4.4.5. In this archipelago, island area accounts for 69% of the variation in plant species richness and the z-value, as calculated in the equation mentioned in the introduction on island biogeography theory (page 12), is 0.33 (adjusted r = 0.693, tiz = 5.51, P = 0.0(X)1) (Figure 11). 5 CO CO g 4 o tm CO o Adjusted r = 0.693 O 3 & CO c CO B 2 c 1 •5 •4 •3 -2 1 0 1 2 3 Ln (island area) Figure 11. Species-area curve for islands in Bahia de los Angeles. 48 Of the explanatory variables retained after removing highly correlated non- independent variables (area, isolation, mammal species richness, seabird status, percent guano, and number of plant communities), area (stepwise multiple regression, t io= 4.42, P = 0.0010) and seabird status {t lo = -2.54, P - 0.0275) predicted variation in plant species richness among islands. Jorobado Island was an outlier with extremely low plant species richness, and inclusion of this island affected the outcome of the tests. If Jorobado is included, the model, including area and seabird status, accounts for 78.9% of the variation in plant species richness (F2.13 = 25.31, /'<0.0001; Table 6). If Jorobado is excluded, the model, including area and seabird status, accounts for 92.0% of the variation of plant species richness (F3.12 =69.7, P<0.0001; Table 7). Table 6. Estimates of multiple regression coefficients and slopes for the associations between plant species richness with island area and seabird status, including the outlier. Coefficient estimate P-value Area 0.256 O.OOlO Seabird status -0.317 0.0275 Intercept 4.23 <0.0001 Adjusted R~ 0.789 <0.0001 49 Table 7. Estimates of multiple regression coefficients and slopes for the associations between plant species richness with island area and seabird status, excluding the outlier. Coefficient estimate P-value Area 0.221 <0.0001 Seabird status -0.332 0.0007 Intercept 4.26 <0.0001 Adjusted R~ 0.920 <0.0001 6.2 HUMAN IMPACTS Researchers and managers have not specifically documented the rise in ecotourism for the islands in Bahia de los Angeles, but, according to local residents, the recreational use of the islands has increased dramatically in the last 10 years and continues to rise (Martin de Cortes, fisherman/guide, 1998-2001, pers. comm.; Antonio and Beatrice Resendiz, Sea turtle researchers for Centra Regional de Investigacion Pesqiiera [Regional Center for Fisheries Research], December 2000, pers. comm. Caroline Shepard Espinoza, director of the Museo de Natiiraleza y Cultiira in Bahia de los Angeles, September 26, 2001, pers comm.). The islands are affected by human use (Table 8). Using this impact index, I performed a stepwise multiple regression that included all of the above-mentioned variables and the human impact index. After accounting for island area and seabird status, I found that the human impact index did not predict variation in plant species richness (t LO = 0.56, P = 0.591). Table 8. Human uses and impacts on islands in Bahia de los Angeles. s 68 e e 0^ t E TS .2 *«5 e 3 u C8 Island 1 m 3 3 csu f e e s cs a s 'S £ 3 S s Path-making use Garbage depo! (shoreline) Garbage depo! (inland) s Ed Camping X Coronado/Smith 1 I 1 I 1 1 6 Ventana I I 0 I I I 5 Cabeza de Cabal lo 1 0 0 1 1 0 3 Piojo 1 0 0 I I I 4 Mitlan I 0 0 1 I 0 3 Pata 1 0 0 I I 1 4 Flecha I 0 0 0 1 0 2 Bota I 0 0 I I 0 3 Coronadito I 0 0 0 0 1 2 Gemelito East 1 0 0 I 0 0 2 Jorobado 1 0 0 I I 0 3 Cerraja 1 0 0 I 1 0 3 Llave I 0 0 0 0 0 i Gemelito West I 0 0 1 I 0 3 1 = present, 0 = absent 51 Table 9. Estimates of multiple regression coefficients and slopes for the associations between plant species richness with area, seabird status, and human impact index including the outlier. Coefficient estimate P-value Area 0.216 0.0430 Seabird status -0.317 0.0337 Human impact index 0.0655 0.5907 Intercept 3.95 <0.0001 Adjusted R~ 0.775 0.0004 I estimated the percent of the island areas impacted to range from 1 to 25%; the areas on the islands that are most impacted are beaches and established trails (Table 10). 52 Table 10. Estimated percent of islands used by humans and areas most heavily used. Island Percent of island Areas most used by humans used by humans (estimated) Coronado/Smith 1-5% Four beaches (including mangrove swamp), trail to the volcano's summit Ventana 5-10 % Two beaches, trail between the two, and study plots Cabeza de Caballo 1-5% Ridge trail to summit Piojo 1-5% Two trails to island summit, beach on south end Mitlan 5-10% Trail to middle of island Pata 1-5% Sandy beach on the eastern end Flecha I-5% Trail up ridge of island Bota 1-5% Trail starting on eastern end Coronadito 5-10% Trail from boat launch in small bay on south side Gemelito East 1-5% Trail on northwest side used by researchers Jorobado 1-5% Sand slide to summit and trail along ridge Cerraja 10-25% Trial to summit and small trails throughout the island Llave 10-25% No specific trails, but erosion from landing site to summit Gemelito West 5-10% Trail to summit on northwest side. some erosion in flat area above this trail 53 6.3 POTENTIAL THREATS Two non-native plant species are present on bay islands: crystalline iceplant {Mesembryanthemum crystallinum, an aggressive South African annual) and nettleleaf goosefoot {Chenopodiiim murale\ Appendix F). Islands with large monospecific stands of crystalline iceplant are Coronadito, Gemelito West, Llave, and Cerraja (Table II), and those with small stands are Coronado/Smith, Ventana, Cabeza de Cabailo, and Rata Islands (Table 11). Islands where nettleleaf goosefoot grows all host roost sites or colony nesting sites for seabirds during some part of every year (Coronadito, Jorobado, Llave, Cerraja, and Gemelito West; Sanchez-Pinero and Polis 2000). This plant does not grow in monospecific stands, but is scattered over the surface of these islands. More than 230 non-native plant species are currently found in the Sonoran Desert (Nabhan et al. in press). Appendix H is a compilation of information on 24 non-native plant species, within 200 km of Bahfa de los Angeles, that may be potential bay island invaders; Table 12 summarizes the information in Appendix H and assesses the magnitude of the threat of each species. Many of the threatening plants need more water than is available on the bay islands: Barbados aloe {Aloe vera), Bermuda grass {Cynodon dactylon), bougainvillea (Bougainvillea spp.) castorbean (Ricinus communis), date palm {Phoenix dactylifera), feral watermelon (Citndlus lanatiis), giant reed {Ariindo donax), gum trees (Eucalyptus spp.), Mexican palo verde (Parkinsonia aculeata), oleander (Nerium oleander), puncturevine (Tribulus terrestris), saltcedar {Tamarix aphylla), slimbristle sandbur (Cenclinis brownii), sourclover (Melilotus indica), and tamarisk (Tamarix ramosissima). Because no perennial water is present on these islands, I do not consider these species a major threat to native plant communities. Table 11. Non-native plant species cover on Bahfa de los Angeles islands. Non-native plant Island Approximate % Island area species cover (m') Crystalline iceplant Coronado/Smith < I <0.00001 Ventana < I <0.000008 Cabeza de Cabal lo 3 0.0004 Pata < 1 <0.0007 Coronadito 50-100 0.069 - 0.14 Cerraja 25-50 0.069-0.14 Llave 10-25 0.0045-0.11 Gemelito West 5-10 0.025 - 0.05 Nettleleaf goosefoot Coronadito 10-25 0.014-0.035 Jorobado 10-25 0.026 - 0.064 Cerraja 10-25 0.027 - 0.068 Llave 10-25 0.0045-0.11 Gemelito West 50-100 0.125-0.25 55 Nine species threaten to invade or spread on the islands. Of these nine, two have a high rating as threats to plant communities on the bay islands: buffelgrass {Pennisetiun ciliare, an African perennial grass) and crystalline iceplant (Table 12). Table 12. Threat status of non-native plant species near Bahfa de los Angeles islands. Species common name Threat score Threat Arabian grass {Schismus arabicus) 3-5 Medium to high Buffelgrass (Pennisetum ciliare) 6 High Cheeseweed mallow (Malva parviflora) 1-4 Low to medium Crystalline iceplant {Mesembryanthemum ij High crystallinum) Malta starthistle (Centaurea melitensis) 3-5 Medium to high Nettleleaf goosefoot (Chenopodium 2-3 Medium miirale) Stork's bill (Erociium cicutarium) 2-5 Medium to high Threadstem carpetweed (Moliugo 2-5 Medium to high cerviana) Tree tobacco (Nicotiana glaiica) 2-3 Medium 56 7 DISCUSSION 7.1 FLORISTIC ANALYSIS The absence of many non-native species that appear capable of surviving on these islands is notable. As of the writing of this text, these islands are relatively unimpacted by the presence of non-native plant species. Compared with other floras in the Sonoran Desert, the bay islands' 2% is much lower. Felger et al. (1992) and Felger (2000) compare the percentages of non-native species in seven areas within the Sonoran Desert: Quitoboquito, Organ Pipe Cactus National Monument (Bowers 1980, Felger 1990), Gran Desierto dunes and Sierra del Rosario (Felger 1980), all of northwestern Sonora (Felger 2000), Tumamoc Hill (Bowers and Turner 1985, Burgess et al. 1991), Arizona (T. L. Burgess, pers. comm. 1990 in Felger et al. 1992), and the entire Sonoran Desert (pre- 1964; Felger 1980, Shreve and Wiggins 1964). In all of these areas the percentage of non-native species ranges from 2 to 16% with a mean of 9.9% (Felger et al. 1992). The current number of non-native plant species in the Sonoran Desert region (-230) is approximately 9%, confirming previous findings (Nabhan et al. in press). There is a simplicity of floral composition, as indicated by the low species numbers, on the bay islands and in many desert areas that can make the addition of even one species have profound influences on the nature of the vegetation in an area (Shreve 1951). The percentage of Sonoran Desert endemic species for these islands is 24% which is very similar to the 23.2% endemics found on the peninsula as a whole (Shreve and Wiggins 1964). The percent of plant endemics to only these islands is only 1% across the 57 archipelago area of approximately 12 km". Near Bahia de los Angeles, the Vizcaino Biosphere Reserve in the Central Desert region has 7.9% endemics over 25,400 km" (Leon de la Luz et al. 1995). The vegetation of the bay islands fits into many categories of major and minor plant communities, but is also unique because of the location of the islands and the maritime influences on them. The archipelago vegetation is unique, because the islands are between the gulf and the peninsula and fall near the boundaries of two Sonoran Desert phytogeographic subdivisions (Shreve 1951, Wiggins 1980). Because the islands are located in the transition zone between the Central Gulf Coast and the Lower Colorado Valley subdivisions, the island vegetation has affinities with both. The area also bridges the two vegetation communities that Wiggins (1980) defined: sarcocaulescent desert and microphyllous desert. Although Wiggins (1980) identifies creosote bush as the dominant species in the microphyllous desert, this plant is not found on the islands. Other microphyllous plants (Wiggins 1980); such as ocotillo, bursage, and littleleaf elephant- tree; are present. The species that Wiggins (1980) uses to distinguish the sarcocaulescent desert are the large cacti, such as cardon, senita (Lophocereus schottii), and pitaya agria (Stenocereus giimmosiis), which are also found on the islands, as well as in large numbers on the adjacent mainland. This area is an ecotone with coastal influences that does not fit well into definitions of areas to the south or north of it. 58 7.1.1 Nati ve Species of Concern Researchers have found the diversity and abundance of plants and animals on smaller islands to be less than on the same area within larger landmasses such as the adjacent mainland or larger islands (MacArthur and Wilson 1967). Cronk and Fuller (1995) stated that islands having fewer species are more susceptible to loss of species and decreased numbers of individual plants especially by human visitation; these small islands may be more susceptible to damage from human use than other larger islands in the Midriff region. This susceptibility, coupled with the expected increase of use, could lead to extreme damage to the islands if strict management in the form of regulations and enforcement is not implemented. The species on these islands that are of most concern are Bahia de los Angeles barrel cactus {Ferocactus gatesii), fishhook cactus {Mammillaria sp.), and Echinocereus ferreiriamis. All of these cacti have restricted distributions and are in high demand in the horticultural industry, and may also be collected by local residents for home gardens. The distribution of the Bahfa de los Angeles barrel cactus is limited to the islands in Bahfa de los Angeles (Lindsay 1996). The type specimen of what Lindsay (1955) called Ferocactus gatesii was collected on the Bahfa de los Angeles islands. Unger (1992) suspects that the barrel cactus on these islands is a hybrid between two other species in the Gulf of California region (Ferocactus acanthodes and F. peninsulae): other taxonomists believe it to be F. gracilis ssp. gatesii (Anderson 2001). The taxonomy and relationships remain to be clarified. It seems unlikely that a population of a hybrid would persist on these small islands without also occurring on the nearby peninsular shore. 59 Bahia de los Angeles barrel cacti ultimately grow tall, fail over, expose their roots, and die (Figure 12). From my observations, their demise does not seem to be due to human-caused erosion in most cases. I have seen young plants, suggesting that the species reproduces successfully (Figure 13). The ecology of the cactus remains to be studied. Figure 12. Uprooted Bahfa de los Angeles barrel cactus (Ferocactus gatesii) on Llave Island. 60 y f , /' •• ., ••v^ •n.. ^ •-,r- Figure 13. A juvenile Bahia de los Angeles barrel cactus, demonstrating reproductive recruitment. The identity of the islands' fishhook cacti remains to be determined. The Fishhook cactus (Figure 14 and Figure 15) on the islands may be the endemic island fishhook cactus {Mammillaria insularis) that has a distribution limited to the bay islands and also to San Marcos Island that is more than 200 km south of Bahia de los Angeles. My collections have all been identified as resembling strawberry cactus (Mammillaria dioica), but this species is easy to confuse with M. verhaertiana and M. angelensis. The latter two are found in the Bahia de los Angeles area (Shreve and Wiggins 1964, Bravo- Hollis and Sanchez-Mejorada 1991). Figure 14. Mammillaria sp. on Pata Island. - Figure 15. Fruiting Mammillaria sp. on Cerraja Island. 62 Echinocereus ferreirianus has a distribution that is limited to the nearby mainland and islands near Bahia de los Angeles. The species is highly prized by collectors for its rarity and the beauty of its bright pink flowers. Figure 16. Echinocereus ferreirianus on Cerraja Island. In order to be able to protect and manage these cactus species, I suggest that the stands be mapped and monitored to evaluate whether detected changes are detrimental to the island populations (Menges and Gordon 1996). To be effective, monitoring should involve mapping, monitoring demographics, measuring reproductive recruitment, and assessing survivorship (Menges and Gordon 1996, Philippi et al. 2001). I suggest that this be done by setting up permanent plots for monitoring all individual plants on small 63 islands and plants along selected transects on larger islands to evaluate recruitment, population dynamics, and reproductive efforts. Worldwide, trade in wildlife, plants, and wildlife products has often led to overharvesting, especially of rare species, and cacti are the most heavily-traded group of plants (Fuller and Fitzgerald 1987, Oldfield 1997, lUCN 1980, Groombridge 1992). In Mexico, the particular threats to cacti and other succulents are (in decreasing order of severity): 1) agricultural development, 2) infrastructural development, 3) horticultural collecting, and 4) stone mining (Taylor 1997). Increased enforcement of laws against importing cacti and succulents into the U. S. have decreased the impacts of the market in the U. S., but demands from Europe continue (Fitz Maurice and Anderson 1997). This illegal collecting continues, despite the availability of legal sources of seeds and plants of most species (Taylor 1997). While conducting a web search on the species, I frequently encountered sites selling seeds and plants of these cacti. All of these plants have limited distributions, which indicates that the original collections (legal or illegal) came from Bahia de los Angeles and the surrounding areas; in the case of Bahfa de los Angeles barrel cactus they must have been collected on the islands, and in some cases the websites mention the island from which they were collected. It is not clear if these collections were obtained legally or not. Because of their value to collectors and the horticultural industry, these spjecies (Bahfa de los Angeles barrel cactus, fishhook cactus, and Echinocereiis ferrerianus) should be protected from overharvesting. I suggest that horticultural collecting be evaluated, and if it is occurring on these islands, efforts should be put into enforcing the 64 regulations, to stop collection of seeds and plants, that are already in place. Scientific collection of these three species should also be minimal and directly related to their conservation, taxonomic clarification, and monitoring. 7.1.2 Target Areas of Concern It is clear that the islands in Bahia de los Angeles can expect increased visitation, especially if development plans come to fruition. The amount of environmental impact of increased visitation will be a direct result of management policies and enforcement. Putting restrictions on an area that has long been thought of as a wilderness is challenging, but without such limitations the "pristine" beauty that is treasured by tourists will be ruined. The areas that are in danger of being most heavily impacted by increased visitation are the beaches used for camping (especially the area near the mangrove swamp on Coronado/Smith) and islands where birds nest and roost. These areas should be more intensively monitored and controlled. Education about the reasons for regulations and limitations should make enforcement easier. Especially susceptible to damage from human use is the mangrove esturary on Coronado/Smith Island, the northernmost such estuary on the east side of the Baja California penninsuia (Flores-Verdugo et al. 1992). This area should be accessible, but increased educational materials, such as signs in the area and pamphlets describing the area, should make the threat of overuse clear to visitors. I suggest moving the camping area, which is now located at the mangrove swamp, to a nearby cove without mangroves (Figure 17). 65 Figure 17. Red mangrove (Rhizophora mangle) with developing viviparous "fruit." Ecologically, the islands with nesting and roosting birds should be monitored intensively, not only to protect the birds themselves (Anderson and Keith 1980), but because these islands seem to be more susceptible to non-native species invasions (or native colonizer generalists) and subsequent decreases in species diversity. The visitation on these islands should be minimal, to avoid disturbing birds that might then move to other areas of an island or to other islands and begin a new cycle of ecological disruption. 7.2 BIOGEOGRAPHICAL ANALYSIS Since MacArthur and Wilson (1967) proposed their theory of island biogeography, many researchers found that "area" can be a good predictor of species richness (Hecnar and Closkey 1998, Roden 1998, MacNally and Lake 1999, Sadler 1999). In contrast, researchers have found differing results concerning other factors that may influence species richness on islands (Buckley 1985, Deshaye and Morisset 1988, Hill et al. 1994). As expected from the MacArthur-Wilson model (1967), island area was positively associated with plant species richness (Figure 11). Contrary to the MacArthur-Wilson model, distance to the nearest plant propagule source (isolation) was not found to be associated with trends in plant species richness. Morrison (1997) showed that distance was more important in predicting plant species richness in archipelagos where larger distances exist between islands and islands are larger. The theory of small island effects predicts anomalous species-area relationships (Woodroffe 1986). Because these islands are extremely small and not far from each other or the shore, the anomalous result of distance having no association with plant species richness is not surprising. This conclusion is consistent with the findings of Heatwole (1991), who suggested that the proximity of islands in the Great Barrier Reef might be causing anomalous species-area relationships on some archipelagos. Anderson and Polis (1999) have shown that, on the islands in Bahia de los Angeles, nutrient input that results from guano deposition is associated with differences in plant biomass among these same islands (Figure 18). In this study, I found seabird status to be negatively associated with plant species richness. There are several possible explanations for this pattern: high nutrient input and physical disturbance may be creating a niche for colonizer species or the effective area of the islands may be decreased because of uninhabitable areas (both areas too steep for plant colonization and areas so severely 67 disturbed by birds that they do not support plant life). A combination of these two explanations may also be contributing to the lower numbers of species on islands with intensive seabird use. Figure 18. Calavera Island covered in guano deposits. Eight islands have non-native plant species (Coronado/Smith, Ventana, Cabeza de Caballo, Pata, Coronadito, Gemelito East, Llave, Gemelito West, and Jorobado). Islands with bird-nesting colonies have a higher abundance of those non-native plant species. High nutrient input that is associated with seabird soil disturbance can change dynamics in communities and lead to the dominance of a few competitive species (Tilman and Pacala 1993, Dean et al. 1994, Vidal et al. 1998). I hypothesize that the high nutrient 68 input in association with physical disturbance from bird colonies is helping r-seiected (or ruderal) generalist plant species outcompete the more specialized species that are adapted to low nutrients and less disturbance (Barbour et al. 1999). Two of the most common r- selected (colonizer) annual species on these islands (nettle-leaf goosefoot [Chenopodium murale] and careless weed [Amaranthus watsonii]) dominate the vegetation of the islands where seabird activity is present (Anderson and Polis 1999). The monospecific population of crystalline iceplant on Coronadito Island also supports this hypothesis. MacArthur and Wilson (1967) predicted that z-values for islands should fall between 0.2 and 0.4, with higher values for more isolated areas. The 0.33 z-value for the plants on these islands matches the value for ant species richness (Boulton and Ward in press). The z-value measures the difficulty of establishing reproductive colonies on islands; thus this result suggests that colony establishment is similar in difficulty for ants and for plants in this region. Holt et al. (1999) reported z-values for plants on islands in the Gulf of California to be 0.424, so these small islands are less difficult for plants to reach than islands in the gulf in general. The z-value for scorpions in the gulf is 0.162 (Reference), which is much lower, but not surprising, because it would be more difficult for a scorpion species to start a breeding population on an island. The z-value for the bay islands is higher than that which Gould (1979) found to be a standard value for a variety of taxa in a variety of circumstances. Multiple regression can give an accurate accounting of which factors can be helpful in predicting species richness, but does not confirm a causal relationship. The conclusions of this study cannot be used to generalize across all Gulf of Califomia 69 islands, because the sample was not chosen randomly from a larger group of islands, nor could I apply random "treatments" of bird nesting colonies, guano deposition, human impact, animal species richness or size randomly to the islands. Therefore, any causal inference or application of the results to a larger population of islands is only speculative. 7.3 HUMAN IMPACTS I found that human impacts do not explain variation in plant species richness on the islands. According to my analysis, these islands are not yet heavily impacted by humans, even though visits are becoming more frequent. As use increases, as predicted by SEMARNAP (1999), negative impacts are likely to grow. The infrastructure development of tourism facilities and the subsequent increases in tourism, anticipated from the plan for the Escalera Ndiitica, will undoubtedly boost visitation of the islands. Continued monitoring is important to assure that these rises in use are not affecting sf)ecies richness or ecological health. (See Future Research section for specific monitoring suggestions.) An indirect consequence of greater human visitation to protected areas has been the introduction on non-native species; this is especially true for islands (Loope et al. 1988, Atkinson 1989, Whittaker 1998). 7.4 NON-NATIVE SPECIES Worldwide, non-native species invasions are a major threat to biological diversity and endemic species in most natural areas, but particularly to fragile island ecosystems (DiCastri 1989, Vitousek et al. 1996, Whittaker 1998). Although Loope et al. (1988) 70 suggested that for the most part arid areas are not as threatened by non-native species, they also conclude that there are a few species, such as tamarisk, that could seriously threaten arid areas. Shreve (1951) believed that, because of the simplicity of plant species composition found in the Sonoran Desert, non-native invaders could dramatically change the physiognomy of the vegetation. 7.4.1 Plants Nettle-leaf goosefoot, present on bay islands, is naturalized in many arid areas and has been present in the gulf region for hundreds of years. Seeds have been found in the adobe bricks from 1797 (Hendrey and Bellue 1925). However, because of common human use of the plant and because the Comcaac name for the plant has no secondary meaning, Felger (1990) argues that it might actually be native. Native people of the area could have spread the seeds of this plant from place to place (Felger and Moser 1985). Whether native or not, this species seems to have established some kind of equilibrium with local systems and does not form monocultures in areas where it is found in the Gulf region. Crystalline iceplant (Figure 19) is a threat in many arid areas. It grows rapidly and can survive on only salt water after germination. Crystalline iceplant may be more likely to thrive in the presence of the disturbance and nitrogenous waste deposition that is associated with human use (Meigs 1935; Aschmann 1959). Natividad Island is overrun by the species, possibly due to the disturbance and guano of bird nesting colonies (Junak and Philbrick 2000b; X. Basurto, pers. comm., October 1999). Crystalline iceplant has 71 invaded abandoned agricultural flelds in San Quintin (Figure 20). The species has been present in the gulf region for more than one hundred years, but may become a more serious threat if disturbance increases. 1?V> • * -.f t • * » Figure 19. Crystalline iceplant {Mesembryanthemum crystallinum). 72 Figure 20. Monospecific stand of crystalline iceplant in abandoned cornfield in San Quintin, Baja California. Buffelgrass {Pennisetum ciliare) is also a serious threat. This species has already been found on two other Midriff islands (Alcatraz and Tiburon Islands; West and Nabhan 2002). Although the nearest known population of buffelgrass is approximately 100 km away (on Tiburon Island), Alberto Burquez, official investigator for the Institute of Ecology at Universidad Nacional Autdnoma de Mexico in Hermosillo, states that no matter what the rate of spread is for buffelgrass, one car trip or boat trip from an infested area could bring buffelgrass to Bahi'a de los Angeles (pers. comm., December 2001). The chances of buffelgrass surviving in sufficient numbers to impact plant community composition and ecosystem disturbance regimes on the islands are unknown. The low 73 abundances of the two perennial grasses (shoregrass [Monanthochloe littoralis] and California threeawn [Aristida califomica var. califomica]) present on the islands indicates that low precipitation may prevent large-scale invasions of buffelgrass in Bahfa de los Angeles. Careful monitoring and management could prevent bufflegrass establishment, especially if it is detected and eradicated early. The four plants in the medium- to high-threat category (Table 12) are Arabian grass (Schismus arabicus), Malta starthistle (Centaurea melitensis), stork's bill (Erodium cicutarium), and threadstem carpetweed (Mollugo cerviana). These plants are not an immediate threat, but might be in the future. Each has a different probability of becoming invasive because of the factors listed in Appendix H. I suggest that these plants be on a priority list of plants to monitor for on islands. Stork's bill and threadstem carpetweed probably do not threaten the species richness or ecological processes of the islands, but Arabian grass and Malta starthistle are likely threats. Arabian grass is an annual that forms stands that can carry fire and consequently cause damage to perennial species. Its establishment would lead to major changes in the disturbance regime of fire. This species is capable of explosive growth in arid areas (Felger 1990, Felger 2000) and should be watched carefully for expansion of its populations at Agua Amarga (Figure 3) and for movement onto the islands. Managers should also monitor for Malta starthistle. CalEPPC (California Exotic Pest Plant Council; 2002) lists Malta starthistle on their "List B; Wildland Pest Plants of Lesser Invasiveness" as a plant that is more serious an invader than has been recognized. This plant should be included in any list of plants to watch for and monitor on the islands. especially because it currently grows between San Diego and Bahfa de los Angeles on Highway 1. Reichard (1997) suggests that "hotspots" of invasion should be monitored after seasonal rains. I suggest that in this area the invasion hotspots would be the same "areas of concern" mentioned earlier. An effective protocol would include monitoring extensively in years after rains above 10 mm and doing yearly less-intensive monitoring in drier years. Managers could monitor for new invasions on the bay islands between March and May to effectively eliminate new stands before they become invasions or before they become established in the seedbank. 7.4.2 Animals People have intentionally or accidentally introduced old world house mice, Norway and black rats, European rabbits, goats, cats, dogs, and donkeys to islands in northwestern Mexico. I found no documented evidence that animals have ever been introduced to the Bahia de los Angeles islands. If the disruption that these animals have caused on other islands in northwestern Mexico is any indication, these animals would harm native plants on these islands, and may even cause losses of species (Donlan 2000, ICEG 2002). If any of these species were intentionally or accidentally introduced to these islands, their detrimental effects on vegetation could be minimized with early detection and rapid eradication. This work does not detail any of the other effects that might occur for other groups of organisms (such as disturbance to bird colonies or introduction of mammalian diseases). The Island Conservation and Ecology Group (ICEG) has been 75 successful removing mammals from small islands in northwest Mexico, for instance they have eradicated Norway rats and house mice from Rasa Island, and that island has been free from both since 1998 (Donlan 2000). Rabbits have been extremely destructive to vegetation on islands in northwest Mexico on which they have been introduced. They are capable of selectively devouring preferred native species that they prefer. There also may be synergistic relationships; for example, if European rabbits were introduced to Coronadito, the crystalline iceplant might be able to sustain a group of rabbits that could not survive on the native vegetation alone. The rabbits could also spread the seeds of the crystalline iceplant (N. Vivrette, pers. comm., September 1998) and may increase the size of the crystalline iceplant infestation. Cats could have a top-down effect on the vegetation on the islands; because their detrimental effects on the native mammals and birds on islands may alter ecological interactions (Donlan 2000). Goats and donkeys have also been very detrimental to islands in northwestern Mexico; they browse heavily on perennial vegetation, and eat native annuals before the plants have a chance to reproduce. There does not seem to be enough fresh water to support goats for a long period of time; however, if goats were introduced to any of these islands, the vegetation could suffer irreparable damage, and erosion would increase from ground disturbance and vegetation removal in steep areas. It seems unlikely that goats or donkeys will be accidentally introduced, but people have intentionally introduced these animals to northwest Mexico islands such as the San Benitos Islands (Donlan 2000). 76 Dogs are unlikely to establish feral populations on these islands. However, the dogs that visitors bring to the islands (personal observation) could be a vector for spreading the seeds of non-native species to the islands and could cause increased erosion. 7.4.3 Managing for Non-native Species Because there are already some non-native species present on the islands and others that are within a day's travel time to the islands, management and monitoring of non-native species on the islands will be increasingly important as use of the islands increases. The best way to control invasions of non-native plants is to block their spread to the islands. The second best strategy is to eradicate them while their populations are small. Monitoring should entail periodic checks of the islands by knowledgeable people, including government employees, local and visiting guides, and researchers working on the islands. A system for these visitors to report the presence of non-native species would assist managers in early identification and eradication of problem non-native plant and animal species. This early detection is essential, because the initial populations are an important focus in controlling the spread of non-natives (Moody and Mack 1988). Once a stand becomes established and a seedbank accumulates, the eradication of an infestation can be expensive and sometimes impossible (Hobbs and Humphreys 1995). Education will be an essential part of prevention of the spread of these species. Educational materials must be accessible to all users of the islands and especially to 77 guides. I suggest that different educational materials, detailing how to identify the plants and how to report those plants to SEMARNAT for monitoring and eradication, be developed for each of these groups. For guides, I suggest that a comic book be made specifically for these islands with information about how to protect the areas and species of concern, as well as how to prevent the spread of threatening species. Materials must be in both Spanish and English and be appropriate to the audience. I suggest using the comic book on the dangers of introducing mammals that was created by SEMARNAP and ICEG (1998) as a template for these educational materials. I also suggest a yearly presentation developed for Gulf of California guides that includes the basics of protection to the natural areas and updated information, on cleaning procedures for clothing and equipment to keep seeds of non- native species from traveling from the mainland to islands and from island to island. The programs developed to educate river guides in the Grand Canyon could serve as a model for this effort. 7.5 FUTURE ANALYSES Over the course of this study it became clear that this area should be protected for its intrinsic value, but also its scientific value as a natural laboratory for the study of ecological processes and specific species of interest. The beauty of the bay and islands is what draws ecotourists and kayakers, thus ecological health is also important for the local economy. Preserving biodiversity is of national and international concern. Although the findings of this research provide some of the information needed for management of 78 these islands and small islands elsewhere, many new questions arise as a result of this research. These questions fall into three categories: Human impacts, ecological interactions, and taxonomic clarification. Relative to human impacts, researchers and managers should investigate 1) the amount of illegal cactus collection, if any, that is taking place on the islands; 2) the detrimental effects of increasing visitation on floral richness and other types of diversity; and 3) ways to buffer the impacts of increasing use of the islands. Ecologists could add to the knowledge of this archipelago by 1) examining the causal relationship between guano input and r-selected generalist plant species dominating the vegetation of an island, 2) designing an experiment to test the competitive differences between plants on islands with low guano input and those on islands with high guano input, and 3) analyzing the base soil characteristics independently of guano input. Taxonomic questions remain regarding two species of cacti found on the archipelago. A study of the genetic make-up of the Bahfa de los Angeles barrel cactus could clarify taxonomy and phylogenetic relationships. The island Mammillaria species should also be studied. Knowing the number of species on these islands and their distributions will assist managers in protecting these vulnerable plant species. 79 8 APPENDIX A - LIST OF ACRONYMS AND TRANSLATIONS Acronym Spanish English ARIZ The Herbarium of the University of Arizona ASDM Arizona-Sonora Desert Museum CalEPPC California Exotic Pest Plant Council CEC Council on Environmental Cooperation CITES Convention on International Trade in Endangered Species CONABIO Comision Nacional para el National Commission for Conocimiento y Uso de la Knowledge and Use of Biodiversidad Biodiversity CONANP Comision Nacional de Areas National Commission of Natiirales Protegidas Natural Protected Areas FONATUR Fondo Nacional de Fomento National Fund for the al Turismo Promotion of Tourism GATT General Agreement on Tariffs and Trade ICEG Island Conservation and Ecology Group lUCN International Union for Conservation of Nature and Natural Resources NAFTA North American Free Trade Agreement OECD Organization for Economic Cooperation and Development PROFEPA Procuraduria Federal de Office of the Attorney General Proteccion al Ambiente for Environmental Protection SD the herbarium of the San Diego Narural History Museum 80 Acronym Spanish English SDNHM San Diego Natural History Museum SEDESOL Secretaria de Desarollo Social Secretariat of Social Development and Environment SEMARNAT Secretaria de Medio Secretariat of the Environment Ambiente, y Recursos and Natural Resources Naturales SEMARNAP Secretaria de Medio Secretariat of the Environment, Ambiente, Recursos Naturales Natural Resources and Fisheries y Pesca UABC Universidad Autonoma de Autonomous University of Baja Baja California California 81 9 APPENDIX B - MANAGEMENT AND CONSERVATION TIMELINE OF THE GULF OF CALIFORNIA This list is a compilation of management activities listed in other publications (MacDonald et al. 1997, Mufioz 1997, Kiy and Wirth 1998, SEMARNAP 1999, Carabias-Lillo et al. 2000). These events have had some influence on conservation and management of the islands in the gulf, some indirectly. This list puts current activities into perspective. Unless otherwise indicated, listings are actions of the Mexican (federal) government. Date 7 February 1936 U.S.-Mexico Convention for the Protection of Migratory Bird and Game Mammals. 1936 U.S.-Mexico-Canada Migratory Bird Treaty. 1939 The Organic Law of Anthropology and History. 20 May 1942 Rules and Regulations of National and International Parks. 6 July 1946 Soil and Water Conservation Law. 5 February 1952 Federal Hunting Law. 15 March 1963 Decree declaring Tiburon Island as a Natural Reserve Zone for the National Wild Fauna. 13 May 1964 Decree declaring Rasa Island as a Natural Reserve Zone and Seabird Refuge. 1971 Federal Law to prevent and control environmental pollution. 29 March 1973 Rules and Regulations for the Security and Control of Waters. 82 30 August 1973 U.S.-Mexico International Boundary and Water Commission, Minute 242, provided defmitive solution to the international problem of the salinity of the Colorado River. 26 May 1976 General Law of Human Settlement. 12 October 1976 U.S.-Mexico-Canada Agreement for the Protection of Plants. 13 November 1976 Decree declaring a system of an Exclusive Economic Zone. 24 November 1976 U.S.-Mexico Agreement Concerning Certain Maritime Boundaries. 1976 Organic Law of the Federal Public Administration. 4 May 1978 U.S.-Mexico Treaty on Maritime Delimitation. 2 August 1978 Decree declaring the establishment of a reserve zone and refuge for migratory birds and the wild fauna on the related islands situated in the Gulf of California. 21 September 1978 Organization for Economic Cooperation and Development (OECD) Council recommendation on strengthening international cooperation on environmental protection in border regions. 8 December 1980 Decree of the Isabel Island National Park. 30 December 1980 Public Works Law. 15 April 1981 Agreement for the National Contingency Plan to combat and control sea discharges of hydrocarbons and noxious substances of a permanent nature and of social interest. 8 February 1982 General National Welfare Law. 1982 Federal Law on Environmental Protection to prevent and control pollution and foster the improvement and restoration of the environment. 1983 Planning Law. 8 January 1986 Federal Seas Law. 83 February 1986 Presidential decrees on reforestation, regulation of air pollution, water purification, relocation of industries, and environmental awareness. 29 October 1986 Decree for the determination of reserve zones and refuge sites for the protection, conservation, re-population, development, and control of the species diversity for sea turtles, including the spawning and nesting locations of these species. 7 June 1988 Rules and Regulations of the General Law of Ecological Balance and Environmental Protection. 13 July 1988 Rules and Regulations of the Forestry Law. 1991 Law that reforms, adds, and repeals various arrangements relative to the federal law dealing with matters related to national parks, flora and fauna, environmental impacts and prevention and control of contamination. 16 March 1991 Agreement to regulate the capture of breeding animals of all shrimp species in federal jurisdiction, for the development of aquicultural activities that have occurred in recent years. 17 May 1991 Agreement to standardize the utilization of the shrimp species of the upper gulf waters of the federal jurisdiction of the Gulf of Mexico and the Caribbean Sea, as in the Pacific Ocean. 26 September 1991 Agreement for the reform of the standard of utilization of the shrimp species in federal jurisdiction waters of the Gulf of Me.xico and the Caribbean Sea, as in the Pacific Ocean. 30 November 1991 Law of Ecological Balance and Environmental Protection of the State of Baja California South. 1991 Mexico signed the CITES agreement. 84 16 March 1992 Agreement for the creation of the National Commission for the Knowledge and Use of Biodiversity. 21 June 1992 Rules and Regulations of the Fisheries Law. 25 June 1992 Fisheries Law. 1 July 1992 Federal Law regarding metrology and standardization. 1 July 1992 Federal Law for metrology and standardization to expedite the Official Mexican Standards (NOM) for fisheries, ecology, forestry, and tourism, and among others that compliment the application of the environmental protection criteria and conservation with the principle of sustainable development. 1 December 1992 National Waters Law. 22 December 1992 Forestry Law. 1992 Establishment of the Attorney General's office for the Protection of the Environment (under SEDESOL). 1992 Amendments to Article 27, which allow privatization of land- holding and allow non-Mexicans residents to own land. 18 June 1993 Federal Animal Health Law. 19 July 1993 Ports Law. 10 August 1993 Project of Mexican Official Standard NOM-002-PESC-1993, to organize the utilization of the shrimp species in waters of federal jurisdiction of the United States of Mexico. 31 December 1993 Tourism Law. 1993 Official Mexican Norm NOM-003-PESC-1993 which regulates the harvesting of the Monterrey sardine, pifia, crinuda, bocana, japonesa and several species of mackerel and anchovy by offshore craft in the waters of federal jurisdiction of the Pacific Ocean including the Gulf of California. 85 1993 Official Mexican Standard NOM-004-PESC-1993 regulates the harvesting of the catarina Clam in waters of the states of Baja California and Baja California Sur under federal Jurisdiction. 1993 Official Mexican Standard NOM-006-PESC-1993 regulates the harvesting of all the species of lobster in the waters of Federal jurisdiction of the Gulf of Mexico and the Caribbean Sea, and Pacific Ocean including the Gulf of California. 1993 Official Mexican Standard NOM-012-PESC-i993 established measures for the protection of the species of totoaba and vaquita in the waters of the Gulf of California under federal jurisdiction. 4 January 1994 Navigation Law. 12 January 1994 Rules and Regulations of the National Waters Law. 11 November 1994 Reform of the Agreement of 16 March 1992. 1994 Federal Administrative Procedure Law. 1994 Rules and regulations for the use and utilization of territorial seas, navigable water ways, beaches, federal maritime lands and gained territories of the sea. 1994 Rules and regulations of the Federal Tourism Law. 21 April 1995 Agreement about that which constitutes the National Advisory Board and four Regional Consultation Advisory Boards for sustainable development. 3 April 1996 Decree for the testing of the Program for the Environment 1995- 2000. 8 July 1996 Internal rules and regulations for the Secretary of Environment, Natural Resources and Fisheries. 86 19 July 1996 Decree declaring as a Natural Protected Area, in the form of a National Marine Park, the zone known as Loreto Bay, and the area near the municipal coast of Loreto, Baja California Sur, with a total area of 206,580.75 hectares. 8 August 1996 Agreement about that which constitutes the National Advisory Boards of Natural Protected Areas. 23 January 1997 Rules and regulations for the prevention and control of maritime contamination of the sea by verified waste and other materials. 23 January 1997 Agreement about that which negatively effects the environment or that which simplifies the ecosystems of the presentation of the Manifesto of Environmental Impact, under the presentation of informed preventive actions. 1997 Rules and regulations of the General Law of Ecological Equilibrium and Environmental Protection in Natural Protected Areas. 1997 Agreement for the establishment of prohibitions for the species and subspecies of sea turtles in the waters of Federal jurisdiction of the Gulf of Mexico and the Caribbean Sea, similar to those of the Pacific Ocean including the Gulf of California. July 1999 Draft management program for the islands of the Gulf of California. 2000 Published final draft of the management program for the Islands of the Gulf of California. 2000 President Fox changed SEMARNAP to SEMARNAT, removing fisheries management from management of other environmental and renewable resources. 87 10 APPENDIX C - COMMON NAMES FOR PLANTS MENTIONED IN THE TEXT AND APPENDICES Common name Species Family Agave Agave cerulata ssp. cenilata Agavaceae Alkaliweed Cressa tncxillensis Convolvulaceae American threefold Trixis califomica var. califomica Asteraceae Amole Stegnosperma halimifolium Phytolaccaceae Arabian grass* Schismus arabiciis Poaceae Arizona lupine Lupinus arizonicus Fabaceae Bahia de los Angeles barrel Ferocactiis gatesii Cactaceae cactus Baja California buckwheat Eriogomim austrimim Polygonaceae Baja California desert-thorn Lycium brevipes Solanaceae Barbados aloe* Aloe vera Asphodeliaceae Barrel cactus Ferocactiis spp. Cactaceae Beetle spurge Euphorbia eriantha Euphorbiaceae Bermuda grass* Cynodon dactylon Poaceae Blazing star Mentzelia adhaerens Loasaceae Blazing star Mentzelia hirsiitissima var. Loasaceae stenophylla Blazing star Mentzelia sp. Loasaceae Bougainvillea* Bougainvillea spp. Nyctaginaceae Boundary ephedra Ephedra aspera Ephedraceae Buffelgrass* Pennisetiim ciliare Poaceae Bursage Ambrosia spp. Asteraceae Bush arrowleaf Pleurocoronis pluriseta Asteraceae California sun-cup Canimisonia califomica Onagraceae 88 Common name Species Family California threeawn Aristida califomica var. califomica Poaceae Carddn Pachycereus pringlei Cactaceae Careless weed Amaranthiis watsonii Amaranthaceae Castorbean* Ricinus communis Euphorbiaceae Cedros sun-cup Cammisonia cardiophylla ssp. Onagraceae cedrosensis Cheeseweed mallow* Malva parviflom Malvaceae Cholla Opuntia alcahes var. alcahes Cactaceae Cholia peiona Opimtia cholla Cactaceae Chuckwalla delight Bebbia juncea var. jimcea Asteraceae Clavelina Opuntia molesta var. molesta Cactaceae Cliff spurge Euphorbia misera Euphorbiaceae Coast saltbush Atriplex barclayana Chenopodiaceae Coyote tobacco Nicotiana obtusifolia Solanaceae Creosote bush Larrea tridentata Zygophyllaceae Crystalline iceplant* Mesembryanthemum crystallinum Aizoaceae Date palm* Phoenix dactylifera Arecaceae Desert bean Phaseolus filifonnis Fabaceae Desert cambess Oligomeris linifolia Resedaceae Desert holly Atriplex hymenelytra Chenopodiaceae Desert rock daisy Perityle emoryi Asteraceae Desert saltbush Atriplex polycarpa Chenopodiaceae Desert snapdradon Antirrhinum cyathifemm Scrophulariaceae Desert thomapple Datura discolor Solanaceae Desert trumpet Eriogomun inflatum var. deflatum Polygonaceae Desert wolfberry Lycium andersonii Solanaceae 89 Common name Species Family Emory indigo bush Psorothamnus emoryi Fabaceae Fagonbush Fagonia pachyacantha Zygophyllaceae Feral watermelon* Citrulliis lanatus Cucurbitaceae Fishhook cactus Mammillaria sp. Cactaceae Forget-me-not cryptantha Cryptantha racemosa Boraginaceae Fremont wolfberry Lycium fremontii Solanaceae Ghost flower Mohavea confertiflora Scrophulariaceae Giant reed* Anmdo donax Poaceae Glasswort Salicomia siibterminalis Chenopodiaceae Guadalupe catseye Cryptantha maritima var. maritima Boraginaceae Guayacan Viscainoa geniculata var. geniculata Zygophyllaceae Gum tree Eucalyptus spp Myrtaceae Hairy lotus Lotus strigosus Fabaceae Hedgehog cactus Echinocereus ferrei rianus Cactaceae Hedgehog cactus Echinocereus spp. Cactaceae Holly-leaf bursage Ambrosia ilicifolia Asteraceae Iodine bush Allenrolfea occidentalis Chenopodiaceae Island ground vine Vaseyanthus insularis Cucurbitaceae Jojoba Simmondsia chinensis Simmondsiaceae Littleleaf elephant-tree Bursera microphylla Burseraceae Littleseed muhly Muhlenbergia microsperma Poaceae Long-lobed four o'clock Mirabilis tenuiloba Nyctaginaceae Louse spurge Euphorbia pediculifera var. Euphorbiaceae pediculifera Malta starthistle* Centaurea melitensis Asteraceae Mexican palo verde Parkinsonia aculeata Fabaceae 90 Common name Species Family Mojave seablite Suaeda moquinii Chenopodiaceae Narrow-leaf sandpaper Petalonyx linearis Loasaceae plant Narrowieaf stillingia Stillingia linearifolia Euphorbiaceae Nettleleaf goosefoot* Chenopodiiim miirale Chenopodiaceae Ocotillo Fouqiiieria splendens ssp. splendens Fouquieriaceae Oleander* Nerium oleander Apocynaceae Palmer's seaheath Frankenia palmeri Frankeniaceae Palo adan Fouqiiieria diguetii Fouquieriaceae Peninsular barrel cactus Ferocactus peninsulae Cactaceae Pitaya agria Stenocereus giimmosus Cactaceae Puncturevine* Tribiiliis terrestris Zygophyllaceae Pygmy cedar Peucephylliim schottii Asteraceae Red elephant-tree Biirsera hindsiana Burseraceae Red mangrove Rhizophora mangle Rhizophoraceae Rock hibiscus Hibiscus denudatus Malvaceae Rock stingbush Eiicnide nipestris Loasaceae Saltcedar* Tamarix aphylla Tamaricaceae Sand mat Achyronychia cooperi Caryophyllaceae Scorpion-weed Phacelia pedicellata Hydrophyllaceae Senita Lophocereiis schottii var. schottii Cactaceae Shoregrass Monanthochloe littoralis Poaceae Shoreline seapurslane Sesuvium portulacastnim Aizoaceae Silky prairie-clover Dalea mollis Fabaceae Sixweeks grama Boiiteloiia barbata Poaceae Sixweeks threeawn Aristida adscensionis Poaceae 91 Common name Species Family Slender poreleaf Porophyllum gracile Asteraceae Slimbristle sandbur* Cenchnis brownii Poaceae Small seed sandmat Euphorbia polycarpa Euphorbiaceae Smooth desert dandelion Malacothrix glabrata Asteraceae Sourclover Melilotus indica Fabaceae Stork's bill* Erodiuni cicutarium Geraniaceae Strawberry cactus Mammillaria dioica Cactaceae Succulent poreleaf Porophyllum crassifolium Asteraceae Tamarisk* Tamarix ramosissima Tamaricaceae Teddybear cholla Opuntia bigelovii var. bigelovii Cactaceae Threadstem Nemacladus glandulifera Campanulaceae Threadstem carpetweed* Mollugo cerviana Molluginaceae Trailing windmills Allionia incamata Nyctaginaceae Tree tobacco* Nicotiana glauca Solanaceae Turkey peas Astragalus nuttallianus var. Fabaceae cedrosensis Turpentine bush Ericameria laricifolia Asteraceae Turtleweed Batis maritima Bataceae Wand holdback Hoffinannseggia microphylla Fabaceae White brittlebush Encelia farinosa Asteraceae White-haired Guadalupe Cryptantha maritima var. pilosa Boraginaceae catseye Whitestem milkweed Asclepias albicans Asclepiadaceae Woolly plantain Plantago ovata Plantaginaceae Yellow nightshade Physalis crassifolia Solanaceae eroundcherrv 92 Common name Species Family Yuma siiverbush Ditaxis serrata Euphorbiaceae - Coreocarpus parthenioides var. Asteraceae parthenioides - Calandrinia maritima Portulacaceae - Cryptantha fastigiata Boraginaceae - Drymaria holosteoides var. Caryophyllaceae holosteoides - Euphorbia sp. Euphorbiaceae - Ferocactus acanthodes Cactaceae - Hofineisteria fasciculata var. Asteraceae fasciculata - Lycium sp. Solanaceae - Xylorhiza fnitescens Asteraceae * Non-native species 93 11 APPENDIX D: GEOGRAPHICAL CHARACTERISTICS OF ISLANDS IN BAHIA DE LOS ANGELES Island Highest Isolation Perimeter Islands Area elevation (km)" (km)" (km-)" (m)" Coronado/Smilh 8.684 2.187 465 19.81 Ventana 1.275 3.15 120 5.16 Cabeza de 0.704 2.015 140 3.96 Cabal io Piojo 0.533 6.323 60 3.25 Mitlan 0.156 1.96 40 1.87 Pata 0.136 2.559 40 1.58 Flecha 0.129 2.907 50 1.68 Bota 0.093 2.919 40 1.43 Coronadito 0.072 2.913 15 1.09 Gemelito East 0.047 0.826 20 0.89 Jorobado 0.039 2.179 25 0.89 Cerraja 0.037 2.957 12 0.96 Llave 0.022 2.957 8 0.58 Gemelito West 0.020 0.848 20 0.62 •* Polis et al. 1997, " BouUon and Ward in press 12 APPENDIX E - SPECIES RICHNESS, PRESENCE AND INFLUENCES FROM ANIMALS Islands Ant species Mammal species Bird % Guano Herpetological Scorpion species richness" richness** status*^ cover' species richness** richness*' Coronado/Smith 24 2 1 0 8 3 Ventana 12 1 I 0 4 1 Cabeza de 9 1 1 3 I 0 Caballo Piojo 2 1 3 8.5 5 0 Mitlan 5 2 1 0 2 0 Pata 7 2 1 0 1 0 Flecha 6 1 2 23.9 I 0 Bota 9 I 1 0 1 0 Coronadito 6 1 2 13.6 2 0 Gemelito East 3 0 3 20.6 0 0 Jorobado 7 0 2 21.5 0 0 Cerraja 6 0 2 5.5 1 0 Llave 3 0 2 23.5 0 0 Gemelito West 5 0 3 16.() 0 0 ''Boulton and Ward in press; Stapp, unpublished data; Sanchez-Pinero and Polis 2000: 1= non-bird, 2 = roosting, 3 = nesting; Due 1992; "^Williams 1980;' Due 1992 10 APPENDIX F - PLANT SPECIES LIST FOR ISLANDS IN BAHIA DE LOS ANGELES Common name Coronado/Smith Cabeza de Caballo Ventana Piojo Endemic status Coronadito Mitlan Pata Flecha Bota Gemelito East Cerraja Gemelito West Llave (Mexican common name) Jorobado Calavera GYMNOSPERMS EPHEDRACEAE Ephedra aspera Engelm. ex S. boundary ephedra 4 4 Watson (canatillo) ANGIOSPERMS Magnoliopsida (Dicots) AIZOACEAE *Mesenihryanthemiim crystalline iceplant 4 4 4 4 2 2 3 3 crystallinum L. (hielitos) Sesuvium portulacastrum (L.) L. shoreline seapurslane 4 3 (verdolaga de playa) AMARANTHACEAE Amaranthus watsonii Standi. careless weed 4 1 3 1 1 i i 1 1 (bledo) vO Common name Coronado/Smith Cabeza de Caballo Coronadito Piojo Pata Endemic status Mitlan Flecha Bota Gemelito East Cerraja Ventana Llave Gemelito West Jorobado (Mexican common name) Calavera ASCLEPIADACEAE Asclepias albicans S. Watson whitestem milkweed 3 3 4 4 4 3 (yamete, matacandeiilla) ASTERACEAE (COMPOSITAE) Ambrosia ilicifolia (A. Gray) holly-leaf bursage 3 Payne Behhia jtincea (Benth.) Greene chuckwalla delight 3 4 var. jimcea Coreocarpus parthenioides S XXX XXX XXX X Benth. var. parthenioides Encelia farinosa Torr. & A. Gray white brittlebush 3 3 3 3 3 3 3 4 (incienso) Ericameria laricifolia (A. Gray) turpentine bush 4 Shinners Hofineisteria fasciculata (Benth.) - B 4 3 4 3 3 4 Walp. var. fasciculata Malacothrix glahrata A. Gray smooth desert dandelion 4 4 Perityle emoryi Torr. desert rock daisy XXX XXX XXX X X X X Peucephyllum schottii A. Gray pygmy cedar (romero) 3 3 3 Common name Cabeza de Caballo Coronado/Smith Gemelito East Gemelito West Endemic status Coronadito Cerraja Ventana Piojo Mitlan Pata Llave Flecha Bota Jorobado (Mexican common name) Calavera Pleurocoronis pluriseta (A. bush arrowleaf 4 4 Gray) R. King & H. Robinson Porophyllum crassifolium S. succulent porcleaf B 3 3 4 Watson P. gracile Bcnth. slender poreleaf 4 (hierba del venado) Trixis californica Kellogg var. American threefold 3 3 3 californica (Santa Luci'a) Xylorhiza frutescens (S. Watson) - B 3 3 3 3 3 4 Greene BATACEAE (BATIDACEAE) Batis maritima L. turtleweed 4 4 (vidrillo) BORAGINACEAE Cryptantha fastigiata I. M. B X X X X X X Johnst. C. maritima (Greene) Greene var. Guadalupe catseye XXX X X X X X X maritima C. maritima var. pilosa I. M. white-haired Guadalupe X X Johnst. calseye Common name Coronado/Smith Cabeza de Caballo Endemic status Ventana Mitlan Coronadito Gemelito East Cerraja Piojo Pata Flecha Bota Gemelito West Llave (Mexican common name) Jorobado Calavera C. racemosa (S. Watson) Greene forget-me-not cryptantha 3 BURSERACEAE Bursera hhulsiana (Benth.) red elephant-tree 4 Engler (torote prieto) B. fuicrophylla A. Gray iittleleaf elephant-tree 3 3 3 4 (copal, torote Colorado) CACTACEAE Echinocereus ferreirianus Gates hedgehog cactus B 3 3 4 4 Ferocactus gatesii G. Lindsay Bahia de los Angeles barrel I 3 2 2 2 2 2 3 cactus Lophocereus schottii (Engelm.) senita 3 4 4 4 4 3 Britton &. Rose var. schottii (tuna barbona, garambullo) Mammiilaria sp. fishhook cactus 3 3 3 2 3 2 2 2 (biznagita) Mammiilaria cf. dioica K. strawberry cactus 3 2 3 Brandegee (biznagita) Opiaitia alcahes F. A. C. Weber (cholla) 3 3 X 3 2 2 2 X 2 2 X 3 var. alcahes 0. bigelovii Engelm. var. teddybear cholla 3 3 3 3 2 2x2 X 3 higelovii (cholla gUera) 00 Common name Coronado/Smith Cal>eza de Caballo Ventana Endemic status Piojo Mitlan Coronadito Pata Flecha Bota C^melito East Cerraja Gemelito West Llave (Mexican common name) Jorobado Calavera O. cholla F. A. C. Weber (cholla pelona) B 4 O. molesta Brandegee var. (clavelina) B 3 3 X molesta Pachycereus pringlei (S. Watson) cardon B+ 3 3 3 2 3 3 3 4 3 3 3 3 3 2 Britton & Rose (card6n) Stenocereus gmnmosus (Engelm.) (pitaya agria) B+ 3 4 4 3 3 4 4 A. Gibson & Horak CAMPANULACEAE Nemacladus gUmdulifera Jepson threadstem X sens. lat. CARYOPHYLLACEAE Achyronychia cooperi Torr. & A. sand mat XXX X Gray Drymaria holosteoides Benth. S X X var. holosteoides CHENOPODIACEAE AUenrolfea occidentalis (S. iodine bush 2 3 3 3 3 Watson) Kuntze (hierba del burro) Alriple.x barclayana (Benth.) D. coast saltbush B+ 1 2 1 1 1 1 1 1 1 1 2 1 2 2 Dietr. sens. lat. (saladillo) vO VO Common name Coronado/Smitli Cabeza de Caballo Coronadito Gemelito East Cerraja Endemic status Piojo Ventana Mitlan Pata Flecha Bota Llave Gemelito West Jorobado (Mexican common name) Calavera A. hymenelytra (Torr.) S. Watson desert holly 3 3 A. polycarpa (Torr.) S. Watson desert saltbush 3 4 3 (chamizo cenizo) *Chenopodium murale L. nettleleaf goosefoot 2 1 3 2 1 (hierba del perro) Salicornia suhterminalis Parish glass wort 3 3 Suaeda ntoquinii (Toir.) Greene Mojave seablite 4 4 (quelite salado) CONVOLVULACEAE Cressa triaillensis Kunth alkaliweed 3 CUCURBITACEAE Vaseyanthus insularis (S. Island ground vine B 2 2 3 3 2 3 Watson) Rose EUPHORBIACEAE Ditaxis serrata (Torr.) A. Heller Yuma silverbush 3 3 4 4 4 4 4 Euphorbia eriantha Benth. beetle spurge 4 E. misera Benth. cliff spurge B+ 3 (liga, jumeton) E. pediculifera Engelm. var. louse spurge 3 4 4 4 pediculifera (golondrina) 8 Common name Coronado/Smith Cabeza de Caballo Endemic status Ventana Piojo Coronadito Gemelito East Pata Mitlan Flecha Bota Cerraja Gemelito West Llave Jorobado (Mexican common name) Calavera E. polycarpa Benth. smallseed sandmat 3 4 4 (golondrina) Euphorbia sp. 4 Stillingia linearifoUa S. Watson narrowleaf stillingia 4 FABACEAE (LEGUMINOSAE) Astragalus nuttallianus DC. var. turkey peas X X X cedrosensis M. E. Jones (cascabelito) Dalea mollis Benth. silky prairie-clover X X X X Hojfmannseggia microphylla wand holdback 3 3 Torr. Lotus strigosus (Nutt.) Greene hairy lotus XXX XXX X X X Lupinus arizonicus (S. Watson) Arizona lupine X X S. Watson (lupino) Phaseolus filiformis Benth. desert bean 3 4 4 4 3 3 Psorothamnus emoryi (A. Gray) Emory indigo bush 3 3 Rydb. FOUQUIERIACEAE Fouquieria diguetii (Van (palo addn) B+ 3 2 2 3 3 Tieghem) I. M. Johnsl. Common name Coronado/Smith Cabeza de Caballo Ventana Endemic status Coronadito Piojo Mitlan Cerraja Pata Flecha Bota Gemelito East Gemelito West Llave (Mexican common name) Jorobado Calavera F. splendens Engelm. ssp. ocotillo 3 2 3 4 3 3 3 splendens (ocotillo) FRANKENIACEAE Frankenia palmeri S. Watson Palmer's seaheath S 3 2 3 (hierba reuma) HYDROPHYLLACEAE Phacelia pedicellata A. Gray pedicellate scorpion-weed X LOASACEAE Eucnide rupestris (Baill.) H. rock stingbush X X X X X X X X Thompson & Ernst. Mentzelia adhaerens Benth. blazing star B X X X X X M. hirsutissima S. Watson var. blazing star X stenophylla (Urb. &. Gilg.) L M. Johnst. Mentzelia sp. X Petalonyx linearis Greene narrow-leaf sandpaper plant S 3 4 3 MALVACEAE Hibiscus denudatus Benth. rock hibiscus 4 NYCTAGINACEAE Allionia incarnata L. trailing windmills 3 4 Common name Coronado/Smith Cabeza de Caballo Endemic status Mitlan Coronadito Gemelito East Cerraja Ventana Piojo Pata Flecha Bota Llave Gemelito West Jorobado (Mexican common name) Calavera Mirabilis tenuiloba S. Watson long-lobed four o'clock 4 ONAGRACEAE Cammisonia califoniica (Nutt.) California sun-cup X Raven C. cardiophyUa (Torr.) Raven Cedros sun-cup B XXX XXX X X X X ssp. cedrosensis (Greene) Raven PHYTOLACCACEAE Stegnosperma halimifolium (amole, tinta) S 4 3 4 Benth. PLANTAGINACEAE Plantago ovata Forssk. woolly plantain 3 3 4 3 3 2 3 (pastora) POLYGONACEAE Eriogomm austrinum (Stokes) Baja California buckwheat B 4 Reveal E. inflatum Torr. & Frem var. desert trumpet 4 deflatum I. M. Johnst. (guinagua) PORTULACACEAE Calandrinia maritima Nutt. \ Common name Coronado/Smith Caiieza de Cabailo Coronadito Ventana Piojo Endemic status Mitlan Pata Flecha Bota Gemelito East Cerraja Gemelito West Llave Jorobado (Mexican common name) Calavera RESEDACEAE Oligomeris linifolia (Vahl) J. F. desert cambess X X X X X Macbr. RHIZOPHORACEAE Rhizophora mangle L. red mangrove 3 (mangle dulce, mangle rojo) SCROPHULARIACEAE Antirrhinum cyathiferum Benth. desert snapdradon S XXX X X X (perritos) Mohavea confertiflora (Benth.) ghost flower X X X X X A. Heller SIMMONDSIACEAE Simmondsia chinensis (Link) jojoba 4 Schneid. (jojoba) SOLANACEAE Datura discolor Bemh. desert thomappie 4 4 (toloache) Lyciwn sp. 3 3 3 2 4 Lycium andersonii A. Gray desert wolfberry 4 (salicteso, frutilla) Common name Coronado/Smith Cabeza de Caballo Endemic status Ventana Coronadito Gemelito East Cerraja Piojo Mitlan Flecha Bota Gemelito West Pata Llave Jorobado (Mexican common name) Calavera L. hrevipes Benth. Baja California desert-thorn 3 3 1 3 3 3 3 3 3 (frutilia) Lfremontii A. Gray Fremont wolfberry 4 4 (tomatillo) Nicotiana obtusifoUa M. Martens coyote tobacco 3 3 3 3 3 4 3 4 2 3 3 & Galeotti (tabaquillo de coyote) Physalis crassifoUa Benth. yellow nightshade 3 3 4 4 3 groundcherry (tomatillo del desierto) ZYGOPHYLLACEAE Fagonia pachyacantha Rydb. fagonbush S 4 3 3 3 4 Viscainoa geniculata (Kell.) (guayacdn) S 3 3 4 3 3 3 3 4 3 4 4 Greene var. geniculata Liliopsida (Monocots) AGAVACEAE agave B 1 1 3 Agave cerulala Trel. ssp. cerulata POACEAE (GRAMINEAE) oUl Common name Coronado/Smith Cabeza de Caballo Ventana Coronadito Endemic status Piojo Gemelito East Mitlan Pata Flecha Bota Cerraja Gemelito West Llave Jorobado (Mexican common name) Calavera Aristida adscensionis L. sixweeks threeawn x x x XXX XXX X (tres atistas de agua) A. californica Thurb. ex S. California threeawn 3 3 Watson var. californica (tres barbas de California) Bouteloua barbaia Lag. sixweeks grama x x X X (navajita anual) Monanthochloe liitoralis Engelm. shoregrass 3 3 (zacate playero) Muhlenhergia microspenua littleseed muhly X X X (DC.)Trin. (liendrilla chica) Total number of species (archipelago = 101) 74 65 38 27 36 38 18 32 21 12 7 20 13 12 2 Number of native plant species 73 64 37 27 36 37 18 32 19 12 6 18 11 10 2 Number of non-native species 1 1 1 0 0 0 0 0 2 0 I 2 2 2 0 * = Non-native species, S = Sonoran Desert endemic, B+ = Mostly a Baja California Peninsula endemic with small populations elsewhere in the Sonoran Desert, B = Baja California Peninsula endemic, 1 = Island endemic to Bahi'a de los Angeles, X = indicates that the abundance was not recorded, 1-4 indicate abundance ratings (Table 1). i 107 14 APPENDIX G. PHOTO-ESSAY OF BAHU DE LOS ANGELES 14.1 THE TOWN OF BAHI'ADE LOS ANGELES The following photos show the town of Bahia de los Angeles, the surrounding shore and the bay islands. The author took all photos unless otherwise credited. The town is surrounded by Sonoran Desert vegetation, despite the development that has occurred in the past 50 years (Figure 21). Figure 21. Three kilometers south of the town of Bahfa de los Angeles. Cabeza de Cabal lo Island (background), July 1999. Aschmann (1959) describes the town as having a few houses occupied by permanent residents and says that in summer months fishermen set up shark-fishing camps along the beaches, and American sport fishermen use the cleared area along the beach as an airstrip (Figure 22). As of the printing of this document, there are over fifty houses in town, especially along the shore (Figure 23). 108 Figure 22. Town of Bahi'a de los Angeles looking north-northeast, prior to 1959 (photo by H. Aschmann [1959]). I^Coronado/Smith Island Figure 23. Town of Bahi'a de los Angeles from the water tank, approximately the same location as Figure 22, December 2000. 109 14.2 CORONADO/SMTTH ISLAND The largest island in the archipelago (8 km^), Coronado/Smith Island (Figures 24 -29) has experienced the most human use, but is among the islands with the lowest percentage of the island area used. Four beaches have coves that aie protected from unpredictable winds. Three of these beaches are on the west side of the island. The southernmost beach that is used for camping is at the Mangrove estuary. The middle beach is across from Mitlan Island and is pebbly. The northernmost beach is at the base of the volcano and is sand. Figure 24. Aerial view of Coronado/Smith Island (tall island in the lower center) and Coronadito (lower right) looking southwest, September 2000. liO Figure 25. Designated camping beach at the southwestern base of Coronado/Smith volcano, December 2000. Figure 26. Saltflat on Coronado/Smith Island with iodine bush, December 2000. Ill Figure 27. Coronado/Smith volcano and beach at its base with morning fog, December 2000. Figure 28. A salt "lake" that is only exposed to the gulf during unusually high tides lies between the central beach and the mangrove swamp on the south end of Coronado/Smith Island, December 2000. Figure 29. Wind-trimmed littleleaf elephant-tree on Coronado/Smith Island, December 2000. 14.3 VENTANA ISLAND Ventana Island is the second largest island in the archipelago (Figures 30-37). There are two beaches used for camping; one has a sign on the beach that discourages fires, collecting plants, disturbing wildlife, bringing pets, and littering (Figure 32). This island shows signs of significant human impact; there are many trails and more erosion than on other islands. 113 Figure 30. Scientific expedition with April Boulton (foreground) camped on the beach at Ventana Island, July 1999. Figure 31. Magnificent Frigatebirds (Fragata magnificens) and western gulls {Lams occidentalis) scavenging the remains from fish processing on the main landing beach of Ventana Island, December 2000. Figure 32. Sign demonstrating regulations on main southern boat landing on Ventana Island, December 2000. Figure 33. The rock window for which Ventana Island is named, March 2000. 115 Figure 34. Rock-lined path from main boat landing to inner bowl of Ventana Island, December 2000. Figure 35. Wash leading from the main boat landing up to the bowl on Ventana Island, December 2000. Figure 36. Juvenile Mammillaria sp. (with pen) on Ventana Island, July 2000. Figure 37. Cliffside overlooking main boat landing on Ventana Island, July 2001. 117 14.4 CABEZADECABALLO ISLAND Cabeza de Caballo Island (Figures 38 and 39) is covered with volcanic boulders and offers no place to camp near the water. A faint trail leads up to the old weather station site on the ridge. There are barren areas at the summit of an unstable eroded trail up the northwest slope of the island. This area may have been used in the past for camping, but seems too exposed to wind to be used regularly. The extensive erosion of the slope indicates use of the island as a hiking area. The main areas of use are the highly-eroded path leading up to the first clearing and the less-eroded trail that travels over volcanic boulders to the south. Figure 38. Cabeza de Caballo Island, view from the lighthouse on Gemelito East Island, December 2001. 118 Figure 39. Pitaya agria {Stenocereus gummosus) on rocky north point of Cabeza de Cabailo Island, July 1999. 14.5 Piojo ISLAND Piojo Island is farthest from the town of Bahia de los Angeles. It is steep, rocky, and unprotected from high winds by other islands (Figure 40). It has a pebble beach that has been used by researchers for camping, but seems to be ignored by recreational users. There is now a sign limiting access to the island. The sloped trail on the southeast side is heavily eroded, but the trail on the southwest seems to have had less use by humans. California brown pelicans (Pelecanus occidentalis califomicus) breed on the island, and Chuckwallas live and breed on it (Figure 41). Human impact is concentrated on the southeast part of the island. Figure 40. Rocky wash on the southwest section of Piojo Island, July 2001. Figure 41. Chuckwalla (Sauromalus hispidus) on Piojo Island, July 2001 120 14.6 MTTLAN ISLAND Mitlan Island is approximately 100 m offshore from Coronado/Smith Island. It lacks a beach suitable for camping, but a trail, with moderate erosion, leads to the center of the island. 14.7 PATA ISLAND This island is favorable for camping. It is centrally located and has a beach that is somewhat protected from winds (Figures 42-43). The rest of the island is steep and rocky and gets little use, but there are obvious signs of humans, such as a shrine (Figure 44). Figure 42. Recreation ists camped on the beach at Pata Island with iodine bush {Allenrolfea occidentalis) in the foreground, December 2000. Figure 43. Shoreline of Pata Island with bank of iodine bush, July 2001. Figure 44. Shrine of rusty metal on Pata Island, July 2001. 122 14.8 FLECHA ISLAND Flecha Island is steep and rocky, and lacks a favourable camping area. The windswept cliffs are not ideal for hiking. Some erosion is evident, especially at the only access point on the south end of the island. The Bahia de los Angeles barrel cactus thrives on this island (Figure 45). Figure 45. Bahia de los Angeles barrel cactus {Ferocactus gatesii) on Flecha Island, July 2001. 14.9 BOTA ISLAND Bota Island has a steep cliff on the south side, and is less than 50 meters south of Pata Island (Figure 46). There is some erosion where people climb up from the landing, but the trails are minimal. There is no good place for camping, but it is close to the camping area on Pata Island. 123 Figure 46. Bota Island's rocky cliffs in the background; Cardon (Pachycereus pringlei) on Pata Island in the foreground, July 2001. 14.10 CORONADITO ISLAND Nesting birds inhabit this rocky volcanic island (Figure 47). There is a rock windbreak on the west end in a clearing that is Hlled with crystalline iceplant (Figure 48). There are some trails and evidence of research (including discarded frames and rock outlines), but human-caused erosion is minimal due to the rocky nature of the island. 124 Figure 47. Rocky slope on the south side of Coronadito Island, Cardon (Pachycereus pringlei) (left) and senita (Lophocereus schottii) (right), December 2000. Figure 48. Coronodito Island bowl above boat landing; the white areas in the foreground are remnants of dead crystalline iceplant {Mesembryanthemum crystallinum), December 2001. 125 14.11 GEMEUTO EAST ISLAND Gemelito East Island has a lighthouse on the northeast comer. The only access to the summit of the island is a steep eroded trail on the northwest side. Tourists and researchers ignore the summit of the island. 14.12 JOROB ADO ISLAND Jorobado Island has a sand-slide that allows the only access to the summit of the island. This island is used for research, but, except for the sand-slide (a sandy slope on the southeast end), does not seem to be used by other visitors. 14.13 CERRAJA ISLAND Flat, wind-swept Cerraja Island offers no protected areas to camp and no safe landing. The vegetation is sparse in dry seasons (Figure 49); bird-nesting is apparent. The island is used for research and possibly by daytime recreationists, but probably no one camps there. 126 Figure 49. Northwest arm of Cerraja Island with Opuntia alcahes var. alcahes, July 2001. 14.14 LLAVE ISLAND Llave Island is also flat and windswept (Figure 50). The erosion from the boat landing to the low summit of the island is a sign of some use, but probably not by campers because there are no protected flat areas to set up tents. Research occurs and is evident on this island. 127 Figure SO. Cerraja Island (foreground), Llave Island (middle) and Flecha Island (background) in a dry year, July 1999. 14.15 GEMELITO WEST Gemelito Island is small and steep. It is mostly used for research, and is impacted mostly by moderate erosion along the path to the summit of the island (Figure 51). 128 Figure 51. Gemelito West Island looking westward from the lighthouse on Gemelito East Island, December 2000. 12 APPENDIX H - NON-NATIVE PLANT SPECIES AND PREDICTED THREAT TO ISLANDS CS bi ^ 5'"a> 5.S CBS^U'S.S*'® aaSa'SCBS'S •"£sSa "''u M'S ScSQ mCS ^ 2 «w I'SS'Scog"! S-a-e-® i-g 1 ^ —:=E S&v§s<^s£esg.'£« lb CA toa Cs<'a>-k- Minor threats Apocynaccae Oleander Town of Few Yes No ? Yes ? No ? Bahia (7) (A OA Closest stand (distance in km) Causes ecological Species Family Fertile seed production Fresh-water dependant Thrives in disturbance Vegetative reproduction Apomictic or self-pollinatii disturbance Allelopathic properties Xeric habitat Arecaceae Date palm Town of Medium Yes No 7 No Yes No 7 Bahia (7) Asphodeliaceae Barbados aloe Town of None Yes Yes ? 7 7 No Yes Bahi'a (7) Cucurbitaceae Feral watermelon Tiburon Medium Yes No 7 7 7 No Yes Island (100) Euphorbiaceae Castorbean Punta Prieta Medium Yes No 7 7 7 No Yes (62) Fabaceae Mexican palo verde Town of Medium Yes No 7 7 7 Yes Yes Bahia (7) Fabaceae Sourc lover Agua Amarga Medium Yes No 7 7 7 No Yes (29) Geraniaceae Stork's bill Town of Medium Yes No 7 7 7 Yes Yes Bahia (7) Molluginaceae Threadstem Tiburon Many Yes No 7 7 7 Yes Yes carpet weed Island (100) Myrtaceae Gum tree Town of 7 Yes No 7 7 Yes No 7 Bahia (7) Nyctaginaceae Bougainvillea Town of Few Yes No 7 7 7 No No Bahia (7) Poaceae Bermuda grass Town of Many Yes Yes 7 7 Yes No Yes Bahia (7) U) O CA en •D e b .£ o u S s TS c « 'S w 2 2 — Si 1 •s .1 £ ^ B Z .S B ® -5 s U S es 2 es cs ^ se ^ 3 a H •e 9i a 1? 1 Q. •2 g. u SSO .2M ^B a 3 *C •c 2 9> £ •- Causes Species ecologia Family Fresh-water • 35 a dependant > £ < S < a •3 X 1 1 Poaceae Giant reed Tiburon None or Yes Yes No 7 Yes No Yes Island (100) Few Poaceae Slimbristle sandbur Tiburon Few Yes No 7 7 7 No Yes Island (100) Solanaceae Tree tobacco Punta Prieta Many Yes No ? 7 No Yes Yes (62) Tamaracaceae Saitcedar Town of None Yes ? No Yes Yes No Yes Bahia (7) Tamaricaceae Tamarisk Tiburdn Many Yes Yes Yes Yes Yes No Yes Island (100) Zygophyllaceae Puncturevine Town of Medium Yes No 7 7 7 Yes Yes Bahia (7) This table is compiled from information from the following sources; Robbins, Bellue, and Ball 1951; Parker 1972; Felger and Lowe 1976; Vivrette and Muller 1977; Everitt 1980; Stevens 1985; Fulbright and Fulbright 1990; Felger 1990; El-Gareeb 1991; Winter and Zeigler 1992, Bourillon-Moreno 1996; Frandsen 1997, Anderson 1999; West and Nabhan 2002; this study; West, unpublished fieldnotes. 132 16 REFERENCES Anderson, C. A. 1950. The 1940 E. W. Scripps cruise to the Gulf of California. Part 1; Geology of the islands and neighboring land areas. Geological Society of American Memoir 43:1-53. Anderson, D. W., and J. O. Keith. 1980. The human influence of seabird nesting success: conservation implications. Biological Conservation 18:65-80. Anderson, E. F. 2001. The cactus family. Timber Press, Portland, Oregon. 776p. Anderson, W. B. and G. A. Polis. 1999. Nutrient fluxes from water to land: seabirds affect plant nutrient status on Gulf of California islands. Oecologia 118(3):324- 332. Anderson, W. P. 1999. Perennial weeds: characteristics and identification of selected herbaceous species. Iowa State University Press, Ames, Iowa. 228 p. Aschmann, H. 1959. The Central Desert of Baja Califomia: Demography and Ecology. University of Califomia Press, Berkeley, Califomia. 315 p. Aschmann, H. 1997a. The Baja Califomia highway. P. 71-80 in M. J. Pasqualetti, editor. The evolving landscape: Homer Aschmann's geography. The Johns Hopkins University Press, Baltimore, Maryland. 445 p. Aschmann, H. 1997b. Desert genocide. P. 47-55 in M. J. Pasqualetti, editor. The evolving landscape: Homer Aschmann's geography. The Johns Hopkins University Press, Baltimore, Maryland. 445 p. Atkinson, I. A. E. 1989. Introduced animals and extinctions. P. 54-75 in D. Western and M. C. Pearl, editors. Conservation for the twenty-first century. Oxford University Press, New York, New York. 365 p. 133 Bahre, C. 1983. Human impact: the Midriff islands. P. 290-306 in T. J. Case and M. L. Cody, editors. Island biogeography in the Sea of Cortez. University of California Press, Los Angeles, California. 508 p. Bahre, C. J. and L. Bourillon. In press. Human impact: the Midriff islands. In T. J. Case, M. L. Cody, and E. Ezcurra, editors. Island biogeography in the Sea of Cortez, second edition. University of California Press, Los Angeles, California. Baja Almanac. 1997. Baja Almanac Publishers, Inc., Las Vegas, Nevada. 65 p. Barbour, M. G., J. H. Burk, W. D. Pitts, F. S. Gilliam, and M. W. Schwartz. 1999. Terrestrial Plant Ecology, third edition. Benjamin/Cummings, Menlo Park, California. 649 p. Bates, K., C. Bates, and Sunset editorial staff. 1971. Sunset travel guide to Baja California. Lane Books, Menlo Park, California. 80 p. Boulton, A. M. and P.S. Ward. In press. Biogeography of and communities on islands in the Sea of Cortes in T. J. Case, M. L. Cody, and E. Ezcurra, editors. Island biogeography in the Sea of Cortez, second edition. University of California Press, Los Angeles, California. Bourilion-Moreno, L. F. 1996. Actividad humana en la region de las grandes islas del Golfo de California, Mexico. Maestro en Ciencias. Institute Technologico y de Estudios Superiores de Monterrey, Guaymas, Sonora, Mexico. 230 p. Bowen, T. 2000. Unknown island: Seri Indians, Europeans, and San Esteban Island in the Gulf of California. University of New Mexico Press, Albuquerque, New Mexico. 548 p. Bowers, J. E. 1980. Flora of Organ Pipe Cactus National Monument. Journal of the Arizona-Nevada Academy of Sciences I5;l-l 1,33-47. Bowers J. E. and R. M. Tumer. 1985. A revised vascular flora of Tumamoc Hill, Tucson, Arizona. Madrono 32:225-252. 134 Bravo-Hollis, H. and H. Sanchez-Mejorada R. 1991. Las cactaceas de Mexico, volumen m. Universidad Nacional Autonoma de Mexico, Ciudad Universitaria, Mexico. 643 p. Buckley, R. C. 1985. Distinguishing the effects of area and habitat type on island plant species richness by separating floristic elements and substrate types and controlling for island isolation. Journal of Biogeography 12:527-535. Burgess, T. L., J. E. Bowers, and R. M. Turner. 1991. Exotic plants at the Desert Laboratory, Tucson, Arizona. Madrono 38:96-114. Carabias-Liilo, J., J. de la Maza-Elvira, D. Gutierrez-Carbonell, M. Gomez-Cruz, G. Anaya-Reyna, A. Zavala-Gonzalez, A. L. Figueroa, and B. Bermudez-Almada. SEMARNAP and CONANP. 2000. Programa de manejo: Area de Proteccion de Flora y Fauna - Islas del Golfo de California. SEMARNAP and CONANP, Mexico D. F. 262 p. Case, T. J. and M. L. Cody, editors. 1983. Island biogeography in the Sea of Cortez. University of California Press, Los Angeles, California. 508 p. Case, T. J., M. L. Cody, and E. Ezcurra, editors. In press. Island biogeography in the Sea of Cortez, second edition. University of California Press, Los Angeles, California. 592 p. Clavigero, F. X. 1789. Storia della California. Venice. 2 vols. S. E. Lake and A. A. Gray, translators. 1937. The history of Lower California. Stanford University Press, Stanford, Califomia. 413 p. Comision Nacional del Agua. 2001. Gerencia regional de la Peninsula de Baja Califomia, subgerencia regional tecnica, jefatura de proyecto de meterologia, estacion no. 002 "Bahfa de los Angeles," Bahia de los Angeles, Municipio de Ensenada, Baja Califomia, inicia operaciones el 10 de Septiembre de 1953. Costa, C. S. B. and A. J. Davy. 1992. Coastal saltmarsh communities of Latin America P. 179-199 in U. Seeliger, editor. Coastal plant communities of Latin America. Academic Press, Inc., San Diego, Califomia. 392p. 135 Cronk, Q. C. B. and J. L. Fuller. 1995. Plant invaders: the threat to natural ecosystems. Wwf Manuals in Plant Conservation Vol. 1. Stanley Thomes Publishers Limited, Cheltenham, England. 255 p. D'Antonio, C. M. and P. M. Vitousek. 1992. Biological invasions by exotic grasses, the grass/fire cycle, and global change. Annual Review of Ecology and Systematics 23: 63-87. Dean, W. R. J., S. J. Milton, P. G. Ryan, and C. L. Moloney. 1994. The role of disturbance of indigenous and alien plants at Inaccessible and Nightingale Islands in the South Atlantic Ocean. Vegetatio 113:13-23. Delgadillo, J. 1998. Flonstica y ecologia del norte de Baja California. Univerisdad Autonoma de Baja California, Ensenada, Mexico. 412 p. Delgado-Argote, L.A. and J. Garcia-Abdeslem. 1999. Shallow Miocene basaltic magma reservoirs in the Bahia de los Angeles basin, Baja California, Mexico. Journal of Volcanology and Geothermal Research 88(l-2):29-46. Deshaye, J. and P. Morisset. 1988. Floristic richness, area and habitat diversity in a hemiarctic archipelago. Journal of Biogeography 15:747-758. DiCastri, F. 1989. History of biological invasions with special emphasis on the old world P. 1 -30 in J. A. Drake, H. A. Mooney, F. DiCastri, R. H. Groves, F. J. Kruger, M. Rejmanek, M. Williamson. Biological invasions: a global perspective. John Wiley and Sons, New York, New York. 525 p. Donlan, C. J. 2000. Islands and introduced herbivores: using conservation to investigate top-down and bottom-up processes. Master's thesis. University of California, Santa Cruz, California. 94 p. Due, A. D. 1992. Biogeography of scorpions in Baja California, Mexico and an analysis of the insular scorpion fauna in the Gulf of California. PhD. dissertation, Vanderbilt University, Nashville, Tennessee. 141 p. 136 El-Gareeb, R. 1991. Vegetation and soil changes induced by Mesembryanthemum crystallinum L. in a Mediterranean desert ecosystem. Journal of Arid Environments 20:321-330. Everett, B. L. 1980. Ecology of saltcedar: a plea for research. Environmental Geology 3:77-84. Felger R. S. 1980. Vegetation and Flora of the Gran Desierto, Sonora, Mexico. Desert Plants 2:87-114. Felger, R. S. 1990. Non-native plants of Organ Pipe Cactus National Monument, Arizona. Technical Report No. 31. U.S. Geological Survey Cooperative Park Studies Unit, the University of Arizona and National Park Service, Organ Pipe Cactus National Monument, University of Arizona, Tucson, Arizona. 93 p. Felger, R. S. 2000. Flora of the Gran Desierto and Rio Colorado of Northwestern Mexico. The University of Arizona Press, Tucson, Arizona. 673 p. Felger, R. S., B. Broyles, M. Wilson, and G. P. Nabhan. 1997. The binational Sonoran Desert biosphere network and its plant life. Journal of the Southwest 39(4):411- 560. Felger, R. S. and C. H. Lowe. 1976. The island and coastal vegetation and flora of the northern part of the Gulf of California, Mexico. Natural History Museum of Los Angeles County, Contributions to Science 285:1-59. Felger, R. S. and M. B. Moser. 1985. People of the desert and sea: ethnobotany of the Sen Indians. University of Arizona Press, Tucson, Arizona. 435 p. Felger, R. S., P. L. Warren, L. S. Anderson, G. P. Nabhan. 1992. Vascular plants of a desert oasis: flora and ethnobotany of Quitoboquito, Organ Pipe Cactus National Monument, Arizona. Proceedings of the San Diego Society of Natural History 8:1-39. 137 Fitz Maurice, W. A. and E. F. Anderson. 1997. Mexico. P. 89-99 in S. Oldfleld, editor. Status survey and conservation action plan; cactus and succulent plants. lUCN/SSC Cactus and Succulent Specialist Group, Gland, Switzerland. Flores-Verdugo, F., F. Gonzalez-Farias, D. S. Zamorano, and P. Ramirez-Garcia. 1992. Mangrove ecosystems of the Pacific coast of Mexico: distribution, structure, litterfall and detritus dynamics P. 269-288 in U. Seeliger, editor. Coastal plant communities of Latin America. Academic Press, Inc., San Diego, California. 392p. FONATUR. 2001. Proyecto Escalera Nautica del Mar de Cortes: documento basico. Escalera Nautica del Mar de Cortes: el megaproyecto turistico del siglo XXI. Fondo Nacional de Fomento al Turismo, 9 July 2001. Frandsen, P. R. 1997. Team Arundo: Interagency cooperation to control giant cane (Arundo donax). P. 244-248 in J. O. Luken and J. W. Thieret, editors. Assessment and management of plant invasions. Springer, New York, New York, 324 p. Fulbright, N. and T. E. Fulbright. 1990. Germination of two legumes in leachate from introduced grasses. Journal of Range Management 43(5):466-467. Fuller, D, and S. Fitzgerald, editors. 1987. Conservation and commerce of cacti and other succulents. TRAFFIC (USA). WwF-US, Washington DC. Gastil, G., J. Minch, and R. P. Phillips. 1983. The geology and ages of the islands. P. 13- 25 in T. J. Case and M. L. Cody, editors. Island biogeography in the Sea of Cortez. University of California Press, Los Angeles, California. 508 p. Gentry, H. S. 1949. Land plants collected by the Velero III, Allan Hancock Pacific Expeditions 1937-1941. Allan Hancock Pacific Expeditions 13(2). The University of Southern California Press, Los Angeles, California. 245 p. Gerhard, P. and H. E. Gulick. 1962. Lower California Guidebook: a descriptive traveler's guide. The Arthur Clark Company, Glendale, California. 243 p. 138 Gentry, H. S. 1978. The agaves of Baja California. California Academy of Sciences, Occasional Papers No. 130:119p. Gould, F. W. and R. Moran. 1981. The grasses of Baja California, Mexico. San Diego Society of Natural History Memoir 12:1-140. Gould, S. J. 1979. An allometric interpretation of species-area curves: the meaning of the coefficient. American Naturalist 114:335-343. Groombridge, B., editor. 1992. Global biodiversity: status of the earth's living resources. Chapman & Hall, London, England. 585 p. Heatwole, H. 1991. Factors affecting the number of species of plants on islands of the Great Barrier Reef, Australia. Journal of Biogeography 18:213-221. Hecnar, S. J. and R. T. Closkey. 1998. Species richness patterns of amphibians in southwestern Ontario ponds. Journal of Biogeography 25:763-772. Hendrey, G. W. and M. K. Bellue. 1925. The plant contents of adobe bricks. California Historical Society Quarterly 4:361-373. Heywood, V. H. 1989. Patterns, extents and modes of invasion by terrestrial plants. P. 31-60 in J. A. Drake, H. A. Mooney, F. DiCastri, R. H. Groves, F. J. Kruger, M. Rejmanek, M. Williamson. Biological invasions: a global perspective. John Wiley and Sons, New York, New York. 525 p. Hill, J., P. J. Curran and G. M. Foody. 1994. The effect of sampling on the species area curve. Global Ecology and Biogeographical Letters 4:97-106. Hobbs, R. J. and S. E. Humphreys. 1995. An integrated approach to the ecology and management of plant invasions. Conservation Biology 9:761-770. Holt, R. D., J. H. Lawton, G. A. Polis, and N. D. Marinez. 1999. Trophic rank and the species-area relationship. Ecology 80(5): 1495-1504. 139 Hunter, J. 1977. Offbeat Baja. Chronicle Books, San Francisco, California. 156 p. Island Ecology and Conservation Group (ICEG). 2002. Island Conservation Database. ICEG, Santa Cruz, California. March 3,2002. International Union for Conservation of Nature and Natural Resources (lUCN). 1987. World conservation strategy. lUCN, Gland, Switzerland. 367 p. Jerez L. C. 1992. Conservation priorities on the Northern Gulf Coast of Baja California; a biogeographic analysis. Master's thesis. University of California, Los Angeles, Los Angeles, California. 221 p. Junak, S. A. and R. Philbrick. 2000a. Flowering plants of the San Benito Islands, Baja California, Mexico. P. 235-246 in D. R. Brown, K. L. Mitchell, and H. W. Chaney, editors. OCS Study 99-0038. U. S. Minerals Management Service, Camarillo, California. CD-ROM. 749 p. Junak, S. A. and R. Philbrick. 2000b. Flowering plants of Natividad Island, Baja California, Mexico. P. 224-234 in D. R. Brown, K. L. Mitchell, and H. W. Chaney, editors. OCS Study 99-0038. U. S. Minerals Management Service, Camarillo, California. CD-ROM. 749 p. Kiy, R. and J. D. Wirth, editors. 1998. Environmental management on North America's borders. Texas A M University Press, College Station, Texas. 320 p. Krutch, J. W. 1961. The forgotten peninsula: a naturalist in Baja California. The University of Arizona Press, Tucson, Arizona. 277 p. Leon de la Luz, J. L., R. Coria Benet, and J. Cansino. 1995. Listados flon'sticos de Mexico: XI Reserva de la Biosfera El Vizcaino, Baja California Sur. Universidad Nacional Autonoma de Mexico, Instituto de Biologfa, La Paz, Mexico. 30 p. Lindsay, G. 1955. Ferocactus gatesii - A new species. Cactus and Succulent Journal 27:150-151. 140 Lindsay, G. 1996. The taxonomy and ecology of the genus Ferocactus: explorations in the USA and Mexico. Tireless Termites Press, USA. 444 p. Loope, L. L., P. G. Sanchez, P. W. Tarr, W. L. Loope, and R. L. Anderson. 1988. Biological invasions of arid land nature reserves. Biological Conservation 44:95- 118. MacArthur, R. H. and E. O. Wilson. 1967. The theory of island biogeography. Princeton University Press, Princeton, New Jersey. 224 p. MacDonald, G. J., D. L. Nielson, and M. A. Stem. 1997. Latin American environmental policy in international perspective. Westview Press, Boulder, Colorado. 292 p. MacNally, R. and P. S. Lake. 1999. On the generation of diversity in archipelagos: a re- evaluation of the Quinn-Harrison "saturation index." Journal of Biogeography 26:285-295. Mack, M. C. and C. M. D'Antonio. 1998. Impacts of biological invasions on disturbance regimes. Trends in Ecology and Evolution 13(5); 195-198. Martinez, M. 1979. Catalogo de nombres vulgares y cientiTicos de plantas mexicanas. Fondo Cultura Economica de Mexico, Mexico D. F. 1220 p. Meigs, P. 1935. The Dominican mission frontier of Lower California. University of California Press, Berkeley, California. 231 p. Menges, E. S. and D. R. Gordon. 1996. Three levels of monitoring intensity for rare plant species. Natural Areas Journal 16(3)227-237. Miller, T. and E. Baxter. 1977. The Baja book II: a complete new map-guide to today's Baja California. Baja Trail Publications, Inc. Huntington Beach, Califomia. 180 p. Moody, M. E. and R. N. Mack. 1988. Controlling the spread of plant invasions: the importance of nascent foci. Journal of Applied Ecology 25:1009-1021. 141 Morrison, L. W. 1997. The insular biogeography of small Bahamian cays. Journal of Ecology 85:441-453. Munoz, H. 1997 Free trade and environmental policies: Chile, Mexico, and Venezuela. P. 113-129 in G. J. MacDonald, D. L. Nielson, and M. A. Stem, editors. Latin American environmental policy in international perspective. Westview Press, Boulder, Colorado. 292 p. Nabhan, G. P., P. West, R. S. Felger, M. O'Brien, J. O'Brien, T. R. Van Devender, A. L. Reina-Guererro, S. P. McLaughlin, P. Jenkins, and J. C. Stromberg. In press. Appendix B: naturalized exotic species in the Sonoran region - flora in B. Tellman, editor. Invasive exotic species in the Sonoran region. The University of Arizona Press, Tucson, Arizona. Noble, I. R. 1989. Attributes of invaders and the invading process: terrestrial and vascular plants. P. 301-314 in J. A. Drake, H. A. Mooney, P. DiCastri, R. H. Groves, F. J. Kruger, M. Rejmanek, M. Williamson. Biological invasions: a global perspective. John Wiley and Sons, New York, New York. 525 p. Oldfield, S. 1997. Cactus and succulent plants: status survey and conservation action plan. lUCN, Gland, Switzerland. 214 p. Pacheco-Ruiz, I. and J. A. Zertuche-Gonzalez. 1996. Green algae (Chlorophyta) from Bahia de los Angeles, Gulf of California, Mexico. Botanica Marina 39(5):431- 433. Parker, K. F. 1972. An illustrated guide to Arizona weeds. The University of Arizona Press, Tucson, Arizona. 338 p. Philippi, T., B. Collins, S. Guisti, and P. M. Dixon. 2001. A multistage approach to monitoring for rare plant populations. Natural Areas Journal 21(1)111-116. Phillips, R. P. 1964. Geophysical investigations of the Gulf of California. Ph.D. dissertation, University of California at La Jolla, La Jolla, California. 250 p. 142 Polis, G. A. and S. D. Hurd. 1996. Linking marine and terrestrial food webs: allochthonous input from the ocean supports high secondary productivity on small islands and coastal communities. American Naturalist 147:396-423. Polis, G. A., S. D. Hurd, C. T. Jackson, F. Sanchez-Pinero. 1997. El Nino effects on the dynamics and control of a terrestrial island ecosystem in the Gulf of California. Ecology 78:1884-1897. Poorman, F. L. and L. H. Poorman. 1978. Additional molluscan records from Bahfa de los Angeles, Baja California Norte. Veliger 20(4):369-374. Ramsey, F. L. and D. W. Schafer. 1997. The statistical sleuth: a course in methods of data analysis. Duxbury Press, San Francisco, Califomia. 742 p. Rebman, J. P., J. L. Leon de la Luz, and R. V. Moran. In press. Vascular plants of the Gulf Islands. In T. J. Case, M. L. Cody, and E. Ezcurra, editors. Island biogeography in the Sea of Cortez, second edition. University of Califomia Press, Los Angeles, Califomia. Reich, P. L. 1984. Statistical abstract of the U. S. Mexico borderland. UCLA Latin America Center Publications, Los Angeles, Califomia. 179 p. Reichard, S. E. 1997. Prevention of invasive plant introductions on national and local levels. P 215-248 in J. O. Luken and J. W. Thieret, editors. Assessment and management of plant invasions. Springer, New York, New York. 324 p. Robbins, W. W., M. J. Bellue, and W. S. Ball. 1951. Weeds of Califomia. Documents and Publications, Califomia State Department of Agriculture, Sacramento, Califomia. 547 p. Roberts, N. C. 1989. Baja Califomia plant field guide. Natural History Publishing Company, La Jolla, Califomia. 309 p. Roden, C. M. 1998. Persistence, extinction and different species pools within the flora of lake islands in westem Ireland. Joumal of Biogeography 25:301-310. 143 Rose, M. D. and G. A. Polis. 1998. The distribution and abundance of coyotes: The effects of allochthonous food subsidies from the sea. Ecology 79(3):998-1007. Sadler, J. P. 1999. Biodiversity on oceanic islands: a paleoecological assessment. Journal of Biogeography 26(l):75-87. San Diego Natural History Museum. 1991. Voucher procedures. San Diego Natural History Museum Herbarium, San Diego, California. Photocopy. 13 p. Sanchez-Pinero, F. and R. L. Aalbu. In press. The desert specialists: tenebrionid beetles. In T. J. Case, M. L. Cody, and E. Ezcurra, editors. Island biogeography in the Sea of Cortez, second edition. University of California Press, Los Angeles, California. Sanchez-Pinero, F. and G.A. Polis. 2000. Bottom-up dynamics of allochthonous input: direct and indirect effects of seabirds on islands. Ecology 81:3117-3132. SDNHM. 1999. Database of plant collections. San Diego Natural History Museum, San Diego, California. 14 p. Secretaria de Medio Ambiente, y Recursos Naturales (SEMARNAP). 1999. Draft: Programa de manejo: Islas del Golfo de California. SEMARNAP, Guaymas, Sonora, Mexico. 216 p. Secretan'a de Medio Ambiente, y Recursos Naturales (SEMARNAP) and Island Conservation and Ecology Group (ICEG). 1998. Pescadores: rescate en el mar. SEMARNAP and ICEG, Guaymas, Sonora, Mexico. Seminoff, J. A., W. J. Nichols, and A. Resendiz S. Hidalgo. 2000. Chelonia mydas agassizii (East Pacific Green Turtle), Diet. Herpetological Review 31:103. Shreve, F. 1951. Vegetation of the Sonoran Desert. P. 1-186 in F. Shreve and I. L. Wiggins. 1964. Vegetation and Flora of the Sonoran Desert, 2 vols. Stanford University Press, Stanford, Califomia. 1740 p. 144 Shreve, F. and I. L. Wiggins. 1964. Vegetation and Flora of the Sonoran Desert, 2 vols. Stanford University Press, Stanford, California. 1740 p. Spalding, M. J. 2001. Escalera Nautica: stair steps to preserve beauty or to despoil nature? Borderlines Updater 18 April 2001. http://us-mex.org/borderlines/updater/2001/aprl8glob.html. Standley, P. C. 1922-1926. Trees and shrubs of Mexico, vols. 1-5. Contributions from the U. S. Herbarium Vol 23:1- 1721. Stevens, L. E. 1985. Invertebrate herbivore community dynamics on Tamarix chilensis Loureiro and Salix exigua Nuttall in the Grand Canyon, Arizona. Master's thesis. Northern Arizona University, Flagstaff, Arizona. Taylor, N. P. 1984. A review of Ferocactus Britton &. Rose. Bradleya 2/1984:19-38. Taylor, N. P. 1997. Cactaceae. P. 17-20 in S. Oldfield, editor. Status survey and conservation action plan: cactus and succulent plants. lUCN/SSC Cactus and Succulent Specialist Group, Gland, Switzerland. Tershy, B. R., L. Bourillon, L. Metzler, J. Barnes. 1999. A survey of ecotourism on islands in northwestern Mexico. Environmental Conservation 26(3):212-217. Tershy, B. R., D. Breese, and D. A. Croll. 1997. Human perturbations and conservation strategies for San Pedro Martir Island, Islas del Golfo de California Reserve, Mexico. Environmental Conservation 24(3):261-270. Tilman, D. and S. Pacala. 1993. The maintenance of species richness in plant communities. P. 13-25 in R. E. Ricklefs and D. Schluter, editors. Species diversity in ecological communities: historical and geographical perspectives. University of Chicago Press, Chicago, Illinois. 576 p. Turner, R. M., J. E. Bowers, and T. L. Burgess. 1995. Sonoran Desert plants: an ecological atlas. The University of Arizona Press, Tucson, Arizona. 504 p. 145 Turner, R. M. and D. E. Brown. 1994. Sonoran desertscrub. P. 181-223 in D. E. Brown, editor. Biotic Communities: Southwestern United States and Northwestern Mexico. University of Utah Press, Salt Lake City, Utah. 342 p. Tuxili, J. D., G. P. Nabhan, E. Drexier, and M. Hathaway. 1998. Plants and protected areas: a guide to in situ management. Stanley Thomes Publishers Limited, Cheltenham, England. 262 p. Unger, G. 1992. Die groBen Kugelkakteen Nordamerikas. Graz, Leibnitz, Austria. 467 p. Vidal, E., F. Medail, T. Tatoni, P. Roche, and P. Vidal. 1998. Impact of gull colonies on the flora of the Riou Archipelago (Mediterranean islands of south-east France). Biological Conservation 84(3):235-243. Vitousek, P. M, C. M. D'Antonio, C. M. Loope, and R. Westbrooks. 1996. Biological invasions as global environmental change. American Scientist 84:468-478. Vivrette, N. J. and C. H. Muller. 1977. Mechanism of invasion and dominance of coastal grassland by Mesembryantliemiim crystallinum. Ecological Monographs 47:301- 318. Wells. R. 1996. Little alters everywhere. Broken Moon Press, Seattle, Washington. 240 p. West, P. A. and G. P. Nabhan. 2002. Invasive weeds: their occurrence and possible impact on the Central Gulf Coast of Sonora and the Midriff Islands of the Sea of Cortes. In B. Tellman, editor. Invasive exotic species in the Sonoran region. University of Arizona Press, Tucson, Arizona. West, P. A., J. Rebman, G. A. Polis, and L. D. Humphrey. In press. Appendix 4.4: plants of some smaller islands. In T. J. Case, M. L. Cody, and E. Ezcurra, editors. Island biogeography in the Sea of Cortez, second edition. University of California Press, Los Angeles, California. Wiggins, I. L. 1980. Flora of Baja California. Stanford University Press, Stanford, California. 1025 p. 146 Williams, S. C. 1980. Scorpions of Baja California, Mexico, and adjacent islands. Occasional papers of the California Academy of Sciences 135:1-127. Winter, K. and H. Zeigler. 1992. Induction of crassulacean acid metabolism in Mesembryanthemum crystallinum increases reproduction success under conditions of drought stress and salinity stress. Oecologia 92:475-479. Wheelock, W. and H. E. Gulick. 1975. Baja California guidebook: complete current information and maps for the traveler, fifth edition. The Arthur H. Clark Company, Glendale, California. 232 p. Whittaker, R. J. 1998. Island biogeography: ecology, evolution, and conservation. Oxford University Press, New York, New York. 285 p. Woodroffe, C. D. 1986. Vascular plant species-area relationships on Nui Atoll, Tuvalu, Central Pacific: A reassessment of the small islands effect. Australian Joumal of Ecology 11:21-31.