*
BIOGEOGRAPHY OF FRESHWATER FISHES OF
NORTHWESTERN MEXICO
by
Heidi Blue Blasius
A Thesis Presented in Partial Fulfillment of the Requirements for the Degree Master of Science
ARIZONA STATE UNIVERSITY
December 1996 ABSTRACT
Northwestern Mexico provides the connecting link in a broad geographic transition between continental ichthyofaunas of the Western Hemisphere. A. biotic assemblage with diversified relationships results from a varied biogeographic history involving two much larger regions, Nearctic in the
north and Neotropical to the south. This thesis delineates and analyzes
relationships of the regional ichthyofauna within this broader pattern of
transition. Three levels of specimen records were used (Level I, those in
museums; II, peer-reviewed literature; and HI, "gray" literature) to address
two questions: 1) are within-region distributions more a function of ecologic
or geologic history, or 2) are ecologic and geologic histories so inexorably
intertwined they cannot be separated one from the other? The fauna proved
strongly northern in affinity, comprised of three Nearctic (salmonids,
catostomids, cyprinids), one transitional Nearctic (ictalurids), two transitional
Neotropical (poeciliids, cichlids), and two shared (cyprindontids, clupeids)
families that occur across diverse geologic structure and through temperate
and tropical habitats to form a distributional mosaic most closely attuned to
latitudinal and altitudinal ecology of the region.
111 DEDICATION
For my Mom, Sondra Katherine Blasius and Dad, Gary Lee Blasius who loved and
supported me throughout graduate school, and my beautiful daughter
Nashashibi Tahara Blasius whom I love dearly. I love you all.
iv ACKNOWLEDGEMENTS
I wish to thank my committee members, Dr. M. J. Fouquette, Jr., and Dr. D. J.
Pinkava for their critical review and comments on this manuscript, and Dr. W.
L. Minckley who greatly assisted and supported me during the duration of this
thesis.
I am particularly indebted to Dr. W. L. Minckley, my major professor, who
accepted me as his graduate student and allowed me to pursue the Master of
Science Degree. During this time I was provided with continuous direction,
answers to my many questions, and the confidence to think and learn on my
own. Dr. Minckley was also very instrumental in the preparation and
finalization of this thesis. Thank you. I would also like to thank Jana Frye,
who developed and implemented the GIS system used for this study; Peter
Unmack who patiently and diligently perfected the distribution maps contained within this manuscript; and Tim Hurst and Connie Fontes who
assisted with digitizing.
I thank the following individuals and institutions that provided me with
level one data (museum specimens and locality data), Barbara Brown,
American Museum of Natural History (AMNH); Mary Anne Rogers, The Field
Museum of Natural History (FMNH); Dan Hough, The University of Oklahoma
(UOMZ); Cynthia Klepadlo, Scripps Institution of Oceanography (SIO); Douglas
W. Nelson, The University of Michigan (UMMZ); Jeff Williams, U. S. National
Museum of Natural History (USNM); Academy of Natural Sciences of
Philadelphia (ANSP), and Arizona State University (ASU).
Special thanks goes to my dear friend Rick Olson, with whom I shared many
lunches and confidences. I will always remember the loyalty, encouragement,
V and kindness he showed me during some very trying and unhappy times while pursuing this degree.
My sincerest gratitude and much love goes to my very special mom who loved and believed in me. During my graduate studies my mom provided me with emotional and financial support, and sacrificed time and many years in helping me raise my daughter. This was done with one goal in mind, for me to have a better life than she has had. I love you.
Much love, appreciation, and graditude goes to David D. Oakey who spent many hours helping me with maps, proofreading sections of my thesis, and talking to me about fishes and geology. This help and encouragement was much needed and appreciated.
Many thanks goes to Jeffery Alan Conn who patiently put in the page numbers that I spent months trying (unsuccessfully) to figure out.
I sincerely thank Dean Gary Kraenbuhl who personally made sure that I would have funding during the duration of my graduate work.
Without this continuous support this work would not have been completed.
vi TABLE OF CONTENTS Page
LIST OF TABLES ...... v ii
LIST OF FIGURES ...... ix
LIST OF MAPS ......
INTRODUCTION ...... 1
STUDY AREA ...... 3
Geologic History ...... 3
Physiography ...... 4
Vegetation ...... 5
Aquatic Habitats ...... 5
MATERIALS AND METHODS ...... 9
RESULTS AND DISCUSSION ...... 12
Distribution of Sampling Sites ...... 12
Accounts of Native Species ...... 1 3
Nonnative Fishes ...... 21
Species Richness ...... 22
SUMMARY AND CONCLUSIONS ...... 23
LITERATURE CITED ...... 26
APPENDIX
A TABLES ...... 34
B FIGURES ...... 39
C MAPS ...... 48
vii LIST OF TABLES
Table Page
1. Scientific and English and Spanish common names of native freshwater fishes of northwestern Mexico mentioned in text 35
2. Nonnative fishes recorded from rivers of northwestern Mexico. Species marked with an asterisk (*) are known to have been planted one or more times in the United States in drainages of the dos Yaqui, de la Concepcion, or Sonoyta, which does not imply an absence of additional introductions in Mexico ...... 37
viii LIST OF FIGURES
Figure Page
1. Map of the study area, and environs showing major river basins ...... 40
2. Fish collection sites upon which this report is based, 1854-1994 ...... 42
3. Fish collection sites in the study area, southwestern United States and northwestern Mexico from: A) 1854-1930; B) 1931-1960; C) 1961-present; and D) 1978 ...... 44
4. Regressions of river basin size and numbers of fish taxa for: A) 11 river basins in southwestern United States and northwestern Mexico; and B) the same area, but with the two largest basins excluded ...... 46
ix LIST OF MAPS (Distributions of inland fishes in northwestern Mexico)
Map Page
1. Distribution of inland fishes in northwestern Mexico: squares, trout(s) (Oncorhynchus sp.) and triangles, Pacific shad (Dorosoma smithi) ...... 49
2. Distribution of inland fishes in northwestern Mexico: longfin dace (Agosia chrysogaster) ...... 5 1
3. Distribution of inland fishes in northwestern Mexico: Mexican stoneroller (Campostoma ornatum) ...... 53
4. Distribution of inland fishes in northwestern Mexico: ornate minnow (Codoma ornata) ...... 55
5. Distribution of inland fishes in northwestern Mexico: beautiful shiner (Cyprinella formosa) ...... 57
6. Distribution of inland fishes in northwestern Mexico: squares, Sonoran chub (Gila ditaenia); dots, undescribed chub (Gila sp.) of upper Rio Yaqui; and triangles, Yaqui chub (. purpurea) 59
7. Distribution of inland fishes in northwestern Mexico: desert chub (Gila eremica) ...... 61
8. Distribution of inland fishes in northwestern Mexico: squares, Yaqui roundtail chub (Gila minacae), and triangles, undescribed chub (Gila sp.) of Rfo Concepcion ...... 63
9. Distribution of inland fishes in northwestern Mexico: Yaqui sucker (Catostomus bernardini) ...... 65
10. Distribution of inland fishes in northwestern Mexico: dots, Opata sucker (Catostomus wigginsi); squares, Cahita sucker (C. cahita); and triangles Leopold sucker (C. leopoldi) ...... 67
11. Distribution of inland fishes in northwestern Mexico: Yaqui catfish Octalurus price i) ...... 69
12. Distribution of inland fishes in northwestern Mexico: dots, Rio Grande mountain sucker (Pantosteus plebeius); triangles, desert pupfish (Cyprinodon macularius); squares undescribed pupfish (Cyprinodon sp.); and diamonds Sinaloan cichlid Map Page
(Cichlasoma beani) ...... 71
13. Distribution of inland fishes in northwestern Mexico: Sonoran topminnow (Poeciliopsis occidentalis) ...... 73
14. Distribution of inland fishes in northwestern Mexico: Topminnow (P. monacha) ...... 75
15. Distribution of inland fishes in northwestern Mexico: Topminnow (P. prolifica) ...... 77
16. Distribution of inland fishes in northwestern Mexico: all-female topminnows (P. monacha X P. occidentalis) ...... 79
17. Distribution of inland fishes in northwestern Mexico: collective distribution of nonnative fishes ...... 8 1
xi INTRODUCTION
The Republic of Mexico comprises the connecting link in a broad geographic transition between Nearctic and Neotropical biotas of the Western Hemisphere
(Smith & Miller 1986). This results in large part in Mexico's remarkably diverse freshwater ichthyofauna of more than 500 species in nearly 50 families (Miller 1986). Conditions varying from water-deficient, unstable desert streams to far more predictable rivers in tropical rainforest provide more than sufficient ecological heterogeneity for a high diversity of aquatic organisms to coexist within this latitudinal gradient. Local species diversity is influenced by geology, climate, evolution, and more recently, by anthropogenic impacts.
A small but important part of this fauna occupies streams that drain through some of the hottest, most arid lands of North America in extreme northwestern Mexico, primarily in the State of Sonora (Fig. 1). Four river basins, the dos Sonoyta, Concepcion, Sonora, and Matape north to south, get their water largely from below-ground sources, then attempt to force their way across the surface through Sonoran Desert lowlands to the Gulf of
California (Sea of Cortez). None achieves that goal. Their waters are lost to evapotranspiration or percolation into coarse alluvial fill west of the mountain fronts. Only major floods reach the sea. Southward, the Rio Yaqui with a large part of its headwaters in the high Sierra Madre Occidental, succeeds in flowing through less arid terrain to enter the sea. Rio Mayo, draining a wetter more tropical area immediately south of the Rio Yaqui, also drains the Sierra Madre to enter the Gulf of California south of the desert. 2
According to recorded history and inferences from palaeoclimatic data, this situation has prevailed for millennia, resulting from progressive regional desiccation (Axelrod 1979; Betancourt et al. 1990). Freshwater fishes in the desert basins have thus survived population fragmentation, high rates of population extinction, and at best unpredictable and sporadic connectedness among habitats and populations for a long period of time (Minckley et al.
1986). With recent intervention of technological humans, such factors have intensified. Water resources are being developed, and due to historical events in both the United States and Mexico (Deacon & Minckley 1991), much of this fauna is now or soon will be imperiled.
The present paper delineates and analyzes the freshwater ichthyofauna of northwestern Mexico relative to geologic and ecologic history, with emphasis on latitudinal, altitudinal, and interspecific relations of species' distributions.
Since technological development is only commencing, it also provides a baseline for study of future changes in aquatic resources that may allow more satisfactory interpretations than have been possible in arid lands of the adjacent United States. STUDY AREA
Geologic History
The study region is geologically and hydrographically complex (Ferrusquia-V.
1993, Minckley et al. 1986). Sporadic and sometimes isolated geologic forces have been responsible for establishing the hydrographic systems in evidence today (Maldonado-K. 1964). Extensive orogenic and volcanic activities in
Tertiary times produced impressive highlands, dominated by isolated or series of mountains (sierras or ranges) sculpted into rugged relief by erosion. The
Sierra Madre Occidental, a linear, northwest-elongated, plateau-like pile of thick volcanic rocks (Sedlock et al. 1993), comprises the region's highest mountain range, contributing directly or indirectly to headwaters of all major drainages.
During Cretaceous (136-65 million years ago [mya]), northwestern Mexico was beneath the sea. Rocks deposited at that time indicate a relatively stable marine environment extending southward from southern Colorado (Smith &
Miller 1986). End of the Cretaceous was marked by onset of widespread and intensive tectonism, termed the Laramide Orogeny, that initiated an epoch of mountain building that created the Cordilleran Plateau. Mountain building continued into Eocene (53-38 mya). Oligocene (38-25 mya) was characterized by final withdrawal of coastal seas and development of freshwater habitats, including development of some drainages that now persist in parts of the
Western Cordillera of northwestern Mexico.
Miocene (25-5 mya) was marked by Basin-and-Range orogenics, which disrupted and obscured several northeast-southwest drainages that had formed 4 in southeastern Arizona and adjacent Mexico (Melton 1960). For the most part, rivers maintained their courses by filling consecutive intermontane basins with sediment, incising intervening barriers, and thereby coming to occupy the series of developing northeast-southwest-trending structural troughs that now characterize Basin-and-Range topography of the region.
Uplift in Late Miocene (15-5 mya) severed southeasterly connections of the upper Gila River, which ultimately succeeded by Pliocene times (5-2 mya) in connecting westward to the lower Colorado River. Regional uplift also was responsible for turning some of the drainages of northern Mexico southward
(Hendrickson et al. 1981), and may have been involved (along with headwater stream captures) in apparent faunal transfers between the now-disrupted Rio
Grande (Rio Bravo del Norte) basin and Rio Yaqui in Pleistocene (beginning about 2 mya).
Physiography
Collectively, the six river watersheds I studied comprise nearly 1.35 X 105 km2 , including some of the most rugged and inaccessible landscape in North
America. On the east is an elevated plateau, the "Mesa del Norte," punctuated by isolated escarpments, mountain ranges, and mountains as it grades westward into the Sierra Madre Occidental. Major rivers pass across the Mesa del Norte at gentle gradients, then plunge through deep canyons or barranc as for which the region is famous, through the Sierra Madre axis. West of these mountains the streams traverse variably broad alluvial slopes and narrower coastal lowlands toward the Gulf of California (Hendrickson et al. 1981).
Broadly coalescing alluvial fans (bajadas) and gently-sloping alluvial plains are particularly common in northwestern parts of this area (Brown 1994). 5
Vegetation
Transitions among terrestrial vegetative communities are the rule (Brown
1994). At low elevations west of the Sierra Madre, trends are from Sonoran
Desertshrub in the north grading through Sinaloan Thornshrub to Sinaloan
Deciduous Forest in the south. Heterogeneity of vegetative cover relative to elevation is even more dramatic, with desertshrub giving way as one ascends in elevation to grassland, shrubland, woodland, then dense conifer forest on the highest peaks. Isolated mountain peaks and ranges in northern parts of the region and on the Mesa del Norte often stand island-like (Gehlbach 1981), surrounded by a virtual "sea" of arid-adapted plant communities.
Aquatic Habitats
Since aquatic habitats are significantly influenced by terrestrial plant communities in which they occur (Minckley & Brown 1994), aquatic diversity in this region is high. Some general patterns in habitat characteristics are definable (Hendrickson et al. 1981; Minckley et al. 1986). Montane creeks tend to be clear, cool, turbulent, and perennial enough to support permanent aquatic biotas. Streams, medium-sized rivers, springs, and cienegas at intermediate elevations are even more reliable if their watersheds are large enough and collectively include examples of most aquatic habitat types available in North America. (Cienegas are stream-associated riparian marshlands, characterized by low, emergent aquatic plants and hydric-adapted trees such as willows [Hendrickson & Minckley 1985]). Unpredictability of water supplies increases dramatically at lower elevations and, as noted above, the lowermost parts of creeks and rivers are often too unreliable to support other than transient populations, except where impervious strata force 6 groundwater to the surface to form local, permanent reaches where fishes persist year-around.
Patterns of discharge of the more northern river basins are bimodal, with flashy, violent floods from local monsoonal rainfall in summer and larger, more sustained flooding in winter from more general rains and snowmelt on the highest mountains. Drought prevails in spring and autumn (Tamayo 8z
West 1964). The hydrograph of Rio Mayo differs in tending to have more of a single, late-winter period of high discharge, commensurate with the pattern of periodicity in annual precipitation farther south. Papers in Brown (1994) detail the climatic data from which these generalities were derived.
Rio Sonoyta, the most northern river system in my study area, is a former tributary to the Colorado River Delta that drains about 3400 km2 of extremely arid terrain along the boundary between Arizona and northwestern Sonora.
Average annual discharge is about 1.9 X 106 m3 (Tamayo & West 1964). Rio
Sonoyta was diverted south by the Pinacate Lava Flow in Pleistocene (Hubbs &
Miller 1948). Historically, the area was desertshrub and desert grassland, through which Rio Sonoyta flowed in a cienega-lined swale (Bryan 1925).
Floods in 1891 entrenched the stream and lowered the water table. Grasses were soon replaced by desert shrubs, cienegas dried, and fishes must have declined coincident with reduced surface water (Gehlbach 1981). Permanent fish habitats consist today of intermittent, slow-moving, shallow segments flowing through an incised, sand-walled arroyo (McMahon & Miller 1985).
Next south is Rio de la Concepcion, originating in low foothills of the
Sierra Madre Occidental west of the twin cities of Nogales, Arizona and Sonora.
Surface flow of this stream disappears soon after passing through Valle de
Magdalena. The system has an estimated average annual discharge of 1.51 X 7
106 m3 (Tamayo & West 1964), mostly impounded for use as irrigation and
domestic water supplies (Hendrickson et al. 1990).
Rio Sonora and its major tributaries also rise in low foothills of the Sierra
Madre Occidental near the Arizona-Sonora border, flowing south and then
southwest across the Plains of Sonora toward the Gulf of California (Fig. 1).
The average annual discharge is 1.71 X 106 m3 (Tamayo & West 1964), most of
which is also captured for human use.
Rio Matape is next, sandwiched between the lower dos Sonora and Yaqui.
Its relatively small watershed is comparable in size to that of the Rio Sonoyta
(Fig. 1), with upstream origins presumably in springs or underflow from the
Plains of Sonora. I was unable to find data on hydrology of the system, which too is dammed and diverted for human purposes, at least locally.
The master stream of the region is the Rio Yaqui, extending from nearly
0 27° to 33° N latitude and 107° to 110 W longitude. Its watershed includes about
70,000 km2 in Mexico and 1500 km2 in the United States. The basin was integrated into a single hydrologic unit over geologic time from two or more discrete sub-basins (DeMarais 1991). A system in the northern Sierra Madre
Occidental now comprises the Rio de Bavispe, which, when connected with the
Rio Papigochic that drains even higher-elevation parts of the Sierra in the
State of Chihuahua, forms the lower mainstem. A northwestern complex, dos
Moctezuma-Nacozari and other lesser tributaries, make up about 20% of the total watershed but contributes only a little water from that desert side of the system. Annual discharge of the Rio Yaqui near its mouth is 27.9 X 108 m3
(Tamayo & West 1964; Hendrickson et al. 1981), more than 75% of the average annual yield of all other streams in the study region. The abundant runoff is 8
reflected in substantial development of irrigated agriculture on the delta as
well as concentrations of energy and water-demanding human communities
elsewhere in the basin, which has prompted construction of storage and power-generating impoundments upstream in the Rio Yaqui and the adjacent
Rio Mayo as well.
The Rio Mayo system drains about 12,000 km2 of tropical-subtropical mountainous terrain immediately south of the Rio Yaqui basin. The watershed enjoys far more rainfall than any basin to the north (Minckley & Brown
1994), producing far more runoff per unit area of watershed (average annual discharge 9.37 X 108 m3; Tamayo & West 1964). Its south-flowing tributaries interdigitate with those of the Rio Papigochic in their northern headwaters
(Fig. 1). MATERIALS AND METHODS
Fish records used herein are from diverse sources, so it was important to
assess their relative quality, integrity, and information content. Raw data
were separated into three "levels," as follows: I) documented by specimens
permanently deposited in museums; II) published in peer-reviewed literature
that might or might not be based on existing specimens but are nonetheless
verified against the knowledge of peer review; and III) identifications in
agency reports and elsewhere, supported neither by preserved specimens nor
critical peer evaluation. Considerable knowledge of distributions, collecting
methods, and other aspects of fish ecology are required to evaluate the validity
of Level III records. However, unlike in the United States (Minckley et al.
1991), "gray literature" has yet to proliferate in Mexico, so only a few Level III
records were available
These three separate levels of data were plotted as points (i.e., spatial data)
on topographic maps. All available tabular information for each point was
further stored as "attributes" in standardized data fields, as follows: unique
record number; data level (I, II, or III); genus, species, subspecies (if
applicable); country, state, county (or other political subdivision, if
applicable); river system, basin, drainage; date of collection; number of
specimens; collector(s); museum abbreviation (following Leviton et al. 1985)
and catalog number; citation(s), 7-minute and/or 15-minute U.S. Geological
Survey quadrangles (or Mexican equivalents); collection localities; and
comments. Collection localities were digitized manually from topographic
maps through use of a Calcomp 91.5- X 70-cm DB-III digitizing table. 1 0
Basemaps for digitizing raw data were obtained through the Arizona State
University Noble Science Library from the Secretaria de Programaci6n y
Presupuesto, Coordinacion General del Sistema Nacional de Informaci6n,
Mexico, D.F., Mexico. Included were a total of 16 quadrangles (1: 250,000) entitled Puerto Peiiasco (H12-1), Nogales (H12-2), Agua Prieta (H12-3), Caborca
(H12-4), Canaiiea (H12-5), Nacozari (H12-6), Hermosillo (H12-8), Madera (H12-
9), Sierra Libre (H12-11), Tecoripa (H12-12), Buenaventura (H13-7), Chihuahua
(H13-10), San Juanito (G13-1), Guaymas (G12-2), Ciudad Obregon (G12-3), and
Huatabampo (G12-6).
ARC/INFO software (ESRI, 380 New York, Redlands, California) was used for data entry and compilation on a Hewlett-Packard Unix Workstation. The basemap for Figure 1 and subsequent data presentations was modified from a digital basemap of the World, scale 1: 1 million, also made available from ESRI.
Basin sizes (km2 ) for comparisons with species richness are from Tamayo &
West (1964), U.S. Geological Survey (1974), or measured from appropriate topographic maps.
Specimens housed at Arizona State University Department of Zoology
(ASU), Tempe, Arizona, and the University of Michigan Museum of Zoology
(UMMZ), Ann Arbor, Michigan, were specifically checked if questionable locality data or species' identification were not otherwise resolvable. Those from other museums were not, and when questionable were excluded.
Included were collections of the Academy of Natural Sciences of Philadelphia,
Philadelphia, Pennsylvania; American Museum of Natural History, New York,
New York; Field Museum of Natural History, Chicago, Illinois; U.S. National
Museum of Natural History, Washington, D.C.; and Scripps Institution of 11
Oceanography, LaJolla, California. Catalog numbers and other data for all
collections used herein are available from ASU.
Locality data for Level II and III, along with biogeographic, ecologic, and
other information not repeated here or cited elsewhere in text may be found
in Baird and Girard (1854), Girard (1856, 1859), Abbott (1861), Rutter (1896),
Meek (1902, 1903, 1904), Hubbs and Miller (1941), Miller and Simon (1943),
Miller (1943a-b, 1960, 1983), Miller and Schultz (1959), Branson et al. (1960),
Smith (1966), Moore et al. (1970), Minckley (1973, 1985), McNatt (1974), SiIvey
(1975), Burr (1976), Schoenherr (1977, 1988) Vrijenhoek et al. (1977), Minckley
et al. (1979), Hendrickson et al. (1981), Rinne and Belfit (1982), Hendrickson
(1983, 1986), Meffe et al. (1983), U.S. Fish and Wildlife Service (1984, 1989,
1992b), Contreras-B. and Escalante-C. (1984), Williams et al. (1985), Van
Devender et al. (1985), Burton (1986), Siebert and Minckley (1986), Galat and
Gerhardt (1987), Galat and Robertson (1988, 1992), Hendrickson and Varela-R.
(1989), Hendrickson and Juarez-Romero (1990), Minckley and Vives (1990),
DeMarais (1991, 1992), Juarez-R. et al. (1991), Liebfried (1991), Varela-R. et al.
(1992), and DeMarais and Minckley (1992, 1993). RESULTS AND DISCUSSION
Distribution of Sampling Sites
On a spatial basis (Fig. 2), sampling sites in the study area are concentrated in the United States and along major transportation routes in Mexico. Large gaps in sampling intensity (as measured by gross number of collections, with disregard for times at which they were made) exist in central parts of both the
Mayo and Yaqui systems where rivers pass through the rugged and the even- now inaccessible barrancas. On the other hand, an absence of sampling sites on lower reaches of the more northern rivers almost certainly reflects the general lack of perennial water at low elevations. Surprising and unexplained is a similarly-general absence of collecting sites on deltas of the dos Mayo and
Yaqui, now largely developed for agriculture and criss-crossed with myriad canals and other artificial waterways. The fish fauna of that vast area was highly altered before any detailed sampling was accomplished (Juarez-R. et al.
1991).
Temporal relations of collecting sites (Fig. 3a-c) include little sampling at all before the 1930's, and then only associated with the early railroad, mostly in the Rio Yaqui along the extreme headwaters east of the Sierra Madre
Occidental. To the west, early sampling was mostly concentrated downslope from the Sierra, with some incursions to the interior along major travel routes. Between 1931 and 1960, collections were added at numerous localities between these east and west access corridors, but it was not until later (mostly in 1978; Fig. 3d) that extensive collections were made within the rugged Sierra itself. 13
Accounts of Native Species
Eight families containing 13 genera, and 20 species comprise the native freshwater ichthyofauna of the study region. When all informally recognized and "hybrid" taxa are included (see later), a total of 25 entities may be tallied.
Common and scientific names of fishes discussed in text are in Table 1, and distributions for each are depicted on Maps 1-17. In the following accounts, elevational limits for collection sites (meters above mean sea level) are provided in parentheses.
Salmonidae. Native trouts of the genus Oncorhynchus are recorded from northeastern Rio de Bavispe, southeastern Rio Papigochic (1390-2000 m), and uppermost Rio Mayo (1800-2100; Map 1). Other populations are known from the Rio Casas Grandes system immediately east of the Yaqui basin (Needham &
Gard 1964, Miller 1959, Contreras-B. 1978). None has been formally described.
Relationships of these stocks are with the rainbow trout (a. Dukiss) series, and most intimately perhaps to Q. g. gilae and Q. g. apache of the Gila River basin,
Arizona-New Mexico (Behnke 1992).
Clupeidae. Clupeids are represented by Dorosoma smithi (Map 1), mostly on the delta of the Rio Yaqui (50-100 m) and presumably that of the Rio Mayo (no known records exist). The species was reported in Presa Novillo (350 m) by
Minckley et al. (1979), but it was not known if that population is natural, enhanced by creation of reservoir conditions, or a result of unrecorded translocation.
Nearest relatives of this species are all are in Atlantic drainages, including 12. c epe di anu m of the Rio Grande (Rio Bravo del Norte) system, JL. anale in southeastern Mexico (Hubbs & Miller 1941), and D_ chavezi Meek in 1 4
Nicaragua (Villa 1982). To my knowledge, no phylogenetic relationships have
been proposed within this group, but there seems a general inference that a
smithi is derived from a_ cepedianum (Hendrickson et al. 1981) and thus
probably arrived through connections over northern Mexico. Although
speculative, an alternative exists that D__ smithi might have been derived from
a progenitor dispersing near sea level in a transcontinental corridor just
north of the Yucatan Peninsula. Shallow-sea deposits on the Isthmus of
Tehuantepec date from Late Miocene (Ferrusquia-V. 1993) and more recent
saltwater incursions are probable in this tectonically active and complex area.
Other taxa that could conceivably be involved in such a pattern of dispersal
include ictalurid catfishes, cichlids, and poeciliids (see below).
Cyprinidae. Cyprinid fishes are the most speciose and widely distributed
family in the study area, occupying essentially all available habitats from sea
level to the maximum elevations from which fish collections have been made.
Four species comprise a large proportion of all locality records. First,
Agosi a chrysogaster (Map 2) is shared by all river basins (90-1600 m) except
Rio Matape, from hot desert through essentially all intermediate-elevation
habitats into montane reaches, and mostly in smaller and intermediate-sized
streams and rarely in large rivers. Camp o st oma ornatum (Map 3), also
occupies all basins (380-2360 m) except dos Matape and Sonoyta. Most samples
of this species are from less than 1000 m in both mainstem rivers and
tributaries. Most collections of C.. ornatum from the Rio Mayo are between 300-
500 m, with a single, isolated record at 2100 m, with the hiatus most likely
reflecting a general lack of collecting between lower and higher elevation habitats in that river basin (compare Fig. 2 and Map 3). Collections of Codoma 15 ornata (Map 4) are most common above 1500 m in dos Papigochic and Bavispe, although ranging downslope to 430 m in southeastern parts of the former
(430-2135). Last of the four is Cyprinella formosa (Map 5), represented in the
Rio Yaqui basin by two subspecies: 1) Cyprinella f. mearnsi in Rio de Bavispe,
Moctezuma- Nacozari, and lowermost Yaqui (250-2360); and 2) an unnamed form in the Rio Papigochic (1800-2130 m) (Hendrickson et al. 1981). One record (UMMZ 161457) from the Rio Sonora at Bacoachi (900 m) most likely results from erroneous locality data. It was not plotted in Map 5, nor is it considered further.
All the last four minnows are most likely derived, directly or indirectly, from the Rio Grande (Rio Bravo de Norte), and related in turn to the vast
Mississippi River fauna. Nearest relatives of Campostoma ornatum and
Cyprinella formosa are canomalum and C_. lutrensis, respectively, widely distributed in Atlantic drainages of eastern North America (Burr 1976, Mayden
1989). Relationships of Codoma are less obvious, but may either be with
Cyprinella or Pimephales (Miller 1976; Hendrickson et al. 1981; Mayden 1989), again of the Rio Grande-Mississippi fauna. Agosia chrysogaster is more difficult to place in phylogenetic and biogeographic perspective. On the basis of genetic data, Alana Tibbits and Thomas Dowling (Arizona State University; pers. comm.) consider it a derivative of an "eastern minnows" group, and speculate it to represent (as may Codoma) an early lineage isolated on the
Mexican Plateau.
Species of the genus Gila are collectively as widely distributed as the other minnows just discussed, although most have more limited ranges. Gila ditaenia is endemic to Rio de la Concepcion (290-1900 m), where it occupies essentially all the watershed (Map 6; Miller 1945, U.S. Fish & Wildlife Service 1992a, 1 6
Hendrickson & Juarez-Romero 1990). Gila eremica (Map 7) is more widespread,
occurring in the dos de la Concepcion (1000 m), Sonora (200-1600 m), Matape
(250-500 m), and Yaqui (250-500 m) (DeMarais 1991). It is known from only
one locality in Rio de la Concepcion (Cienega La Atascosa; DeMarais & Minckley
1992), where hybridizing with an undescribed species of Gila and also perhaps
with A. ditaenia. The undescribed species (just mentioned; Map 8) and a.
purpurea (Map 6) both have highly restricted geographic ranges, the former
at a single known locale and the latter in a limited segment of the extreme
northern Rio de Bavispe drainage (1100 m) in Mexico and the United States.
Gila purpurea has been successfully translocated to a number of localities up
to 1700 m elevation (Map 6) as part of efforts to maintain its populations
(DeMarais & Minckley 1992, U.S. Fish & Wildlife Service 1995).
Gila minacae (Map 8) is exceptional among its congeners in a relatively
wide geographic distribution in moderate to large creeks and rivers over an
impressive altitudinal range (90-2300 m), in both the dos Yaqui and Mayo
basins. The name A. rninacae is applied instead of A. robusta (the two were synonymized by Miller 1976) as a result of genetic data provided by Dowling
(Arizona State University; pers. comm.) which indicates marked differences
between the Rio Yaqui and more northern populations of the Colorado River
basin. Upper parts of the Rio Yaqui and Rio Mayo support yet another
undescribed species of Gila (1100-2500 m; Map 6), formerly confused with A. pulchra (Girard) of the adjacent Rio Conchos watershed (Minckley et al. 1986).
Relationships of the species of Gila are complex at best. Gila minacae and
A. ditaenia are part of a "A. robusta group" of subgenus Gila, occupying rivers tributary to the Gulf of California from the Colorado River system in the north 17 to Rio Culiacan in the south (Smith et al. 1979; Hendrickson 1983). They are generally thought to have originated in the Colorado River basin or its precursor (Miller 1976). Gila ditaenia was assigned to subgenus Temeculina
(Miller 1945) until realigned with the subgenus Gila as a result of genetic studies by DeMarais (1992). Gila sp. (upper dos Yaqui/Mayo) seems most closely allied with a Gila pandora-a. nigrescens lineage of subgenus Gila that occupies the Rio Grande and Lago de Guzman basins north and east of my study area and has been recorded from farther south and east as well (Smith & Miller
1986). Gila purpurea, a. eremica, and Gila sp. (Rio de la Concepcion) are part of
Miller's (1945) subgenus Temeculina, ranging from northwestern Mexico northward along the west coast of North America well into California.
Catostomidae. Five native catostomids occur in the region. Catostomus bernardini is widespread geographically and altitudinally (90-2100 m) throughout much of Rio Yaqui as well as the Rio Mayo basin (Map 9). I consider a single record at about 900 m in Rio Sonora (UMMZ 161453) in error, and it is neither mapped nor treated further. The second-most widespread species is c.... wigginsi of the Rio Sonora (600-1570 m), where it occupies the uppermost reaches and mainstem as well (Map 10). A single record of C. wigginsi from Rio Moctezuma (UMMZ 161467) also is considered in error (Van
Devender et al. 1985).
The other three catostomid species are more upland in distribution.
Catostomus cahita (Map 10) occurs in both the Rio Mayo (300-2100 m) and southeastern Rio Yaqui basins (1280-2135), in both headwater and mainstem situations where broadly sympatric with C. bernardini. Catostomus leopoldi
(Map 10) is in the uppermost Rio de Bavispe (higher than 1900 m) and is 1 8
known from upper tributaries of the adjacent Rio Casas Grandes (Lago de
Guzman drainage; Fig. 1). Catostomus leopoldi is syntopic with Pantosteus
plebeius (higher than 2000 m) in the single stream where the latter has been collected in the Rio Yaqui basin (Map 12).
Catostomids are clearly northern in their broader relationships, although
C.. bernardini has apparent affinities to a series of local populations (generally
referred to C. bernardini) as far south as Rio Lorenzo (Hendrickson 1983;
Minckley et al. 1986), eastward with C. conchos of the Rio Conchos basin (Smith
& Miller 1986), and north to C. insignis (Miller 1976; Hendrickson 1983; Smith &
Miller 1986). Catostomus cahita and C. leopoldi have no apparent relatives other than one another, unless one considers some level of relatedness mentioned by Siebert and Minckley (1986) to other small, higher altitude- latitude suckers in northern California. Catostomus wigginsi is most likely a western representative of the C. bernardini complex. Pantosteus plebeius in the upper Rio Yaqui is almost certainly derived by stream capture or other headwater exchange from the adjacent Rio Casas Grandes basin. That species is widely distributed as a series of local forms (Ferris et al. 1982) from the southern Rocky Mountains of the United States, south to the upper Rio
Mezquital of western Mexico (Smith 1966).
Ictaluridae. The single native ictalurid known from the study area,
Ictalurus pricei, is distributed essentially throughout the Rio Yaqui basin (Map
9), from two perhaps questionable localities in Rio Sonora basin (Chamberlain
1904, UMMZ 157258), in the Lago de Guzman drainage to the east (Smith &
Miller 1986), and represented by a related form in the Rio Mayo and southward
(Hendrickson 1983). Ictalurids are generally distributed in the Rio Grande- 19
Mississippi River region, from where this species was presumably derived
(Minckley et al. 1986), as well as in Atlantic-slope rivers as far south as the
Yucatan (Smith & Miller 1986).
Ictalurus pricei is generally considered most closely related to taxa of the
Rio Grande-Mississippi valley (Minckley et al. 1986). Another possibility, however, is its derivation from the south through some transcontinental connection across southern Mexico. As with the origin of Dorosoma 5 mithi discussed above, this will remain speculative until information becomes available on phylogenetic relations of Mexican ictalurids.
Cyprinodontidae. Two pupfishes of the genus Cyprinodon represent this family. Cyprinodon macularius occurs as one or two subspecies in the Rio
Sonoyta basin (C_. m_. eremus and possibly another undescribed form), formerly a tributary to the lowermost Colorado River (see above) where c_. na_. macularius holds forth (Miller & Fuiman 1987; U.S. Fish & Wildlife Service 1993). All collection sites for both forms (Map 12) are at less than 500 m elevation. The second pupfish species is undescribed and exceptional in occurring at high elevation (1800-2300 m); it is restricted to the upper Rio Papigochic (Map 12) and thought to be represented by another population in the Rio del Carmen drainage of the Lago de Guzman basin, Chihuahua (Echelle & Dowling 1992).
Poeciliidae. Representatives of this family of small, live-bearing fishes occur from the Rio de la Concepcion basin south through the Rio Mayo.
Included are at least one all-female form of hybrid origin called Poeciliopsis monacha X occidentalis, and one or more undescribed species. Identifications of museum samples and often literature records may be questionable or 20 equivocal. To avoid further and future confusion, specimens identified only to genus or as "Poeciliopsis sp." are excluded from maps or further discussion.
The most widespread form is Poeciliopsis occidentalis (Map 13), existing as two named and one unnamed subspecies (Vrijenhoek et al. 1985) in diverse habitats from Rio de la Concepcion southward through Rio Mayo. The northernmost form is E. a. occidentalis (90-1500 m), with a range extending northward into the Gila River basin of the United States (Miller 1959; Minckley
1973; Hendrickson et al. 1981; Minckley et al. 1986). Poeciliopsis a. 5onoriensis
(1100-1900 m) occupies Rio San Bernardino, the northernmost tributary of Rio de Bavispe, with headwaters in the United States (Minckley 1973; U.S. Fish &
Wildlife Service 1984). A third, unnamed form is distributed mostly in the lower dos Mayo and Yaqui (Vrijenhoek et al. 1985). Zones of intergradation and/or genetic interactions among these subspecies have not yet been precisely delineated (U.S. Fish & Wildlife Service 1984).
Localities in the study area for P. monacha (60-1650 m) and E. prolifica
(50-700 m) tend to be at lower elevation and more southern in range than those for E. occidentalis, respectively ranging from the lower Rio de la
Concepcion (Map 14) and lower Yaqui (Map 15) southward. The hybrid form,
E. monacha X occidentalis (90-1300 m), holds forth from the Rio de la
Concepcion south to Rio Mayo basin (Map 16).
The genus Poeciliopsis is tropical in distribution, reaching the northern limit of its range with E. a. occidentalis of the Gila River basin of southern
Arizona and New Mexico (Rosen & Bailey 1963). It tends to be salt tolerant, is often estuarine in distribution, and therefore most likely entered the area through dispersal in coastal waters. However, movements among drainages 21 north of the Rio Yaqui could have included headwater transfers across the
Plains of Sonora or other lowlands during wetter periods.
Cichlidae. A single native species of cichlid, Cichlasoma beani (90-600 m) is known from lowland streams of dos Yaqui and Mayo (Map 12). As with poeciliids, cichlid fishes tend to be salt tolerant, so dispersal into the area through estuarine connections from the south seems a likely origin for the group. Interrelations of New World cichlids are yet to be determined, so only a general, southern affinity can be defined at present. Presence of c_. beani thus cannot be used to explore the hypothesis of dispersal over a possible, southern transcontinental route as proposed above for Dorosoma smithi and lc talurus pricei.
Nonnative Fishes
Only a few nonnative fishes (Table 2) are indicated by available collections as abundant or widely distributed in the study area. A total of 8 families and 19 species is nonetheless represented, most of which almost certainly originated through intentional introductions for sport fisheries, as forage or through releases of bait used for sportfishing, or as potential human food.
Apparent tendencies for clustering of collection sites for nonnative species near the United States-Mexican Boundary, near major reservoirs, and coastal (compare Fig. 2 and Map 17), may respectively be explained by: 1) introductions of species in the United States and their subsequent dispersal into Mexico; 2) stockings for development of sport and food fisheries in reservoirs; and 3) as a result of human concentration, both of populations and through travel along major highways, in coastal areas. 22
Species Richness
A number of adjacent desert river systems, the Gila and Mimbres basins of the
United States and del Carmen, Santa Maria, and Casas Grandes (Lago de Guzman basin) of Mexico, were added to those of the study area to increase sample size for an assessment of regional species richness (number of taxa, for present purposes) and watershed (basin) size. As demonstrated in other studies (Smith
1981, Smith & Miller 1986), species richness for native taxa and basin size are strongly and positively related (r = 0.60, df = 9, p = .005; Fig. 4a). That measure, in turn, is a positive correlate of other measures such as stream size (width, length, depth), discharge, and/or habitat complexity (data not presented here). Thus, among systems included, the largest Gila and Yaqui systems support the greatest numbers of fish taxa (richness) and the smallest Sonoyta,
Matape, and Mimbres the fewest.
When the largest streams, Rio Yaqui and Gila River, are removed from the analysis, strength of the relationship between species richness and basin size decreases dramatically and is not significant (r = 0.02, df = 7, p = 0.756; Fig. 4b).
I attribute this to basin-size-related components in habitat heterogeneity.
Small desert river basins may either not be large enough to provide adequate quality or quantity of things required to maintain a diverse ichthyofauna, or, alternatively, they may have become too small to have maintained required quality and quantity during severe climatic cycles in the past, during which certain taxa were lost, and now be too isolated for extirpated faunal components to reinvade. SUMMARY AND CONCLUSIONS
Six river basins in extreme northwestern Mexico, draining from highlands of
the Mesa del Norte and Sierra Madre Occidental westward through Sonoran
Desert to enter the Gulf of California, support a total of 8 families including 13
genera, and 20 species of freshwater fishes. When informally recognized (yet
undescribed forms) and "hybrid" taxa are included, a total of 25 entities is
present.
Relationships of this regional ichthyofauna within the broader pattern of
transition between Nearctic-Neotropical distributions of freshwater fishes are
clearly biased toward the Nearctic biota, yet comprise mostly a subset of
adjacent, larger faunas characterized by regional endemics (which I define as
restricted to the region but not necessarily to a single river basin; marked
below with an asterisk). A minimum of seven taxa, Agosia chrysogaster,
Campostoma ornatum, *Cyprinella formosa, Codoma ornata, *Gila sp. (upper
rios Papigochic/Mayo), Pantosteus plebeius, and *Cyprinodon sp. (upper Rio
Papigochic) have their closest relatives north and east in the Rio Grande (Rio
Bravo del Norte) and associated watersheds on and near the northern Mexican
Plateau. *Catostomus cahita and *C. leopoldi, of undetermined affinities, are nonetheless Nearctic in their broad relationships.
Another group of nine species, including *Oncorhynchus sp., *Wia purpurea, *a. eremica, *a. ditaenia, *Gila sp. (Rio de la Concepci6n), a. minacae, Catostomus bernardini, *C. wigginsi, and *Cyprinodon macularius
(one or two subspecies), have strong affinities to the north and west (Colorado
River and California coastal drainages). I speculate that two additional species,
Dorosoma smithi and Ictalurus pricei, might have entered the study area from 24 the south, but both are ultimately of Rio Grande-Mississippi River derivation.
Thus, a total of 20 species, 83% of the total known ichthyofauna, is Nearctic in relationships. Only four species (17%) clearly have Neotropical affinities,
*Poeciliopsis occidentalis (three subspecies), *P.. monacha, *E.. prolifica. and
Cichlasoma beani.
Species-level endemism is regional (as described above) rather than characterizing single river systems. A total of 13 of 24 species (54%) is essentially restricted to the study region, although often occurring in two or more adjacent watersheds. Single-basin endemics include only Gila purpurea
(uppermost Rio de Bavispe), Q.,_ ditaenia. and Gila sp. (Rfo de la Concepcion), and
Cato stomus wigginsi (Rio Sonora), collectively comprising 21% of the regional fauna.
Ichthyofaunal mixing among watersheds has presumably been enhanced, among other factors, by: 1) regional availability of stream habitat to potential dispersants over a long period of geologic time; 2) interdigitation and intimate contact among headwaters in high, relatively well-watered mountains; and 3) relatively low latitudes for temperate fishes, which allows them to penetrate far into headwaters from which they are excluded just a few degrees north by cold water temperatures (Hendrickson et al. 1981).
In part as a result of the features just listed, within-region distributions seem more a function of present-day ecology than geologic history. Broader biogeographic relations clearly relate to past connections and exchanges of parts of watersheds (Minckley et al. 1986), but from the basin-by-basin view, the region is small and similar enough, at least in patterns of heterogeneity, that the mostly-generalist fishes that persist enjoy comparatively wide and 25 continuous intraregional distributions. Relationships of measures of basin size and diversity to species richness (as numbers of species per basin) are positive but weak, reflecting constraints of the harsh, arid-land environment on aquatic systems.
Nonnative species, clearly a major problem in conservation of native fishes in the adjacent United States (Minckley & Deacon 1991), have begun their spread from introduction sites to occupy parts of the region. Assuming patterns documented here are consistent, as development proceeds in northwestern Mexico with greater regulation of streams and creation of reservoirs, lentic-adapted, nonnative species will become increasingly prevalent at the expense of the native biota. The distributional data presented here provide a means for identifying areas of concentration of native species, thereby defining places that may be emphasized for conservation purposes. I strongly recommend such a program begin promptly, since development in northwestern Mexico will proceed far faster than it did in adjacent United
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, 32
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TABLES 35
Table 1. Scientific and English and Spanish common names of native freshwater fishes of northwestern Mexico mentioned in text.
Scientific Name English Spanish
Oncorhynchus sp. Yaqui trout trucha de Yaqui
Dorosoma5mithi Hubbs & Miller Pacific shad sardinita del Pacifico
Agosiachrysogaster Girard longfin dace charalito aleta larga
Campostoma ornatum Girard Mexican stoneroller rodapiedras mexicano
Codoma ornate (Girard) ornate minnow sardinita ornata
Cyprinella formosa (Girard) Beautiful shiner sardinita hermosa
Gila ditaenia Miller Sonora chub charalito sonorense
• eremica DeMarais desert chub charalito del desierto
• purpure (Girard) Yaqui chub charalito Yaqui
• minacae Meek Yaqui roundtail charalito aleta redonda
Gila sp. (Concepcion) charalito
Gila sp. (Yaqui/Mayo) charalito
Catostomus bernardini Girard Yaqui sucker matalote Yaqui
C cahita Siebert & Minckley Cahita sucker matalote Cahita
C leopoldi Siebert & Minckley Leopold sucker matalote de Bavispe
C wigginsi Herre & Brock Opata sucker matalote Opata 36
Table 1. Continued.
Scientific Name English Spanish
Pantosteus plebeius Rio Grande Mountain- matalote del Rio (Baird & Girard) sucker Bravo
Ictaluruspricei (Rutter) Yaqui catfish bagre del Yaqui
Poeciliopsis occidentalis (Baird & Girard) Sonora topminnow charalito sonorense
E. monacha Miller charalito
P. monacha-occidentalis charalito
E. prolific a Miller charalito
Cyprinodon macularius Baird & Girard Desert pupfish cachorrito del desierto
Cyprinodon sp. whitefin pupfish cachorrito aleta blanca
Cichlasoma b e an i (Jordan) Sinaloan cichlid mojarra sinaloense 37
Table 2. Nonnative fishes recorded from rivers of northwestern Mexico. Species marked with an asterisk (*) are known to have been planted one or more times in the United States in drainages of the rios Yaqui, de la Concepcion, or Sonoyta, which does not imply an absence of additional introductions in Mexico.
Species Probable intent or circumstances of introduction Sport Bait/forage Food Accid. Otheri-/
*Oncorhynchusmykiss (Walbaum) X X
*Salvelinus fontinalis (Mitchill) X
Cyprinus carpio Linnaeus X
*Carassius auratus (Linnaeus) X
*Pimephales promelas Rafinesque X
Cyprinella lutrensis (Baird & Girard) X
Carpiodes carpio (Rafinesque)
Ictalurus furcatus (Lesueur) X
punctatus (Rafinesque) X
Pylodictis olivaris (Rafinesque) X
*Ameiurus melas Rafinesque X
*Gambusia affinis Baird & Girard X 38
Table 2. Continued.
Species Probable intent or circumstances of introduction Sport Bait/forage Food Accid. OtherU
*L. macrochirus Rafinesque
*Lepomis cyanellus Rafinesque
L. megalotis (Rafinesque) ? ?
L. microlophus (Gunther) X ?
Pomoxis annularis Rafinesque X
*P. nigromaculatus (Lesueur) X
Tilapia, Sarotherodon, Oreochromis X X ?
*Micropterus salmoides (Lacepede) X
1/ "Other" must be considered a possibility for all species, since contaminants in shipments of sport and forage/bait fishes often are common, and almost any species, especially those small in adult body size or as young individuals, here might well be so translocated (therefore classed as an "accident"). Many such "accidents" might have resulted from contamination. Public health authorities in the United States almost certainly stocked western mosquitofish (Q. affinis) in Cochise County, Arizona for mosquito control, from where they had access to the upper Rio Yaqui. African cichlids (Magi& Sarotherodon, Oreochromis) have been generally distributed in Mexico to augment food supply, but in some instances are translocated as a means of biological control of aquatic plants. APPENDIX B
FIGURES 40
Figure L. Map 9.11.1IT study area and environs. showing major river basins. 41
112 108
100 0 100 Kilometers 42
Fi gure 2.,_ Fish collection sites upon which this report a based. 1854-1994, 43
100 0 Kilometers 44
Figure 1, Fish collection sites LA the study area. southwestern United States an d
northwestern Mexico. from: AL 1854 - 1930: EL. 1931 - 1960: C.). 1961 - present-,
AN AL 1978.
46
Figure 4_,. Regressions of river basin size and numbers 2F. fish jaxa for: A
river basins ja5outhwestern United States and northwestern Mexico: and B1
1JIE.5AME area. but with the two largest river basins excluded. 47 A.
30 Y= 4.9177 + 65.299X FIA2 = 0.599
20
10
O 00 0.1 0.2 0.3
B. SPECIES NUMBER Y = 4.8663 + 48.082X RA2 = 0.032
0.01 0.02 0.03 0.04 0.05
BASIN SIZE APPENDIX C
MAPS 49
Map I. Distribution 12f inland fishes innorthwestern Mexico: squares. trout(s1 LOncorhynchus sp.) and iriangles. Pacific shad LiDorosoma smithil. 50
112 108
100 0 Kilometers 51
Map L. Distribution s2ljn1and fishes innorthwestern Mexico: Jongfin dace fAgosia chrysogasterl. 112 108
100 0 Kilometers 53
Map 1. Distribution afjnland fishes in.porthwestern Mexico: Mexican
stoneroller LCampostoma ornatumL 54
112 108
100 0 Kilometers 55
Map zi, Distribution PL. jnland fishes inporthwestern Mexico: ornate ininnow LCodoma ornataL 56
112 108
100 0 Kilometers 57
Map Distribution D.finland fishes hiporthwestern Mexico: beautiful shiner
LCyprinella formosaL 58
112 108
100 0 Kilometers 59
Map Di stri buti on of inland fishes innorthwestern Mexico: squares,
Sonoran chub £Gila ditaeniah dots. undescribed chub LGila sp.) of upper Rio
Yaqui: and triangles. Yaqui chub LG. purpureaL 60
112 108
100 0 Kilometers 61
Map 1. Distribution at inland fishes iaporthwestern Mexico: desert chub
LGILA EREMICAL 62
112 108
100 0 Kilometers 63
Map 8, Distribution of inland fishes in northwestern Mexico: squares. Yaqui
roundtail chub (Gila minacae) and triangles. undescribed chub (Gila 5p.) of Rio
Concepcion. 64
112 108
112 108
100 0 Kilometers 65
Map 2,_ Distribution sAjnland fishes iaporthwestern Mexico: Yaqui sucker
LCatostomus bernardiniL 66
112 108
100 0 Kilometers 67
Map 10. Distribution 2f inland fishes iuriorthwestern Mexico: dots. Opata
sucker LCatostomus wigginsilz squares. Cahita sucker LC. cahitali And triangles,
Leopold 5ucker LC. leopoldiL 68
112 108
100 0 Kilometers 69
Map 11. Distribution atinland fishes innorthwestern Mexico: Yaqui catfish
Octalurus priceiL 70
112 )08
100 0 Kilometers 71
Map 12,_ Distribution slf inland fishes ja northwestern Mexico: dots. Rio
Grande mountain sucker gantosteus plebeiush. triangles. desert pupfish
LCyprinodon maculariush squares. undescribed pupfish f_Cyprinodon sp.): And
diamonds. Sinaloan cichlid LCichlasoma beaniL 72
112 108
100 0 Kilometers 73
Map 13. Distribution plinland fishes japorthwestern Mexico: onoran
topmin now goeciliopsis occidentalisL 74
112 108
100 0 Kilometers 75
Map 14. Distribution plinland fishes in_ northwestern Mexico: topminnow LP.
monachaL 76
27
112 108
100 0 Kilometers 77
Map 15. Distribution oljnland fishes janorthwestern Mexico: topminnow LP.
prolifical, 78
112 108
100 0 Kilometers 79
Map 16. Distribution oljnland fishes in. northwestern Mexico: all-female
topminnow LP. monacha X P. occidentalis), 80
112 108
100 0 Kilometers 81
Map 17. Distribution plinland fishes in porthwestern Mexico: collective
distribution sLf.ponnative fishes,
82
112 108 100 0 Kilometers s