Great Basin Naturalist Memoirs

Volume 2 Intermountain Biogeography: A Symposium Article 6

3-1-1978 The flora of Great Basin mountain ranges: diversity, sources, and dispersal ecology K. T. Harper Department of Botany and Range Science, Brigham Young University, Provo, 84602

D. Carl Freeman Department of Botany and Range Science, Brigham Young University, Provo, Utah 84602

W. Kent Ostler Department of Botany and Range Science, Brigham Young University, Provo, Utah 84602

Lionel G. Klikoff Department of Biology, Allegheny College, Meadville, Pennsylvania 16335

Follow this and additional works at: https://scholarsarchive.byu.edu/gbnm

Recommended Citation Harper, K. T.; Freeman, D. Carl; Ostler, W. Kent; and Klikoff, Lionel G. (1978) "The flora of Great Basin mountain ranges: diversity, sources, and dispersal ecology," Great Basin Naturalist Memoirs: Vol. 2 , Article 6. Available at: https://scholarsarchive.byu.edu/gbnm/vol2/iss1/6

This Article is brought to you for free and open access by the Western North American Naturalist Publications at BYU ScholarsArchive. It has been accepted for inclusion in Great Basin Naturalist Memoirs by an authorized editor of BYU ScholarsArchive. For more information, please contact [email protected], [email protected]. THE FLORA OF GREAT BASIN MOUNTAIN RANGES: DIVERSITY, SOURCES, AND DISPERSAL ECOLOGY

1 1 2 K. T. Harper', D. Carl Freeman , W. Kent Ostler , and Lionel G. Klikoff

Abstract.—The high elevation floras of 9 mountainous "mainlands" (3 in the Sierra-Cascade system and 6 in the High Plateau-Wasatch-Teton system) and 15 isolated mountain "islands" in the Intermountain Region have been analyzed. Mainland floras support more species per unit area and show a smaller increase in diversity as

area is increased than islands. In this respect, the isolated mountains behave as true islands. The number of en-

demics is low on the islands (never exceeding 5 percent of any flora), however; and the island floras are over- whelmingly dominated by species with no apparent modifications for long-range dispersal. Furthermore, the east- ern mainland has exerted a far greater influence on the flora and the vegetation of the islands than has the

western mainland, despite the fact that the former is downwind of the islands. Thus, evidence from endemics,

dispersal ecology, and sources of the floras suggests that the isolated mountains have not acquired their full floras by long-range dispersal. We conclude that although the floras of the islands have many insular characteristics,

they were less isolated in the relatively recent past than at the present. The island floras do not appear to be in equilibrium in the sense that immigrations equal extinctions.

The biogeography of disjunct segments of and Wilson 1970, Brown 1971a, Heatwole similar habitat has intrigued biologists since and Levins 1972, and MacArthur, Diamond, the days of Charles Darwin (1859) and A. and Karr 1972). R. Wallace (1880). Their pioneering obser- In this paper we consider the vascular

vations were based primarily on oceanic is- floras of islandlike enclaves of mesic lands, but others have analyzed the biology environment on high mountains in the of such habitats as caves (Culver, Holsinger, deserts of the Great Basin. In the strictest and Baroody 1973), woodlots (Curtis 1956), sense, these high mountains are less isolated fresh water lakes (Barbour and Brown than oceanic islands, since dispersing prop- 1974), and isolated patches of herb land in agules or their carriers may rest in the high-elevation forests (Vuilleumier 1970). desert and survive to move on again. Also, The appeal of islandlike environments to species of the mountain islands could evolve biologists is partially explained by the fact (and apparently often have) from the floras that complete inventories of selected taxa of the unfavorable environments that sepa- can be prepared for several disjunct points rate the islands (Billings 1977). Furthermore,

in a reasonably short time. Furthermore, is- evidence suggests that at varying times in land systems are ideally suited for the anal- the Pleistocene many of the islands were ysis of such dynamic processes as dispersal, connected by vegetation similar to that now competition, and evolution. Basic principles confined to the slopes of the mountains of community structure and trophic dynam- (Wells and Jorgensen 1964 and Wells and ics also appear to have been better demon- Berger 1967). Nevertheless, the tops of the strated and more easily studied in island high mountains of the arid West provide systems than in larger, more heterogeneous disjunct patches of habitat that may have environments (Lindeman 1942, Simberloff much in common with real islands.

'Department of Botany and Range Science, Brigham Young University, Provo, Utah H4WI2 'Department of Biology, Allegheny College, Meadville, Pennsylvania 16335.

81 82 GREAT BASIN NATURALIST MEMOIRS No. 2

Methods and the Teton-Wasatch-High Plateau system in Wyoming, Idaho, and

This paper is based entirely on published Utah) have long had relatively free access

floras or checklists of workers who have to large floras adapted for life at high ele- collected extensively on specific mountain vations and thus qualify as mainland floras ranges. We utilize 9 floras from the more- in the parlance of island biogeographers. or-less continuous mountain systems that The mountain islands have been assigned flank the Great Basin on the west and east discrete boundaries which are defined by and floras or checklists for 15 mountain the 7500 foot contour line. The size and

ranges in or near the Great Basin (Fig. 1, elevation of these islands and their distance

Table 1). We have assumed that the floras from the mainlands were taken from topo- of the relatively continuous flanking moun- graphic maps. Island-to-mainland distances tain systems (the Cascade-Sierra system in were computed by summing the distances

Fig. 1. Location of the floras considered. 1 1

1978 INTERMOUNTAIN BIOGEOGRAPHY: A SYMPOSIUM 83

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across inter-island barriers of desert (areas ranges than is now available. Accordingly, below 7500 feet) along the shortest route we have used only area, elevation, and loca- possible from a particular island to the tion in our analysis of factors controlling nearest edge of each mainland. plant diversity.

It should be noted that our island areas The component species of each checklist and distances to mainlands do not always have been individually considered for in- agree with those reported by Brown clusion in our study. We have eliminated (1971a), Johnson (1975), and Behle (1977), species from the checklists which are not who have used some of the same islands known to occur above 7500 feet. Species that we have. Those discrepancies arise that are potentially able to survive and re- from the manner in which the mainland produce in desert environments have also and island borders are defined by the sever- been excluded. This latter criterion was al authors. Brown (1971a), for example, used to improve the likelihood that the is- combined the White and Inyo ranges, but lands considered are at least currently func- the flora used in our work (Lloyd and Mit- tioning as islands. We experienced difficulty chell 1973) covers only the White Moun- in rigidly applying this last criterion, since tains. Johnson (1975) let the lower edge of some species which occur above 7500 feet forest or woodland serve as the edge of his along the eastern edge of the Great Basin islands, while we have followed Brown do not extend above that elevation in the (1971a) and used the 7500 foot contour as Sierras. We have included all species which the island edge. In Johnson's (1975) work, occur above 7500 feet on the eastern edge the Pine Valley Mountains were considered of the Great Basin (that do not tolerate to be part of the mainland, but our criteria deserts) but normally occur below that ele- dictate that those mountains be considered vation on the western mainland. an island. For each species included in the study, As noted elsewhere in this symposium we have noted lifeform, likely means of dis-

(West et al. 1977), distance to the nearest persal, and geographic range. The lifeform mainland is a weak ecological variable in categories recognized are: 1) annual, 2) per- the Great Basin, since each mountain range ennial forb, 3) perennial graminoid, 4) has probably received migrant species from shrub, or 5) tree. Categories of dispersal in- both mainlands. We measured the width of clude: 1) megawind, 2) miniwind, 3) stick- valley barrier between each mountain sys- tight, 4) fleshy fruit, or 5) no apparent mod- tem and both mainlands in an effort to ob- ification. Species were placed in the tain a better understanding of the bio- following groups with respect to geographic geographic consequences of distance. range: 1) occurring on both mainlands, 2) Johnson (1975) and Harner and Harper confined to the western mainlands and a (1976) demonstrated that habitat diversity few isolated mountains, 3) confined to the exerts a strong influence on diversity of eastern mainlands and a few isolated moun- birds and vascular , respectively. John- tains, or 4) known only from one or a few son (1975) used plant criteria to quantify mountains in this study. Because the authors habitat diversity for birds on Great Basin of the several checklists were uneven in mountains, but his criteria for habitat diver- their treatment of taxa of subspecific rank, sity would lead to circular logic if they we have ignored such taxa. were used to help explain plant diversity. It will be recognized that many arbitrary Conceivably, one could devise a habitat di- decisions are required to classify all of the versity measure based on physical character- species in respect to the foregoing charac- istics of the sample areas, but a useful mea- teristics. We have followed the lifeform sure would probably require more classification given in the index of Hol- information about individual mountain mgren and Reveal (1966), except that we 1978 INTERMOUNTAIN BIOGEOGRAPHY: A SYMPOSIUM 85

have separated annual plants from perennial ciencies of the geographic range lists, we herbs. We consider megawind propagules to have used them for certain analyses that be dust-like seeds (as in orchids) and seeds would have been otherwise impossible to with large plumose appendages (as in milk- make. weeds) that can be expected to be regularly We have used Holmgren and Reveal

transported over a mile by wind. Miniwind (1966) as our nomenclatural authority for all propagules are considered to include such species occurring in the Great Basin. No- fruits as winged utricles of some chenopods, menclature of species that occur in Califor-

samaras of maples, grass caryopses that have nia but do not occur in the Great Basin fol- large surface-to-volume ratios, and winged lows Munz and Keck (1959). Species seeds of conifers. Normal dispersal distance mentioned that occur to the south of the of miniwind propagules is probably no more study area but not in California are named than a few yards. The sticktight category according to Kearney and Peebles (1951) or includes "hitchhiker" fruits such as those of Clokey (1951). Problems of synonymy were Xanthium, Arctium, Circaea, and Bidens largely resolved with the Holmgren and Re- which are presumably adapted for dispersal veal (1966) checklist. on the fur or feathers of vertebrates. Under the heading of fleshy fruits, we include drupes, pomes, berries, and fleshy cones Results such as those borne by Juniperus. We as- The Study Areas sume that such propagules appeal to and are often dispersed by birds. Propagules des- Our floristic samples are drawn from 6

ignated as having no modifications for dis- states and from areas ranging in size from 1 persal are produced by a great variety of to 3,630 square miles. The mainland floras dry-fruited species in which seeds are rela- are distributed across a north-south gradient

tively large, have a small surface-to-volume of about 450 miles in the west (3 floras) and

ratio, and are without wings or plumose ap- 600 miles in the east (6 floras). The 15 is- pendages. lands are geographically centered on the The categorization of individual species Great Basin and are spread across more according to geographic range also present- than 400 miles of distance in both north-

ed difficult problems. Once the floras were south and east-west directions (Fig. 1). Max- recorded on computer cards, the species imum elevation varies from 14,495 to 9105

were separated into the four floristic groups ft above sea level among mainland areas

previously mentioned. Examination of the and from 14,246 to 8235 ft among islands

lists thus compiled demonstrated that some (Table 1). of the species that supposedly occurred only Unfortunately, few climatological stations on western mainlands did in fact also occur are maintained at high elevations in the re- infrequently on the eastern mainlands, even gion. The few data that are available sug- though they were not encountered on any gest that the climates of eastern and west- of the checklists. In like manner, some spe- ern mainlands are somewhat similar in

cies on the list of taxa found only on check- respect to annual precipitation and poten-

lists from the eastern mainlands are known tial evaporation at comparable elevations, to occur (usually sparingly) on the western while the island areas tend to receive less

mainland. Finally, species that occur on is- precipitation and to experience greater po-

land checklists but not on mainland lists are tential evaporation than either mainland. rarely local endemics, but are instead north- Conditions conducive to aridity appear to ern or southern species or uncommon main- be maximal on the more southerly of the land species that have reached some of the mountain islands considered ( isolated mountains. Despite these defi- Department of Interior 1970). GREAT BASIN NATURALIST MEMOIRS No. 2

The Flora Species confined to the western mainland or

that occur on the mainland and a few iso- A total of 2,225 different species occur lated mountains include the following: above 7500 ft elevation in the 24 floras in this paper. considered Approximately 27 Agropywn pringlei (Scribn. & Sm.) Hitchc. percent of those species occur on both Allium obtusurn Lemmon mainlands and on occasional mountain Artemisia douglasiana Bess. Bromus breviaristatus Buckl. ranges between the mainlands. Some 29 Carex amplifolia Boott percent of the species appear on the west- Carex tahoensis Smiley ern but not the eastern mainland, and Cheilanthes gracillima D.C. Eaton roughly 30 percent of the species are repre- Cryptantha mohavensis (Greene) Greene sented on the eastern but not the western Hulsea brevifolia Gray mainland. The remaining species (about 14 Libocedrus decurrens Torr. Mimulus torreyi A. Gray percent) were recorded only on island Oryzopsis kingii (Bol.) Beal checklists (Table 2). Pinus jefferyi Grev. & Balf. Species representative of those occurring Populus trichocarpa Torr. & Gray on both mainlands include the following: Prunus emarginata (Dougl.) Walp. Sequoiadendron giganteum (Lindl.) Stipa californica Merr Davy Aconitum columbianum Nutt. & Taxus brevifolia Nutt. Balsamorhiza sagittate. (Pursh) Nutt. Trifolium andersonii A. Carex aurea Nutt. Gray Tsuga mertensiana Carex lanuginosa Michx. (Bong.) Carr. Elymus glaucus Buckl. Species confined to the eastern mainland or Epilobium angustifolium L. Equisetum arvense L. to that mainland and a few islands are rep- Fritillaria atropurpurea Nutt. resented by the species listed below. Geum macrophyllum Willd. Abies lasiocarpa (Hook.) Nutt. Glyceria eUita(Na.sh) A. S. Hitchc. Acer grandidentatum Nutt. Hackelia floribunda (Lehm.) I. M. Johnst. Balsamorhiza macrophyllum Nutt. Lonicera involucrata (Rich.) Bank Besseya wyomingensis (A. Nels.) Rydb. Qsmorhiza chilensis Hook. & Am. scopulorum Populus tremuloides Michx. Calamagrostis M. E. Jones Pinus ponderosa Laws. Ceanothus martini M. E. Jones Chlorocrambe hastata (S. Wats.) Rydb. Purshia tridentata (Pursh) DC. Ribes cereum Dougl. Clematis columbiana (Nutt.) Torr. & Gray Erigeron ursinus D.C. Eaton Sitanion hystrix (Nutt.) J. G. Smith (R. Br.) Ser. Thalictrum fendleri Engelm. odorata (L.) Beauv. Viola Hierochloe adunca J. G. Smith Mertensia arizonica Greene Moldavica parviflora (Nutt.) Britton Orthocarpus tolmiei Hook. & Arn. Pinus edulis Engelm. 2. General distributional character- Table Picea pungens Engelm. istics of the flora considered. parryi A. Gray Quercus gambelii Nutt. Total species 2.225 Ribes wolfii Rothrock Species occurring on checklists Thermcypsis montana Nutt. from both mainlands 613 Species confined to western mainland or occurring on western mainland Species occurring on the checklists of some and some islands but not on of the isolated mountains but on neither eastern mainland mainland include local endemics as well as to mainland Species confined eastern more widespread species that penetrate our or occurring on eastern mainland area from primarily northern or southern and some islands but not on western mainland 678 floras. Representatives of each of these Species recorded only on islands 288 groups are listed below. 1978 INTERMOUNTAIN BIOGEOGRAPHY: A SYMPOSIUM 87

Endemics Listed by Location close to and well removed from the main- Ruby Mountain Area lands) do not differ significantly (Table 3). Castilleja linoides Gray We had anticipated that since perennial Eriogonum kingii Torr. & Gray forbs show a preference for more mesic Primula capillaris Holmgren & Holmgren sites (Harner and Harper 1973) and the is- Spring Range land habitats appear to be more xeric than Angelica scabrida Clokey & Mathias soliceps Blake the mainlands, such species might be under- Castilleja clokeyi Pennell represented on the isolated mountains. The Cirsium clokeyi Blake data lend no support to that idea. Woody Opuntia charlestonensis Clokey species and graminoides are also uniformly Penstemon keckii Clokey distributed among the floristic groups re- Potentilla beanii Clokey 3. Silene clokeyi C. L. Hitchc. & Maguire ported in Table Synthyris ranunculina Pennell The number of annual species is consid- Tanacetum compactum Hall erably higher on the western as opposed to Toiyabe Mountains the eastern mainland (Table 3). In fact, if Draba arida C. L. Hitchc. only herbaceous species are considered, Chi- Mertensia toyabensis Macbr. Wheeler Peak square analysis demonstrates that the num- Eriogenum Holmgrenii Reveal ber of annual species on the two mainlands Species Entering from North departs significantly from random expecta- Castilleja viscidula A. Gray tions. Also, significantly fewer annual spe- Cymopterus nivalis S. Wats cies occur in the combined flora of the is- Erigeron watsoni (A. Gray) Cronq. the selaginoides (L.) Link lands than on the western mainland, but Species Entering from South island flora does not differ from that of the Agastache pallidiflora (Heller) Rydb. eastern mainland in this respect. Chabot Antennaria marginata Greene and Billings (1972) have noted that annual Aqailegia triternata Payson species are more common in the alpine Arenaria confusa Rydb. Eleocharis montana (H.B.K.) Roem. & Schult. flora of the Sierras than in other alpine Festuca arizonica Vasey floras of North America. Muhlenbergia wrightii Vasey Floristic Diversity Considerations

In respect to lifeform characteristics, the Species-area relationships for the total floras of the mainlands and islands (both flora and various lifeform subsamples there-

Table 3. Lifeform relationships of the floras considered. The criterion for separation of near and far is- lands was a barrier width of less than or greater than 100 miles. The following four islands constitute the "far islands" category: Deep Creek, Jarbidge, Santa Rosa, and Spring. Expected numbers of species in

each category (assuming random distribution of lifeform classes among floras) is enclosed by parentheses.

Lifeform Class

Floristic Perennial Herbs Group Shrubs Forbs Graminoides Annuals Total

W. mainlands 88 GREAT BASIN NATURALIST MEMOIRS No. 2 of are shown for both mainlands and islands under study do exhibit strong similarities in Figure 2. Three generalizations can be with true islands. drawn from that figure: 1) there are con- The third observation may be partially sistently more species per unit area on the attributable to the classification of a single mainlands than on the islands, 2) floristic di- flora. We have treated the Bryce Canyon versity increases faster on islands than main- flora as mainland, but Figure 2 demon- lands as area increases, and 3) area usually strates that its flora and lifeform subsamples accounts for more of the variation in spe- consistently fall on the species-area trend cies diversity on islands than on mainlands line for islands and well below the trend

(i.e., correlation coefficients for species-area line for mainlands. Correlation coefficients relationships are usually larger for islands for both mainlands and islands would have than for mainlands). Observations 1 and 2 been improved had we classified Bryce have been duplicated in numerous island Canyon as an island. The area lies at the biogeographic studies (MacArthur and Wil- southern extremity of the more-or-less con- son 1967) and are commented on here only tinuous system of highlands extending south to emphasize that the isolated mountains from northern Utah and along the western

AREA ISO MILES)

Fig. 2. Species-area relationships for mainland and island floras. Relationships for the total flora and various lifeform subsets thereof are shown. Mainland data are represented by dots; insular floras are shown with triangles. The individual floras are identified in the diagram for total species combined: numbers cor- respond to specific floras identified in Table 1. Subscript c indicates mainland correlation coefficients or regression equations; subscript i indicates island coefficients and equations. S represents number of species and A represents area. 1978 INTERMOUNTAIN BIOGEOGRAPHY: A SYMPOSIUM

edge of the Plateau. We initially decreasing likelihood of an island being col- considered the habitat breaks along the onized by dispersing taxa as size decreases highland corridor to be short and in- and 2) increased likelihood of local extinc- consequential as migration barriers and thus tion of small populations on little islands. settled on the mainland classification for the Brown (1977) reports Z-values of 0.165

area. In retrospect, it seems likely that the for boreal birds and 0.326 for boreal mam- narrowness of the corridor has combined mals on sites of isolated Great Basin moun- with general climatic differences and unusu- tains. He has previously reported a Z-value

al soils to effectively filter out numerous of 0.428 for boreal mammals, using a more northern taxa that would otherwise be ex- restricted group of species and a different pected in the area. set of mountains (Brown 1971a). Our Z- Slopes (Z-values) for the species-area value for vascular plants on isolated moun- regression lines of Figure 2 are shown as tains thus lies between those for boreal the exponents of area (A) in the equations birds, which seem definitely to be in equi-

associated with the figure. The Z-value of librium on the moimtains (i.e., neither in-

0.11 for total flora on the mainlands is creasing or decreasing in respect to number slightly smaller than values commonly re- of species per unit area over long time peri-

ported (e.g., 0.12-0.17 by MacArthur and ods), and small boreal mammals, which are Wilson 1967). The average Z-value of .19 believed to be losing species by local ex- reported for nested quadrats in pinyon- tinction faster than new taxa can colonize. juniper ecosystems of Utah and New Mexi- Plants in general appear to behave more co (Harner and Harper 1976) should prob- like mammals than like birds on the moun- ably not be compared to the Z-values ob- tains considered, and perennial herbs yield

tained for mainlands in this study, since it Z-values that are especially steep and ap- seems likely that Z-values for nested quad- proach the values reported for mammals.

rats where the largest sample area is only a Both area and maximum elevation of the few acres will always be larger than values mountain ranges were strongly positively for regional floras from areas ranging in size correlated with total vascular species on

from a few to several hundred square miles. those ranges in this study (Table 4). There The Z-value of 0.31 for the total flora of was a weak negative correlation between

islands (Fig. 2) is well within the range of number of species and distance to the near- values (0.20-0.35) reported for a variety of est mainland. In multiple correlation analy-

kinds of biota on true islands and close to sis, only area makes a large contribution to the theoretically expected value of the coefficient of multiple determination

2 0.26-0.27 (MacArthur and Wilson 1967). (R ). Elevation appears to be so closely cor- We call attention in passing to the fact that related with area (r = 0.66) that it brings woody plants have flatter species-area re- little new information into the multiple cor- gression lines than perennial herbs on both relation analysis. Distance also enters the

mainlands and islands. multivariate equation; but it, like elevation, The flatness of species-area regression contributes only slightly over 0.01 to the

lines for mainlands has been attributed to Revalue (Table 4). the fact that small sample areas there carry The overwhelming dominance of area in

individuals of many species that are poorly the multiple correlation analysis is, in all adapted to the sample area but nevertheless probability, an illusion. Wyckoff (1973) and occur there because vigorous populations of Harner and Harper (1976) have demon- each such taxon exist in nearby, suitable strated that both environmental favorability habitats (MacArthur and Wilson 1967). The (annual precipitation and/ or soil texture)

steepness of species-area trend lines for is- and environmental heterogeneity (variation

lands is related to at least two factors: 1) in soil characteristics, elevation, and/or ex- 90 GREAT BASIN NATURALIST MEMOIRS No. 2 posure) exert a strong influence on the number of species in simple correlation number of species per unit analyses, but it makes a sizeable contribu- area. However, since area subsumes all of tion in the multiple correlation analysis. these variables, it alone consistently ac- The dissimilar results for species number- counts for a highly significant amount of distance relationships for species of western the variation in floral diversity in almost or eastern mainland origin may be related any suite of samples. Unfortunately, data on to the fact that the islands considered environmental favorability and hetero- are on the average more distant from the geneity are not available for the sample of western mainland (149 miles) than from the mountains considered here. We have thus eastern (117 miles). In any event, the results resorted to the use of the less definitive but in Table 5 seem to suggest that use of a nevertheless useful variables of area, eleva- single distance (distance to nearest main- tion, and distance. land) as in Table 4 may obscure the impor- We commented earlier on the com- tance of distance in studies of island floras. plicating effect of two close mainlands in is- We recognize also that a decrease in spe- land biogeography studies. In order to bet- cies of any given checklist is to be expected ter evaluate the influence of distance as one moves away from the center of the between island and mainland on floristic di- geographical area sampled for the checklist. versity of the islands, we have measured the Such a decrease with distance would be ex- width of unfavorable habitat separating pected even in large continental areas of every island from each mainland. Then, by relatively uniform climate, topography, geo- using only species that appear to be con- logical substratum, and geological history fined to one mainland or to one mainland and may have nothing to do with dispersal and a few islands (i.e., species common to habits of the species. The decrease may re- both mainlands or unique to islands were flect nothing more than the difficulty expe- excluded), we used simple and multiple cor- rienced by locally evolved taxa as they at- relation to analyze the relative influence of tempt to expand their range through area, elevation, and distance from mainland established vegetations. on the number of species from either east- Sources of the Flora ern or western mainlands on the 15 islands.

The results (Table 5) show that distance In this section we consider the question now becomes the major factor influencing of source of the floras of the isolated moun- the number of western mainland species on tains. How important a contribution do lo- the islands. For eastern mainland species, cal endemics make to the floras of the iso- distance is not significantly correlated with lated ranges? Are the island floras derived

Table 4. Factors influencing the number of vascular plant species on the 15 mountain islands. Distance

is measured to the nearest mainland area having an elevation over 7500 ft.

Factor

Area of island Elevation of highest peak Distance to mainland 1978 INTERMOUNTAIN BIOGEOGRAPHY: A SYMPOSIUM 91 equally from eastern and western mainlands, In order to evaluate the relative contribu- or is one source more important than the tion of western and eastern mainland floras other? to individual islands, we have separated out In respect to endemics, the data suggest species unique to western as opposed to that their contribution to the floras of the eastern mainlands (see Table 2). The rela- isolated mountains is comparatively minor. tive contribution of uniquely western or The number of endemics of moderate-to- eastern species on individual islands is high elevations appears to be considerably plotted against distance to the respective larger on the Spring Range (the Charleston mainlands in Figure 3. The data demon- Mountains which Clokey [1951] studied are strate that the eastern source area con- part of this range) than on any other range sistently contributes many more species to considered here. Yet even on the Spring the islands than does the western source Range, which Clokey (1951) considered to area. On only one island (the White Moun- be about five million years old, endemics tains) does the western mainland contribute account for only about 5 percent of the a larger percentage of the total flora than flora above 7500 ft. Endemics account for the eastern. As will be shown later (Fig. 4), less than 2 percent of the White Mountain the preeminence of the eastern source area flora (Lloyd and Mitchell 1973). In contrast, in island floras can be demonstrated for all plant endemics on many remote oceanic is- dispersal types. lands account for over 50 percent of the To further illustrate the relative contribu- flora (Carlquist 1974). Such data force one tion of the respective mainlands to the is- to conclude that the mountain ranges con- land floras, we have compiled a similarity sidered are far less isolated than remote matrix for all possible combinations among oceanic islands such as St. Helena, the Ha- the 24 floras (Table 6). Various inter- waiian Islands, or New Caledonia, where relationships among floras are summarized the majority of the flora is endemic. in Table 7. At first glance, the low sim-

Table 5. Factors influencing the number of vascular plant species on the islands when species occur- ring on both mainlands and on islands only are excluded. Width of barrier (distance) separating an island from each mainland has been determined for all islands.

Western Mainland Species Contribution to Simple Correlation Coefficient of

Coefficient (r) with Multiple (R 2 Factor Number of Species Determination )

Area of island .502 Elevation of highest peak .644 .092 Distance to W. mainland .646 .417

Total .509 R = .714 Eastern Mainland Species Contribution to Simple Correlation Coefficient of

Coefficient (r) with Multiple

2 Factor Number of Species Determination (R )

Area of island .590 .348 Elevation of highest peak .306 Distance to E. mainland .137 .156

Total .504 R = .710 92 GREAT BASIN NATURALIST MEMOIRS No. 2

ilarity values seem to indicate little com- the western, mainland. The second of the monality among floras, but those values foregoing items indicates, as one might ex- must be evaluated in light of the way in pect, that the flora of individual mountain which they are computed: for example, the islands tends to be a more random assem- 37 percent similarity value between the blage of species than is found in individual Ruby and Deep Creek Mountains represents floras on either mainland. Items 3 and 4 in- 223 species common to those ranges. Read- dicate that the island floras have been more ers are referred to the similarity equation influenced by the eastern than the western given in the legend for Table 7 for details mainland, despite the fact that they lie of computation. "downwind" (in this case, the prevailing Several relationships reported in Table 7 westerly winds) from the western mainland. merit attention: 1) internal similarity of the This last fact is visually conspicuous in the floras from the western mainland is almost field since many of the dominant plants of identical to the comparable figure for east- most of the isolated mountain ranges have ern mainland floras, 2) the island floras are eastern affinities. Examples of such domi- less similar to each other than are floras nant, or at least abundant, plants include from either mainland, 3) island floras are, the following: on the average, more similar to eastern Agropijron spicatum (Pursh) Scribn. & Smith mainland floras than to western mainland Amelanchier alnifolia (Nutt.) Nutt. floras, and even islands closest to the 4) Amelanchier atahensis Koehne western mainland have slightly closer floris- Artemisia arbuscula Nutt. tic affinities with the eastern, rather than Artemisia tridentata Nutt.

40,—

W 30 m Q LU 20 1978 INTERMOUNTAIN BIOGEOGRAPHY: A SYMPOSIUM 93

Bromus anomalus Rupr. Caltha leptosepala DC. Ceanothus martini M. E. Jones

Delphinium occidentale (S. Wats.) S. Wats. Geranium fremontii Torr. Holodiscus dumosus (Hook.) Heller Juniperus osteosperma (Torr.) Little Lathyrus pauciflorus Fern. Lewisia rediviva Pursh Oenothera eaespitosa Nutt. Pachistima myrsinites(Puish) Raf. Phlox longifolia Nutt. Primula pamji A. Gray Ranunculus jovis A. Nels. Valeriana occidentalis Heller

Since others (McMillan 1948 and Major and Bamberg 1967) have speculated about the relative effectiveness of northern and southern migration lanes from the western outliers of the Rocky Mountains in provid- ing species for interior Great Basin moun- tains, we have investigated that problem us- ing the similarity matrix of Table 6. Below we have summarized the relations of four interior ranges in the Basin (Deep Creek, Ruby, Toiyabe, and Wheeler Peak) with three northern sources (northern Wasatch, Mount Timpanogos, and Red Butte Canyon) and two southern sources (Bryce Canyon National Park and Pine Valley Mountains).

Average Percent Similarity with Three Two Northern Southern Mountain Range Sources Sources

Deep Creek 94 GREAT BASIN NATURALIST MEMOIRS No. 2

Kalmia polifolia Wang. ered in Table 8. Species having miniwind Ledum glandulosum Nutt. propagules contribute between 28.8 and Finns Engelm. albicaulis 33.5 percent of the species. Together, these Rubus parviflorus Nutt. two dispersal types account for almost 85 Southern Route ArctosUiphtjlos patula Creene percent of the species considered. On the Nieotiinui attenuata Torr. average, species having propagules modified Pivaphullum ramosissimum (Nutt.) Rydb. for long-range dispersal by wind (megawind Engelm. Pinus aristata dispersal type) contribute almost 7.5 per- Pinus ponderosa Laws. cent of all species in our floras. Fleshy fruited species contribute slightly fewer spe- Dispersal Ecology cies (average 6.1 percent of all species), and Plant dispersal habits in both mainland species dispersed by sticktights contribute and island floras are dominated by types the few remaining species (about 2.5 per- which have no apparent modifications for cent). dispersal and types with weak modifications Our data indicate that dispersal types for dispersal by wind (Table 8). For conven- modified for long-range movement (i.e., ience, we refer to the latter category as the fleshy fruit and megawind categories) show "miniwind" modification. Species whose no tendency to be overrepresented on the propagnles have no apparent modifications remote islands (Table 8). In contrast, for dispersal account for from 50.4 to 53.7 Carlquist (1967) has shown that as many as percent of the species in the floras consid- 58 percent of the plant species that reach

Table 6. Similarity among the 24 floras as determined with the Jaccard (1912) similarity index. Values report-

ed are percent similarity for all possible pairs of floras. Checklist numbers correspond to those assigned to each

area in Table 1. 1978 INTERMOUNTAIN BIOGEOGRAPHY: A SYMPOSIUM 95 remote oceanic islands are dispersed inter- of the remote islands. He considered ecolog- nally by birds (mostly fleshy fruits). Prop- ical conditions on the island to be strong agules borne externally on birds by virtue of determinants of the dispersal types that suc- being held in place by barbs or prickles ceeded.

(sticktights) also account for many (fre- In contrast to Carlquist's findings, Hed- quently over 20 percent) of the in- berg (1970) found wind-dispersed plants to troductions. He found windborne seeds to represent almost 30 percent of the flora be poorly represented (usually less than 10 above about 7900 ft on the mountains of percent of the flora) on all save the closest east Africa. In Hedberg's study, plants dis-

Table 7. Floristic similarity relations among the floras considered. The index of similarity used is that

of Jaccard (1912). Jaccard's index is computed as follows: C SI X 100.

In the equation, C represents the number of species common to the two floras, A is the number of species in flora A, and B is the number in flora B.

No. of No. of Average Floras Comparisons Percent Areas Considered Involved Averaged Similarity

Western mainland (internal similarity) 3 Eastern mainland (internal similarity) Mountain islands (internal similarity) W. mainland compared with islands E. mainland compared with islands W. mainland compared with E. mainland Four closest islands to W. mainland compared to W. mainland Four closest islands to W. mainland compared to E. mainland Four closest islands to E. mainland compared to W. mainland Four closest islands to E. mainland compared to E. mainland 96 GREAT BASIN NATURALIST MEMOIRS No. 2 persed internally by birds accounted for The great disparity between correlation only 1 to 2 percent of the alpine flora of coefficients for saturation-distance analyses east Africa. for eastern and western species in Figure 4

The relationship between various dis- is noteworthy. In five of the six analyses the persal types and island-to-mainland distance r-values are much larger for western spe- is presented in Figure 4. There, we regress cies. It seems possible that those values re- percent saturation of species of various dis- flect a differential in age of the two floristic persal habits (i.e., the number of species of elements on most of the islands. If the a given dispersal habit on each island is ex- Rocky Mountains are much older than the pressed as a percentage of the number of Sierras, as Billings (1977) reports, it is pos- species of that dispersal habit that would be sible that the eastern floristic element has expected in an area of comparable size on dispersed essentially to its limit and is now the appropriate mainland) against distance. poorly related to distance, while the west-

As expected, the regression lines all have ern element is still actively dispersing. negative slopes, and there is a slight (but Finally, we call attention to a con- statistically nonsignificant) tendency for dis- spicuous relationship between range limits persal types that are easily dispersed over of species and plant lifeform. Our data long distances (megawind and fleshy fruit demonstrate that woody plants and per- types) to have regression lines with gentler ennial graminoid species are over- slopes than are obtained for species that are represented in the broad-range category less likely to be dispersed far from the par- (i.e., occurring on both mainlands) and un- ent plant. Average slope values for western derrepresented in the category of species and eastern mainlands and each dispersal unique to islands (Table 9). Perennial forbs, type are shown below. on the other hand, display a significant ten- dency toward underrepresentation in the Dispersal Average broad-range category and over- Type Slope Value representation in the island-only class. An- Megawind .03 nual species show no significant trends in Fleshy Fruits .05 this respect. It seems possible that the pat- Miniwind .08 terns observed reflect evolutionary rather Sticktight .(MS

No Modification .07 than dispersal processes. In general, woody plants and graminoides appear to be ecolog- The data in Figure 4 also support our ically broad niched and to have the ability earlier conclusion that the eastern mainland to become community dominants. In con- has exerted a greater influence on the trast, many perennial forb genera seem to mountain islands than has the western main- be narrow niched and to rarely achieve a land. Every dispersal type shows greater dominant place in their community. saturation for eastern species than for spe- cies from the western mainland. Since the number of species originating from each of the two mainlands is roughly equal (see Discussion

Table 2), the results in Figure 4 suggest that Mountains as Islands species from the eastern mainlands have been about four times as effective in reach- One might expect an island flora to be ing and surviving on the islands as those distinguished from that of the nearest main- from the west. On the average island, west- land in a variety of ways. As we began this ern species have a saturation value of 8 per- study, it seemed to us that insular floras cent, but the comparable value for species should display 1) an overrepresentation of from the eastern mainland is 36 percent. species modified in one way or another for 1978 INTERMOUNTAIN BIOGEOGRAPHY: A SYMPOSIUM 97 long-distance dispersal, 2) fewer species per and/ or extinction (See Critchfield and Al- unit area than observed on the mainland, 3) lenbaugh 1969 for range details for these steeper species-area curves than for main- and other conifers in the Great Basin.) land floras, 4) uneven stocking of species Our expectations relative to an over- ecologically preadapted for existence on representation of species modified for long- available islands, and 5) higher rates of en- range dispersal on the islands in large part demism than the mainland. failed. The isolated mountains are over- Our results demonstrate that the isolated whelmingly dominated by species with no mountains of the Intermountain West satisfy obvious means for being dispersed great dis- some of our preconceived notions and thus tances. Furthermore, there is no tendency qualify as islands, but they fail to qualify on for species with modifications for long-dis- other counts. The islands do indeed have tance dispersal to be overrepresented on fewer species per unit area than adjacent even the most distant islands (Table 8). Our mainlands, and species-area trend lines for data do, however, show a weak tendency islands are steeper than those for main- for percent saturation of poorly dispersed lands (Fig. 2). Although the amount of en- species (i.e., no-modification, miniwind, and demism is low on the islands (always less sticktight categories) to decline faster and than 5 percent), the amount still appears to more reliably (larger r-values) with distance be higher than on areas of comparable ele- than for megawind and fleshy-fruited spe- vation and size on the mainlands. Too, cies, which are probably more easily dis- there is uneven stocking of species on the persed (Figure 4). islands. The Pine Forest Mountains of ex- Recent literature references demonstrate treme northwestern , for example, that at least some of the species that we are stocked by Engelm., the have classified as unmodified for dispersal Santa Rosas by Pinus flexilis James, while are, in fact, highly adapted for dispersal by the Jarbidge and Ruby Mountains to the vertebrate animals. Although we placed all east and the Sierras to the west have both. conifers with unwinged seeds in the unmo- The observed distribution pattern for these dified-for-dispersal category, a recent paper and many other species [e.g., Abies concolor by Vander Wall and Balda (1977) shows (Gord. & Glend.) Lindl. and Picea engel- that the Clark's Nutcracker regularly dis- mannii Parry ex Engelm.] seems explainable perses the seeds of several pines (P. edulis, only in terms of randomness of colonization P. albicaulis, and P. flexilis) in a sublingual

Table 9. Plant lifeform relative to the range limits of the species considered. Expected number of spe- cies appears in parentheses in each category.

Range Category 98 GREAT BASIN NATURALIST MEMOIRS No. 2

pouch and caches them in soil suitable for cantly narrowed the barriers between is- their germination and growth. In addition, lands. the Nutcracker is known to occasionally Our discussion of mountains as islands feed on the winged seeds of Pinus aristata would not be complete without some com- and Pinus ponderosa in northern . ment on the question of equilibrium of spe- Vander Wall and Balda (1977) have evi- cies number on the islands. Brown (1977) dence for the dispersal of seeds over 13 contends that birds are and small mammals miles in a single flight by the Nutcracker. are not in equilibrium on isolated mountains In California, the Nutcracker regularly in our study area. Are the plants in equilib- feeds on and caches the seeds of Pinus mon- rium? It will be recognized that the equilib- ophylla Torr. & Frem. and Pinus jefferyi as rium argument is based on two assumptions: well as Pinus albicaulis and Pinus flexilis 1) local extinctions do occur, and 2) new in- (D. Tomback, personal communication). troductions occur as often as extinctions on Johnson (1975) suggests that the Pinon Jay each island. Both assumptions are difficult, and the Band-tailed Pigeon may also be in- if not tactically impossible, to test con- volved in long-distance transport of con- clusively. A definitive test would require iferous tree seed. Pederson (personal com- that of every population of every J. we know munication) reports that the Band-tailed species on every island, and that we mon- Pigeon has been taken several miles from itor each island regularly enough (preferably the nearest Quercus gambelii in south- annually) in order to know when a species eastern Utah with a crop full of unbroken became extinct or immigrated and became acorns. Staniforth and Cavers (1977) demon- established there. Obviously, such data are strate that some seeds of two Polygonum not available for any island in our study. As species (P. lapathifolium L. and P. pensyl- a consequence, any statement about the vanicum L.) retain viability after passing status of our islands relative to the equilib- through the digestive tract of the cottontail rium question must be based on inferences, rabbit in eastern Canada. The foregoing not facts. data lead us to suspect that large seeds from With respect to extinctions, there is con- the dry fruits of many species will eventu- clusive evidence that Pinus aristata and ally be shown to be dispersed by vertebrate Pinus flexilis coexisted with Abies concolor animals. and Juniperus osteospenna on Clark Moun-

The foregoing discussion is an acknowl- tain in southeastern California about 25,000 edgement that we have underestimated the years ago (Mehringer and Ferguson 1969). number of plant species that are modified Today neither of these pines occurs there. for long-range transport on our islands. Similarly, Pinus monophylla and Juniperus Nevertheless, the number of species in the osteosperma existed on the Turtle Range no-modification and miniwind categories is 14,000 years ago (Wells and Berger 1967), so great on the islands that we are still but do not occur there now. The relatively forced to conclude that the vast majority of steep species-area curves for herbs (Fig. 2) the species there did not reach those sites may indicate extinctions, but we can offer by long-range dispersal. Although the high no evidence in support of that possibility. elevation community types may never have Concerning new immigrations onto the been able to survive on the valley floors at isolated mountains, there are abundant re- any time during the Pleistocene, as Wells cords of exotic species invading at lower and Berger (1967) argue, many of the com- elevations (Young, Evans, and Major 1972). munity components may have been able to Nevertheless, we know of no documented migrate directly across valley floors during cases of unaided immigrations onto the that period. Also, as Billings (1977) empha- mountains of species that cannot survive in sizes, climatic cooling would have signifi- at least some microsites on the valley floors. 1978 INTERMOUNTAIN BIOGEOGRAPHY: A SYMPOSIUM

There is strong evidence that species pine flora (Billings 1977) of the isolated modified for long-range dispersal are not mountains. The evidence seems to imply overrepresented on the islands relative to that three basic factors have combined to the mainlands (Table 8). If extinctions and give the Rocky Mountain element an ad- immigrations had been in equilibrium, even vantage over that from the Sierra. Those since the close of the Pleistocene, one might factors are: 1) time, 2) geological parent have expected long-range dispersal types to material, and 3) climate. be at least somewhat overrepresented on is- As Billings (1977) has noted, most of the lands; but even that tendency is not ob- Great Basin mountains are younger than the served (Table 8). As noted above, there is a Rockies and older than the present Sierra weak tendency for percent saturation of Nevada and Cascade ranges. Thus, species long-distance dispersal types to decline less from the east have had longer to colonize rapidly against distance from the mainland the isolated mountains than high-elevation than for supposedly less well-dispersed taxa. taxa from the Sierra, since that flora must

These two bits of evidence lead us to ten- have arisen much later than the first. In ad- tatively conclude that the flora of the iso- dition, propagules of species unique to the lated mountains is not in equilibrium, even western mainlands would have had great though some species do appear to be mov- difficulty establishing themselves on the ing about in the area. mountain islands even after reaching them, If the islands are not in equilibrium, the since most habitats would have already extinction rate must be low for all plant been occupied by eastern taxa. groups and especially so for the woody taxa. Plants originating at higher elevations on We draw this inference from the relative the western mainland could generally be ex- flatness of the species-area curve for most pected to be adapted to acidic soils, since plant groups (Fig. 2) in contrast to mam- the Sierra Nevada is primarily composed of mals (Brown 1977). Intuitively, this infer- acidic, igneous rock (Major and Bamberg ence seems valid since herbaceous plants as 1967). Soils on the isolated Mountains, how- primary producers should be able to main- ever, have prevailingly basic to circum- tain larger populations than their vertebrate neutral soils. Again, taxa from the eastern consumers. Woody plants (especially trees) mainland would have an advantage in colo- would be expected to maintain smaller pop- nizing the islands, since the western outliers ulations than their vertebrate consumers, of the Rockies are prevailing formed from but would have far greater longevity. Tro- calcareous rocks. In this connection, it phic position and longevity likely have is significant that Billings (1950) found as- much to do with the relative extinction rate semblages of Sierra plants in the western of vertebrates and plants. Plant groups of Great Basin to be confined to acidic habi- differing trophic habit (e.g., vascular sap- tats on hydrothermally altered rocks. rophytes and nongreen parasites such as Co- Finally, western plants have evolved in rallorhiza and Orobanche, respectively, ver- an environment that is less continental (i.e., sus photosynthetic forms) and longevity more moist and thermally less variable) than should show different extinction rates. that associated with the isolated mountains We had not expected to find the eastern of concern or the western outliers of the mainland (Rocky Mountains) floristic ele- Rockies. Johnson (1977) considers the cli- ment to be so much more successful than matic variable to be highly influential in the western mainland (Sierra) element on confining western bird species to the the Great Basin mountains. As others have Sierras. We believe that continentality may noted in this symposium, the Rocky Moun- similarly increase the difficulty of estab- tain element also dominates the avian fauna lishment of western plant species that are (Behle 1977 and Johnson 1977) and the al- dispersed to the mountain islands. As in the 100 GREAT BASIN NATURALIST MEMOIRS No. 2 preceding cases, species from the east can be seen with particular clarity in the would be better preadapted for life on the southwest corner of Cache Valley, Utah. islands. Although Chamaebatiaria millefolium (Torr.) Maxim, occurs on both of the main- Niche Expansion lands recognized in this study, it is rarely a Brown (1971b) has shown that the altitu- conspicuous component of the vegetation dinal range of a normally low-elevation on either. On the remote islands, however, chipmunk (Eutamias dorsalis) expands up- Chamaebatiaria is often common and a con- ward on Great Basin mountains which lack spicuous part of the vegetation. a high elevation congener (£. umbrinus). In Finally, West et al. (1977) review evi- the course of our work on isolated moun- dence suggesting that the anomalously high tains in the Region, we have observed sev- upper elevation of the juniper-pinyon zone eral cases in which plant species also dis- on many of the isolated mountains of the play a niche expansion in the absence of Great Basin may be attributable to the low normal competitors. Although quantitative diversity of the high-elevation flora and the data are lacking, we take this opportunity paucity of well-adapted competitors. They to put such anecdotal evidence as is avail- note also that the niche of both juniper and able on record. pinyon appears to be severely compressed

An apparent case of niche expansion is on the west flank of the southern and presented by Abies lasiocarpa in the Jar- middle Wasatch Range where Quercus gam- bidge Mountains. There, in the absence of belii and Acer grandidentata combine to its common coniferous competitors (e.g., form a dense woodland. Both juniper and Abies concolor, Picea engelmannii, Picea pinyon occur in the flora there, but neither pungens, and Pseudotsuga menziesii (Mirb.) is an important part of the vegetation. Franco), Abies lasiocarpa plays a major role Adequacy of Checklists in forest vegetation from the sagebrush-grass and streambank communities at low eleva- In the inception of this study, we were tions to timberline. We know of no other concerned that the checklists on which our place where this species succeeds in such a work would be based would be too in- variety of habitats. complete to give meaningful results. In ret-

A double zone of Artemisia tridentata oc- rospect, we acknowledge that all of the lists curs on mountainsides of Nevada and west- are probably incomplete. Undoubtedly, ad- ern Utah. There the species commonly ditional effort will add a few species to dominates a wide belt both below and some lists and many to others. Nevertheless, above the juniper-pinyon zone. It appears the lists have yielded results that seem rea- likely that Artemisia has simply moved into sonable and defensible. Furthermore, the a zone that is elsewhere dominated by sample on hand is already sufficiently large larger mesophytes such as Quercus gambelii, to minimize the possibility that new collec- Pinus ponderosa, or a rich mixture of moun- tions will seriously alter species-area rela- tain brush species. tionships or lifeform and dispersal-type In the northern Wasatch Mountains, the spectra for the floras. range of Acer grandidentatum extends manv Management Implications miles farther north than that of its common associate in the south, Quercus gambelii. In Species-area curves reveal much that mixed stands of Acer and Quercus, Acer is should be useful to natural resource man- normally conspicuous only on slope bases agers. The curve for trees on islands in Fig- and ravine edges. North of the limits of ure 2, for example, suggests that the Santa Quercus, however, Acer dominates both Rosa Mountains are drastically understocked slopes and depressions. The phenomenon with trees. Could trees be successfully in- 1978 INTEHMOUNTAIN BIOGEOGRAPHY: A SYMPOSIUM 101

troduced there to provide shelter for ani- from the lake but still in the open pine mals or construction materials for man? groves. Water could have been piped to the Since other islands in the study support so campground with minimal disturbance to many more tree species than that range, we the natural system around the lake. Instead, suspect that introduction of one or a few the current plan places every visitor in a carefully selected tree species into favorable position to disturb the several unusual plant sites would have a high probability of suc- and animal species that perhaps occur at cess there. only that spot on the entire range. Species-area curves also have many useful implications for conservation programs for ACKOWLEDGMENTS unusual and rare plant and animal species. Managers will find the basic theory relative We are indebted to Dr. Noel Holmgren to rare species and size of reserves nicely (1972) for his exhaustive pioneer work on capsulized in the following short, non- the biogeography of the Intermountain technical papers: Terborgh (1974 and 1976), West. It has been an invaluable aid as we

Diamond 1976, Whitcomb et al. (1976), and have planned and pondered this paper. Dr. Simberloff and Abele (1976). William E. Evenson prepared most of the Johnson (1975) developed a habitat diver- computer programs used in our analyses. sity index that accounted for a major por- Our research has been supported in part by tion of the observed variation in number of a grant from the National Science Founda- bird species on isolated mountains in the tion (GB-39272) and another from the Be- Great Basin. Behle (1977) has verified that search Division, Brigham Young University. the index is a useful indicator of bird diver- A grant from the U.S. Bureau of Beclama- sity throughout the Basin. Since that index tion through the Utah State Division of is based on various plant parameters and Water Besources has helped defray pub- the presence or absence of free flowing wa- lication costs for this paper. ter, it has relevance to our discussion here. Many of our small, arid mountain ranges in Literature Cited the Intermountain West have only a few acres of complex forest habitat (a prime Allred, K. W. 1975. Timpanogos flora. Unpub- lished master's thesis, Brigham Young Univer- variable in Johnson's index) in a single loca- sity, Provo, Utah. tion and but a few score feet of flowing Arnow, L. A. 1971. Vascular flora of Red Butte water. Since the index shows that bird di- Canyon, Salt Lake County, Utah. Privately versity is highly dependent upon such habi- printed by the author, Salt Lake City, Utah. N. D., L. Higgins. 1976. Checklist tat, it would seem prudent for developers Atwood, and C. of plants of Pine Valley Mountains, Utah. Un- interested in preserving the natural biotic published report. diversity of the environment to insure that Behle, W. H. 1977. Avian biogeography of the roads, campgrounds, or buildings not in- Great Basin and Intermountain Region. Great fringe upon such habitats. Yet, unfortu- Basin Naturalist Mem. 2: 55 -80. nately, our developments often are centered Billings, W. D. 1950. Vegetation and plant growth as affected by chemically altered rocks in the directly on such microenvironmental rari- western Great Basin. Ecology 31: 62-74. ties. By so locating developments, we al- 1977. Alpine phytogeography across the most insure that we will lose some and per- Great Basin. Great Basin Naturalist Mem. 2: haps many plant and animal species from 105-117. Brown, H. 1971a. Mammals on mountaintops: the entire range. The campground at Blue J. nonequilibrium insular biogeography. Amer. Lake on the Pine Forest Bange in north- Naturalist 105: 467 -478. western Nevada is a prime example of such 1971b. Mechanisms of competitive exclusion devel- faulty planning. With foresight, the between two species of chipmunks (Eutamias). opment could have been placed well away Ecology 52: 305-311. 102 GREAT BASIN NATURALIST MEMOIRS No. 2

1977. The theory of insular biogeography Heatwole, H., and R. Levins. 1972. Trophic struc- and the distribution of boreal birds and mam- ture stability and faunal change during recoloni-

mals. Great Basin Naturalist Mem. 2: 209-227. zation. Ecology 53:531-534. Buchanan, H. 1973. Checklists of vascular plants of Hedberg, O. 1970. Evolution of the Afroalpine

the Albion, Black Pine, Cassia, and Sublette flora. Biotropica 2: 16-23. Mountain ranges of southern Idaho. Unpub- Holmgren, A. H. 1972. Vascular plants of the lished report. Northern Wasatch, 4th ed. Privately printed by Buchanan, H., and G. T. Nebeker. 1971. Checklist the author, Logan, Utah. of higher plants of Bryce Canyon National Park, Holmgren, A. H., and J. L. Reveal. 1966. Utah. Weber State College Printing Depart- Checklist of the vascular plants of the Inter- ment, Ogden, Utah. mountain Region. U.S. Forest Service Research

Carlquist, S. 1967. The biota of long-distance dis- Paper INT-32.

persal. V. Plant dispersal to Pacific Islands. Holmgren, N. H. 1972. Plant geography of the In- Bull, of the Torrey Bot. Club 94: 129-162. termountain Region, pp. 77-161. In: A. 1974. Island biology. Columbia University Cronquist, A. H. Holmgren, N. H. Holmgren, Press, L. Reveal. New York. and J. Intermountain flora, vol. I. Hafner Publ. Chabot, B. F., and W. D. Billings. 1972. Origins Co., New York. P. and ecology of the Sierran alpine flora and veg- Jaccard, 1912. The distribution of the flora in etation. Ecol. Monogr. 42: 163-199. the alpine zone. New Phytol. 11: 37-50. Johnson, N. K. 1975. Controls of numbers of bird Clokey, I. W. 1951. Flora of the Charleston Moun- species on montane islands in the Great Basin. tains, Clark County, Nevada. University of Cali- Evolution 29: 545-567. fornia Press, Berkeley. 1977. Patterns of avian geography and speci- Critchfield, W. B., and G. L. Allen- ation in the Intermountain Region. Great Basin baugh. 1969. The distribution of Pinaceae in Naturalist Mem. 2: 137-159. and near northern Nevada. 12-26. Madrono 19: Kearney, T. H., and R. H. Peebles. 1951. Arizona Culver, D. C, R. Holsinger, R. J. and Baroody. flora. University of California Press, Berkeley. 1973. Toward a predictive cave biogeography: Lewis, M. E. 1971. Flora and major plant commu- the Greenbrier Valley as a case study. Evolution nities of the Ruby-East Humboldt mountains 2: 689-695. with special emphasis on Lamoille Canyon. Re- Curtis, T. 1956. The modification J. of mid-latitude port to Humboldt National Forest, Elko, Ne- grasslands and forests by man, pp. 721-736. In: vada. W. L. Thomas (ed.), Man's role in changing the 1973. Wheeler Peak Area species list. Report face of the earth. University of Chicago Press, to Intermountain Region, U.S. Forest Service, Chicago, Illinois. Ogden, Utah. Darwin, C. 1859. On the origin of species by 1975. Plant communities of the Jarbidge

means of natural selection (reprint of the first Mountain complex, Humboldt National Forest. edition). Watts and Co., London. Report to Intermountain Region, U.S. Forest Despain, D. G. 1975. Flora of Yellowstone National Service, Ogden, Utah. Park. Yellowstone Library and Museum Associ- 1976. Flora of the Santa Rosa Mountains, ation, West Yellowstone, Idaho. Humboldt National Forest. Report to Inter- 1976. Island con- mountain Region, U.S. Forest Service, Ogden, Diamond, J. M. biogeography and servation: strategy and limitations. Science 193: Utah. 1027-1029. Lindeman, R. L. 1942. The trophic-dynamic aspect Gillett, W., 399-418. G. J. T. Howell, and H. Leschke. of ecology. Ecology 23: 1961. flora of A., T. The Lassen Volcanic National Linsdale, M. J. Howell, and J. M. Park, California. 1952. Plants of the Toiyabe Wasmann J. Biology 19(1): Linsdale. Moun- 1-185. tains area, Nevada. Wasmann J. Biol. 10: Graham, E. H. 1937. Botanical studies in the Uinta 129-200.

Basin of Utah and Colorado. Ann. Carnegie Lloyd, R. M., and R. S. Mitchell. 1973. A flora of Museum, Pittsburgh, Pennsylvania, 26: 1-432. the White Mountains, California and Nevada.

Harner, R. F., and K. T. Harper. 1973. Mineral University of California Press, Berkeley. Karr. composition of grassland species of the eastern MacArthur, R. H., J. M. Diamond, and J. Great Basin in relation to stand productivitv. 1972. Density compensation in island faunas. Bot. Ecology 53: 330-342. Can. J. 51: 2037-2046. 1976. The role of area, heterogeneity, and fa- MacArthur, R. H., and E. O. Wilson. 1967. The

vorability in plant species diversity of pinyon- theory of island biogeography. Princeton Uni- juniper ecosystems. Ecology 57: 1254-1263. versity Press, Princeton, New Jersey. 1978 INTERMOUNTA1N BIOGEOGRAPHY: A SYMPOSIUM 103

MacDougall, W. B. 1947. Plants of Grand Can- year record of colonization. Ecology 51: yon National Park. Grand Canyon Natural His- 934-937. B. P. tory Association, Grand Canyon, Arizona. Staniforth, J., and B. Cavers. 1977. The im-

S. A. Bamberg. 1967. Some cordille- portance of cottontail rabbits in the dispersal of Major, J., and spp. 14: ran plants disjunct in the Sierra Nevada of Cali- Polygonum J. Applied Ecology 261-268. Preservation fornia and their bearing on Pleistocene ecologi- Terborgh, J. 1974. of natural diversity: cal conditions, pp. 171-188. In: H. E. Wright the problem of extinction-prone species. Bio- and W. H. Osburn (eds.), Arctic and alpine en- Science 24: 715-722. vironments. Indiana University Press, In- 1976. Island biogeography and conservation: dianapolis, Indiana. strategy and limitations. Science 193: McMillan, C. 1948. A taxonomic and ecological 1029-1030. study of the flora of the Deep Creek Mountains United States Department of Interior, Geological of central western Utah. Unpublished master's Survey. 1970. The National atlas. U.S. Geo-

thesis, University of Utah, Salt Lake City. logical Survey, Washington, D.C. P. Vander Wall, S. B., and B. P. Balda. Mehringer, J., Jr., and C. W. Ferguson. 1969. Pluvial occurrence of bristlecone pine 1977. Coadaptations of the Clark's Nutcracker (Pinus aristata) in a Mojave Desert mountain and the Pinon pine for efficient seed harvest

range. Interim Besearch Beport No. 14, Dept. and dispersal. Ecol. Monogr. 47: 89-111. of Geochronology, University of Arizona, Tuc- Vuillemier, F. 1970. Insular biogeography in con-

son. tintental regions. I. The northern Andes of Millican, M. T. 1969. Transect flora of the Eagle South America. Amer. Naturalist 104: 373-388. Peak Begion, Warner Mountains, Modoc Coun- Wallace, A. B. 1880. Island life. MacMillan and thesis, ty California. Unpublished master's Co., London. State College, Areata, California. Humboldt Wells, P. V., and B. Berger. 1967. Late Pleisto- 1959. California Munz, P. A., and D. D. Keck. A cene history of coniferous woodland in the Mo- Press, Berkeley. flora. University of California jave Desert. Science 155: 1640-1647. Nebeker, G. T. 1975. Manual of the flora of the Wells, P. V., and C. D. Jorgensen. 1964. East Tintic Mountains, Utah. Unpublished mas- Pleistocene woodrat middens and climatic ter's thesis, Brigham Young University, Provo, change in the Mojave Desert: a record of juni- Utah. per woodlands. Science 143: 1171-1173. S. 1950. Floristic and ecological fea- Preece, J., Jr. West, N. E., B. Tausch, K. H. Bea, and P. T. tures of the Baft Biver Mountains of north- J. Tueller. 1977. Phytogeographical variation western Utah. Unpublished master's thesis, Uni- within juniper-pinyon woodlands of the Great versity of Utah, Salt Lake City. Basin. Great Basin Naturalist Mem. 2: 119-136.

A., and S. K. Stocking. 1969. Bockwell, J. B. F., L. Lynch, P. A. Opler, C. S. Whitcomb, J. and of Sequoia-Kings Canyon Checklist of the flora Bobbins. 1976. Island biogeography and con- Park. Sequoia National History Associ- National servation: strategy and limitations. Science 193: ation, Three Bivers, California. 1030-1032. 1973. Annotated list of vascular plants Savage, W. 1973. effects of soil texture on Wyckoff, J. W. The basin, Nevada Coun- of Sagehen Creek drainage species diversity in an arid grassland of the ty, California. Madrono 22: 115-139. eastern Great Basin. Great Basin Nat. 33: Simberloff, D. S., and L. G. Abele. 1976. Island 163-168. biogeography and conservation: strategy and A., B. A. Evans, Major. 1972. Young, J. and J. limitations. Science 193: 1032. Alien plants in the Great Basin. J. Bange Man- Simberloff, D. S., and E. O. Wilson. 1970. agem. 25: 194-201. Experimental zoogeography of islands. A two-