Grcttt lJtrsin llird.; 9.20O1 . pp. 8 - 20 Vol. 9 FLEISHMAN AND DOBKIN O 2007 by the C;rcat Basin Birtl Observatoy

taxonomic groups (Pilttel'son et ll. 1998). Previous work in tlre Grcat Basin Response ofavian species richness to elevation in the ccntral (]reat Ilasin docunrentecl statistically sigrrificant relritionships betwcen species richness of montane butterl-lies and elevation. The functional fiirrn ol' the relationsl'rip, ERIC]A FLEISHMANI.] AND DAVID S. DOBKIN2 howevcr', varied among nountain ranges. ln the Toiyabe Range' species richness decrcased unirr-rodally as clevttion increased (Fleishman ct al. 1998)' wheleas in the Toquirna Rlnge, eastern Sierra Nevada, and Wassuk Range, ' C ortn, .7t,, Ct t n :; e rrta t ictn f) iokt g1' species richness incleased linearly as elevation increased (Fleishnlan et al. Deltrt rltn ent t tf B io b g ic al St: i ertc e,s 2000, 2001). ln other mountain rangcs, including the Shoshone Mountains ernd S tcutfo rt l. U r t. i.v e r.s i I L S tunt'o rtl, CA 9 I 3 0 5 Spring Mountains, the relationship betwecn species richness and elevation was

2 not statisticrlly significrnt (Fleishman et al. 2001). Range-specific gradients in trl i g h D o.r' n rt Ec d o g i.r: nL R e s e tr r r: h I t t,s tit ut e clirnatic severity appearecl to inf-luence these patterns (Flcishman ct al.2000). /5 Colorado Avcnue, Suite 300, Bentl, OR 97702 ^S.W. Hcle, we examine whether- the species richness of breecling bilcls respor-rds 3Current predictnbly to elevation in threc mountain ranges o['the central Great Basin. We atJtLres,s: also evaluate whcther elevational pattcrns vary among sr.Lbsets of bircl species N o t i.o na l C e n te r r Ec o Lo g i c ct l Ana l,ts i s tmtl S), nt he.s i,s .frt r.l ith dill'ercrrt lc\uutcc rctluiretnents. 7-15 Stote Street, Suitc -J00, StLnttt Barbara. CA 9-l l0l

( 80 5 692 -2 5 3 0, Le i,s hm an. @ n c e us. ut's b. e tl u ) .l METHODS INTRODUCTION Data 1-or oul analyscs were collected in three adjacent mountain ranges in the central Great Basin that have sirnilar biogeographic and hurrran land- Elevation is constrain known to the spatial and ternporal distributions of use histories: the Shoshone Mountirins (1850 km2, approximate north-south numerolls taxonomic groups (c.9., Merriarr 1890, Tcrbolgh 198-5, Fernlindez- bor.rnclaries 39'lzl'to 38'57'). Toiyabc Range (3100 km2.39"54'to 38'30') Palacios and de Nicollis 199.5). Species richness ol'ten decreascs. either ancl Toqnima Rangc (17-50 kur2,39'17'to 38'29') (Larrder ancl Nye counties, monotonically or witlr an intcrntediate-elevltion pcak. l'rom the lowest to Nevada). Numerous canyons incise the east ltnd west slopes of the t'anges. thc highest end elevational gradient (Terborgh ol'an 1977, Brown 1988, Yu Resource lgencies generally develop separate management plans ltrr individual 199,1, Lieberman ct al. 1996, Fleishman et rl. 1998). Noncthcless, positive mountain ranges under their juriscliction. Within mountain ranges' land correlations between spccies richrress and not precedent clcvation tre without uses cornmonly are dclinelted at the extcnt of individual or several adiacent (Obseo 1992. Wettstein ancl Schmid 1999). Undcrstanding whether spccies canyons. richness responcls predictably to major environmental graclients, arrd whether Our clata collection incorporatcd establishecl techniques that reliably those patterns gencralize across spacc. is highly relevant to planning ancl detect spccies prescltce irnd pcnnit asscssnent of distributional trends (Bibby dccision-making rranlged lanclscmpes in such as the Greal Basin. Data on et aI. 2000). We provide au abbreviated description here; these rnethods have current elevational patterns of species richness also mly irnprovc prcclictions of been clesclibed in considclable detail in previous publications, as well as testcd how climate change will afI'ect the legion's fauna and flora. for adecFracy in sampling the species present i-tt each location throughout the Numerous ecological hypotheses have been proposecl to explain why breeclin-u season (e.g., Dobkin and Wilcox 1986. Dobkin and Rich 1998, Mac spccies richness tends to be corclated with elevation. Islancl biogeography. Nally ct al. 20021). fbr instance. suggcsts negative thtt correlalions between spccics richness We sampied birds duling thc breeding season (late May through Junc) and elevation are driven by decreasing area and increasing isolation at higher r:sir-rg 75-m variable-r'adius point counts. Species that do not brecd in mountains elevatious (MacAlthur and Wilson 1967). Other directional cnvironmental in thc central Great Basin and species detected beyond 7-5 m were not includcd changes along graclients elevational that rnay :rccount for variation in spccies in our analyses. All dctections within 75 m of the point centcr were trc:rte(l t'ichness inclucle resource or prirnlry divelsity productivity and clirnatic severity cqually. Most point centers wcre at least 350 m apart. Points were locltecl along or unpredictability (Lawton et 1987, 1994). cxample, mean al. Olson For air the full elevzrtional graclient of every canyon wc sampled, typically with two or temperature, which clrops 0.65'C is with cvery 100 m inclease in clcvation, threc points pcr 100 rn vcrtical elevation change. Points were locatcd to sample, closely linked to ancl the clistlibution viability of many plants. Although some in approximate proportion to areal extcnt, the dominant vegetation types observed associations between species richness and elcvation may reflect or throughout the canyon as judgecl by rescarchers with considerable experience in be exacerbated by sampling design, ecological rncchanisrns generally play an tl-re stucly systern (e.g.. aspen, willow, pinyon juniper, wet meadow, sagebrush). (Wolda in.rportant rolc 1987, McCoy 1990, Colwell ancl Hurtt 1994). Dominlnt vegetation was consistent within the point. Wc did not attempt The response of biodiversity patterns to elevation rnay dil-fer arlong to classify points according to land use becanse the spatial distribution ancl

\ l0 SPECIES RICHNESS AND ELEVATION MARCH 2OO7 Vol. 9 FLEISHMAN AND DOBKIN il intensity of livestock grazing and human recreation, the dominant land uses in Tablc l. Species ol'brecding bircls recorded lion-r the Shoshone Mountaius Toiyabe the study area, ale inconsistent over time. Rangc and Toquimir Range aud classification rvith rcspcct to nesting typc and dcgree ol During each visit, we recorded by sight or sound all birds using ten'estrial riparian dependence. habitat within the point. Point counts were conducted only in calm weather, Ncst Riparian and none were conducted > 3.5 hours after dawn. Each point was visited three Spccics Site' DcpcndenceL' times per year fbr five minr-rtes per visit. Three surveys arc considered sufficient Black-crowncd N ight-Heron Nvt l iutrut n.tct i corax to determine which species of birds are present at point count locations in Turkey Vulturc Cdl/1ut'|eS dura (Buckland a given year et al. 2001, Siegel et al.200l); in our work, species Northern I larrier Oircus t:yuneus accr-rmulation curves generally approached an asymptote before the tlrird ror-rnd Coopcr's Hau'k ,4cciltiter cooperii of surveys (Betrus 2002). Northern (iosharvk Au:ipiter gentilis From 2001 - 2005, we condr,rcted point counts in 218 locations fbr two or' Red-tailed Har'r,k Buteo jamuicensi,s Fulco .sparverius more years. Our analyses included 53 points in the Shoshone Mountains, 55 Amcrican Keslrel Prairie Falcon Falco n'tericantt,v points in the Toquima Range, and ll0 points in the Toiyabe Range. Sampled Chukar Alet:loris chukar elevations ranged fiom 1939 to 3038 m. Mourning Dovc Zenuida mocroura ln addition to examining the relationship between species richness of Whitc{hroatecl Sri, i ft A e r o n o ttte.s s a r ukil i.s all breeding birds and elevation, we investigated the response of number of Broadtailcd Hurnmingbird S e la.s p h o rus p I al: t:e rc u s species glouped by nest site and by dependence on riparian areas. Each ofthese Nortlrern Flickcr (loluples auratu.s Sphyrapitus nuchuIis traits had a moderate number of classes, and assignment of species to classes Rcd-naped Sapsucker Dorvny Wooclpecker Picoides pube.scens was rclatively unambiguous based on extensive knowledge of the species Hairy Woodpccltcr Picoides villo,su,s (e.g., Ehrlich et aL 198tt) and ecological system. Riparian dependence was Wcstcrn Wood-l'ewee Contoptts .sordidulus of particular interest because water tends to be a lirniting resource Ibr many Gray Flycatcher Tv ra n nus dominicen.s i,s animals in the Gr"eat Basin and because much land management fbcuses on Dr"rsky Flycatcher Empidonar oberholseri maintenance and restoration of riparian areas (e.g., Chambers and Miller 2004). Clordilleran Flycatchcr Empido n ux occ identa I is Nest site categories were ground or low shrub cup, high shrub ol canopy cup, Plumbeous Vireo Vireo plumheus Warbling Virecr I/ireo gilwts and tree cavity. Species that build nests in other locations (e.g., clifl.s, rocks, Cllarl<'s Nutcracltcr Nut: iy'zga r:o lu nilt iana tunnels) and an obligate nest parasite were not inclLrded in our analyses because Wcstern Scrub-.lay A1the I ot om a ca I iJb rn ic ct (one sample sizes were small to six species per mountain range). Pinyon Jay G y n nrt r h i ntts t:v u no c ep ho lu.s We examined relationships between species richness and elevation Black-billed Magpic Picus httdsonia with both linear regression (testing for monotonic responses) and quadratic American Clrorv Oo rv u s b rachyrhyn t: hos (.on:us regression (testing lbr unimodal responses). Across taxonomic groups, linear Conrmon Raven crtrttx Hornccl Lark E re mop hilct a lpes I ri,s and unimodal responses to elevation are the most common fur-rctional Violet-grccn Su,allow Tar: hvc ine Id I ha los s ina relationships the li1er (e.g., I I reported in ature Brown 988, McCoy 990, Stevens Juniper Titmousc BueolophLts ridgwayi 2 1992l. ln addition, as noted above, both types of response have been observed Mountain Clhickadee Poecile ganbeli fbr butterflies at different mountain ranges in the Great Basin. l}rslrlit Psahriponts minimus 2 Brown Creepcr Certhiu umericana RESULTS Wh ite-hrcastcd NLlthatch Sitla ccn olinensis 3 Rcd-breasted Nuthatcli Sitta t:anatlensis 3 Houso Wren Troglod.ytes tedon Across the three mountain rirnges. we recolded 79 breeding species Rock Wrcn Su lp i n t: I es o l:tso I etu s 1 ol birds (Table l). We recorded 65 species in the Shoshone Mountains, 73 Canyon Wren Catherpes met icttntt,s 1 species in the Toiyabe Range, and 48 species in the Toquima Range. Across Amcrican Dipper C'inclu.s mericanus 4 all mountain ranges, the number ol points in which each species was recorded Blue-gray Gnatcatcher Pol ioptila coerulea ranged flom I to 180 (38 t zll, mean t SD). Individual species were recorded Mountain Bluebird Sialia mexicanrrs Townsend's Solitaire Myadestes tov,nsendi in I t

t3 T2 SPECIES RICHNESS AND ELEVATION MARCH 2OO7 Vol. 9 FI-EISHMAN AND DOBKIN

Table 2. Species richness ofbreeding birds and ofbirds in different functional groups in Table 1. (continued) theShoshoneMountains,ToiyabeRange,andToquimaRuL

Nest Riparian Shoshone Toivabe Toquima qp""t". Sit." D.P Breeding species 65 73 48 Sage Thrasher Oreoscoptes montanus 3 Nest site 15 Cedar Waxwing Bombycilla cedrorum 1 Ground / low shrub cup l9 26 29 23 Orange-crownedWarbler Vermivoracelata 1 High shrub / canopy cup 27 Virginia's Warbler Vetmivora virginiae 2 Tree cavity 1.2 11 7 Yellow-rumped Warbler Dendroica coronato Riparian dependence Black-throatedGrayWarbler Dendroica nigrescens Obligate l4 21. 8 Yellow Warbler Dendroica petechia Intermediate 25 24 1.7 MacGillivray's Warbler Oporornis tolmiei Non-riparian 26 28 23 Common Yellowthroat Geothlypis trichas Yellow-breasted Qhat Icteria virens Westem Tanager Piranga ludoviciana The mean elevation of riparian points (n = 103) versus non-riparian Green-tailed Towhee Pipilo chlorurus points (n = 115) was not significantly different across the three mountain Spotted Towhee Pipilo maculatus ranges or within any mountain range (anaiysis of variance, P > 0.05; Table Chipping Spanow Spizella passerina 3). The proportion of riparian versus non-riparian points, however, differed Brewer's Sparrow Spizella breweri considerably among the three mountain ranges. In the Toiyabe Range,T5Vo of Lark Sparrow Chondestes grammacus and just Black-throated Spanow Amphispiza bilineata points were riparian, as compared wtth347o in the Shoshone Mountains Sage Sparrow Amphispiza belli 57o in the Toquima Range. Fox Sparrow Passerella iliaco The mean elevation of points dominated by diff'erent types of vegetation Song Sparow Melospiza melodia (aspen, mixed tree, pinyon--juniper, non-riparian shrub, and willow) was not Vesper Sparrow Pooecetes gramineus significantly different across the three mountain ranges or within any mountain White-crowned Spamow Z o no tr ic hia I euc o p h ry s proportion points Dark-eyed Junco Junco hyemalis range (analysis of variance, P > 0.05; Tabte 3). The of Black-headed Grosbeak Pheucticus melanocephalus 2 dominated by trees versus shrubs dilTered somewhat among the three ranges Lazuli Bunting Passerina amoena 1 (40Vo in the Shoshone Mountains, 69Vo in the Toquima Range, and 52% in Westem Meadowlark Sturnella neglecta 1 the Toiyabe Range), but not as markedly as the proportion of riparian to non- Red-winged Blackbird Agelaius phoeniceus 1 riparian points. Brewer's Blackbird Euphagus cyano c ephalus 2 Brown-headed Cowbird Mololhrus ater 5 2 Cassin's Finch Carpodacus cctssinii Table 3. Elevation in meters of sampling points representing different types ofhabitat for 2 House Finch Carpodacus mexicanus birds in the Shoshone Mountains, Toiyabe Range, and Toquima Range. Values are rnean Pine Siskin Carduelis pinus 2 + standard deviation. A1l P > 0.05. Neither the mean elevation ofriparian versus non- 2 American Goldfinch Carduelis tristis riparian points nor the mean elevation ol points dominated by different types of 1: ground / low shrub cup 2: high shrub / canopy cup 3: tree cavity 4: other (e.g. vegetation was significantly different across the three mountain ranges or within any cliff rocks tunnel) 5: obligate nest parasite mountain range (P > 0.05). b 1: obligate 2: intermediate 3: non-riparian Shnshnne Tniwahe Toottima Ail Riparian (n - 103) 2250+r44 2369+\82 2254+90 2345 +179 Aspen 2468 2252+147 2394+136 2301 +155 Mixed tree 2266+ 183 2418 +261, 2373 +14r 2383 +218 Willow 2205 + $0 2305 + 180 2381 +238 2294+175 Non-riparian (r - 115) 2369 + 195 2343 +281 2351 +r15 2355 +210 Pinyon juniper 2233+130 2322:'148 2355 + 176 2309 +159 Non-riparian shrub 2t8t + 193 2319+206 2293+205 2365+203 15 t4 SPECIES RICHNESS AND ELEVATION MARCH 2OO7 Vol. 9 FI,EISHMAN AND DOBKIN

In all cases, quadratic regression yielded better fits to the observed data, a. Shoshone Mountains in terms of both statistical significance and proportion of variance explained, than linear regression; whether the association between species richness and elevation was positive or negative, species richness peaked at an intermediate C elevation. Therefore, all results reported here refer to quadratic regression. ijl r'l GC aastGs t When data for the three mountain ranges were pooled, several of the i ,-.+aC aa q- = 15 /*r tested relationships between species richness and eievation were statistically .g ai \ Gaal, \ a proportion of the variance in species richness was a a '\ significant, but only small +1n Ga a explained by elevation (Table 4). All statistically significant correlations in the * Shoshone Mountains, Toiyabe Range, and across the three mountain ranges were 5 negative (i.e., species richness decreased unimodally as elevation increased), whereas all statistically significant corelations in the Toquima Range were ?rrl0 ?2rlLr 2{n 2Et0 positive (species richness increased unimodally as elevation increased) (Fig. Elerstion (ml b. Toiyabe Range 1). Although there is considerable scatter in these plots, the "factor-ceiling," or upper limit of the point cloud, suggests that elevation places a ceiling on species richness (Thomson et al. 1996). The response of species richness to elevation iac l- t Gi in the Toiyabe Range generally was not statistically significant. Regardless of i$i c a$a a * across ta $ c whether the data were examined at the mountain range level or mountain 6C Eir GS'C ranges, the response of species richness of ground and low shrub cup nesters to !lr-s----{ .! . { Ga tltt G 's elevation also was not statistically significant. .! G * \G -/a a aa $ .-i a a a G aG a

GG G \ Table 4. Associations between species richness and elevation in the Shoshone i Mountains, Toiyabe Range, and Toquima Range, and for data pooled across mountain ** *, ranges. values are R2. *, P < 0.05; **, P < 0.0 I ; P < 0.00 1. All statistically significant associations in the Shoshone Mountains, Toiyabe Range, and across the three lE0r i00t tl[0 ?4ni tB0D tE00 t0r]rl tr00 whereas al1 in the Toquima Range were mountain ranges were negative, associations Eletrtion (m) positive. c. Toquima Range Shoshone Toivabe Toquima All All breeding species 0.19** 0.03 0. 19* * 0.04* Nest site 0.00 ai Ground / low shrub cup 0.03 0.02 0.06 a GS High shrub / canopy cup 0.18** 0.03 0.03* GG 0.18** a i a*s Tree cavity 0.24*4* 0.04 0.21** 0.05*x clr,f,-+$ t ts -\, Riparian dependence aaF-cc--' * t * /aa Obligate 0.1 6* 0.06* 0.03 0.02 t_iaG Internediate 0.26**4 0.03 0. l3* 0.03* Non-ripariar, 0.02 0.02 0.1 3* 0.01

t4rtrt tEoo

Ele ratien (mll

Figure 1. Relationship between elevation and species richness of breeding birds for sampling points in three mountain ranges in the central Great Basin. Note that axis values differ among ranges. .) 11 l6 SPECIES RICHNESS AND ELEVATION MARCH 2007 Vol. FLEISHMAN AND DOBKIN

DISCUSSION Regardless of the functional fbrm of the relationship between species richness of birds and elevation, the proportion of variance in species richt-tcss Although climate, land cover, land use, and tzrunal assemblages are explainecl by elevation was relatively low (maximttm 0.26, Table 4). The direct broadly similar across the central Great Basin, our work demonstratcs that and indirect efl-ects of elevation may contribute to, but certainly do not explain fundamental ecological patterns may not be generalizable anrong mountain fully, pltterns of species richness within or among mountain ranges. As a result, ranges. Species richness of birds was negatively correlated with elevation in simple moclels of climate change that assllme vegetation communities (when the Shoshone Mountains, positively correlated with elevation in the Toquirna usecl as a surrogate meastue of habitat) and associated wildlif-e in the Grcat Range, and uncorrelated with elevation in the Toiyabe Range. In virtually all Basin will move tipward at a unifbrm rate as tenperatures incrcase (McDonlld cases, these patterns were consistent fbr the entire assemblage of birds and fbr and Br"own 1992, Murphy and Weiss 1992) ale unlikely b predict accurately subsets of species detined on the basis of nest site or dependence on riparian the l.uture clistribr-rtion of birds. In addition, differences in the response of birds areas. The three mountain ranges described here are adjacent, with similar ancl butterflies to elevational gradients highlight the dilficulty of generalizing types of land cover and land use and pools of species, but there are dramatic how natural or anthropogenic environntental change will affect native species. difl'eler-rces in propoltion of lzrnd-cover types and avlilability of surface water among ranges. These cliffbrences may drive the establishment of distinct avian ACKNOWLEDGMENTS assctnblages with dilferent numbers and proportions of riparian obligates and difI'crent cli stributional patterns. Thanks to C. Betrus. L. P. Bulft-rck, G. Horrocks, G. MarkofT, N. McDonal, Our work echoes previous resealch on relationships between species N. Losin. G. Johnson and M. Ban for collection of field data integral to this richness of butterf-lies and elcvation in the same region in two ways. Filst, the work and to J. Fay fbr technical support. Thanks to M. Betrus and J. Br-rlluck functional relationship between species richness of birds and elevation, as with for lield assistance and to Grant Ballarcl ancl Ryan Burnctt fbr comments on butterflies, valied among mountain ranges. Second, in both taxonomic gt'oups, the manusct'ipt. Financial support was provided by the Nevada Biodiversity and contrary to general biogeographic cxpectations, species richness wzls Research and Conservation Initiative and by the Joint Fire Science Program via positively correlated with elevation in tl-re Toqr.rirna Range. the Rocky Mountain Research Station, U.S. Departrnent of Agriculture Forest Distinct gradients of resource availability and climatic severity in difl'crcnt Service. mountain ranges may be driving species richness patterns of both birds ancl buttelllies. Among thc common lancl cover typcs in the central Great Basin, LITERATURI c]trF]) riparian areas genelally havc the greatest diversity of nesting sites and fbod resources tbr birds (as well as fbr br,rtterf-lies). Accordingly, habitat quality Retrus, C.J. 2002. Refining the umbrella index complex: an application to of ripririan areas is relatively high. Tn the Toiyabe Ran-ue, r'iparian habitat is bird and butterfly communities in montane canyons in the relatively abundant and distributed fuirly evenly along thc clevartional gradient. Greatllasin. MS thesis, Miami Univcrsity, Oxfbrd, Ohio. This distribution may ilccount fbr the lack of corlelation betwccn birds and elevation in the Toiyabe Range. In addition, or,rr data suggest that riparian- Bibby, C.J., N.D. Burgess, D.A. Hill, and S. Mustoe. 2000. Bird census obligate birds will cstablish breeding territories alon-q the firll elevational techniqucs. Acldemic Press, London. graclient in a canyon with some riparian habitat. In other words, if one or more patches ofriparian h;rbitat are present in I given canyon, riparian-obligate birds Brown, J.H. 1988. Species diversity. Pp -57-89 in A.A. Myers and P.S. may nest anywhere within the canyon. The distribLrtion of specics richness Giller(ecls.), Analytical biogeography: an integrated approach to the of br-rttcflies in the Toiyabe Ran-{e (which deciines as elevation increases), study of animal and plant distributions. Chapman and Hall, London. by contrast, rnty be constrained at high elevations by colcl temperatures. strong winds, and low availability of host plants and nectar sources (Hicly and Buckland, S.T., D.R. Anderson, K.P. Burnharn, J.L. Laake, D.L. Borchcrs' Klicfbrth 1990. McCoy 1990). and L. Thomas. 2001. Introduction to distance sampling: estimating In tl-re Toquima Range, riparian habitat and, more generally, availability of abundance of biological populations. Oxford University Press, New wilter may be limiting fbr both birds and butterflies. Dccreases in temperature York. and increases in precipitation along an increasing elevational gradient in the Toquirla Range rr-ray lranslate into grcatcr abundance of resolu'ces and Chambers. J.C. and J.R. Millcr', editors. 2004. Great Basin riparian prolongecl availability of resources at higher elevations. ecosystems-ecology' management' and restoration. Islar-rd Press, Wrshington, D.C. Vol. c) FLEISHMAN AND DOBKIN l9 l8 SPECIES RICHNESS AND ELEVA'|ION MARCH 2OO7

Colwell, R.K. and G.C. Hurtt. 19921. Nonbiological gradients in species Mac Nally, R.. E. Fleishman, L. Bulluck, and C. Betrus. 2004. Cornparative richness and a spurious Rapoport effect. The American Naturalist influence of spatial scale on beta diversity within regional assemblages of I 44:570-595. birds and butterflies. Journal of Biogeography 3l:917 929.

Dobkin, D.S. and A.C. Rich. 1998. Comparison of line-transect, spot- MacArthur, R.H. and E.O. Wilson. 1961 . The theory of island ntap,and point-count surveys for birds in ripar-ian areas ()1'the Great biogeography. Princeton University Press, Princeton, New Jersey. Basirr. Journal of Field Ornithology 69 130 ,1.43. McCoy, E.D. 1990. The distribution of insects along elevational gradients. Dobkin, D.S. and B.A. Wilcox. 1986. Analysis of natural firrest fiagrnents: Oikos -58:313-322. liparian birds in the Toiyabe Mountains, Nevada. pp 293 299 tn J. Verner, M.L. Morrison, and C.J. Ralph (eds.), Wildlife 2000: McDonald, K.A. and J.H. Brown. 1992. Using montane mammals to model modeling habitat relationships of terrestrial vertebrates. University of extinctions dr.re to climate change. Conservation Biology 6:409 415. Wisconsin Press. Madison. Merriam, C.H. 1890. Results of a biological survey of the San Francisco Ehrlich. P.lt., D.S. Dobl

Fleishn.ran, E.. G.T. Anstin, and D.D. Murphy. 2001. Biogcography ol'Great Olson, D.M. 1994. The distlibution of leaf litter invertebrates along a Basin buttcrflies: r'cvisiting patterns, paradigrns, ancl clinrate change Neotropical trltitudinal gradient. Journal of Tropical Ecology l0: 129 scenarios. Biological Journal of the Linnean Society 7,1:-501-5 15. I 50.

Fleishman,8., J.P. Fay, and D.D. Murphy.2000. Upsides anci downsides: Patterson, B.D., D.F. Stotz, S. Solari, J.W. Fitzpatricl<, and V. Pacheco. 1998. contrastir-rg topographic gradients in species richness and associated Contrasting patterns of elevational zonation fbl birds and mammals in the scenarios fbr climate change. Journal of Biogeography 27:1209-1219. Andes of southeastern Peru. Journal of Biogeography 25:593-601.

Hidy, G.M. and H.E. Kliefirrth. 1990. Armospheric processes and the climates Siegel, R.8., D.F. Desante, and M.P. Nott.2001. Using poir.rt counts to of thc Basin and Range. Pagcs l7-42 in C.B. Osmond. L.F. pitelka, and establish conservation priorities: how r-nany visits arc optimal'l G.M. Hidy (eds.), Plant biology of thc Basin and Range. Journal of Field Ornithology 12:228-235. S pringer-Verlag, Berlin. Stevens, G.C. 1992. The elevational gradient in altitudinal range: an extension Lawton, J.H., M. MacGarvin, ancl P.A. Heads. 1987. Ef'fects of altitude on the of Rapoport's latitudinal rule to altitude. The American Naturalist abundance and species richness insect of hcr.bivores on br.acken. l zl0:tt93 9l l . Journal of Animal llcokrgy 56:141-160. Terborgh, J. 19'11. Bird spccies divelsity on an Andean elevational gradient. Lieberman, D., M. Lieberrnan, R. Peralta, and G.S. Hartshorn. 1996. Trcpical Ecology 58:1007-1019. forest structure and composition on a large-scale altitudinal gr.adient in Costa Rica. Journal oflLcology 84 l3l-152. Terborgh, J. 1 985. The role of ecotoncs in the distlibution of Andean birds. Ecoltrgy 66:1237 1246. flusin llinls 9. 2001. pp. 2l 34 20 SPECIES RICHNESS AND b,LEVAT]ON MARCH 2OO7 Grett O 2007 by thc Cireat Basin Birtl C)hservrtoy

Thomson, J.D., G. Weiblcn, B.A. Thomson, S. Alflro, and P. Legendrc. 1996. Springs and sky islands: influence ofsprings and elevation on breeding Untangling multiple factors in spatial distributions: lilies, gophels, and bird communities in the Spring Mountains of southern Nevada

locks. Ecology 11 : 1 698-17 1 5. T. WILL RICHARDSON, LISA H. CRAMPTON, AND DENNIS D. MURPFIY Wettstein, W. and B. Schrrid. 1999. Conservation of arthropod diversity in montane wetlands: effect of altitr-rde, habitat quality and habitat Grttduale Progntm. i.tt Ecolttgl', EvoLutiort, ttnd Conservutiott Biobgv fi'agmentation on br-rtterflies and grlsshoppers. Journal of Applied IJniversitt' of Nevuda, Rentt NV 89557 Ecofogy 36:363-313. INTRODUCTION Wolda, H. 1987. Altitude, habitat and tropical insect divelsity. Biological Journal of the Linnean Society 30:3 I 3-323. A clominarrt climatic f'eature of the Great Basin and Mojlrve Desert region is aridity. The lack of moisture, coupled with high temperatures and intense solar Yr-r. I{. 1994. Distribution and abundancc of srnall mammlls along a racliation, imposes severe limitations on vegetation communities. and the animals subtropical elevational gradicnt in central Taiwan. Journal of Zoology that depend upon them, thloughout the region. Mountains supply most ol'the 234:511 6OO. water the region receives: crossing air nrasses cool tht'ough orographic uplift, and moisture precipitates out at thc higher elevations. This precipitation can generate surtace streams and springs thtt carry the wlter to the lower elcvations. In the aricl and semi-arid western United States, these springs and spring-l-ecl acluatic systcms sLrpport a substantial proportion of aquatic and riparian species, ancl may provide resources for as many of 80c/c of terrestrial species ilt some systems (Thomas et al. 1979, Williarrs and Koenig 1980, GLrbanich and Panik 19U6, Hershler et al. 2002). The moistel, cooler climates fbr,rnd at the higher elevations of Gfcat Basin and Mojave mounlain ran-{es also providc refuge for- unique assenrblages ol' plants and animals. "Sky isllnds" such mountain ranges ale ffecluently called, each isolated lrom one another by a vast setr ofdesert valley bottoms. Nevada's most classic sky island is the Spring Mountain range, on the northern edgc of thc Mojave Desert. The Spring Mountains are home to a lich collection ol species, a large number ol which appeal to be sustained by one or more of the nearly 300 namesake springs that clot the mountains lrom theil arid fbothills to their alpine summils. The challenge of conserving the unique and isollted biota of the Spling Mountains has becorne immediate and pressing as expanding Las Vegas, at the very fbot of the range, increasingly exefts urban impacts upon whnt until recently was hrgely wilderness. Both springs and their distinctive ecological comrnunities have sufl'ered significantly fi'om the eff'ects of watel impoundment, invasion of aggressive weeds, and trarnpling and grazing by f'eral horses and burros and transplanted elk. Increased recreatior] in the Sprin-q Mountains has addecl new clisturbances, concentrated at springs and their associated ecological communities. Few baseline data exist, but disturbances to the springs and their communities can have sever-e consequences for the species that depend on them. A tinyspecies()f sprin-{snail (Pyrgukrysis sp.)thatwasunique totherangewaslost in the 1990s (Sada and Vinyard 2002), and the Mount Chilleston blue butterfly (lt:aricia shosta ch.urlestonen'sis),last seen in 2005, may have lecently ioined the ranks ofthe extinct. These continuing, and ofien increasing, disturbances put many other Spring Mourrtains species at similar risk of disappearing.

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