introduction to the arizona sky island arthropod project ... · introduction to the arizona sky...

144 USDA Forest Service Proceedings RMRS-P-67. 2013

In: Gottfried, Gerald J.; Ffolliott, Peter F.; Gebow, Brooke S.; Eskew, Lane G.; Collins, Loa C., comps. 2013. Merging science and management in a rapidly changing world: Biodiversity and management of the Madrean Archipelago III; 2012 May 1-5; Tucson, AZ. Proceedings. RMRS-P-67. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station.

Introduction to the Arizona Sky Island Arthropod Project (ASAP): Systematics, Biogeography, Ecology, and Population Genetics of Arthropods of the Madrean Sky Islands

Wendy Moore, Wallace M. Meyer, III, Jeffrey A. Eble, and Kimberly Franklin Department of Entomology, University of Arizona, Tucson, Arizona

John F. Wiens and Richard C. Brusca Arizona-Sonora Desert Museum, Tucson, Arizona

Abstract—The Arizona Sky Island Arthropod Project (ASAP) is a new multi-disciplinary research program at the University of Arizona that combines systematics, biogeography, ecology, and population genetics to study origins and patterns of arthropod diversity along elevation gradients and among mountain ranges in the Madrean Sky Island Region. Arthropods represent taxonomically and ecologically diverse organisms that drive key ecosystem processes in this mountain archipelago. Using data from museum specimens and specimens we obtain during long-term collecting and monitoring programs, ASAP will document arthropod species across Arizona’s Sky Islands to address a number of fundamental questions about arthropods of this region. Baseline data will be used to determine climatic boundaries for target species, which will then be integrated with climatological models to predict future changes in arthropod communities and distributions in the wake of rapid climate change. ASAP also makes use of the natural laboratory provided by the Sky Islands to investigate ecological and genetic factors that influence diversification and patterns of community assembly. Here, we introduce the project, outline overarching goals, and describe preliminary data from the first year of sampling ground-dwelling beetles and ants in the Santa Catalina Mountains.

Introduction Theoutcomeofmillionsofyearsofmountainbuilding,the7250km longNorthAmericanCordilleraor “WesternCordillera” runsfromnorthernAlaskatosouthernMexico.Thisgreatcordillera,thespine of theNorthAmerican continent, has but one break, a lowsaddlebetweentheRockyMountains/ColoradoPlateauandtheSierraMadreOccidental,whichformsabiogeographicbarrierbetweenthemontanebiotasoftemperateandtropicalNorthAmerica(Heald1951;Marshall 1957;McLaughlin 1986, 1995;Warshall 1995; BowersandMcLaughlin1996).TheMadreanSkyIslandsaretheisolatedmountainrangesthatspanthisCordilleranGap.Sometimescalledthe“MadreanProvince”or“MadreanArchipelago,”thesemountainrangesareauniquesubsetoftheBasinandRangeProvinceandcoverabout168,400sq.km.(~77,700sq.km.intheUnitedStates). AlthoughmanyoftheplantsandsomeoftheanimalsoftheSkyIsland Region have been well studied, little is known about the

arthropods(e.g.,insects,isopods,millipedes,mites,spiders,scorpions,etc.).Yet,theseecologicallydiverseorganismsdrivekeyecosystemprocessessuchaspollination,litterdecomposition,nutrientrecycling,andsoilaeration,andtheyareimportantfoodforreptiles,birds,andsmallmammals.Despitetheirecologicalimportance,arthropodsarepoorlyknownbecausemostaresmall,liveinopaquehabitatswhereobservation is difficult, and few taxonomists have specialized onthesegroupsintheSkyIslandRegion(Behan-PelletierandNewton1999).Usingdatafrommuseumspecimensandspecimensweobtainduring long-termcollectingandmonitoringprograms,ASAPwilldocumentarthropodspeciesacrossArizona’sSkyIslandstoaddressanumberoffundamentalquestionsaboutthearthropodsofthisregion,includingthefollowing:

1.WhatarthropodsinhabitArizona’sSkyIslands?Howarethesespeciesdistributedwithintheregion? OneofthegreatestresourcesforthisprojectistheUniversityofArizonaInsectCollection(UAIC),whichcontainsovertwomillionresearchspecimens,83%ofwhichareidentifiedtospecieslevel,mostlyfromtheSonoranDesertRegion,itsSkyIslands,andadjacentbiomesofnorthwesternMexico.Inthelastfewdecades,UAICresearchershaveparticipatedinlong-termsurveysintheSantaCatalina,Babo-quivari,Mule,Huachuca,Chiricahua,andWatermanMountains,andothermontaneareas;aswellasinimpactstudiesoftheMt.GrahamtelescopesiteinthePinaleñoMountainsandtheRosemontMinesiteintheSantaRitaMountains.LocalitydatafromUAICspecimenswill

USDA Forest Service Proceedings RMRS-P-67. 2013 145

Introduction to the Arizona Sky Island Arthropod Project (ASAP): . . . Moore and others

beincorporatedintoaspecimen-leveldatabasefortheASAPProject;thisdatabasealsowillbenetworkedwithotherarthropodmuseumsinthesouthwesternUnitedStates. SpeciesdiversityoftheSkyIslandRegionisalsobeingdocumentedthroughaseriesofcollectingexpeditions.Throughouttheproject,wewillconductsurveysofthearthropodfaunausingavarietyofcollectingmethodsincludinglighttraps,malaisetraps,pitfalltraps,andhandcollectingmethods.AllspecimensfromtheASAPprojectwillbeaccessionedintotheUAIC.Theywillbeidentifiedtospecies,andspecimen-leveldatawillbemaintainedintheUAICspecimen-leveldatabase.Representativesofmanyspecieswillbepreservedinafrozentissuecollectionin-20°Cfreezersandallotherspecimenscollectedwillbemountedonpoints/pinsanddepositedintheUAICpinnedcollectionorpreservedin80%ethylalcoholandarchivedforfuturework.

2.Whatarethebiogeographicaffiliationsandphylogeographicrela-tionshipsoftheSkyIslandarthropods?HavearthropodsdiversifiedorradiatedwithintheSkyIslandRegion? Thedistributionand/orelevationofMadreanSkyIslandspecieshasrepeatedlyshiftedasaresultofcyclicalclimatechangesduringtheQuaternary(Martin1963;Betancourtandothers1990;VanDevenderandSpaulding1990;DavisandBrown1988;VanDevender2002).SeveralstudieshavefocusedonthebiogeographyofspeciesintheArizonaSkyIslandRegionincludingplants,arthropods,birds,liz-ards,andmammals(Brown1971;Downie2004;LinhartandPermoli1994;McCord1995;Sullivan1994;Slentzandothers1999;Barber1999a,b;MaddisonandMcMahon2000;Masta2000;Boyd2002;SmithandFarrell2005a,b;McCormackandothers2008;TennessenandZamudio2008;Oberandothers2011).Mostofthesestudieshavedocumentedsignificantmorphologicalvariationorgeneticstructureamong separate subspecies or populations endemic to differentmountainrangeswithintheSkyIslandRegion.However,noneofthesestudieshaveusedbroadtaxonomicsamplinginthecontextofphylogeographicanalysestolookatthegeographicoriginoftheSkyIslandfauna.InASAP,wewillinfertheevolutionaryrelationshipsandestimatedivergencetimesusingmolecularsequencedatafromfast-evolvingmitochondrialandnucleargenes.Fromthesedata,wewillreconstruct theevolutionaryandbiogeographichistoryof theSky Islandarthropodspecies,and look foremergentpatterns thatmayrevealphylogeographicoriginsofthefaunaandradiationsofspeciesgroupsamongthemountainranges.

3.Whataretheover-archingdriversthatstructurearthropodcom-munitiesintheSkyIslands? Thespatialarrangementofsimilar,isolatedhabitatsrepeatedonnumerousmountainrangesintheSkyIslandRegionprovidesnaturalreplicationforecologicalstudies.Wewillutilizethenaturallabora-toryprovidedbytheSkyIslandstoinvestigateecologicalandgeneticfactorsthatinfluencediversificationandpatternsofcommunityas-sembly.Inparticularwewilladdressthefollowingquestions:(1)Howarespeciesdistributedalongelevationalgradients?(2)Arethepatternscorrelatedwithplantcommunities/biomes,soilpH,precipita-tion,temperature,and/orhumidity?(3)Dohighelevationarthropodcommunitiesdifferinspeciescompositionbetweenisolatedmountainranges?(4)Dolargertracksofwoodlandorforestharboragreaterdiversityofarthropods?Toaddressthesequestions,ASAPmakesthefirstefforttoextensivelyandquantitativelysamplethearthropodfaunaforabroadswathoftheMadreanSkyIslands.Itwillprovidebaselinedataontheabundance,diversity,andcommunitystructurealongelevationgradientsthroughouttheregionforthistaxonomicallyandecologicallydiversegroupoforganisms.

4.Howmightmontanearthropodcommunitiesrespondtorapidlychangingclimateconditions? TheMadreanSkyIslandsprovideamodelsystemforinvestigatingtheeffectsofrapidlychangingclimateonthebiodiversityofisolatedlandscapes.SkyIslandsshowastrongereffectofisolationthanothertypesofisolatedhabitats(WatlingandDonnelly2006).Effectsofclimatechangearealreadyevidenthere(increasedfire,drought,pestoutbreaks,andinvasivespecies).AdditionaltemperatureincreasesofaslittleasafewdegreescouldpushSkyIslandplantandarthropodspecies/communitiestohigherelevations,reducingtheirhabitableareaandpotentiallycausinglocalextinctionsofendemictaxaandevolutionarilyuniquelineages.ProjectionsfromglobalclimatemodelssuggestthattemperaturesintheSouthwestwillincreaseby3-6°Coverthenextcentury(Kupferandothers2005;GutzlerandRobbins2010;OverpeckandUdall2010;Dominguezandothers2010;IPPC2001,2007;CLIMAS2012).Predictionsofwhetherprecipitationwillincreaseordecreasearestillinconflict,andconfidenceinprecipita-tionestimatesislowatthistime.Modelsusedtoexaminehowplantcommunitiesmayrespondtoprojectedclimatechangeindicatethatincreasesintemperaturewillleadtoupslopemovementofcommuni-ties,leadingtoanincreasedareaofDesertscrub(westernSkyIslands)orDesertGrassland(easternSkyIslands)andadecreaseintheareaoccupiedbyMixedConiferForest,thebiomesituatedatthetopofthehighestmountains(Kupferandothers2005).However,increasedprecipitationmightslowupslopemovementsby lesseninggrowthconstraintsimposedbyaridconditions.Ifclimatescontinuetowarmasprojected,specieswillneedtoshifttheirpresentdistributionsoradapttowarmerconditionsrapidly. Anthropogenicactivities are contributing to increased levelsofatmosphericCO2 and thesehigher levels are leading to increasedglobaltemperaturesandchangesinthehydrologiccycle,thuscausingorcontributingtoclimatechange(IPCC2001,2007).Severalreviewshavehighlightedthatlittleisknownaboutthecurrentandpredictedresponses to climate change formost arthropod groups (CoviellaandTrumble 1999; Hughes 2003). Because important ecosystemprocesses, such as litter decomposition and nutrient cycling, aredrivenbyground-dwellingarthropods(Powersandothers2009;YangandChen2009),ecosystemresponsesandsubsequentfeedbackstoatmosphericandclimatechangesmaydependonhowsoilarthropodcommunitiesrespondtotheseperturbations(e.g.,reduceddecomposi-tionrateswilldecreasefeedbackstoglobalcarbon(C)input,whileincreaseddecompositionrateswillincreasefeedbackstotheCcycle;Bardgettandothers2008).Assuch,understandingtheresponseofthesespeciesandcommunitiestoclimatechangeiscriticalifwearetopredicthowsuchperturbationsaregoingtoalterbothbiodiversityandthefunctioningofecosystems. While natural communities may be able to adapt to changingclimatestosomeextent,viashiftsinthedistributionoftheirlocalorgeographicranges,paleontologicaldatasuggestthatcommunitiesdonotrespondtoclimatechangeasentities(Coope1995;JablonskiandSepkoski1996).Rather,speciesresponsestendtobeidiosyncratic,resultinginthedevelopmentofnewassemblagesandassociations(GrahamandGrimm1990;Voightandothers2003).Theseresultsunderscoretheneedforfield-basedinventoriestobetterunderstandcurrentdiversityanddistributionpatterns,whichinturnestablishesa baseline for future comparisons and ecological studies to trackhowspeciesandcommunitiesrespondtofutureclimatechangeintheSouthwest. Wewillusedataacquiredfromourowncollectingandfromspeci-menshousedinmuseumcollectionsincludingtheUAICtodetermineclimaticboundaries for target species; species-specificboundaries


Moore and others Introduction to the Arizona Sky Island Arthropod Project (ASAP): . . .

willthenbeintegratedwithclimatologicalmodelstopredictchangesinarthropodcommunitiesanddistributionsinthewakeofpotentialrapidclimatechange.Todate,thescientificcommunityknowsalmostnothingabouthowarthropodspeciesandcommunitieswillrespondtoclimatechange.Butbecausechangesinbothspeciescompositionandabundancesofarthropodscaninfluenceimportantecosystemprocesses,itisvitaltounderstandhowarthropodsspeciesandcommunitieswillrespondtoclimatechangeandhowarthropodsinfluenceecosystemprocesses.Additionally,becauseclimatechangeispredictedtoleadtoawidespreadreorganizationofspeciesandcommunitypatterns,itisimportanttodocumentthebiogeographyofSkyIslandarthropodspeciesnow,todeterminepatternsofendemismandidentifyspeciesatriskofextinction. TheASAPprojectwillmonitordistributionsofSkyIslandarthropodspeciesoverthenext20–30yearstoseeiftherearedetectableshiftsinspeciesdistributionsasclimatechanges.Wewilluseecologicalnichemodelsandphylogeographicanalysesincombinationtoassesshowarthropodshaverespondedtopastchangesinclimatebyshift-ingdistributionsand/oradaptinginsitu,whichinturnwillhelpuspredicthowspecieswilllikelyrespondtoincreasingisolationandfutureclimatechange.Ultimately,weaimtoidentifyspeciesintheSkyIslandRegionthatmightbeatriskofextirpationorextinctionastheSouthwestwarms,andtoidentifylocationsofrefugiafrompastglaciationeventsthatmaybeareasofhighallelicdiversitythatmeritconservationattention.Wefurtherpredictthateffectsofclimatechangemaybeseeninthisregionofthecountryandontheseisolatedmountainsbeforemostotherareas,andthatbystudyingtheeffectsofclimatechangeherewecanmakebetterpredictionsastowhatwillhappenelsewherelaterintime.

Purpose of This Paper ThepurposeofthispaperistodescribethestudysystemoftheASAP,includingourconceptoftheSkyIslandRegionanditsbiomes,andtopresentpreliminarydataderivedfromourcollectionsintheSantaCatalinaMountainsduringthefirstyearoftheproject.Intheinitialphaseoftheprojectwearedocumentingtheground-dwellingarthropodsoftheSantaCatalinas,andthefirstyear’ssampling(2011)hasbeencompleted.TheprojectwillbeexpandedtootherrangesinsouthernArizona,andeventuallytoselectedrangesinMexicoandtootherarthropods(notjustground-dwellingtaxa).Datacollectedinearlyyearsoftheprojectwillprovideabaselineforfuture/con-tinuingsurveysdesignedtoelucidatehowpopulations,species,andcommunitieschangeasclimatechangesintheSouthwest.

Biogeographic Parameters of the Study

Boundaries and Concept of the Sky Island Region—When theterm“MadreanSkyIslands”wasfirstcoinedinthe1950s,itreferredto those rangespossessingstrongsharedelementswith theSierraMadreOccidental(the“Madrean”flora).Infact,theterm“MadreanSkyIslands”isnotaperfectdescriptoroftheregion,becausemanynorthern(e.g.,RockyMountainorPetran)(Brownandothers1979;Brown1994)speciesreachtheirsouthernmostrangelimitshere,justasmanysouthern(e.g.,Madrean)speciesreachtheirnorthernmostrangelimitsinthisregion.Althoughwearenotsuggestinganamechangehere,conceptuallyitmightbemoreaccuratetothinkofthesemountainrangescollectivelyas“CordilleranGapSkyIslands”andfortheASAPprojectwebroadenthedefinitionoftheMadreanSkyIslandstoincludeall~65oftheisolatedmountainrangesspanningtheCordilleranGap(thatarehighenoughtohaveOakWoodlands)

regardlessofthedegreeofsharedMadreanflora(fig.1).We,therefore,includethenorthernPinalandSuperstitionMountains(Arizona)andtheeasternBigandLittleHatchetandAlamoHuecoMountains(NewMexico),whicharetraditionallynotincludedonmapsoftheMadreanSkyIslands.WedefinethenorthernboundaryoftheMadreanSkyIslandRegionastheSaltRiverValley;northofthislietheMazatzalandBradshawMountains,andotherrangesofArizona’sTransitionZone that grade into the base of the escarpment of theColoradoPlateau’sMogollonRim.ThesouthernmostlimitoftheSkyIslandRegionissomewhatarbitrarilysetat29°Nlatitude(aboutthelati-tudeofHermosillo,Sonora).So,thenorthernmostSkyIslandsarethePinalsandSuperstitions;thewesternmostSkyIslandsareSierraelHumo(inSonora)andtheBaboquivariMountains(inArizona);theeasternmostaretheAlamoHuecoandBigHatchetMountainsofNewMexico;andthesouthernmostSkyIslandistheSierraMazatán70kmeastofHermosillo,Sonora. NearlyalloftheMadreanSkyIslandsexceed1525minelevation,oriffallingshortofthat,theyareconnectedbywoodlandhabitattoanadjacenthigherrangeandthusformpartofaSkyIslandcomplex.TheSierraelHumoreachesanelevationof1650mandhas~1036haofOakWoodland(FleschandHahn2005).TwosmallrangestothewestofSierraelHumohaveoakpatches,buttheydonotexceed1370melevationanddonothavesizeableOakWoodlands(SierraElCobre,1350m;SierraElDuranzo,1210m).TheSierraMazatánreachesonly1545m,butsupportsa largeareaofOakWoodland(~3626ha,withfiveoakspecies)atitshighestelevations,anditissurroundedbya“sea”offoothillsthornscrub(FleschandHahn2005;Dimmittandothers2011). ThenorthernmostSkyIslandranges(thePinalandSuperstitionMountains)largelylackcommonMadreanspeciessuchasthesilverleafoak(Quercus hypoleucoides)thatissocommoninmoresouthernrangesofArizona.Instead,theyharborwoodlandofnorthernspeciessuchasGambeloak(Quercus gambelii)theonlywinter-deciduousoakintheSkyIslandRegion,andPalmeroak(Quercus palmeri).ThePinals,whichreachover2380minelevation,supportalargePetranMontane Pine Forest, surrounded by well-developed OakWoodlandsthatconnecttothewoodlandsoftheSuperstitions,thelatterhavingonlyafewpatchesofponderosapine(thehighestpeakintheSuperstitionsis1900m). Inadditiontothese65ranges(fig.1),severalothersmallrangesinMexicoareapparentlyhighenoughtosupportOakWoodlands,notablyafeweastoftheSierraMazatán.However,plantdataforthese rangesare too sparse todrawfirmconclusionsat this time.We do not consider ranges with only scattered oak patches butlackingtrueOakWoodland—suchasArizona’sTucsonMountains(WassonPeak,1429m)—tobeSkyIslands.Similarly,manyofthesmallmountains inSonora,west of theSierraMadreOccidental,arehighenoughtosupportscatteredpatchesofoaks,especiallyontheirnorth-facingslopes(e.g.,SierraCucurpe),butingeneralthesearenotlargeorcontiguousencinals(OakWoodlands).Totheeast,weincludealloftherangesofappropriateelevationandisolationwestoftheContinentalDivide,plusthreeeastofthedivide(BigandLittleHatchetsandAlamoHuecoinNewMexico).SomeauthorshaveincludedthefareasternCedarMountainsofNewMexicoandothershaveincludedtheSierraSanJavier,130kmeast-southeastofHermosillo.AlthoughincludedonsomeSkyIslandmaps,wedonotincludeSonora’shugeSierraelTigremountaincomplex(i.e.,SierrasElTigre,SanDiego,elOso,andlosPilaresdeTeras)becausethewoodlandsofthoserangesconnecttotheSierraMadreOccidentalsouthofHuachinera(viatheMesaLosTabachines,SierraElGato,andSierraLosTules),whichconnecttotheSierrasatelevationsover1525m,effectivelymakingtheSierraElTigrecomplexa“woodlands



Figure 1—ElevationmapoftheSkyIslandRegionwith65SkyIslandmountainslabeled.Greenshadingindicatesapproximateareaabove1600m(5250ft),roughlytheelevationatwhichoakwoodlandsfirstbegin,althoughthereisconsiderablevariationinthisduetolatitude,slopeandaspect,rainfallpatterns,etc.(MapbasedoncartographicGISresearchbyJoelViers/Lirica.)



peninsula”oftheSierraMadreOccidental.Thissaid,itisknownthatthesewoodlandconnectionshavebeengreatlydiminishedbydrought,fires,and treecuttingand in thenear future this“peninsula”maybecomean“island”asitissurroundedontheotherthreesidesbytheRíoBavispe.Nevertheless,forhistoricalbiogeographicpurposes,theElTigremountaincomplexispartoftheSierraMadre.SouthofthehugeSierraelTigrecomplexinSonora,thornscrubsurroundsmostoftherangessouthtotheSierradeMazatán. The“ApachianFloristicDistrict”(ofMcLaughlin1995)andthe“ApachianSubprovince”(ofthelargerMadreanFloristicProvince)largelycoincidewithourdefinitionsoftheMadreanSkyIslandRe-gion.The12.146-millionha“ApacheHighlandsEcoregion”(ofTheNatureConservancy)somewhatexceedsourviewoftheSkyIslandRegioninthatitextendsnorthwestthroughtheVerdeRiverandBigChinoValleysofcentralArizonatotheMogollonRim,andsouthtoincludethenorthernmostregionoftheSierraMadreOccidental.

Mountain Islands vs. Habitat Islands—Amountainrangeinthisregionistraditionallydefinedasa“SkyIsland”ifitishighenoughtoincludeOakWoodlandhabitatandisnotconnectedbyOakWoodlandstotheCordilleranrangesoftheRockyMountains/ColoradoPlateauor theSierraMadreOccidental (Heald1951;Dimmitt andothers2011).Usingthisdefinition,werecognize~65mountainrangesthatshouldbedesignatedasSkyIslands,32ofwhichareintheUnitedStates(table1).

Inreality,18ofthe32namedmountainrangesnorthoftheborderareconnectedtoatleastoneotherrangebycontiguousOakWood-landandthusthese32rangescanbeclassifiedinto21distinctSkyIslandcomplexes (table2).Manyof theSonoranSky IslandsareconnectedtooneanotherbyOakWoodlandalso,and,inthefuture,withimprovedinformationthesecouldbecombinedintomountaincomplexesaswe’vedoneintable2.The21U.S.mountaincomplexesthatareconnectedbyOakWoodlandcanbethoughtof,ecologicallyand biogeographically as 21 “OakWoodland islands” or “habitatislands.”Manyof thesemountain rangesarehighenough toalsoharborhigherelevationbiomes(e.g.,Pine-OakWoodlands,Chapar-ral,PineForest).However, todate,wehavenotdeterminedhowmanycontiguousvs. isolatedlandscapesofthesehigherelevationbiomesexist.These conceptshaveconsiderable relevance for thebiogeographyofarthropodsthatinhabitthesemontanebiomes. Inaddition,someSkyIslandmountainrangesactuallycomprisetwoormoresubranges,eventhoughmapsandcommonusagetypicallyusethenameofonlythelargestofthese.Forexample,theBaboquivariMountainsactuallycomprisefourranges—theCoyote,Quinlan,PozoVerde,andBaboquivariMountains—separatedfromoneanotherbydistinctvalleys.But,popularusagereferstothemcollectivelyastheBaboquivariMountains.ThissituationisespeciallytroublesomeinMexicowherewehavetriedtodeterminethemostcommonlyusednameforsuchranges.ManyMexicanrangesalsohavemorethanonenameduetolocalusage,etc.,andwehavereliedontheINEGI(InstitutoNacionaldeEstadísticayGeografía)1:250,000mapsofSonoraandChihuahuaforthesenames.WeusedUSGSandINEGIinformation,andaGarmin62SGPSdevice,forestimatingelevationdata.



Biomes of Arizona’s Sky Islands Ecologistsgenerallyagreethatthereareaboutadozenmajorplantcommunitytypesthatoccurworldwide,e.g.,tundra/alpine,temper-atebroadleafforests,Mediterraneanwoodlands/shrublands,tropicalrainforests,coniferousforests,temperateandtropicalGrasslands,temperate and tropical savannahs, tropical dry forests,Chaparral,savannahs,anddeserts.ExamplesofallbutthefirstfourarefoundintheMadreanSkyIslandRegion.Werefertotheseas“biomes”inthisstudy. Here,wefollowtheWhittakerandNiering(1968b),Whittakerandothers(1968),andNieringandLowe(1985)studiesofthevegetationoftheSantaCatalinaMountainsinrecognizingthefollowingbiomesfortheSkyIslandsofArizona:Desertscrub,DesertGrassland,graz-ingdisturbedGrassland,Oak-Grassland,OakWoodland,Pine-OakWoodland,Chaparral,PineForest,andMixedConiferForest.Whit-takerandNiering(1965,1968)listedthesignaturespeciesforeachofthesebiomesintheirnowclassicdiagramsdepictingthebiomesoftheSantaCatalinaMountains.NotalloftheMadreanSkyIslandsarehighenough tohaveallof thesebiomes,andmany lackPineForestand/orMixedConiferForest,especiallyinMexico.However,alleightofthesebiomesoccurintheSantaCatalinaMountains. Theelevationalorderingofthesebiomes,andthestrongMadreancomponentofmostoftheSkyIslands,werefirstformallydescribedbyForrestShreveearlyinthetwentiethcentury(Shreve1915,1919,1922,1936,1951).JosephMarshall’s1957studyofthebirdsofPine-OakWoodlandsoftheborderregionalsodescribedthestackingofbioticcommunitiesoneachislandmountainfromtheMogollonRimtotheSierraMadre,anditwasMarshallwhodefinedthe“MadreanArchipelago”asthosemountainswithMexicanPine-OakWoodlandsintheCordilleranGap.In1951,WeldonHeald,studyingandlivingin the Chiricahua Mountains, coined the evocative and descrip-tivephrase“SkyIslands”for theseranges.Also in the1960s, thepioneeringecologicalstudiesofRobertWhittaker,WilliamNiering,andCharlesLowedescribedthebotanyoftheserangesingrowingdetail.ComprehensivedescriptionsofArizona’sSkyIslandbiomescanalsobefoundintheforthcomingbookA Natural History of the Santa Catalina Mountains, Arizona, with an Introduction to the Madrean Sky Islands(MooreandBrusca,inpress,Arizona-SonoraDesertMuseumPress).

ASAP Surveys in the Santa Catalina Mountains

Catalinas Elevational Gradients

Situated140kmnorthof theUnitedStates-Mexicoborder, theSantaCatalinaMountainsareoneofthebest-knownSkyIslands.Toassessthediversityanddistributionofground-dwellingarthropodsalongelevationandenvironmentalgradients,66samplingsiteswereidentifiedinrecognizablebiomesalongtheelevationgradientsofthesouthernandnorthernsidesoftheSantaCatalinaMountains,alongtheMt.LemmonHighway(southside),theControlRoad(northside),andonMt.LemmonandMt.Bigelow(fig.2).ThesesameelevationgradientsalongthesameroadswerestudiedbotanicallybyLowe(1961),WhittakerandNiering(1964,1965,1968a,b,1975),NieringandLowe(1985),andWhittakerandothers(1968).Whittakerandothers(1968)established30 0.1-haquadrats(20x50m)fortheirplantcensuses.Ourstudyused66belttransects,each0.02hainsize (2x100m)forspecies-X-abundanceplantcensuses.NeitherthestudybyWhittakerandothers(1968)norourinitialstudyexaminedriparian

or“wetcanyon”sites;i.e.,alltransectsitesestablishedduringthefirstyearoftheprojectareuplandsites.Intotalweestablished28siteseachonthesouthernandnorthernslopesoftheCatalinaMountainsand10mixedconifersitesonMt.LemmonandMt.Bigelow. Whilepastworkershavebeeninagreementabouttheover-archingsenseofplantspeciesturnoverandplantcommunitychangewithel-evation,theyhaveagreedonlypartlyinwheretodrawlinesseparatingthesebiomes,andwhattocallthem.ForrestShreve,inhisbenchmark1915paper,separatedtheslopesoftheCatalinaMountainsintothreebroadzonesbasedon thebiogeographicrootsof thepredominantplants:Desertscrub,“encinal”(dominatedbyMadreanspecies),and“forest”(dominatedbyRockyMountain/Petranspecies).Shreve’sideawascompelling,butitdoesnotworkwellforalltheotherSkyIslands, especially those on the fringes of the Sky Island regionwhoseplantcommunityaffinitiesarenotsoclear-cut.ItalsolargelyignoredthegrassesandtheimportanceofGrasslandhabitatontheSkyIslands.InadetailedseriesofpapersbyWhittaker,Niering,andLowe,Shreve’sideaswererefinedintosomethingveryclosetowhatweuseinthispaper.OurschemeisaslightalterationoftheschemepresentedinNieringandLowe’s1985publication,anditisbasedonvegetationanalysesof66transectsitesintheCatalinaMountainsestablishedbytheASAPProject(table3,fig.2). Ineachbiome,100-mlongtransectswereplacedfartherthan0.25kmfromtheroad,tominimizepossibleroadeffects.OnthesouthsideoftherangeweestablishedfivetransectsinDesertscrub(atelevationsof1045–1172m),sixinOak-Grassland(atelevationsof1384–1433m),seveninPine-OakWoodland(atelevationsof1803–2422m),twoinChaparral(atelevationsof1923–2052m),andeightinPineForest(atelevationsof2224–2463m).OnthenorthsideoftherangeweestablishedseventransectsindisturbedDesertGrassland(historicallygrazedareasatelevationsof1323–1451m),sixinrelativelyundis-turbedDesertGrassland(atelevationsof1330–1645m),twoinOakWoodland(atelevationsof1939–2000m),fiveinPine-OakWoodland(2032–2149m),fiveinChaparral(atelevationsof1845–1971m),andfourinPineForest(atelevationsof2218–2305m).TentransectsinmixedconiferhabitatwereestablishedintheMt.LemmonandMt.Bigelowareas(atelevationsof2442–2777m). The southern slope elevation gradient along theMt. LemmonHighwaydoesnothavegoodOakWoodlandorGrassland;allgrasshabitatsonthesouthsideweredeemedtobeOak-Grassland,afactalsoobservedbyWhittakerandNiering(1965),althoughgoodDesertGrasslandcanbefoundbyhikingwest fromMolinoBasina fewmileson theArizonaTrail.Thenorthern slope elevationgradientalongtheControlRoadhasnoDesertscrub,itbeginsnearthetownofOracleat1220minelevation,afactobservedbyForrestShreveandallsubsequentworkssincethe1920s.However,thenorthernslopedoeshavehighlydisturbed,overgrazedGrasslandthathasconvertedto scrubland (whichwe sampled) that resemblesDesertscrub asovergrazedGrasslanddoesthroughoutsouthernArizona.Thereduc-tionofgrassesbylivestockandfiresuppression,andthesubsequentinvasionbywoodyandshrubbydesertplantsintheSouthwest,hasbeenknownsinceAldoLeopold(1924)andalargeliteratureexistson thissubject.ThenorthsidealsohadnoOak-Grassland; itdid,however, have relatively undisturbedDesertGrassland and somepatchesofOakWoodland.Ofcourse,ithaslongbeenrecognizedthatthesebiomes,orplantcommunities,intergradecontinuously(Whit-takerandothers1968;BrownandLowe1980),andlocalvariationsinvegetationareduetogradientsofslope,soiltype,slopeaspect,etc.ThiswasamajorfocusofWhittakerandhiscolleagues’workintheSkyIslandsformanyyears.Adetailedseriesofpapers(Whit-takerandNiering1964,1965,1968a,b,1975;Whittakerandothers1968)exploredrelationshipsbetweenplantspeciesandavarietyof



Figure 2—TheSantaCatalinaMountainsfromspaceshowinglocationofmajortopographicfeaturesaswellastheMt.LemmonHighwayandtheControlRoad.



(continued)



environmentalfactors.Itisnotourgoaltorepeatthoseanalysesbutrathertoaccuratelydescribeandclassifythebotanyofourarthropodtransectsites. Transectsitesforour2011fieldworkintheCatalinaMountainswerecategorizedaccordingtosixenvironmentalvariables:elevation,slope,aspect,biome,aswellasgroundtemperatureandhumidity.ALog-TagHAXO-8temperatureandhumidityrecorderwasplaced2cmabovethesoil/litterinthecenterofeachofthe66transects.Log-TagswereplacedinthefieldonMay6,2011andtheyrecordeddataevery30min.AveragetemperaturedataforeachsitealongtheelevationgradientsfromMay7,2011,throughSeptember14,2011,isplottedaccording toelevationandbiome (fig.3).Althoughwedidnotstatisticallyanalyzethetemperaturedata,itisapparentthatnorth-andsouth-sidetemperatures(perelevation)werenotmark-edlydifferent,andthisisprobablypartlyduetothefactthatthiswasthehottesttimeoftheyear,althoughdifferencesinslopeaspectandotherfactorsprobablyalsocontributedtoeveningouttheseaverages.Nonetheless,theoverallnegativecorrelationbetweentemperaturevs.elevationandbiomeisclear.

Ground Dwelling Arthropod Surveys

Weset10pitfalltrapsarranged10mapartalongeach100-mtransectline.PitfalltrapdesignwasadoptedfromHiggins(2010).EachtrapconsistsofaheavyPyrexglass“testtube”(3.2cmdiameter,25cmdeep)insertedinaPVCsleeve(3.8cmindiameter,28cmlong)thathadbeenburiedintheground.Theopeningofthetrapisflushwiththesoilsurface,andtheglasssamplingtubescanbeexchangedwhileleavingthePVCsleeveinplace.Trapswerechargedwithpropyleneglycol(50%full).APVCrainshieldcoverstheopeningofthetrap,3–4cmabovetheground.Whentheglasstubesarenotinplace,thePVCsleevesarecapped toprevent them fromfillingwithdirtorinadvertentlycapturinganyanimals. In 2011 we sampled for 2 weeks in the spring (pre-monsoon, May1–15)and2weeksinthelatesummer(post-monsoon,September1–15).Thisprojectrepresentsthefirstefforttoextensivelyandquan-titativelysamplethearthropodfaunaofanyoftheSkyIslandsoftheMadreanArchipelagoand,assuch,willprovidebaselinedataontheabundance,diversity,andcommunitystructureofthisexceptionallydiversegroupforfuturestudies.



Figure 3—Average summer temperatures collected 7-May-2011 to 14-Sept-2011 along the transect elevation gradients in the Santa Catalina Mountains. Top: A comparison of average temperatures at sites on the South and North sides of the mountain, as well as those found at the highest elevations on Mt. Lemmon and Mt. Bigelow. Bottom: A comparison of average tem-peratures at sites in different plant biomes.

Here,wepresentpreliminaryspecieslistsoftheantsandcarabidbeetlesbasedonourfirstroundofpitfall-trapsampling.Thesedataweresupplementedfromspecimen-leveldata in theUniversityofArizona InsectCollection to developworking lists of the knownspeciesfromtheSantaCatalinaMountains.Weexpectthesespeciesliststogrowwithfuturecollectingandmonitoringefforts.

Ants—Theants,familyFormicidae,arepossiblythenumericallydominantfamilyofinsects.Antsrepresent10–15%oftheentireanimalbiomassinterrestrialecosystems(HölldoblerandWilson1990).Ants

haveplayedasignificantroleintheevolutionofmodernterrestrialbioticcommunitiesforatleastthelast40–50millionyears.MorespeciesofantsoccurinArizonathaninanyotherU.S.State(Johnson1996). WhiletherehavebeennoextensivesurveysoftheantfaunaoftheSantaCatalinaMountains,weexpecttheirdiversitytobesimilartothatofotherSkyIslandsofcomparableareaandelevationrange.Themostwell-knownSkyIslandantfaunaisthatoftheChiricahuaMountainswhere187specieshavebeendocumented,representing59%ofthetotalknownantfaunaofArizona(StephanCover,personal



communication).Todate,intheSantaCatalinas,88specieshavebeenidentifiedthroughourpitfalltrapsandtheUniversityofArizonaInsectCollection(table4).

Ground Beetles—Thegroundbeetles,familyCarabidae,compriseoneofthelargestbeetlefamilieswithatleast40,000describedspeciesworldwide.Mostgroundbeetlesrepresentapexpredatorsofmostsoilarthropodcommunitiesand,thus,playanimportantecologicalroleinalmosteveryterrestrialhabitat.Becauseofthis,theyhavebeenimportantsubjectsinecologicalandclimatechangestudiessuchas

thelong-termclimatechangestudypresentlybeingconductedbytheNationalEcologicalObservatoryNetwork(NEON).Thereareover2500describedspeciesofCarabidaeknownfromNorthAmerica.BasedontheholdingsoftheUAIC,over300speciesoccurintheSkyIslandRegionofArizona.TransectsamplesandUAICcollec-tionrecordsdocument69speciesofCarabidaeoccurringintheSantaCatalinaMountains(table5). InitialanalysesofpatternsofspeciesdistributionofcarabidsandantsfindpatternsforthefaunaoftheSantaCatalinaMountainssimilarto



thoseHalffter(1987)recognizedinthemountainsofMexico.Specieswithtemperateancestraldistributionsaregenerallyfoundathigherelevations(PineForestandMixedConiferForest),whileNeotropicalspeciesaregenerallyfoundatlowerelevations(Desertscrub,DesertGrassland,andOakWoodland).ThispatternisalsosimilartothosereportedinthestudiesofBall(1968),Liebherr(1994),andMarshallandLiebherr(2000)formontanecarabidsinMexico.Forexample,

in the Catalinas, the temperate genus Scaphinotus is representedbyonespecies, Scaphinotus petersi catalinae VanDyke, whichisrestrictedtoPineForestandMixedConiferForestand thetropicalgenus Goniotropis, representedbyGoniotropis kuntzeni Bänninger,which isrestrictedtoOak-Grassland.TheMadreanArchipelagoandtheneighboringnorthernSierraMadremountainsaretheonlyareasintheworldwheremembersofthesetwogenera,withsuchdisparateancestraldistributions,canbefoundwithinthesamemountainrange.



Plant Surveys

PlantsurveyswereconductedAugust5-14,2011.Surveysweremadeforeachtransectsiteintwoways.First,thetransectlinewaswalkedandeveryplantrecordedwithinonemeteroneithersideoftheline.Thisproduceda200-m2belttransectrecordofplantspeciesandabundance.Then,thetransectwaswalkedagain,thistimescan-ningthebroaderareaoutsidethe200-m2area,notingthepresencebutnotabundancesofanyplantsthatmightnothavebeeninthebelttransectitself.Forpracticalreasons,RockyMountainponderosapineandArizonapinewerecountedtogether,andnoattemptwasmadetodistinguishbetweenthesetwospecies.IntheCatalinaMountains,theCoronadoNationalForestmanagestheseasa“singlespecies,”andpastworkershaveconsideredArizonapine tobeavarietyofponderosa(P. ponderosavar.arizonica),althoughthisisnotcurrentopinion. Surveysofplantsinthe66transectsitesintheCatalinaMountainsrecordedatotalof316species:24trees,30woodyshrubs,23stemandrosettesucculents(includingonehybridagave),38grasses,and201smallshrubs,herbsandannuals.Dataaresummarizedintable6,andacompletelistofplants-by-biomeisgivenintable7.Foreachbiome,therearetwospecieslists,oneof“commonspecies”thatoccurredintwoormoretransectsandtheotherof“uncommonspecies”thatoc-curredinonlyonetransect.ThecompleteplantdatabaseisavailablefromW.Moore.WhittakerandNiering’s(1964)benchmarkstudyofthesouthernslopesoftheCatalinaMountainslisted700plantspecies(thoseabove2743mbeingfromthesouthernslopesofthePinaleñoMountains),buttheydidnotreporttheseplantoccurrencesrelativetospecificbiomesaswedointhispreliminarystudy.Instead,they

reportedthemrelativetoalargematrixofenvironmentalvariablesandgrowthforms.Althoughwedonotusethatapproachhere(weareinterestedindocumentingplantspeciesassociatedwithourarthropodtransectsites),theASAPprojectiscollectingdetailedenvironmentaldataandmayundertakesuchananalysisinthefutureasrelevanttoarthropodspeciesandcommunities.Also,noneofthepublicationsbyWhittaker,Niering,orLoweanalyzedplantoccurrencesstatisticallyintheCatalinaMountainsrelativetoelevationorbiome. Afterclassifyingsitesaccording tobiomeusing thecategoricalsystempreviouslydescribed,weusedaseriesofanalysisofsimilarity(ANOSIM)testsasimplementedinPRIMER5.2.9(ClarkeandGorley2001)toaskiftheplantcommunitiesinthesebiomessignificantlydiffer from one another. We calculated the Bray-Curtis distanceamongallpossiblepairsofsitesbasedonspeciescompositionandabundanceofthe77speciesoftrees,perennialwoodyshrubs,andsuc-culentsfoundinoursites.WethenusedANOSIMtoestablishoveralldifferencesamongplantbiomes, followedbya seriesofpairwisebiomecomparisons.Tovisualizetherelationshipsamongsitesweprovidethemultidimensionalscaling(MDS)ordinationplot(fig.4).ANOSIMrevealedsignificantoveralldifferencesinplantcommunitycompositionamongbiomes (R=0.858,P<0.001).Furthermore,pairwisecomparisonsindicatethatallplantbiomessignificantlydifferfromoneanother,whichsuggeststhatourclassificationsystemdoesidentifysitesthatareuniquewithregardtotheirplantassemblages.Oak-Woodlandsiteswereexcludedfromtheseanalysesbecauseofthelowsamplesize(twosites).Tothebestofourknowledge,theANOSIManalysisofour66sitesbasedonplantabundanceandspe-ciescompositionisthefirststatisticalanalysisofplantdistributionsinthisrange.

Table 6—Biomes sampled in the Santa Catalinas, with numbers of plant species recorded from transects in each.

Biome a

Commonspecies b

Uncommonspecies c Total species

Elevation range sampled

Desertscrub (S)5 transect sites

44 30 74 1045-1172 m(3428-3845 ft)

Desert Grassland (N)5 transect sites

61 70 131 1330-1645 m(4364-5397 ft)

Grazing-Disturbed Grassland (N)7 transect sites

51 48 99 1323-1451 m(4340-4760 ft)

Oak-Grassland (S)6 transect sites

52 36 88 1384-1433 m(4541-5030 ft)

Oak Woodland (N)2 transect sites

9 21 30 1939-2000 m(6362-6562 ft)

Chaparral (N)5 transect sites

32 22 54 1845-1971 m(6053-6467 ft)

Chaparral (S)2 transect sites

10 17 27 1923-2052 m(6309-6732 ft)

Pine-Oak Woodland (N)5 transect sites

29 17 46 2032-2149 m(6667-7051 ft)

Pine-Oak Woodland (S)7 transect sites

26 24 50 1803-2422 m(5915-7946 ft)

Pine Forest (N)4 transect sites

10 13 23 2218-2305 m(7277-7562 ft)

Pine Forest (S)8 transect sites

25 20 45 2224-2463 m(7297-8081 ft)

Mixed Conifer Forest (MTN) 10 transect sites

24 19 43 2442-2777 m(8012-9111 ft)

a N = northern slopes of range (along Control Road). S = southern slopes of range (along Mt. Lemmon Highway). MTN = Mt. Lemmon and Mt. Bigelow sites. b “Common Species” are species found in two or more transects in the given biome. c “Uncommon Species” are species recorded from only a single transect in the given biome.



Cont.



Table 7—Continued

Cont.



Table 7—Continued

Plantdiversitydataaresummarizedintables6and7.ThehighestplantdiversityoccurredinourDesertGrasslandsitesonthenorthside of the CatalinaMountains, where the relatively undisturbedtransectsiteshadatotalof131speciesandthegrazing-disturbedsiteshadatotalof99species.ThiswasfollowedbythesouthernslopeOak-Grasslandsiteswith88species,andtheDesertscrubsiteswith74species.Pine-OakWoodlandsiteshad46plantspecies(northernslopes)and50species(southernslopes).ThelowestdiversitysiteswerePineForestofthenorthernslopes(23species)andChaparralonthesouthernslopes(27species).ThisisthesamebiomediversitytrendnotedbyWhittakerandNiering(1965)andotherworkersovertheyears.AnumberofourplantrecordsarenewspeciestotheCata-linaMountains,orsignificantelevationextensions,andthesewillbediscussedinfuturepapers.

Desertscrub—BecausethebaseoftheCatalinaMountainsonitsnorthernsideis~1220m,thereisnoDesertscrub.Instead,thebiomeatthebase(thestartoftheControlRoad,inthetownofOracle)isGrassland.However,awell-developedArizonaUplandDesertscrubisatthebaseofthemountainonthesouthside,anditcontainsallofthesignatureplantsofthisSonoranDesertsubprovince(table7).Whittaker andNiering (1965) called this the “SonoranDesert ofMountainSlopes”biome,even thoughForrestShrevehadcoinedthewell-acceptednameArizonaUplandin1951forthissubprov-inceoftheSonoranDesert.ThreeofourDesertscrubsitesarenearBabadDo’agViewpoint,alongtheBabadDo’agTrail.Becauseofitselevation(1133–1160m)andproximitytotheopeningofMolinoCanyon,theBabadDo’agsitesarewetterthantheotherDesertscrubsite(1045m),andthusvelvetmesquite(Prosopis velutina)anddesert



hackberry(Celtis pallida)arepresent(andpaloverde/Parkinsoniasp.andsaguaro/Carnegiea giganteaarefewerinnumber);alsoshindag-geragave(Agave schottii),turpentinebush(Ericameria laricifolia),limberbush(Jatropha cardiophylla),sprawlingpricklypear(Opuntia phaeacanthavar.major),andmanywildflowers.Forexample,purplegroundcherry(Physalis crassifolia),desertwindmills(Allionia in-carnata)andspikemoss(Selaginella arizonica)occuratthiswettersite,indicativeofitsproximitytothetransitionintoGrasslandhabitat.Althoughnoneofourtransectshadinvasivebuffelgrass(Pennisetum ciliare),largepatchesofitoccuracrosstheDesertscrublandscapeonthesouthernslopesoftheCatalinaMountainsandintheBabadDo’agTrailarealargepatchesofinvasiveLehmannlovegrass(Eragrostis lehmanniana) alsoarefound.Desertscrubhabitatextendsto~1177monthesouthernslopesoftheCatalinaMountainsalongtheMt.LemmonHighway.

Undisturbed Savanna-like Habitats: Desert Grassland and Oak-Grassland—Abouthalftheplantspeciesfoundinthesetwosavanna-likebiomesareshared,sowediscussthemtogether.TherearenolargeswathsofDesertGrasslandalongtheMt.LemmonHighwayonthesouthsideofrange,andthereDesertscrubtransitionsquicklyintoOak-GrasslanddominatedbyEmoryoak,Arizonawhiteoak,andfourgrasses-side-oatsgrama(Bouteloua curtipendula),canebeardgrass(Bothriochloa barbinodis),Arizonapanicgrass(Urochloa arizonica),andtheelevationallywide-rangingbullgrass(Muhlenbergia emersleyi)(atotalof14grasseswererecordedinourOak-Grasslandtransects).OtherabundantplantsofourOak-Grasslandsitesarepointleafman-

zanita(Arctostaphylos pungens),shindaggeragave,sotol(Dasylirion wheeleri),beargrass (Nolina microcarpa),mountainyucca (Yucca madrensis), scarletcreeper (Ipomoea cristulata),Amaranth(Ama-ranthusnr.palmeri),andthreespeciesofPortulaca.AlthoughourGrasslandandOak-Grasslandsitessharemanyspecies,eachalsohasmanyuniquecomponents(table7).ThetransitionbetweenGrasslandandOak-Grasslandbiomesismosteasilyseenintheturnoverofgrassspeciesalongelevationalgradientsandtheincreasingabundanceofoakswithhigherelevations.AlthoughArizonawhiteoak(Quercus arizonica)andmanzanitamaketheirfirstappearanceinthesegrassyhabitats,theseareelevationallybroad-rangingplantsthatarealsofoundinChaparral,OakWoodland,andPine-OakWoodland.Incontrasttothesouthernslopes,thenorthsideoftheCatalinaMountainshasaccessible,expansive,rollinghillsofDesertGrasslandbutnowell-developedOak-Grassland(alongtheControlRoad).Thesenorth-sideDesertGrasslandsitesharbored131plantspecies,makingthisthemostbotanicallydiversebiomeinourstudy,including22grassspe-cies,although4speciesdominatedinabundance:side-oatsgrama,Arizonapanicgrass,Mexicanpanicgrass(Panicum hirticaule),andtheinvasiveLehmannlovegrass.Inadditiontothesegrasses,velvetmesquite,whitethornacacia(Acacia constricta),wait-a-minutebush(Mimosa aculeaticarpa),fairyduster(Calliandra eriophylla)wereallpresentinhighnumbers, indicativeofsomehistoryofgrazingdisturbance.OnGrasslandsiteswithstronglimestonepresence,themostabundantplantsincludedahalf-dozentypicalDesertscrubspe-cies,withocotillo(Fouquieria splendens)dominating.Groundcover

Figure 4—MDS ordination of sites based on Bray-Curtis similarity values. Sites were classified according to the composi-tion and abundance of 77 species of trees, perennial woody shrubs, and succulents found in the transect sites. Plant biome designations for each site were determined a-priori using the criteria outlined in this paper. Note that the MDS ordination shown in this figure is a 2-dimensional compression of a multi-dimensional clustering of the sites, so graphical representa-tion is not perfect. However, the stress value of 0.07 indicates that information in the 2-dimensional figure does a good job of describing patterns in the multi-dimensional space.



bygrasseswashighinallDesertGrasslandtransects,often90%,andsometimesdominatedbytheinvasiveLehmann’slovegrass.

Grazing-Disturbed Grassland—OnthenorthsideoftheCatalinaMountains,mostGrasslandhabitatshavebeenconvertedto“scru-bland”byoveracenturyofgrazing,givingthelandscapeadesert-likeappearance.SeventransectswereestablishedinthishighlydisturbedDesertGrasslandnearthebaseofthemountainalongtheControlRoad,from1337to1451m.Allofthesesitesshowedevidenceofdecadesofheavylivestocktraffic,withagreatdealofdisturbed,baredirtanddisruptedsoiland,insomeareas,erosiondowntobedrock.Thesetransectshad99plantspeciesthatwereamixofDesertGrasslandandDesertscrubspeciescharacteristicoflong-overgrazedGrasslandsofsoutheasternArizona.TypicalinvasivenativeDesertscrubplantsincludedvelvetmesquite,whitethornacacia,catclawacacia(Acacia greggii),fishhookbarrelcactus(Ferocactus wislizeni),slimragweed(Ambrosia confertiflora), and fairyduster,and theabundanceandbiomassofthesespeciesgenerallyexceededthatoftheGrasslandspecies.Thelargenumberofgrassspecies(19)inthesedisturbedsitesmightbedue,inpart, tothehistoryoflivestockgrazingandimportedforage.Thiswastheonlysitewherewefoundredbrome(Bromus rubens),anexoticinvasivegrass.

Oak Woodland—OakWoodlandisgenerallycharacterizedbystandsofoaks,withjunipersandpinyons.ThisbiomereachesitsmaximumdevelopmentintheSierraMadreofMexico,andingeneral,morenorthernSkyIslandshavelessOakWoodlandthanmoresouthernranges.IntheCatalinaMountains,well-developedOakWoodlanddoesnotoccuralongtheMt.LemmonHighway,onthesouthsideofthemountains.However,onthenorthsideoftheCatalinaMoun-tains,patchesofOakWoodlanddooccuralongtheControlRoad,andinourtwotransectsitesinthishabitattherewasatotalof30plantspecies(tables6and7).SevenoftheninesignaturespeciesofthisbiomelistedbyWhittakerandNiering(1968b)occurredinoursitetransects.Thesewoodlandsaredensewithfoliage,thelargedominantsbeingArizonawhiteoak,silverleafoak,Chihuahuapine(Pinus chihuahuana), alligator juniper (Juniperus deppeana), andFendlerbuckbrush(Ceonothus fendleri).Bullgrasscoversmuchofgroundbetweenthetrees.IntheCatalinas,theelevationallybroadlyoccurringalligatorjuniper,Fendlerbuckbrush,andadder’stonguemaketheirfirstappearancesinOakWoodlandsandarethenfoundallthewayintoPineForesthabitatandinthecaseofadder’stongueintotheMixedConiferForest.

Chaparral—InteriorChaparraloccursonboththenorthandsouthsidesoftheCatalinaMountains,butitismoreextensivelydevelopedalongtheControlRoadonthenorthernslopes.OurChaparralsitesonthesouthsideoftherangehad27plantspecies,whereasthenorthernsiteshad54.Eventhoughtheplantdiversityonthenorth-sidesiteswasgreater,neitherborderpinyonnorsotolwerefoundinthosetran-sectsites.Thenorth-sideChaparraltransectshadabundantalligatorjuniper,Arizonawhiteoak,Emoryoak(Quercus emoryi),Fendlerbuckbrush,mountainmahogany(Cercocarpus montanus),silktasslebush(Garrya wrightii),andmountainyucca—allmissingfromthemoredepauperatesouth-sidesites(tables6and7).ThisisnottosaythesetypicalChaparralplantsdonotoccuronthesouthernslopesoftheCatalinaMountains;theydo,butjustnotinourtransectsites.VirtuallyalloftheChaparralalongtheMt.LemmonHighwaywasburnedinthe2003Aspenfire,includingourtwosouth-sidetransectsites(nearManzanitaVistaandWindyPointVista),anditislikelythiswasatleastpartlythereasonthesesitesweredepauperaterelativetothoseonthenorthsideofthemountains(noneofourfivenorth-sideChaparralsitesburnedintheAspenFire).Thesesouth-sideplantcom-munitiesareonlynowbeginningtoshowstrongrecovery.Chaparral

transects onboth sidesof the rangeweredominatedbypointleafmanzanita,silverleafoak,golden-floweragave(Agave chrysantha),beargrass,andspidergrass(Aristida ternipes var. ternipes).Higherplantdiversityinthenorth-slopesitesislikelyalsoduetothegreatervarietyofsoiltypesthere,includinglimestonesoils.WhittakerandNiering(1965)andothershaveshownthatlimestonesoilsshiftplantbiomesupwardonSkyIslandmountains,suchthatatelevationswhereGrasslandwouldnormallyoccuronefindsDesertscrubplants(withastrongpresenceoflimestone-lovingspeciessuchasocotillo).Thisshiftpresumablyoccursbecauselimestoneisporousanddoesnotretainmoisture,creatingamorexericsoilconditionthatDesertscrubplantsareadaptedto.SeveralofourChaparralsiteswereonlimestonesoilsandtheseshowedtheexpectedup-elevationshiftinDesertscrubplants.

Pine-Oak Woodlands—OurPine-OakWoodlandtransectshadatotalof50species(southslopes)and46species(northslopes).Abun-dantonbothslopeswerealligatorjuniper,Chihuahuapine,RockyMountainponderosapine/Arizonapine,RockyMountainDouglas-fir(Pseudotsuga menziesii var. glauca),silverleafoak,Fendlerbuckbrush,mountain yucca, cudweed (Pseudognaphalium sp.),NewMexicogroundsel (Packera neomexicana), goldenrod (Solidago wrightii),andbullgrass.ItisherethatRockyMountainDouglas-firandRockyMountainponderosapine/ArizonapinemaketheirfirstappearanceintheCatalinaMountains,tocontinueallthewayintoMixedConiferForest.Silverleafoak,withitsbroadelevationalrange,occursfromPine-OakWoodlandandChaparralwellintoPineForesthabitat.AllsixofWhittaker andNiering’s (1968b) signatureplant speciesofPine-OakWoodlandoccurredinourtransectsites.

Pine Forest—OurPineForesttransectsiteshadatotalof45species(southslopes)and23species(northslopes).AbundantonbothslopeswereRockyMountainponderosapine/Arizonapine,southwesternwhitepine(Pinus strobiformis),RockyMountainDouglas-fir,silver-leafoak,Fendlerbuckbrush,brickellbush(Brickelliasp.),butterweed,goldenrod, pineland dwarf mistletoe (Arceuthobium vaginatum),cudweed,brackenfern(Pteridum aquilinum),andbullgrass.Althoughwhitefiroccurredinsomeofthesouth-sidePineForesttransects,this tree ismore typicalof theMixedConiferForest anddidnotoccurbelow2255minour transects.RockyMountainponderosapine/Arizona pinewas dominant conifers in both thePineForestandMixedConiferbiomes.WhittakerandNiering (1968b)notedfivesignatureplantspeciesofPineForest,althoughtwowerelower-elevationtransitionalstoPine-OakForest/Woodland,andallbutoneofthese(theirtransitionalnetleafoak/Quercus rugosa)alsooccurredinourPineForesttransects.ItisintheupperPine-OakWoodlandandPineForestbiomesthatponderosaPineForestsdominatethevisuallandscapeoftheCatalinaMountainsandmostofArizona’sotherhighSkyIslands.

Mixed Conifer Forest—TransectsitesinourMixedConiferForestsites,onMt.LemmonandMt.Bigelow,at2442–2777mhad43spe-cies(tables6and7).Dominants,intermsofnumbersofindividuals,wereRockyMountainponderosapine/Arizonapine,whitefir(Abies concolor), southwesternwhitepine,RockyMountainDouglas-fir,pineywoods geranium (Geranium caespitosum), Oxalis sp. (anunidentified Oxalidaceae), mountain parsley (Pseudocymopterus montanus), braken fern, meadow rue (Thalictrum fendleri), andViolaspp(anunidentifiedviolet).Corkbarkfir,whichisraresouthoftheMogollonRim,occurredinonly2ofour10MixedConiferForest transects.Therearenonaturallyoccurringspruces (Picea)intheSantaCatalinaMountains,andprobablyalsonolimberpine(Pinus flexilis),amorenorthernspecies,despitesomeold(dubious)recordsfromtheCatalinaMountains.WhittakerandNiering(1964)



andWhittakerandothers(1968)subdividedtheMixedConiferForestintotwoelevationalzones,“montanefirforest”and“subalPineFor-est”(above2440m/8000ft).Theydistinguishedtheir“montanefirforest”biomebysixspeciesthatoccurredonoursamplingtransects.

Summary TheArizonaSkyIslandArthropodProject(ASAP)waslaunchedin2011.Parametersandover-archinggoalsoftheproject,andpreliminaryresultsofyearone,arepresentedhere.WedefinetheboundariesoftheMadreanSkyIslandRegionsomewhatmorebroadlythantheyhavebeeninthepast,withlessofanemphasisontheMadreanfloracomponentsandmoreofanemphasisontheirlocationasisolatedCordilleranGapranges.TheMexicanSkyIslandsarestillnotwellknownandadjustmentsregardingtherangeandextentoftheSkyIslandRegionwillnodoubtbefinetunedinthefuture.Wepointoutthe important difference between “mountain islands” vs. “habitatislands.”WepresentthefirststatisticalanalysisofplantspeciesandbiomesintheSantaCatalinaMountains,andusethistopreliminar-ilyestablishthebiomenamesandboundariesthatwewilluseinourarthropodanalyses.Yearoneantandgroundbeetle(Carabidae)datafortheCatalinasarepresented;bothgroupsarehighindiversity(88antspecies,69groundbeetlespecies)andshowatrendofspeciesaffiliationtoplantbiomes.

Acknowledgments Thispaperwouldnothavebeenpossiblewithouttheassistanceofmanypeople,whogenerouslyhelpedinthefieldandwiththeresearch,andwhoputupwithourendlessbadgeringwithquestions.Grate-fulthanksgotoDavidBertelsen,MarkDimmitt,GeorgeFerguson,GeorgeMontgomery,andJulieWiensfortheirbotanicaltutorials.ThankstoAaronFleschforinformationonSonoranSkyIslandsandforhisreviewofthemaps.OurthanksarealsoextendedtoStevenCoverforhishelpidentifyingtheantsinthisstudy.Thisworkwouldnothavebeenpossiblewithouttheassistanceofmanyundergradu-atestudentsincludingRebeccaCompoy,KaylaJones,HeeJu,ChrisMcGinnis,GabeOropeza,ChelseaPowers,ShawnaRodgers,CarolTepper, andErynWouri.Special thanksgo toEmmanuelBernal,ReillyMcManus,JeffHenkel,RyanMcInroy,GarrettHughes,PaulMarek,JasonSchaller,andJamesRobertsonfortheirhelpsettingandharvestingpitfalltrapsandsortingpitfalltrapsamples.OurworkintheCatalinasisfacilitatedbyU.S.ForestServiceSpecialUsePermit#SAN0287.ThankstoLindaBrewerandGoggyDavidowitzfortheircarefulreviewsofthismanuscriptthatgreatlyimprovedthequalityofthispaper.TheUniversityofArizona’sDepartmentofEntomologyandCenterforInsectScience,aswellasNationalGeographicSoci-ety(8964-11)andtheNationalScienceFoundation(EF-1206382)providedfundingforthisproject.

Authors NoteThispaperrepresentsthecombinationoffourpresentationsmadebytheauthorsinaSessiononBiodiversityofArthropodsattheconfer-ence.Thetitlesofthesepresentationswere“TheArizonaSkyIslandArthropodProject(ASAP):Systematics,Biogeography,Ecology,andPopulationGenetics ofGround-DwellingArthropods,” “DoPlantBiomesAlongtheElevationGradientintheSantaCatalinaMountainsHarborUniqueArthropodCommunities?”“DiversityandSpecies

CompositionofAntAssemblagesintheSantaCatalinaMountains,”and“HiddenBiodiversityofSkyIslandArthropods.”

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