Oavid C.,Shaw d,o Ronald J. Taylor D.o".tr.a'l,o, Boroq, Wo F W.' r'o .t,.o, L 86 g.d !4o11lo 98ll5

Polljnation Ecologyof an Alpine Fell-FieldCommunity in the North Cascades

Abstract 'ruh-!f '{ rlr loliiirlion.''1!1og\of an alpir tul]ficld lo.areit ir LheNIounr Ilater areaoJ washingtonStar. ras ronducred iru.nsth' Lumtrrr''ol l93l llllhation svndrocsGtraregie!)ofth.dorrinanrptantswerearemophrrv.g,ine.arjze.t.nlomoph ilr' and sl"ializ'd ent'nophilv lrs.cr 'Ihe !isitationsro ptantspecies werc q"-tir;,"t "".l i"""",g prenorog! nut $as denrin,n"u. inldtant pollinrrorsrere t,unblcl,rs, srrplid nr"., -a ,,-*"ri iii"., "i'];,". ,",0",,,,,"" $ere hurrerliesand p'imitivf llic' Plantserhitririne specializ*1 entornophily appearcdro oinin;e comperi,i"' l, .""p"-,r"" of ltowerjng NIanyot rheplants lrhiliring rinrcs. gL:neralizedenrooopt,ili norercrt s1mhron",.r,, p".r,.,p.f* ' "r" .,\ ,,",a*,arion to alra.t h.ge nunbcrs 1. 1, ,..r.,i,.. 1 , r-t'^\ .,.,4Lhi F tt,{pr:

Introduction rcducrng competition for pollinators. Foraging behavior of flies and butterflies is variable Pollin.rriuner-ul'rgr i. a rapidh gror.ing -uh- anJ "olJ-fa.lrr,,rrnJ' lesslell known (Proctor and yco l9?3, Faegri dr- inline.l bi,,log\.rccen \ e,ndVand"r Pijl l,r7q,.In gnrreral.ili,.. proier erpanJirrglrnrrr .r nrinrarilrdc", riprir, to an .i- llo\1crj sith n,rn-con.erl,d rerarrl., Jo not perimenlal science.Howerer, although therc are .peeializ".und appcarirr rlpirr,.r"ommunitie. a, number of excellent tcxts, c.g., Faegri and earll in the season.Buttcrflies preler tubular Vander Pijl (1979),Jones and LitJe (1983),proc- llorcrs with toncealed rcwards, have a higher tor and Yeo (1973), and Richards (1978), ancl level of floral constancythan flies, and app"ar nunrerou:arlr"ter , "nc, rningpollination biolugr. much later in the season. rhcrcare lp\ .rLdic.thar de.rl sp,.rificallr uirh F,'r6rr.'rn, trnalpin. plrnt r'umrnunl\\!a\ pollirrati.'nnr,,logr oiLrll,irr,, "ornmuliri... I hi. . !'.lp.tc,lb., au5. ,ri irss irn plir.irr . la,k "f d i,ru is espcciallv truc of the North Cascades. r. bance, and, perhaps, more obvious plant-inscct The nost comrnonh cited insect pollinaror coadaptations,i.e., relationship betr,reenfloral groups (orderslfamilies)in alpine areasof North rnorphologr/color and trpe of insect pollinator. Amcric.aare bumtriebecs(Hl menopteralApidae); By delinition (Douglasand Bliss l97T) the alpine srrphid flies (DiprcraiSvrphidae); Muscoid flies ls that area in the mountains abore the limit of (Diptera/Anthomvidae,Muscidae, Calliphoridae, upright tree growlh, characterizcd by soil and Sarcophagidae, Tachinidac); and buttcrllies r,arh"r errrern,..(Bli.: Iq? t. Billing. lo74t.Ou|. (LepidoprcraiPapiiionoidea, Lvcacnrdae, -lutl\ , L,n.i-ttsd,'f ,rnalr.e. ui tlosnring Satyridae,Nvmphalidae)([Ioldenke 1976, l9?9; phenologv and insect visitation. Flowerini ltoldenke and Lincoln 1979; Levcsquc and phenologyis an irnportant componcnt of poilina, Burger 1982: Bauer, l9B3). tion ecologvbecause it determinesthe availabili_ Bumblebeesare social insecls and nlust tr of resourccsto animal pollinatorsano thc com- foragc for colont nceds as ueli as rlclr own. petilir.e rclationships among plants for these Accordinglr lhe) foragc ven intcnsirch,ald visit poliinators (Levin and Andcrson l9?0, Mosquin nurit.r,'u.rl,,\1cr-. \. a t,h,,,..Ine,.ulonr es.urnp- 1971,Pojar 197,1,Heinrich l9?.5,procror lO7B, a gcneralistrole. r isiting a n ide variet.r, of flor er Plcasalts 1980).The pattern of pollinator rroe.. visita_ Hnu,r"r. ,n,lir,drr.rl.r,rrd ru -1,,.,.ialize lron rs rmportanl (nra.itrr) becau-qeit ha-sa direct efTect nrr,'rr, ur tt\u-rr,., ie- x1. n, gt\H,' tlnrc on thc relroductive successand gene flow rate tH.inrich lq-bd. lo,,rt.\lanr r,l.,ri-p""i,.. arn of plants (Nlacior l9?1, Procror and yco l9?3, nrore'or-less .lependcnt on buntblebecs for Richardsl9?8, Facgri and Vanrlerpijl 1979),anj pollination anrl havedeveloped sequential llorer_ makcs it po-ssibieto quartjtati\.ell assessrre rm_ ing tirncs (Pojar l9?4; Ileader l9?5; Heinrich portance o1specific polJinatorsn,ithin an aipine l9?5. 1976b; PleasanrsJ980; Bauer l9B3), (in this case)coinrnunitl.

\"rthr'n-' Srien"r. \ o'. r,().\o. l, l'tgr, 2l Methods specics,including each of multiple visitsby single insects,were reL'ordedboth while walking slowly minute ilatch The selected study site was an alpine fell-field along the lransectsand during 20 plots. The number of locatedlear Mt. Baker on Cho$der Ridge, a pro- periods of the 2 m squarc limited bv iime po-qedresearch natural area (Ta,\'orand Douglas \tatch periodsand transectsrvere In addition to the 19?8)(Figure I). The ridge is relativclv inacccs- to a maxirnun! of sjx per daY from the study area, sible irnd remains urrdisturbed. The arca of quantitalire data collccted sd: olong th' lull sampling consisled of a 20 x 20 rn plot on a p,'|lirrrt"rLeh,r i',r nnltsLI 'lurinstl'' moderateSE slopeat ca.2041m elevation.The rnngrh't Chu*d.r Ri,lg.p' riodi,.rllr rock,r ridgctop $a-q sparsela- vegetatcd b1 su rmers of 1980-l9B'1. \!J- lu collP,I repr,5l.rrldli\"s clumpcd, cushion plants, a typical fell-field com' \rj allpnrpl tnadp insectfor iden- munitl (Tallor and Douglas 1978).fhc commu- of eachdiscernable flower-r'isiting Identificationsuere nity stmcture as dctermincd in August 1980, tification to gcrtusor famill. al (19?6) and lt'cre con- using the cxperirncntaldcsign describedbl Bliss madc using Borrer el (Western Washington (1963).In total, sixtr 20 x 50 crn quadrats \{ere firrned by G. Kraft used for nreasurirlgcovcrage (following f)aubert- Unir.ersit,r'). and eight syr- mire 1959, l968) and frcquenc,v lmporlance or An anahsis of four bumblebees to supplement prominencet alues$ere cirlculatedfor eachplant phid fly pollcn loads uas made bast'don observedin_ speciesb)-mulliplying its mean perccnt covcr bY constancvdeterninations corbiculae were thc squarcroot of its frequencl'.Plants were iden- sect behavior. For bumblebee-", insecl as uscd, tified using Hitchcock and Cronquist (1973)and usedifor syrphid flies the entire the gut as well Hitchcock er a1.(1955-1969) thus countsincluded pollen *ithin PerccIIt pollcn The pollination studv was carried out during as grains attached erternallY insect the surnmerof l98I. Plant speciesof the fell-field tvpes was determined for each quantified using fbur community \r'erc assigned a floral color class' Flowering phenologr vas io(raliono[ the following the s1'stemdescribed by Kevin (1972a). 20 m permancnt lransects.The rnarkirg the northern The color classassignment does not relate to the transectsvas establishedbJ areaat I meter insect visual rangc, trhich at least in sonle cascs and southernborders of the slud) choosing a lneler e\tends into the ultra-r'iolctspectrun. Follotring inlervals (l-20) ard randomly rvithin each of Proctor and Yco (1973),floral morphologv uas locus (l-4, 6-9, ll-I4, lfi'19) from flo$ers (flouer classified into the follo*ing t,rpes:(l) open- the four 5+neter intervals. All open e.g, more-or-lessbowlshapecl $ ith exposedrcrards; clustersin the caseof denseinlloresccrces, Pha<:eLirtsericea, (2)partially exposed usuailvsome lorlion of the those of Orltropis catnPestris, Lant:eolatum) periarth iuscd re-qullingin sornevhdtdif1icult ac- SoLiLago nultiradiala, and Sedant thc lranseclwere ccssto rc$arcls;(3) cLoscd llover structured i withirl a one meter swathalong oncc each$cek sucli a r,at so as to exclude visitation L! non- counted.Phenolo€ry was recordcd season. specializedpollinators; ('t) small tubular flowers throughout the l981 f1o*ering lrith short tubtlar corollas,e.g., co Fosilae,lr ith littlc restriction of rcwards; (5) large tubular- "tongur:d" Results and Discussion long tubular floners requirilg long Ridge fell-fielcl in-.ectsto rcach concealednectar. On the basis The planl -rpeciesof the ChoNder l, alolg rvith their of floral rnorphologl, plant specics\rerc assrgned communit-rare listed in Table strateg-l' pollination strategies: lind (anernophilr'), prominencc value (l'V), pollinirtion " '1.,r. ti'ilL'f:' gcneralist (gencralized entomophil-v),specialist flnralnrorphulugr.l1.,ra' cnd i'r'Pcl f)t1'tropis (specializedentomophil,r'). See table 1 fbr pollina- Dominant planls, bas.d on PVs, nerc lgroplro conr tion slrategicsand related charactcristicsof the canrpestris,Cerasliunt arNense, predominantplant spcciesof our studl- nun, Phlox clLlfLLsa,and Potentilla dixerslfulia. (69 Within the 20 \ 20 m studv afea,insect grouP Bare ground erceeclcrl.50 Pcrcent coveragr fell-fieldrr)nrrnunities actir.il.,-was quantifit'd using 20 m transects(ran- pcrcenl),a characteri-cticof wcre scattcred' domll selcctedfronr metcr loci I through 20) and (Douglas anclBliss 197?).Plants exhibited a cushion 2 m squareobserr'ation plots (randonll.r-selcctecl t,-vpicalilclurnped, and most frornthr 100possible). All inscctrisits lo flo*cr grol!th form.

22 ShJ\ und Ta\l,,r Among lhe prirrcipal plant species, the "open" but probably only exploratorily since so few fioral morphology was most common, visitations were recorded. Finally, bumblcbees lbllorved in order of decreasing occurrence by \'!erc "inc'onspicuous" unavailableto take advantageof thc earlv- (graminoids),,,small tubular,' flo".ring:rnd r.rr ahundrnr Phti ,!illuto du'r- (compositae), "partially exposed,,',,largc ing the l98l season(See Table 2). Horvcver,we tubular," "closed." and The lattcr trlo types have frequentlv observedquecn bumLrlebeesfor, '!ere each reprcsented by a single abundant aging on PhLox tliJfusa on Chowder Ridge. species. Itredominant floral colors ryere vello{ Pollcn types collectedfrom four bumblcbees and white. suggest that those bees were majoring on lwo speciesat one time (see Table 3). F ower V sitors Syrphid Jlies-Syrphids, represenrcd lry ser.eralspccies, did not becomeabundalt in lgBl Tablc 2 prcsentsnurnbers of insectvrsrts to until late July. Aftcr this time they uere frequent flowers or inflorescelces of principal plant visitors to rnost gencralist plants and ner(j ob- specres,as determined by watch periods and served to visit species with olher pollinations transects.Unfortunately, based on supplementary strategies, including graminoids (Carer obscrvations, the numbers are biased. During phaeocephaLa and I'oa aQtina) and Phacelia visits to Chonder Ridge prior ro Jull 28, incle- sericea. ln these cases,the svrphids probably ment wcather(Ibg, rain, and evensnow) restricted foragedon pollenlrithout contactingstigmas and insectactivity, especially that of bumblebecs,bur without effecting pollination. terflies, and svrphid flies. Thus, early flowering Pollen samples liom cight svrphid flies in- :p'cie- tl pi, alJrp,,llin.rred br rhe.ein."crs. e.g.. Jicatedrariabin foraging heharior. Some ins.cts Phlox rltlusa, SiLene acaulis, Phacelia sericea, fed exclusivelyon one plant specicsrvhilc others OxJ'tropis carnpestris, and Potentilla species, exhibited little constancv(see Table 3). Syrphids haye loler visitation numbers than would be ex- had large visitation numbers, as shown in Table pected. Also, in Phacelia sericea, Sedum 2, suggestingtheir importance as pollinators in lanceolatum, and thc Compositae,the entire in- alpine habitats. They prcferenrially foraged on florescencer,as treated as a single unit resulting cushion plants with dense mats of flulrers, e.g., in rtrmfaratir"h Iorrrisrtaliun number.rinr" in- Saxifraga bronchialis and Cerastiurn uruense, sectstended to probe scveral flowers per inflor- with severalflowers typically being sampledfronr escencefor cach recorded yisit. each plant. Major l1ower-visitinginsocts, discussedbelorv, Muscoid flies Muscoid flres were were bumblebees,svrphid flies, muscoid flies, representedb! numerousspecies of four families: butterflies, ancl primitive 11ies. Although Anthom_lidae, Muscidae, Callophoridae, and primitive flies are not generallythought to be im- Tachinidae,the anthomyidsbeing the most abun- portant aipine pollinators, Levesqueand Burger dant. The muscoidswere presentin the fell-field (1982) listed daucc (IJmpidioael flies among communilv throughoul the season and, along visitors 1o Mhuarth groenLandica and Kevan rvith primitivc llies, were abundant carll in July (lq72b) ."n.id"r- "nr1,id. ro L.. in,portanl uhen other pollinators lere unavailableor werc pollinators in the high arcric. inactivated by the cold and inclement weathcr. BtLmblebees Three bumblebeespecres rlere Likc the srrphids, thesc llies preferred open, obserr'ed visitilg florversnithin the studv com- borl-shaped flowers such as those of Cerasti.um Inunil\ orl Ch,,r.dnrRide" Bombu: nplanopy arxense, Saxtfraga bronchialis, and PotentiLLa gu-s,R. ,Iali.frons, and B. boleatu.s,the latter otr- spp., 'l'hesc and had high visitatior numbcrs (seeTable served infrequently. bees preferrcd the 2). Ther "insect also visitcd the short-tubular {lowers of speciali-.1" flolers ol Orytropis various Compositae. campestris arrl Phocelia serlcear,rhcn available Butterflies Sevcral spccies of butterflies earl! in the scason, Sedun lanceolatum, Solidago (lepiclopter ids) u ere observcdin the leli-fieldcom- nultiradiota, in midscason, arr.lAster sibiricus munity, the most abundanl being checkerspots rr late scason (see Tabie 2). The latter three and tortoise shclls (Nynphalidae\ and blues (Ly specieshale "generalist" pollination strategies. caenidae). Other lepidopterids observcd rlerc Other "gcneralists" rere r.isitedb,v bumblebecs anglewings and fritillarics (I'yrzplralldae), nhires

PollinationEcologr of an Alpine Fell-FieldCommuniry in the 1r-orrhCascades 23 ? z. == = =e, = :;i .i z i;i; z5 ; ?a E> :!->e='.7=- :]:j::=:: - cc:t.ai.6=/!€

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Pollrnation lleolngr ni rrr {lpirr,. Fcll-Ficld Communitv in the North Cascades 25 a during 2 mertr plor satcb Ircriodsitransectswalk! TABLE 2. NLrmber of olrscrred insecr !,$ts ro llo$ers or hlloresccn.es

Prnniti!e Svrphirl Flies Bulterllits PlanrSpecicsb Fli.s Flics l9i0

Achillean,illelolium 0il li0 10r; t3,til8 63i22 li1 ?r0 Erigeroncon,posirus :il 9t3 33i10 Orytropiscarrpestri" 56i21 3il 6ti28 I it) Phlox di{lusa :1,I lil5 0rl Porentilladiversifolia lil3 iil I '13r12 li0 28rli) t05il.l 0,1 Sarifragabronchialis 224t2r 6i1 6'1 245[8 Sedumlanccolarun' 6?116 22il 2i0 9i0 Solidsgornultiradirta 81i4 25i i67 lAt2 36Ui57 Toral 20il!l 609i106

erpc.ted bccaur peak lloroing for,'lclillca uas altcr counts aThe nunrber of lisir ari{tts ro ,tchiLtea atd PhLorare lo$er lhan in the fell]ield qere n,ade and Pnlot flo$.red bcfore its Drajor pollinarors appelrcd b) ins..ts during {al.h pcriods or transc'ts and bSn." ,p""i"s of thc felt fickt conrrnunirl-uere nor obs.rved to be visited are r}rr:relorcnot included here

it-y(lhree individuals obscrred dur- (Pie r idae), skippers (-Flesperlidae), swallowtails the commu Holever, ladtbird beetles (Papilionidae),alpines (Salyridae), and several inq two field seasons) and werc frequently observedwith undeterminednoths. The lepidopteridsprimarill *Jr" "oln-on buried in flouers, apparentl-vseek- visit tubular flouers such Phlox diffusa' Silene their heads acaalisand Compositae,utilizing their long prob- rng nectar. ing/suckingnrouth parls to reach concealednec' Pollnat on Strategies tui. t" tgSt, ho$cver, butterflies were not ob- pollinatioD slrategres were rell served on ChorvderRidge until aftcr 6 August, Three among the dominant plant specles when P,'rlor and Sllene had finished flowering represented co-t t,.rnit-r, wind (Agropyron (seeFigurc 3 and Table 2). In subsequentyears of thc fell-field Poa alpina), insect generalist 'wehave obscrved butterflies foraging on these caninun and (Cerastiurn anense a:ndPotentilla dixersfuLia), cushion plants on Chowder Ridge. and insect specialist(Orrtropis cdntpestttsard Primitiuefies These Ilies *ere represented Sce Table I for a surnmation ol by three famiiies:Xl,r'celophilidae (fungus gnats), Phlox tti;ffusa). p'llination .trat'gi." .rnd prorninrrrr"erulLr"' Bibionidae (March flies),and Ernpididae (dance cunspi,uou- speci". nf thr lell-field fiics). The"vvere alrundant early in the flower- bn" ol th" Draba palsonii, is reportedly ing scason and rlere most frequcntl-l observed conrmunity, (Mulligan l9?l). fhis dense oi Potentella dixersifoLit' P. xillosa' an'J asamospermic plant ua-qthe first to flower in the fell- Cerastium arxense. cishiolr uas visitedonll b,r primitive M iscellaneu us insects-0thcr observedfl owcr field community and visirors includcd ladybird beetles (CoJeopterai flies. Coccinelidae),piant bugs (Hemipteraitr{iridae)' ng Phenologyand Pol lnation Patterns anclsolitar-v bees (Hl mcrtoptt'ralfamill undeter- Flower 2.4 def i' t th. flo"'ring p'rind. ol l\'"1\P rnined).These insectswerc not consideredto be Fisurc- ir'-.,itpollinated plants in thef'll-tield important pollirators. The bugs and beetlcs did c'mmnn l98l The first ol thescplants ,rnt flu frn- floncr to flol'er and lacked pollcn communitl during flonering was Phlox diJfusa Thls ""rr'rinu "ap", itt. and s,,litarrbee: r'ererure in to peak in

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I'ollination Ecologr of an Alpine Fell-Field Conrmunitr in the North Cascades 27 / ^e! /:-'l o-/ a9

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DATES198I

Figurcs2-1. Flolc.ins periodsof nrajorcrlomop|itous species i rhe atipinctrl.field. Figurc2: Insert generalisrltorers rlirh opennorat morphology. Fisrtf 3: Insed ,Vccialisrllo$frs: partiallv elposed(Phaelid and Silene),laryctubular (Phtor), anil .lose.t(Ory...atta) floratmorphologv Figurc 1: Insectgfneraljst tto$e.-(: shorr rubular (coorpositae) a.d open(Sdam) flofal nrorpholog,,.

Poliination Ecology of an A[ine Fell-Fie]d Community in rhe Norlh Cascades 2t) ins aftcr I September,the datethat lield analyses cariy florveringtrait seemednon_adaptive sincc we-re termin:rted; Hapktpappus l1'allii' which by ih" sp"ciali.t pullittators \!ere not vet availablc did not occur along the phenology tran- at this time (seeTablc 2 and Figure 3) Honever, chance plarts uith prominence vahresof less in ..,i."q,r"rtt to 1981, butterflies and' sccts;and ;'.e".s (sec Table l). csp"cci^llv, bumble[rees have bcen observed than 0l viiitirg PAlor. Phlor is most likelv an inportant ncctar;ource for early seasooqueen bumblebees' Conclusions Potentilld .-illosa and P diler'si/olia flowered Although rve cannot quantifYthc relativeim' s1'nchronouslYirs did Cerastium anrensc and Sat oortanceoi pollilators in the Chouder Ridge fell- iiaea broncitialis(see Figure 2) These four in- ii"l.:l "oro*.,nit-r, it'is obvious from numbers ol .eci-ge,tcralistshad a rccorded (l98l) peak flower visitationsthat bumblebees,svrphid flies' flol'eiing timc of 6 August. This scemsat odds antl muscoid flics are all !err important, butter- t'ith rhe popular ther.rry that the flowering anclprimitive [lies lessso The relationship uhrnol.,si". of -pe,i,'.,haring p'-'llinat"r't'nd flies "fli' florJIlmurl'holng1 anJ in'crt ri'itur s r' io di'..i". in"r"r'ing1"'llination ien'1 and Letqeen expectatiorlsbased on publica' rep.od.,itive su"cessll,evin and Anderson I970' consistent 1!ith Ihe results of phcnoiogical Mosquin l9?l). Howcver, sYnchronousflowering tions cited herein. planls rrith gcneralisl pof -r" a".u" lo attract greater numbers of poten- analvsesildicate that svnchrcrrouslr' tial pollinatorsto alpiie communities,mostly flies lination strategiestend to flol|'er lnsect at- in ihis case, increasing thc chance oi cross oerhaps as an adaptatioll for greater pollination. Macior (19?1) suggesredthis as a iraction, vhile thosc I'ith sperriiriiststrategics where ard p.rhap"du' lu rnrnl'Plilrvc 'cii-at"possibilit-v ir| the alpine .lopography lluecrsPqucnliall\. This often Limit plant population size cJisplacement.It is suggested,horvc!er, that thesc (I982) i,1eais supported brj Williint. and Batzli results mal merelv reflect opportunism on the intcrspccific *ho shorled increascd sced sct in part of the plants and spccialistpollinators (bees) to singlespecies standsoI Pedrcularisas opposcd re.pcctiuell'.Finally, observation-"of alpine com- is that slrlchronous stantls.A third interpretation -uniti"a on Chowder Ridgc over a sereral rear a r' lle' tion of gon"ticallr florrerins i. .implr oerioclhave resulted in our apprcciation of thc i.' . "i rh' plant' rbilit' t'' bcs'J oJuortuni'm, 'i"or tu ueor variation in flolering phenolog'v' of a limited suitable llowering 'fh. 'n'' take adl'antagc llon.ring..,1r"neenl r"prr''entrtir' ie' period. and has littlc to do $'ilh coadaptation\rith remains rnore or less consistentbut the tinle ol insects or uith interspecific intcraction' rhe floncring peak, the lerrgth of the flonering ln contrast to those of fl1'pollinated plants' period, and the extent oI florering overlap varl orak fln$,ring tinrr. ol humhleLe'nraj"r- I'ere consitlerablt according to ragaries of thc .ptuJ "'"r. '.'er 'l "', k' t'e'fiqure' 3 anLll)' "prcferrcd" Aiso, the availabilitr of In rhi- r'.pe't. th" Chos'lrr Rids' t'll-fiel'li' wcather. oollinator-"is influenced bl the rleather, a case similar to other comrnunitieswhere bumlr]ebees being the apparentabsence ol buttcrfLies arc imDortantpollinators (Reader I975, Heinrich in ooinr during the peak flowcring pe lq7oL, l'l..rsenr-la8ot. Aturn. hos"rer' caution ond b,rtttl,lebces diffusa I'n l91l lhe alpinc com- shouli be taken il intcrprtting lhescresults The riod of P/rlor Ridge are esper:ialhsensi apparenl co petitive displacementof llovcring rrruniticsof Chowder e'pc- bccauseof the south- time- rs 'rlrihiteo Ir l'umblel''' rnrrjnr' tile to climatic llucluations lvater stross r:iallt thoseIirh generalistpollinatioil strirtegies' facing exposure and associatcd mal alsosimpll reflect opportunism,this timc on llre parl ul rh,' b' c- Sirr'" b" col''ni" d'pnnd Acknowledgments - ,,r r conlirruL't,:-.,Lrr, " ni floruliouLl' ther ne' Wc rrc,uid likc to thank Dr' C Rousc' tor e-"sarilt major crl species with tcmporall'r dis- assistancewith pollen anallsis; Dr' G Kraft' for persed'phenologies.Specie-c such as !sler si6iri'ds assistancetrith insect identificirtion, Dr' W P' thert becom" bee rnaior-t becaase thcr are Stcphcn. for identification for burnblcbecspeci- availirbleat an opportune tine, rather than hav- nr"rt.l nnd the U S. Forest Scrvice lor allowing inr:crnrreLl -r.ndrrle p, ah llorcrinq I'eriod'irr r'- this studY We gratcfulll acknolledge financial :DUn.clo.umtr.lilion- Inr huml'l'l're 1'ollin'rt"r' ilssistancefrorn S'estcrn Washington Universit'l Phenologicaldata havenot been providedfor: and the Washington \irtive Plalt Societr' Achilled mitkhLiun' rvhichachieved peak 11.'wer-

30 Sharvand'fir.-lor Literature Cited

Bauer,P. J. 1983.Bumtrlelee pollinrtiof rfl!lior,$irrs i)n lhc b.artoothplateau tondra ol southernN{ortana. Amer. J. Bot. i0: l:11.1'11. Billings.U. I). l9;,1.Adrptdri.ns and originsof alpineplaDts. Af.t. Alp. Res.6: 129112. Blis, L. C. i963. Altinc tlnnl conrdrnilicsof the PresidentialRange, Nen Hampshne.Ecologr 11: 678-69?. . l9il. Arctic nn,l alIi.c r,lnnl1il. c!cles.Ann. Rer. Eco1.Srst.2: .105438. Bonor, D. .1..D. \1. I)tloig,rrdC.A. 1.iplcho...l9?6. An Introdu.tionto the Studr of Irse.rs.Holt. Rinehartand Sinston,

Daulennirc, R. 1959.A crropvrov$agc n,dhod o{ r.g.tarional anahsis.Northw. Sci.33: ,1366. . 1968.f'lant Conrrrurities.Harpcr and Ro*. \er York. Doughs,G. It'.. and 1..C. Blis!.197?. A\rine and high subalpineplart communitiesof the Nortb CascadesRangc, WrshinsLon dnd BririshColornbia. Ecol. \{onog.4;: 113150. Faegri,K., and L. ran der Pijl. l9?9. The Pfinciplesof PollinationEcologl. ltrearron l'ress.Nen York. Heinrich.B. 19i5. Bee florers:i hlpothesiion flowrr rariclr and l,loonringtinrcs. Erolution 29t 323331. . l9;6a. The forasiDsspe.ializations ol indiridual trurntrlelees.Ecol. Ilorog. 16: 105.128. l9;6h. Flos.ring phenologies:bog, woodland,ald dislu.bedhrbitals. lcologv 57:890.899. .l9;9. Nt!jorins" and "niroring'br foragingLumblebees. Bonthus Mgrans: an frpcrjmfntal analvris.Lcologr 60: 215255. Hitchcock,C. L. and A. Crorquist.l9iil. Flora of rhe Pacific\orLhrL|st. Urivcrsir) or Uashi.gton Pr.ss.Seattl.. , ,l\{.o{rtcv,andJ.W. l honpson.1955 1969. Vas.ular Planrs ofthe Pacilic Northqest. Vols. 15. tjnirefsirv of lirshirglor lL..s. S.!ttl.. Jo..s, C. 1.. and R. J. Linle. l9l]3-Handbook ol ErperimenralPollinalion Biologv, Scientific and Acadcn,icI.ldition!. Van \ostrand ReinholdCo. Inc. Nev York. Keran.P. C. 1912a.Florat colors in the high arcticwilh referfnceto in,{ffl-1lo\!crtulalio.ships and pollination.Can. J. Bot. 50: 2289-2316. . 19721,.Insc.l pollinationol high arcticflorers. J. Ecol.60 831-81?. Lerentut. C. l\'1.,rr(l J. I.. Burg.r. 1982.Inse.ts (Diptera, Hymenoptera) asvrciated with llnrzarria gfo.rld,di.d (Canophrllaceae) on \1ounr\l'ashington. \er Hanpshire,U.S.A., and their possilleroles.s pollin!lors.Arct. Alp. Rcs. l1: 117.121. Levir, D. A., and tr. trl. Andersor.l9?0. Competition for pollinatorsbi'twccn sidulran.ous llos.ring sp..ies.A er. \ar. 104: ,t;5,167. Macior.L.S.l9il.Co.rvolutioroirrlanl.andanimalsslsrematic iDsights from plant irrect interacrions. Taron 20: 1728. I'loldenLe.^ R. 19i6. Califorrir lrollinationecolog' and regetationtrpes. Phytologia 31: 305J61. qiFrrd lolo l'l.r tr"", g- "i'l 1,1. \p,ddi. I.S.{. Phrt"l".rr l:l:22J 282. , rntl I'. C. Lifco f. 19i9. ldlination ecokrglin montaneColorado, U.S.A.: A communitr analvsis.Phrtologia ,12: ll49 379. Nlosquin.1. li)71.Comtetition for pollinarorsas x slimulusfo. lhr flolulior ol lIxcring l;n,c.0ikos 22; 398'102. Nluilisan.C. A. 19;1.CttoraroDorni. sludies of /)rola spcr:irsol Canniladn,l Aldrka: r. renk^q D. rLaks, D. ?a\'tonii.C.ar. 1. Bor. +9: 11;5 1.160. Pleasants.J. ll. 1980.Cornp,:t,tior ft. bunrhl.bc.pollinators in Rock,,"Ifountain plant comnrunities.Ecology 61: 1,1461.159. Pojar,.l.l9?1. Rrprudur tir r. rlrnarics of four plantconmnnities of south{esternBritish ColunLir. Can.J. Bot.52: l8l9 1834. Proctor,]1. l9iB. In!c.l r).lli.arionsrndromes ii an erolutionarrand ecosystenatic.onrexr.In The Pollirationof Florvers bv lrrscrts.Riclanls, A. J. (.d.). Linn. Soc.Synp. Ser.16. Icadenic t'ress,New York. and I'. Yco. l9;3. Thr Pollirationof Floren. Collirs,London. Rexdfr. R. .1.19i5. C.nrtliri\. relationshipsof vrme trogericails for maior insecl Crn. .1.Bor. 53: 1300-1305. -lh. !olli,rrors. Richrrlr. A. .1.l9;ll. ltiliration of Florie.sby Insects.Linn. Soc.Slrnp. Ser.46. Acadtnic I'rcss.Ner York. 'la,-lor. R. J., and C. U. Dougir!. 19i8. I)ldnt.col.gr a.d nat,rralhistorl olChorder Ridge,trft. Baker:A potentialalpine researchnarural arcr in 1h $c.r.rn \orth Cas.ades.North$. S.i.52: 3;50. Willians.J. B. arrl G. O. Ilatzli.l9il2. I'ollinationan.l dispersal ol tir e speclesof louseron(Pedtczloris) nerr Itkrqrk. Ilaska, t..-s.A.Ar.t. Alp. Res. l.l:;9;.1.

Receixed 28 September 1981 Acceptedlbr puhliratiort1 '1pril l9B5

PollinationEcologl of ar Alpine Fell-FieldComnrunitl in the North Cascades 31