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<br />002421 <br /> <br />The ES.-t mtlkes <br />mati)' re/eretln's to <br />(l species' <br />geographic area or <br />its ra"lW wI/bout <br />defi""',g those <br />terms. <br /> <br />8 <br /> <br />figure 1. A T~'pical F.dge of <br />a Spt::des' Rang:e <br /> <br /> <br /> <br />... <br /> <br />. <br /> <br />. <br /> <br />) <br /> <br />p <br /> <br />~ <br />Out~de the Range <br />. Suitahle lIahiut <br /> <br />. <br /> <br />thc:~(: an," si}o:nificam adapl;lIion~ 10 local cl\\i. <br />funmc:nts, 111h pJ.lh is slow and eXJwnsin... Tht, <br />sl"cond p;uh i~ throug.h Iht' ('merging fidd of <br />D:"'A fillJ.:t'fpriOling. This sri of hitK'ht'mical <br />l(;"chniquc!ol is M.'lhilh"l" c"!lough to allow the dis. <br />crimination of IIldi\'idual organi:o>ms from um' <br />another on the hasis of mort' Of h:..... dirn:t ex- <br />amination of fragments of their gl'IH:lil' malt"- <br />rial. The C;ltq,:orks uf subspecies and dislinCl <br />population sq.:ml'm... could (';lsily hc.' H'tkfim:d <br />in terms of Ihe 0:'\:\ dlfflTl'nn's amon~ popu. <br />lations. Tht" fact Ihal tht"st' unit~ may difkr <br />~omcwhat frum traditionalt.1xonomiC di\'bion.. <br />i-. functi()nall~. unimportam. thl.."y will -.cryc to <br />prntl."ct a.. much gt.twtic dln'~ilY as tht' nalion <br />dl't~m.. ncce....dry <br /> <br />Tht' G/'ographic Rflllf/l' of (J Spt'l-it'S <br /> <br />.\Iarbled murrl'lt.t.. arl' robin-"llTd ..t";lbinh <br />who"l" geogr.lphic rangl. I.'xtt'nd.. acro.....lht. north <br />Pacific. In the ('llltcd :-;tatl.... tht"y on'ur in ~n'al' <br />t...t numher.. in Ala..l.:a but eonunut" dm..-n the <br />CO;l...1 10 cemrJI California_ ant' of the argu- <br />mem.... ad\.;ll\ced in ...uppon of Ii-.ling tht" mar- <br />hlt-d murrelet in Wa...hingwn. Oregon, aOlI <br />California i!'o Ihe fdel thai it.. dhtrihution at the <br />..olllhern limit of II.. ran~t' i!'o patch\. Sl't'':;- Ft.J_ <br /> <br />.'HAl':il \1\lfR 1''''; <br /> <br />- <br /> <br />Rq: ...'),:~2K (Oct I. 1992) The argumellt im- <br />plin that a patchy dbtribution IS e"idl'nee: that <br />human acti\.ltie<; arc modifying the murrele:t'.. <br />habitat :-'<l a.. (0 rt"ntkr it unsuitahle. This b a <br />faIrly common intt:rpretalion of ..uch data by <br />...cit.ntht.. and non~cienti..l.. alikc and h quitt" <br />mi..leading To under..land why. one mu..t ex- <br />amine the l'''"l'epl of a ..pt"l'ies' r.J.ngt'. <br />The E..\.\ mal.:('" many rdt'rt'nccs to a ~pe- <br />cit's' geographic art'a (If il.. range without de- <br />fining tllU...c: It'Tm.. If they wae wt:ll understood <br />by tht" M:ientific l:ommunity, this mi~ht nm ptN: <br />a pmhkm, bUlthey are not. Con..ider Ihe fringe <br />of the rangt. of a hypotht'lical ...pecin drawn in <br />Fi!!;llrt. I The shadt"d arn. 01.1 Ihe top rl'pre~em~ <br />a ..(.t o[location... almo.,t t'\.cf},,'hcfc~uitable for <br />tht' ..pecies and <.'It"arl)' within its range The <br />open art"a ;11 Ihe bottom n:presellls a ..el of 10- <br />Glliuns almust e\.l'~.whnt' unsuitOlhlt.' for Ihe <br />speci~ and. theft'fore, out of ils rangt". Pro- <br />cCl"diog duwn throu~h the fringe ZOOt' (Ine typ. <br />it.'.J.lly ..t.'('., the foll()wjn~ spatial !'oequence of <br />chan~c.. <br />.;lS nmdition.. ~r<ldually !x'come It'ss fa- <br />vor.lhk un an:ragt:. nurmal sitc.to.sit(: varialion <br />hCJ::illS to prodlKt' patchn uf un..uitahlc habitat; <br />. tht"H' palt.ht:s grow in sin' and l.:oakM:c. <br />until ..uilahk hahitat !x'coml's palchy; <br />. population.. in patchy h;lhit;u.. occa..ion. <br />;tlly go t"xtinct, hm t"mpty .,itn an, rt'populatcd <br />by colonist.. from ncarb~. tll'l'UplCd ..itn; and <br />. il1cn"a..ing di..lances hClween sile.. I:"\"('n- <br />tually ma(.;t' r('colonizatiun ..n diffk-ull that fhl' <br />few rClllaiOln~ ..uitahk ...HI.... go unoccupied. <br />A'. nlmpkx a.. Ihis pattern i.., il is funhcr <br />complic;lIt'd by normal ycar.IO.}'t'ar nri,uion in <br />hahitat qualify. which may shift tht" fringe zone <br />up and down O\"l'r time. Gi\"en rhi.. pauem, how <br />don Olll: ddine tht. huunda~. of a ..pt.'cit.s' r,m~c? <br />The olde"l and mo..t common appro;lch is that <br />employed hy systematic hiol~ists Mu~eum dat:! <br />on colkctilln IOt-atioo.. and puhlished range ex- <br />tt'n..ion_... ;In' (tll'"::.!t('d on maps, and a line is dra\\TI <br />around all t/1t''o(' point.. 10 repre"l'lII the di..lri. <br />hutional limil'" Such a rangt. houndary would <br />bt. nt'ar the hUllom of Figuft' I, <br />11th highly II1fq~rati"T approach nlar pool <br />locational data ohlaint'd over tht" COUNoe of mon" <br />than a Cl'l1lUrr Some of tht'..e rt'cord.. Ill:lY in. <br />dudt" ..itt".. lh;u ('(mtdined only a ft.-w plJnts or <br />anitTl.Ib for J ft'w rear.. hm that could not su~. <br />lain a populaliun "fhik -.omt' n)J\lempora~. <br />hIUloJl,I...I.. h.J.\.c t'xpro..cd di~~JlI...f;lCll(1O with <br />lilt. tradition;t! approach" tht"y have nm done so <br />in J. con..i~lC"nt way.) H llrown and ,0\ C. Gih5>On <br />claimed that "thl' limit of tilt' ~l"()grJ.phie range <br />of a ..pccit.... occur.. af the point in ~p.lce where <br />tilt" Itx';tJ pt)pulation dt'n..lt~. llt-dint"s to It'ro.'" <br />a Jdinitillllthat would plan" tht' houndary fairly <br />c1o'I.' to hut ...omt"\\.hal ahon' thai of tilt' tr-.ldi. <br />