Quaternary palaeoecology and ecological theory

O sis, 5: 91 -111 (1990) Qua e na y palaeoecology and ecological heo y Valen í Rull IVIC. Cen o de Ecologia. Ap. 21827. Ca acas 1020-A. Venezuela Key wo ds: climax, ecosys em e olu ion, models, palaeoecological heo y, p edic abili y, Qua- e na y, s abili y, succession. Abs ac . A e iew showing he po en ial con ibu ion o Qua e na y palaeoecology o he ecolo- gical heo y, ocused on he ecosys em e olu iona y p ocesses, is p esen ed. By analyzing oceanic and con inen al Pleis ocene and Holocene eco ds, some e lec ions abou ecological succession, di e si y, hy hms, p edic abili y, s abili y, and modelling a e made, and compa ed wi h heo e i- cal s a emen s de i ed om neoecology. As a gene al conclusion, he necessi y o conside ing palaeoecological indings in ecological heo y is emphasized. In addi ion, i seems essen ial o place palaeoecology in a mo e ecologi- cal amewo k. Resum. Paleoecologia del qua e na i i eo ia ecologica. Aques a icle e isa la possible con ibu- ció que la paleoecologia del qua e na i po eni , en e s la eo ia ecolbgica, especialmen en els p ocessos que es an elaciona s amb I'e ol~lució dels ecosis emes. L'anBlisi de seqüencies pleis o- cenes i holocenes, an con inen als com oceAniques, pe me en e una sk ie de e lexions sob e concep es com: successió ecolbgica, di e si a , es abili a , i mes, p edic ibili a i modela ge, o con as an -les amb aquelles so gides de l'es udi neoecolbgic. S'a iba a la conclusió gene al que els esul a s paleoecolbgics són necessa is en Teo ia Ecolo- gica. També es p oposa la necessi a de si ua la Paleoecologia en un ma c més ecologic. In oduc ion The e ymological de ini ion o palaeoecology is he sho es one -ccpalaeoecology is he ecology o he pas >>- (Bi ks & Bi ks 1980). I is, howe- e , su icien since i con ains he essen ial concep s in ol ed: ecology and ime. The empo al s udy o ecosys ems needs pas e idences o s ic ness, becoming specula i e when p edic i e models a e pu sued. In he middle lies he s udy o he p esen li ing communi ies (neoecology), whose empo al do- main is sca cely ep esen a i e o he ecosys em e olu ion. Ideally, ecology should be conce ned wi h all hese iews: pas , p esen , and u u e. The sea ch o egula i ies in he ecosys ems, which allow de i a e explana- o y and p edic i e models, ha is, he heo iza ion o ecology (Ma gale 1977), a ises gene ally om neoecologial s udies. Thus, models in which ime is an essen ial componen a e de i ed om sho pe iods o obse a ion. The 92 V. RULL e idence is insu icien , and analogies wi h mo e de e minis ic sciences, like ma hema ics o physical he modynamics, become necessa y. This is a easo- nable p ocedu e, because li ing sys ems and beings a e no less han complex physico-chemical en i ies, bu , undoub ely, he possibili y o ob aining a mo e ex ended ime-dep h is be e han ex apola ion. The e o e, he in e ac ion be ween'palaeoecology and neoecology is a mo e app opia e app oach o a empo al unde s anding o ecosys ems. Up o e y ecen ly, palaeoecology was no capable o p o iding much sui- able da a o gene aliza ion and modelling pu poses (Valen ine 1972). The e- o e, heo e ical ecology g ew, o a g ea ex en , on he basis o neoecology. A p esen , al hough gene aliza ion o palaeoecological esul s, wi h ends owa d he de elopmen o heo e ical bases a e inc easing, mos s udies depend upon da a de i ed om neoecology wi h he esul an limi a ions in he independence and uniqueness o in e p e a ions (Olson 1985). The book (<Models in Paleobiologyn (Schop 1972) is a good example o his app oach. Fu he mo e, some w i e s do no ag ee wi h he possibili y o heo iza ion in palaeoecological (Ho man 1979, Olson 1985). Thei opinion is la gely sup- po ed by he use o he so-called cccommuni y econs uc ion app oach,,, which is, acco ding o hese wo ke s, he only alid way o s udy communi y e olu ion and, he e o e, o make gene aliza ions in ime. Since good e- cons uc ions o pas ecosys ems a e di icul and sca ce, due o inhe en p o- blems o he ossil eco d, de ailed knowledge a he in a-communi y le el seems no gua an eed by palaeoecology. The p esen wo k is an a emp o analyze he con ibu ion o palaeoeco- logy o ecological heo y, based on e y di e en p emises. Fi s , de ailed knowledge o a communi y is no he only way o unde s and i s e olu ion. The e a e indica o pa ame e s which a e associa ed o he ends in a ia ion and endences o he ecosys em (Pielou 1974). Second, he palaeoecological s udy is conce ned wi h ex a-ecosys em a ia ions, ac ing as impo an o cing mechanisms, whose s udy con ibu es o elucida e causal ela ionships o he obse ed phenomena. Concep s such as succession, s abili y, climax hy mici y, p edic abili y, and modelling in ime will be he main objec o he p esen e iew. In his a icle, e olu iona y p ocesses a e no conside ed. Undoub ely, e o- lu ion occu ed in he Qua e na y, jus like in o me imes, in e mingled wi h ecological succession. Howe e , only such p ocesses ope a ing and de elo- ping on unchanged species will be conside ed. The ela ions be ween succes- sion and e olu ion a e o g ea ecological signi icance (Ma gale 1986), and need special ea men . ~ime scales: he Qua e na y The ecological phenomena eco ded a e a unc ion o he ime in e al consi- de ed. Se e al classi ica ions o ime scales a e a ailable, bu since coinciden- QUATERNARY PALAEOECOLOGY 93 ces a e clea , ha o Delcou e al. (1983) may be used as example. Acco ding o hese wo ke s, h ee empo al domains can be dis inguished in he 's udy o ege a ional dynamics: 1. Mic oscale: cha ac e is ic phenomena a his le el a e physiological e en s (0-10 yea s), coloniza ion, mo ali y, and g ow h a es (10-100 yea s), in e especi ic ela ionships (50-500 yea s), such as compe ence, p eda ion, and o he s a ec ing he ecological succession. 2. Mac osale: he mos impo an phenomena a e clima ic changes, mig a- ion, ex inc ion, and specia ion p ocesses, a ec ing he ecosys em e olu ion. 3. Megascale, e en s which lie in his ca ego y p oduce biological e olu- ions exceeding he ecosys em ame. Examples a e pla e ec onics and biolo- gical e olu ion. Neoecological s udies p oduce mic oscale da a, wi h he longe p ocesses being e ec i ely obse ed o no mo e han decades o , a mos , a ew cen u- ies. Fu he mo e, a ela i ely comple e unde s anding o he p esen biosp- he e may be conside ed as a c oss sec ion o a complex o ecosys ems in di e- en e olu iona y s ages. This ins an aneous pic u e may be compa ed o a de i a e, a he ime ,, o a hypo he ical unc ion F( ), desc ibing he his o y o he ecosys ems. Fo a eal unde s anding o he biosphe e, as was ecogni- zed long ime ago by Donnan (1936), he in eg a ion o F( ) be ween o and , is he mos sui able p ocedu e. Howe e , whe e does one loca e poin o? Since we a e in e es ed in he p esen li ing communi ies, he poin o ep e- sen s he <<momen >> in which he o igina ed and, he e o e, i is a ma hema i- cal a i ac . Bu a easonable, al hough no conc e e, depa u e poin is possi- ble. The ossil eco d shows ha p esen li ing species a e gene ally no olde han he Qua e na y o La e Te ia y, whe eas o me o ganisms haye beco- me ex inc . As a consequence, he Qua e na y pe iod and, he e oie, he ma- c oscale le el, will be he ime ame o he p esen issue. Qua e na y e olu iona y a es ha e been low, and ex inc ion, as well as some deg ee o€ specia ion we e he mos signi ican p ocesses. Mig a ion, dis- placemen , mixing, isola ion, and o he spa ial eo ganiza ions, co ela ed wi h clima ic a ia ions, a e cha ac e is ic o his pe iod (Dunba 1952, Flin 1971, Bowen 1978). As a consequence, in e -and in a- ecosys em in e play has been in ense, p oducing complex e olu iona y p ocesses as he commu- ni y le el, and esul ing in he p esen , s ill dynamic, si ua ion. The u u e is no less ha he con inua ion o F( ), so any p edic ion mus be based on i . Succession and subs i u ion The classical concep o ecological succession e e s o a communi y de elop- men p ocess which is cha ac e ized by s uc u al and unc ional, ime- o de ed, changes (Odum 1971). This p ocess esul s om he modi ica ion o he physical en i onmen by he communi y, which is he con olling agen , while ime and speed o change a e de e mined by he en i onmen . The 94 V. RULL hypo he ical culmina ion o succession is a s abilized and equilib a ed ecosys- em, called climax. Some gene al c i e ia ha e been p oposed o ecognize di - e en successional s ages. Among hem, he endence o a biomass, comple- xi y, and di e si y inc ease in ime dese e men ion (Ma gale 1977). I has also been s a ed ha s abili y and independence om ex e na1 condi ion aug- men wi h succession (Ma gale 1968). These p inciples a e de i ed om neoecological s udies, mainly om expe imen al, cyclic ( equenly annual), and seconda y successions. Hypo he ical econs uc ions, based on he simul- aneous obse a ion o se e a1 communi ies, which a e in e p e ed as di e- en successional s ages o he same p ocess, a e also used. As a consequence, hese eco ds a e ime-limi ed, and he long- he m in luence o en i onmen al changes is implici ly ejec ed. Be ween he longe p ima y successions eco - ded, hose de eloped on ecen ly deglacia ed a eas a e especially in e es ing. Fo ins ance, Reine s e al. (1971) s udied he coloniza ion o Glac e Bay (Alaska) by he ege a ion, du ing he las 250 yea s. A e deglacia ion, abou 100 km o ba e soil we e apidly exposed, and some he baceous com- muni ies we e he pionee s. The ollowing s ages we e cha ac e ized by Picea, and la e by Tsuga, o es s. The inal communi y is he baceous again. Rela i- ely s able en i onmen al condi ions p e ailed du ing his succession. Di e - si y showed a apid ini ial inc ease, ollowed by a p og essi e a enua ion, and a la e asymp o ic s abiliza ion, which is main ained a p esen . The a e o in- c ease o di e si y was con olled by he addi ion o new species in he ea lie s ages, and he equi abili y o hei abundances, nea he s abiliza ion. The as- sumed clima ic communi y showed maximum di e si y, associa ed wi h a complex mic ohabi a pa e n, suppo ing he iew ha s abili y a ou s di- e si ica ion by p og essi e niche-subdi ision (Ma gale 1963, Connell & O ias 1964, Sande s 1968): Simila coinciden di e si y ends ha e been ound in o he s udies (Bi ks 1980). A longe successional eco d, co e ing he en i e Holocene ( he las 10 000 yea s), and de eloped in a s able en i on- men , was ound in he Galapagos islands (Colin aux & Scho ield 1976 a and b). The ansi ion om he las glacial pe iod o he Holocene was cha ac e i- zed by inc ease in humidi y, and he es ablishmen o opical ain o es s. The ecoloniza ion p ocess abou 1000 yea s. F om abou 9000 yea s be o e p e- sen (BP), bo h clima e and ege a ion emained unchanged, un i1 oday. This su p isingly long pe iod o s abili y seems o be an excep ion among palaeoe- cological eco ds; ecen indings e eal empo al changes in he communi y composi ion. Du ing he Holocene, clima ic luc ua ion ha e been eco ded, including mean empe a u e cha ges o abou 3°C (Den on & Ka lén 1973). The li ing communi ies we e undoub ely a ec ed by hese a ia ions, as shown, o example, by dia om communi ies o some Finish lakes (Koi o 1970). The pos glacial coloniza ion, as well as di e si y ends o hese Holo- cene communi ies, a e e y illus a i e conce ning his poin . The gene al ule o a apid, ichness-dependen , ini ial di e si y inc ease was also eco ded he e. Asymp o ic s abiliza ion, howe e , was no eached. On he con a y, I QUATERNARY PALAEOECOLOGY 95 di e si y a ia ions, co ela ed wi h clima e and ophic s a us we e obse ed. The maximum di e si y coincided wi h phases o oligo ophy and highe em- pe a u e, whe eas dis ophy and empe a u e dec eases we e associa ed wi h low di e si y alues. Thus, no only he in e na1 communi y 'o ganiza ion, bu also ex e na1 o cing ac o s a ec he successional p ocess. In he o me examples, i was assumed ha di e si y measu es, in some way, he complexi y and o ganiza ion o he ecosys em. Howe e , hese poin -di e si y alues may be biased by sampling limi a ions. In palaeoeco- logy, addi ional sou ces o e o mus be conside ed, mainly hose de i ed om di e en ial sedimen a ion (Smol 1981), and p ese a ion o ossils (Las- ke 1976). Ma gale (1968) p oposed a spec al app oach, which conside s he cumula i e di e si y om a sequen ial sampling o an ecosys em, wi h p o- g essi ely lange sample size. These di e si y spec a, like o he measu es o he pa e n-di e si y (Pielou 1966), a e be e measu es o he s uc u al ea- u es o he ecosys em, pe mi ing a mo e clea ela ion be ween di e si y and p ope ies such as o ganiza ion, ene gy luxes, ma u i y, and o he s. A simple communi y, ha is, one ha has ew, homogeneously dis ibu ed compo- nen s, some o hem dominan , has a di e si y spec um wi h an ea ly sa u a- ion poin . On he con a y, an ecosys em composed by many species, none dominan , and wi h complex spa ial pa e ns (like mos opical o es ), p o i- des di e si y spec a di icul o sa u a e. I he spa ial dimension is subs i u ed by a empo al one, he spec um may be used o s udy s uc u al a ia ions in a successional p ocess. To es his me hod, a pollen eco d om he opical Venezuelan Andes is used. Glacie s e ea ed om 3 000 o 4 700 m al i ude, be ween he las gla- cial maximum (p obably 18 000 yea s BP; Schube 1974,1984) and he p e- sen . In a locali y si ua ed a abou 4 000 m, he coloniza ion by ege a ion s a ed a ound 12 000 BP (Rull 1985). The pollen di e si y spec um (whose alues did no coincide wi h hose o ege a ion ep esen ed, bu hei ends a e necessa ily co ela ed) shows ha di e en pollen ypes a i ed by wa es (Fig. 1). To a g ea ex en , equi abili y de e mines he di e si y endences. This implies ha addi ion o disappea an- ce o ypes a e no esponsible o he composi ional changes. The eo ganiza- ion o ela i e equencies is he de e mining ac o . Independen e idence, such as ee line posi ion, indica o axa, and o he s, we e he basis o he cli- ma ic his o y o he si e, showing ha abou 9 000 yea s BP he glacie was lo- ca ed nea he bo ing si e locali y, and no mo e han sca e ed he baceous s ands li ed he e. Poo and luc uac ing communi ies a e sugges ed by he spec um, o his phase. A ypical succesional end, wi h a sa u a ion poin , can be obse ed la e ; howe e , a u he inc ease, coinciding wi h a mean empe a u e ise o abou 1.2" C, occu ed, a ound 2 500 BP. Since all he ypes we e al eady p esen , equi abili y was he esponsible o he composi- ional cha ge. Al hough cha ges in pollen abundances as a consequence o a- ia ions in pollen p oduc i i y o he species in ol ed canno be disca ded, he 96 V. RULL 10.000 YEARS B.P. o PRESENT Figu e 1. Va ia ions o he Shannon-Wea e index o di e si y (Pielou 1966), equi a- bili y (E=H/Hmax), and ype ichness (R), om pollen assemblages ound in he s a- ig aphical analysis o a pos glacial pea bog, om he Venezuelan Andes. Da a in Rull (1985). succession was modi ied, bu main ained. The e m ccmodula ed succession)) seems app opia e o his si ua ion. En i onmen al a ia ions may in e up he successional p ocess, i some h eshold is su passed. As is well known, sea le el changes occu ed-du ing he La e Glacial-Holocene ansi ion (Flin 1971, Kidson 1982). As a consequen- ce, many empe a e coas al lakes expe ienced successi e connec ions.and iso- la ions om he sea. In No way, mos o hem we e saline 10,000 yea s ago, when seale el was abou 40 m abou he p esen (Mange ud e al. 1974). A his ime, dia om communi ies we e domina ed by polihalobious species (S a- bell 1985). A subsequen seale el d op p oduced he isola ion and, he e o e, desaliniza ion o lakes which became eshwa e bodies. As a consequence, he o me li ing communi ies we e eplaced by o he s consis ing o halopho- bus and indi e en species (S abell1985). This ep esen s a signi ican ecolo- gical change, simila o he eplacemen o o es communi ies by open sa an- nas, eco ded in A ica (Bonne ille 1980), and o he opical places, du ing he las glacial epoch. The e m (( o ced subs i u ionn is mo e sui able o des- c ibe his phenomenon because, no only eo ganiza ion, bu subs i u ion o a communi y by ano he accu ed. In his case, a di e si y spec um looks like ha esul ing om a spa ial ansec , c ossing an eco one, an,d go in o ano he con iguous ecosys em. Fig. 2 shows he h ee main si ua ions discussed, which a e cha ac e ized by he magni ude o en i onmen al a ia ion, as well as QUATERNARY PALAEOECOLOGY 97 communi y ole ance. The clima ologic e minology may p o ide some use ul e ms. Majo a ia ions, such as glacia ions, a e called changes. whe eas luc- ua ion means mino oscilla ions (G i i hs 1976). Thus, we can ela e change wi h subs i u ion, luc ua ion wi h modula ion, and he di e si y spec a a e use ul ools o disc imina e be ween hem, and also om non-dis u bed suc- cessional p ocesses. S abili y and he concep o climax I is a widesp ead opinion ha he mo e complex ecosys ems, al hough well adap ed o he p edic able en i onmen in which he e ol ed (May 1975), a e T IME - Figu e 2. Hypo he ical examples o h ee possible successional si ua ions: A) Nondis u bed succession. B) Modula ed succession. C) Induced subs i u ion. 98 V. RULL no able o esis ex e na1 dis u bances. The opical o es is equen ly ci ed as an example o bo h bio ic and en i onmen al cons ancy (Fische 1961, Fe- do o 1966, Schawabe 1968). Howe e , ecen indings showed ha clima ic changes also occu ed in low la i udes. E idences a e ound e e ywhe e (Wal- ke & Chen 1987), and a e o e y di e en na u e, including: pollen analysis, high-moun ain mo aines, allu ial e aces, o me lake basins, dia oms and au ogenic mine als in lake sedimen s, s abilized dunes, and o he s (Li ings o- ne 1980). The glacial pe iods o empe a e zones coincided wi h opical a i- di y, and o es s we e eplaced by open ege a ion and dese s. Thus, he gla- cial-in e glacial al e na ion was cha ac e ized in he opics, by he al e na ion o sa anna (o dese ) and o es (Ga ne 1975). A e uge hypo hesis was p o- posed o explain he pe sis ence o opical ain o es , in spi e o en i onmen- al changes occu ed; o es e uge a eas a e assumed o be locali ies ha we e no a ec ed by he a ia ions, owing o local condi ions, and in which he o- pical o es p obably su i ed (Ha e 1982). The successi e con ac ions (gla- cial) and expansions (in e glacial) o he o es con ibu ed o gene a e mo e bio ic di e si y he e, as a esul o al e na i e mixing and isola ion (P ance 1982). Howe e , he lack o di ec e idence o he e uges (B adbu y e al. 1981, Salgado-Labou iau 1980, Schube & F i z 1985, Schube 1988) inci ed o he al e na i e explana ions o he di e si y o he opical ain o es . The mos popula a e: 1) The occu ence o ex ensi e Holocene e osiona1 and de- posi ional e en s, due o mino clima ic luc ua ions (Campbell & F ailey 1984); 2) Fo es egene a ion by la e al mig a ion o i e s and i e meande s (Salo e al. 1986); 3) Fluc ua ions in he in ensi y and du a ion o d y seasons (Absy 1986); and 4) Occu ence o na u al i es du ing he las 6 000 yea s (Sand o d e al. 1985, Salda iaga & Wes 1986). In sho , luc ua ions we e conside ed mo e impo an han changes, in de e mining he o es composi- ion. O he w i e s conside ha no sub an ial changes in he ex ension, bu in he composi ion o o es occu ed, as a consequence o glacia ion (Conno 1986). Summa izing he p eceding in o ma ion, he his o y o opical lowlands is cha ac e ized by bo h subs i u ions and modula ed successions (see also Flen- ley 1979, Colin aux 1987). The o me ly p esen ed case o he Galapagos Is- lands is an excep ion and, as such, i me i s u he conside a ion. The classic"a1 concep o s abili y conside s en i onmen al dynamism o some deg ee. Ecological s abili y e e s o he endency o an ecosys em o e- main close o some equilib ium poin , o o e u n o i a e a dis u bance (Odum 1971, Ma gale 1977), as a consequence o i s in e na1 p ocesses. Se e- al p ope ies, such as cons ancy, ine ia, elas ici y, ampli ude, and o he s, may be use ul o desc ibe ecosys em beha iou . Fo example, a high ine ia (capaci y o assimila e ex e na1 dis u bances) bu low elas ici y and ampli ude (capaci y o e u n, a e a modi ying dis u bance) a e assumed o opical o- es s, while he con a y would be he ule o empe a e o es s (O ians 1975). The concep s o esilience and a ac ion domain we e in oduced by Holling QUATERNARY PALAEOECOLOGY 99 (1973). Acco ding o him, mo e han one po en ial equilib ium poin (al - hough no anyone) would be possible o a gi en communi y, he sum o hem o ming hei a ac ion domain. Thus, an ecosys em is mo e o less edien , depending on i s abili y o e u n o he domain. Al hough mo e han wel e meanings o s abili y exis (Wi ake 1975), esilience is a sa is ac o y concep in palaeoecology (Delcou e al. 1983). The Qua e na y p o ides good exam- ples o dis u bed ecosys ems, and hei esponses. As shown, plan communi- ies ecolonized he new open spaces c ea ed by glacie e ea , in a successio- nal way. I is in e es ing o s udy he composi ion o hese la e communi ies, and compa e hem wi h hose o me ly inhabi ing he a ea, ha is, be o e he glacial dis u bance. A ecu en cycle in o es ege a ion was eco de o he h ee las in e glacials in G ea B i ain (Godwin 1975, 1977). All o hem a e cha ac e ized by common ends in p o oc a ic (Be ula, Pinus), mesoc a ic (Que cus, Tilia, Ulmus, Alnus), and eloc a ic (Abies, Picea, Fagus), o es ees. Thus, a s anda d in e glacial may be di ided in ou subs ages: 1) p e- empe a e, domina ed by p o oc a ic ees; 2) ea ly- empe a e, wi h mesoc a- ic ees; 3) la e- empe a e, wi h eloc a ic ees; and 4) pos - empe a e, wi h p o oc a ic ees again (Tu ne & Wes 1968). The mos in e es ing ea u e in ou con ex , is he ac ha ela i e abundances o hese axa we e di e en du- ing he h ee in e glacials. The same ege a ional ypes, bu wi h di e en composi ions, de eloped a e each glacial pe iod. In o he wo ds, hese ecosys ems adop ed h ee o hei po encial composi ional sa es, as exp ession o hei esilience. Phenomena o his na u e in ol e di e en bio ic esponses o he same o cing in luence. The communi y esponse is a esul o he indi idual speci ic beha iou o i s componen s. Da is (1969, 1976, 1981) showed he g ea in luence o di e en ial mig a ion a es (a he species le el) on he ege a io- nal composi ion o No h Ame ican ecosys ems, du ing he Holocene ecolo- niza ion. La e , di e ences in esponse ime ( ime lag) we e added as a signi i- can ac o (Da is 1984). The ime lags a e ela i ely sho o some componen s (insec s, bi ds), bu can las a cen u y o mo e in plan s. These di e ences depends on li e his o ies, gene a ion imes, beha iou , means o dispe sal, compe i i e abili y, and o he s, and a e decisi e o de e mine he communi y composi ion a a gi en si e, a a gi en ime (Da is 1984, W igh 1984). In he ligh o his e idence, he en i onen al a ia ions, and he speci ic di e ences in esponse, Da is (1984) p oposed ha ecosys ems ne e a ain an equilib ium, being in cons an adjus emen o he ex e na1 changing condi- ions. This con inuous disequilib ium hypo hesis is some imes c i icized, on he basis o indings ha indica e long pe iodes o en i onmen al and ecologi- cal s abili y (Wa s 1970, 1979). The al e na ion o s able and uns able phases is also p oposed; bu s abili y canno mean cons ancy, because luc uac ions a e always p esen . Mo consis en wi h palaeoecological e idence is he idea o dynamic equilib ium (Delcou & Delcou 1983), acco ding o which V. RULL pa e ns. The model also explained some o he e ec s o changing i e e- quency, sugges ing mechanisms by which i e, compe i ion, and clima e, com- bine o p oduce long- e m composi ional changes. Final commen s Ecology is no an en i onmen al science, because i is conce ned wi h he whole biosphe e, a he communi y o ganiza ion le el. Biosphe e is a mix u e o spa ial g adien s, and empo al ends. The hough on which ecology is based is ha nei he ends no g adien s a e a andom, ha ing egula i ies, and o ganiza ion le els. Ecological heo y is he a m by which ecology a - emp s o ind gene al ules. Palaeoecology is no en i onmen al econs uc ions. I is a pa o ecologi- cal s udy, which possesses a undamen al alue o ecological heo y, becuse i p o ides e idence no a ailable om neoecology. Obse a ions a he human scale (mic oscale) a e insu icien o gene alize abou ecosys em e olu ion. On he o he hand, palaeoecology is a heo izable discipline. Theo y gi es mo e s imuling goals han desc ip i e econs uc ion o pas .en i onmen s, o local clima ic his o ies. I is hus necessa y, no only o gene a e mo e and mo e in o ma ion, bu also hink abou i , unde an ecological amewo k. Hil1 (1981) posed he ques ion: -Why s udy palaeoecology?-. The answe seems o me: -Fo a be e unde s anding o biosphe e-, he same han o : -Why s udy ecology?-. I Acknowledgemen s The o iginal nanusc ip was i np o ed a e he c i ica1 e ision o R. Ma gale , C. Schube , and T. Vegas-Villa ubia. The e ision by wo unknown e e ees is also acknowledged. This wo k was ca ied ou du ing he de elopmen o he esea ch p ojec SI-1843, suppo ed by CONICIT (C. Schube , esponsible in es iga o ). Re e ences Absy, M.L. 1986. Palinology o Amazonia: The his o y o he o es s as e ealed by he palynplogical eco d. In: P ance, G. & Lo eyoy, T. (eds.) Amazonia. Pe ga- mon P ess. Ox o d. pp. 72-82. Bandy, O.L., Bu le , E.A. & W igh , R.C. 1969. Alaskan Uppe Miocene ma ine gla- cial deposi s and he Tu bo o aliapachyde ma da um plane. Science 166: 607-609. Bi ks, H.J.B. 1980. The p esen lo a and ege a ion o he Klu lan Glacie , Yukon, Canada: A s udy in $an succession. ~ua e na ~ Res. 14: 60-86. Bi ks, H.J.B. & Bi ks, H.H. 1980. Qua e na y Palaeoecology. E. A nold. London. Bonne illle, R. 1980. Vege a ion his o y o sa anna in Eas A ica du ing he Plio- Pleis ocene. IV In . Palynol. Con . Lucknow 3:75-89. Bo kin. D.B., Janak, L.F. & Wallis, J.R. 1973. Some ecological consecuences o a compu e model o o es g ow h. Jou . Ecol. 60:849-872. Bowen, D.Q. 1978. Qua e na y Geology. Pe gamon P ess. Ox o d. Bowen, D.Q., Richmound, G.M., Fulle on, D.S., Sib a a, V., Ful on, R.J. & Veli- QUATERNARY PALAEOECOLOGY 107 chko, A.A. 1986. Co ela ion o Qua e na y glacia ions in he No he n Hemisp- he e. Qua e na y Sci. Re . 5: 509-510. B adbu y, J.P., Leyden, B., Salgado-L.abou iau, M.L., Lewis, W.M., Schube , C., Bin o d, M.W., F ey, D.G., Whi ehead, D.G. & Weibezahn, F.H. 1981. La e Qua e na y en i onmen al his o y o lake Valencia, Venezuela. Science 214: 1299- 1305. B ie , G.W. 1964. The luna synodical pe iod and p ecipi a ion in he Uni ed S a es. J. A mosphe ic Sci. 21:386-395. Campbell, K.E. & F ailey, D. 1984. Holocene looding and species di e si y in Sou h- wes e n Amazonia. Qua e na y Res. 21:369-375. Clappe on, C.M. 1983. The glacia ion o he Andes. Qua e na y Sci. Re . 2233-155. Cline, R.M. & Hays, J.D. (eds). 1971. In es iga ions o La e Qua e na y Paleoceano- g aphy and Paleoclima ology. Geol. Soc. A n. Memoi . 145. Colin aux, P. 1987. Amazon di e si y in ligh o he paleoecological eco d. Qua e - na y Sci. Re . 6:93-114. Colin aux, P.A. & Scho ield, E.K. 1976a. His o ical ecology in he Galapagos Is- lands: I.A. Holocene pollen eco d om El Junco Lake, Isla San C is óbal, J. ECOI. 64:989-1012. Connell, J.H. & O ias, E. 1964. The ecological egula ion o species di e si y. Ame . Na u . 98:399-414. Conno , E.F. 1986. The ole o pleis ocene o es e ugia in he e olu ion and biogeo- g aphy o opical bio as. TREE 1:165-168. Cooke, H.B.S. 1973. Pleis ocene ch onolgoy: Long o sho ? Qua e na y Res. 3 206- 220. Cu ie, R.G. 1974. Sola cycle signa1 in su ace ai empe a u e. J. Geophys. Res. 79:5657-5660. Da is, M.B. 1969. Clima ic changes in Connec icu eco ded by pollen deposi ion a Roge s Lake. Ecology 50:409-422. Da is, M.B. 1976. Pleis ocene biogeog aphy o empe a e deciduous o es s. Geo- science and Man 13:13-26. ' Da is, M.B. 1981. Qua e na y his o y and he s abili y o o es communi ies. In: Wes , D.C., Shuga , H.H. & Bo kin, D.B. (eds.) Fo es succession, concep s and applica ion. Sp inge Ve lag. New Yo k, pp. 132-153. Da is, M.B. 1984. Clima ic ins abili y, ime lags, and communi y disequilib ium. In: Diamond, J. & Case, T.J. (eds.) Communi y Ecology. Ha pe & Row. New Yo k. pp. 269-284. Da is, M.B. & Bo kin, D.B. 1985. Sensi i i y o cool- empe a e o es s and hei os- si1 pollen eco d o apid empe a u e changes. Qua e na y Res. 23:327-340. Delcou , H.R. 1979. La e Qua e na y ege a ion his o y o he Eas e n Highland Rim and adjacen Cumbe land Pla eau o Tennessee. Ecol. Monog . 49:255-280. Delcou , P.A. & Delcou , H.R. 1983. La e-Qua e na y ege a ional dynamics and communi y s abili y econside ed. Qua e na y Res. 19:265-271. Delcou , H.R., Delcou , P.A. & Webb, T. 111. 1983. Dynamic plan ecology: he spec um o ege a ional change in space and ime. Qua e na y Sci. Re . 1:153- 175. Den on, G.H. & Hughes, T.J. 1983. Milanko i ch heo y o ice ages: Hypo hesis o ice-shee linkage be ween egional insola ion and global clima e. Qua e na y Res. 20:125-144. 108 V. RULL Den on, H.D. & Ka lén, W. 1973. Holocene clima ic a ia ions. Thei pa e n and possible cause. Qua e na y Res. 3:155-205. an Donk, J. 1976. 0'"eco d o he A lan ic Ocean o he en i e Pleis ocene Epoch. Geol. Soc. Am. Mem. 145:147-164. Donnan, F.G. 1936. In eg al analysis and he phenomena o li e. Ac a Bio heo e ica 2H:l-11. Dunba , C.O. 1952. His o ical Geology. J. Wiley. New Yo k. Eddy, J.A. 1976. The Maunde Minimum. Science 192:1189-1202. Fai b idge, R.W. 1976. E ec s o Holocene clima ic changes on some opical geo- mo phic p ocesses. Qua e na y Res. 6529-566. Fedo o , A.A. 1966. The s uc u e o he opical ain o es and specia ion in he humid opics. J. Ecol. 54:l-11. Fink, J. & Kukla, G.J. 1977. Pleis ocene clima es in Cen al Eu ope: A leas 17 in e - glacials a e he Oldu ai E en . Qua e na y Res. 7:363-371. Fische , A.G. 1961. La i udinal a ia ions in o ganic di e si y. Ame . Scien . 49:50- 74. Flenley, J.R. 1979. The equa o ial ain o es : a geological his o y. Bu e wo hs. London. Flin , R.F. 1971. Glacial and Qua e na y Geology. J. Wiley. New Yo k. Flin , R.F. 1976. Physical e idence o Qua e na y clima ic change. Qua e na y Res. 6:519-528. Flohn, H. 1979. On he ime scales and causes o ab up paleoclima ic e en s. Qua e - na y Res. 12:135-149. Fulle on, D.S. & Richmond, G.M. 1986. Compa ison o ma ine iso ope eco d, he eus a ic sea le en eco d, and he ch onology o glacia ion in he Uni ed S a es o Ame ica. Qua e na y Sci. Re . 5:197-200. Funnell, B.M. & Riedel, W.R. (eds.). 1971. The mic opalaeon ology o he oceans. Camb idge Uni e si y P ess. Ga ne , H.F. 1974. The o igin o landscapes. Ox o d Uni e si y P ess. New Yo k. Ga ne , H.F. 1975. Rain Fo es s, dese s and e olu ion. Ann. Acad. B asil. Ciencias 47, supl.: 127-133. Godwin, H. 1975. The his o y o he B i ish lo a. Camb idge Uni e si y P ess. Cam- b idge. Godwin, H. 1977. Qua e na y his o y o he B i ish lo a. In: Sho on, F.W. (ed.) B i- ish Qua e na y s udies. Cla endon P ess. Ox o d. G een, D.G. 1981. Time se ies and pos glacial o es ecology. Qua e na y Res. 15:265-277. G i i s, J.G. 1976. Applied clima ology. Ox o d Uni e si y P ess. New Yo k. Ha e , J. 1982. Some gene al aspec s o he e uge heo y. In: P ance, G.T. (ed.) Bio- logical di e si ica ion in he opics. Columbia Uni e si y P ess. New Yo k. pp. 6-24. Has en a h, S. 1981. The glacia ion o he Ecua o ian Andes. Balkema, Ro e dam. Hays, J.D., Imb ie, J. & Shakle on, N.J. 1976. Va ia ions in he ea h's o bi : Pace- make o he Ice Ages. Science 194: 1121-1132. Heine, K. 1977. Beobach ungen und Ube legungen zu eiszei lichen Dep ession on Schneeg enze und S uk u bodeng enze in demm T open un Sub open. E dkun- de 31:161-177. Hill, A. 1981: Why s udy palaeoecology? Na u e 293:340. QUATERNARY PALAEOECOLOGY 109 Hi schboeck, K.K. 1979-1980.1; new wo lwide ch onology o olcanic e up ions. Pa- laeogeog . Palaeoclima ol. Palaeoecol. 29:223-241. Ho man, A. 1979. Communi y ecology as an epiphenomenal science. Paleobiology 51357-379. Holling, C.S. 1973. Resilience and s abili y o ecological sys ems. Ann. Re . Ecol. Sys . 4:l-23. Hu chinson, G.E. 1979. El ea o ecológico y el d ama e olu i o ( ad. del inglés). Bb~me, Ba celona. Imb ie, J. 1985. A heo e ical amewo k o he Pleis ocene Ice Ages. J. geol. Soc. 1,ondon 142:417-432. I~nS ie, J. & Kipp, N.G. 1971. A new mic opalaeon ologic me hod o quan i a i e paleoclima ology: applica ion o a La e Pleis ocene Ca ibbean co e. In: K.K. Tu- ekian (ed.) La e Cenozoic Glacial Ages. Yale Uni e si y P ess New Ha en. pp. 71-191. Kaminz, N.A. & Pisias, N.G. 1979. Pleis ocene clima e: de e minis ic o s ochas ic? Science 204:171-173. Kidson, C. 1982. Seale el changes in he Holocene. Qua e na y Sci. Re . 1:121-151. Koi o, L.K. 1970. Species di e si y in pos glacial dia om lake communi ies o Finland Palaeogeog . Palaeoclima ol. Palaeoecol. 19:165-190. K aso , D.D. & Ve bi sky, M. Y. 1981. Causes o an a c ic glacia ion in he Ceno- zoic. Qua e na y Res. 15:l-17. Laske , H. 1976. E ec s o di e en ial p ese a ion on he measu emen o axono- mic di e si y. Paleobiology 2:84-93. Li ings one, D.A. 1980. His o y o he opical ain o es . Paleobiology 6:243-244. Lo enz, E.N. 1976. Nonde e minis ic heo ies o clima ic change. Qua e na y Res. 6:495-506. Mange ud, J., Ande sen, S.T., Be glund, B.E. & Donne , J.J. 1974. Qua e na y s a- ig aphy o No den, a p oposal o e minology and classi ica ion. Bo eas 3:109-127. Ma gale , R. 1963. On ce ain uni ying p inciples in ecology. Ame . Na u . 97:357- 374. Ma gale , R. 1968. Pe spec i es in ecological heo y. Chicago Uni e si y P ess. Chi- cago. Ma gale , R. 1974. Ecologia. Omega, Ba celona. Ma gale , R. 1986. Sucesión y e olución: su p oyección biogeog a ica. Paleon ol. E ol. 20:7-26. Ma golis, S.V. & Kenne , J.P. 1970. An a c ic glacia ion du ing he Te ia y eco - ded in Sub-An a c ic deep-sea co es. Science 170:1085-1087. Ma inson, D.G., Pisias, N.G., Hays, J.D., Imb ie, J., Moo e, T.C. & Shakle on, N.J. 1987. Age da ing and he o bi al heo y o he Ice Ages: De elopmen o a high-sesolu ion O o 300,000 yea s ch onos a ig aphy. Qua e na y Res. 27:l-29. May, ~.hjl. 1975. S abili y in ecosys ems: some commen s. In: an Dobben, W.H. & Lowe-McConnell, R.H. (eds.) Uni ying concep s in Ecology. D . W. Junk. The Hague. pp. 161-168. Mi chell J ., J.M. 1976. An o e iew o clima ic a iabili y and i s causal mechanisms. Qua e na y Res. 6:481-493. Odum, E.P. 1971. Fundamen als o Ecology. W.B. Saunde s. Philadelphia. Olson, E.C. 1985. Ve eb a e paleoecology: A cu en pe spec i e. Palaeogeog . Pa- laeoclima ol. Palaeoecol. 50:83-106. 110 V. RULL O ians. G.H. 1975. Di e si y, s abili y and ma u i y in na u al ecosys ems. In: an Dobben, W.H. & Lowe-McConnell, R.H. (eds.) Uni ying Concep s in Ecology. D . W. Junk. The Hague, pp. 139-150. Pielou, E.C. 1966. Species-di e si y and pa e n-di e si y in he s udy o ecological succession. J. Theo e . Biol. 10:370-383. Pielou, E.C. 1974. Popula ion and communi y ecology. Go don & B each, New Y~ k. Pisias, N. & Imb ie, J. 1986. O bi al geome y, COz, and Pleis ocene clima e. Ocea- nus 29:43-49. Po e , S.C. 1986. Pa e n and o cing o No he n Hemisphe e glacie a ia ions du- ing he las millenium. Qua e na y Res. 26:27-48. P ance, G.T. (ed.). 1982. Biological di e si ica ion in he opics. Columbia Uni e - si y P ess. New Yo k. Reine s, W.A., Wo ley, I.A. & Law ence, D.B. 1971. Plan di e si y in a ch onose- quence a glacie Bay, Alaska. Ecology 523-69. Robock, A. 1979. The Li le Ice Age: No he n Hemisphe e a e age obse a ions and model calcula ions. Science 206: 1402-1404. Rull, V. 1985. Análisis polinico de dos u be as holocenas si uadas en el supe pa amo de 10s Andes enezolanos. M.Sc. Thesis. CEA-IVIC. Ca acas. Rull. V. 1987. E idencias de una oscilacion clima ica ia, con empo anea de la Pe- queña Edad de Hielo, en 10s Andes enezolanos. Bol. Soc. Venezolana A queol. 4: 13-27. Rull, V., Salgado-Labou iau, M.L., Schube , C. & Vals o J ., S. 1987. La e Holoce- ne empe a u e dep ession in he Venezuelan Andes: Palynological e idence. Pa- leogeog . Palaeoclima ol. Palaeoecol. 60: 109-121. Salda iaga, J.G. & Wes , D.C. 1986. Holocene i es in he No he n Amazon basin. Qua e na y Res. 26:358-366. Salgado-Labou iau, M.L. 1980. A pollen diag am o he Pleis ocene-Holocene boun- da y o lake Valencia, Venezuela. Re . Palaeobo . Palynol. 30:297-312. Salo, J., Kalliola, R., Hakkinen, I., Makinen, Y., Niemela, P. Puhakka, M. & Coley, P.D. 1986. Ri e dynamics and he di e si y o Amazon lowland o es . Na u e 322:254-258. Sande s, H.L. 1968. Ma ine ben hic di e si y: A compa a i e s udy. Ame . Na u . 102:243-282. Sand o d, R.L., Salda iaga, J., Cla k, K.E., Uhl, C. & He e a, R. 1985. Amazon ain o es i es. Science 22753-55. Schneide , S.H. & Thompson, S.L. 1979. Ice Ages and o bi al a ia ions: some simple heo y and modelling. Qua e na y Res. 12:188-203. Schop . T.J.M. (ed.) 1972. Models in Paleobiology. F eeman & Coope . S. F ancisco. Schube , C. 1974. La e Pleis ocene Mé ida Glacia ion, Venezuelan Andes. Bo eas 3:147-152. Schube , C. 1984. The Pleis ocene and ecen ex en o he glacie s o he Sie a Ne- ada de Mé ida, Venezuela. E dwiss. Fo sch. 18:269-278. Schube , C. 1988. Clima ic changes du ing he las glacial maximum in No he n Sou h Ame ica and he Ca ibbean: a e iew. In e ciencia 13:128-137. Schube , C. & F i z, P. 1985. Radioca bon ages o pea s, Guayana Highlands (Vene- zuela). Na u wissenscha en 72:427-429. Schwabe, G.H. 1968. Towa ds an ecological cha ac e iza ion o he Sou h Ame ican Con inen . In Fi kau, E.J., Illies, J., Klinge, H., Schwabe, G.H. & Sioli, H. I QUATERNARY PALAEOECOLOGY 111 (eds.) Biogeog aphy and Ecology in Sou h A ne ica I. D . W. Junk. The Hague. pp. 113-136. Sib a a, V. 1986. Co ela ion o Eu opean Glacia ions and hei ela ion o he deep- sea eco ds. Qua e na y Sci. Re . 5:433-441. S nol, J.P. 1981. P oble ns associa ed wi h he use o species di e si y in Paleoli nnolo- gical s udies. Qua e na y Res. 15:209-212. Solo non, A.M., Delcou , H.R., Wes , D.C. & Blasing, T.J. 1980. Tes ing a si nula- ion model o econs uc ion o p ehis o ic o es -s and dyna nics. Qua e na y Res. 14:275-293. S abell, B. 1985. The de elop nen and succession o axa wi hin he dia o n genus F agila ia Lyngbye as a esponse o basin isola ion om he sea. Bo eas 14:273- 286. S enonius, B. & Olausson, E. 1979. Cycles in sola ac i i y, especially o long pe iods. and ce ain e es ial ela ionships. Palaeogeog . Palaeocli na ol. Palaeoecol. 26:89-97. Tai a, K. 1983. Accele a ed paci ic pla e no e nen s and cli na ic changes on i ne- scales o 102-103 yea s in he La e Qua e na y: A syn hesis. Palaeogeog . Palaeo- cli na ol. Palaeoecol. 4:203-214. Thompson, L.G., Mosley-Thompson, E., Dansgaa d, W. & G oo es, P.M. 1986. The Li le Ice Age as eco ded in he s a ig aphy o he T opical Quelccaya Ice Cap. Science 234:361-364. Tu ne , C. & Wes , R.G. 1968. The subdi ision aad zona ion o in e glacial pe iods. Eiszel al e gegenw. 19:93-101. Valen ine, J.W. 1972. Concep ual models o ecosys e n e olu ion. In Schop . T.J.M. (ed.). Models in Paleobiology. F ee nan & Coope . S. F ancisco. pp. 192-215. Walke , D. & Chen, Y. 1987. Palynological ligh on opical ain o es dyna nics. Qua e na y Sci. Re . 6:77-92. Wa s, W.A. 1970. The ull-glacial ege a ion o no heas e n Geo gia. Ecology 51:17-33. Wa s, W.A. 1979. La e Qua e na y ege a ion o cen al Appalachia and he New Je sey Coas al plain. Ecol. Monog . 49:427-469. Willia ns, L.D. & Wigley, T.M.L. 1983. A co npa ison o e idence o La e Holocene su n ne e npe a u e a ia ions in he No he n He nisphe e. Qua e na y Res. 20:286-307. Wi akke , R.H. 1975. The design and s abili y o plan co n nuni ies. In: an Dobben. W.H. & Lowe-McConnell, R.H. (eds.) Uni ying concep s in Ecology. D . W. Junk. The Hague. W igh J ., H.E: 1984. Sensi i i y and esponse i ne o na u al sys e ns o cli na ic change in he La e Qua e na y. Qua e na y Sci. Re . 3:91-131. Manusc ip ecei ed on Sep e nbe 1988.