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ERN.702 – UFSCar - Marco A.R. Mello

Introdução

1. Os níveis de organização2. Indivíduos e populações3. Diversidade: comunidades e ecossistemas4. Resumo5. Para saber mais...

Ao final da aula, nós teremos:

1. revisado conceitos centrais em ecologia dos indivíduos e das populações

2. identificado quais os níveis de organização e escalas temporais que serão estudados

Introdução


Hierarquia

Cada nível de organização possui propriedades únicas

Um nível influencia os demais

Introdução


21

Ambiente: cenário evolutivo

23

Condições

Condições

๏ Umidade๏ pH๏ salinidade๏ poluição

26

Recursos

27

Recursos

Recursos

๏ Tudo que é consumido por um organismo (Tilman, 1982)

๏ Não apenas usado como alimento, mas em uso

Recursos

๏ Nutrientes (água, luz, minerais, outros organismos)๏ Espaço๏ Ninhos e abrigos๏ Parceiros sexuais

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Joseph Grinnell(1877-1939)

Joseph Grinnell(1877-1939)

Grinnell (1917)

Nicho = como o local onde uma espécie vive

Duas espécies não podem ocupar o mesmo nicho

Charles S. Elton(1900-1991)

Charles S. Elton(1900-1991)

Animal Ecology, Elton (1927)

Nicho = a função da espécie em uma comunidade

Nicho ecológico

๏ São todos os fatores necessários para que um indivíduo cresça e se reproduza

๏ Mas quantos são os fatores?

G E. Hutchinson (1903-1991)

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Nicho ecológico

๏ São muitos os fatores:๏ Multi-dimensional (N-dimensional)

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Nicho ecológico

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Hutchinson (1957)

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Competição intra-específica(-/-)

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Competição interespecífica (-/-)

predação / parasitismo / herbivoria (+/-)

Mutualismo (+/+)

Introdução


54

Comunidades

Introdução

Introdução

I am tempted to give one more instance showing how plants and animals, most remote in the scale of nature, are bound together by a web of complex relations

Introdução

A organização da biodiversidade

Estrutura e dinâmica de redes ecológicas

Introdução

E. Odum

Ecossistemas como ... sistemas

R. MargalefR. Lindeman

F. Clements

G. E. Hutchinson

Charles EltonEstrutura e dinâmica de redes ecológicas

Introdução

Espécies em nichos

R. MacArthur

R. T. PaineJ. CohenR. MayEstrutura e dinâmica de redes ecológicas

Introdução

Sistemas ecológicos como redes complexas

Tempo ecológico

Diversidade no tempo evolutivo

70

Competição interespecífica (-/-)

Luz

Sol

Autotróficos

ProdutividadePrimáriaLíquida

Heterótrofos

Calor Respiração Respiração

Exportação Produtividade

PrimáriaBruta

ProdutividadeSecundária

Ecossistemas

Tempo ecológico

Diversidade no tempo evolutivo

Adaptações a predação

in Fig. 2, although derived quite differently. Such models may be sensi-tive to the particular geographic area, taxa and species-area relationshipthat is employed, and have usually used only modern data. However,fossil-to-modern comparisons using species-area methods are nowbecoming possible as online palaeontological databases grow30,31,45. Anadditional, new approach models howmuch extinction can be expectedunder varying scenarios of human impact7. It suggests a broader range ofpossible future extinction magnitudes than previous studies, althoughall scenarios result in additional biodiversity decline in the twenty-firstcentury.

Combined rate–magnitude comparisonsBecause rate andmagnitude are so intimately linked, a critical question iswhether current rates would produce Big-Five-magnitude mass extinc-tions in the same amount of geological time that we think most Big Fiveextinctions spanned (Table 1). The answer is yes (Fig. 3). Current extinc-tion rates for mammals, amphibians, birds, and reptiles (Fig. 3, lightyellow dots on the left), if calculated over the last 500 years (a conserva-tively slow rate27) are faster than (birds, mammals, amphibians, whichhave 100% of species assessed) or as fast as (reptiles, uncertain becauseonly 19% of species are assessed) all rates that would have produced theBig Five extinctions over hundreds of thousands or millions of years(Fig. 3, vertical lines).Would rates calculated for historical and near-time prehistoric

extinctions result in Big-Five-magnitude extinction in the foreseeablefuture—less than a few centuries? Again, taking the 500-year rate as auseful basis of comparison, two different hypothetical approaches arepossible. The first assumes that the Big Five extinctions took placesuddenly and asks what rates would have produced their estimatedspecies losses within 500 years (Fig. 3, coloured dots on the right).

(We emphasize that this is a hypothetical scenario and that we are notarguing that allmass extinctions were sudden.) In that scenario, the ratesfor contemporary extinctions (Fig. 3, light yellow dots on the left) areslower than the rates that would have produced each of the Big Fiveextinctions in 500 years.However, rates that consider ‘threatened’ speciesas inevitably extinct (Fig. 3, orange dots on the left) are almost as fast asthe 500-year Big Five rates. Therefore, at least as judged using thesevertebrate taxa, losing threatened species would signal a mass extinctionnearly on par with the Big Five.A second hypothetical approach asks how many more years it would

take for current extinction rates toproduce species losses equivalent toBigFive magnitudes. The answer is that if all ‘threatened’ species becameextinctwithin a century, and that rate then continuedunabated, terrestrialamphibian, bird and mammal extinction would reach Big Five magni-tudes in ,240 to 540 years (241.7 years for amphibians, 536.6 years forbirds, 334.4 years for mammals). Reptiles have so few of their speciesassessed that they are not included in this calculation. If extinction werelimited to ‘critically endangered’ species over the next century and thoseextinction rates continued, the time until 75% of species were lost pergroup would be 890 years for amphibians, 2,265 years for birds and1,519 years for mammals. For scenarios that project extinction of‘threatened’ or ‘critically endangered’ species over 500 years instead ofa century, mass extinction magnitudes would be reached in about 1,200to 2,690 years for the ‘threatened’ scenario (1,209 years for amphibians,2,683 years for birds and 1,672 years for mammals) or,4,450 to 11,330years for the ‘critically endangered’ scenario (4,452 years for amphi-bians, 11,326 years for birds and 7,593 years for mammals).This emphasizes that current extinction rates are higher than those that

caused Big Five extinctions in geological time; they could be severe enoughto carry extinctionmagnitudes to theBig Five benchmark in as little as threecenturies. It also highlights areas formuch-needed future research. Amongmajor unknowns are (1) whether ‘critically endangered’, ‘endangered’ and‘vulnerable’ species will go extinct, (2) whether the current rates we used inour calculations will continue, increase or decrease; and (3) how reliablyextinction rates in well-studied taxa can be extrapolated to other kinds ofspecies in other places7,20,25,34.

The backdrop of diversity dynamicsLittle explored is whether current extinction rates within a clade fall out-side expectations when considered in the context of long-term diversitydynamics. For example, analyses of cetacean (whales and dolphins)extinction and origination rates illustrate that within-clade diversity hasbeen declining for the last 5.3million years, and that that decline is nestedwithin an even longer-term decline that began some 14million years ago.Yet, within that context, even if ‘threatened’ genera lasted as long as100,000 years before going extinct, the clade would still experience anextinction rate that is an order of magnitude higher than anything it hasexperienced during its evolutionary history46.The fossil record is also enabling us to interpret better the significance

of currently observed population distributions and declines. The use ofancient DNA, phylochronology and simulations demonstrate that thepopulation structure considered ‘normal’ on the current landscape hasin fact already suffered diversity declines relative to conditions a fewthousand years ago47,48. Likewise, the fossil record shows that speciesrichness and evenness taken as ‘normal’ today are low compared to pre-anthropogenic conditions10,27,32,33,42,45,49.

SelectivityDuring times of normal background extinction, the taxa that sufferextinction most frequently are characterized by small geographic rangesand low population abundance38. However, during times ofmass extinc-tion, the rules of extinction selectivity can change markedly, so thatwidespread, abundant taxa also go extinct37,38. Large-bodied animalsand those in certain phylogenetic groups can be particularly hardhit33,50–52. In that context, the reduction of formerly widespread ranges8

and disproportionate culling of certain kinds of species50–53 may be

E/M

SY

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10

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1

0.1

1,000

10,000

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Cretaceous

TH, CR

Triassic

Ordovician

Permian

0.01

Extinction magnitude (percentage of species)

0 20 40 60 80 100

Criticallyendangered

Alreadyextinct Threatened

Figure 3 | Extinction rate versus extinction magnitude. Vertical lines on theright illustrate the range of mass extinction rates (E/MSY) that would producethe Big Five extinctionmagnitudes, as bracketed by the best available data fromthe geological record. The correspondingly coloured dots indicate what theextinction rate would have been if the extinctions had happened(hypothetically) over only 500 years. On the left, dots connected by linesindicate the rate as computed for the past 500 years for vertebrates: light yellow,species already extinct; dark yellow, hypothetical extinction of ‘criticallyendangered’ species; orange, hypothetical extinction of all ‘threatened’ species.TH: if all ‘threatened’ species became extinct in 100 years, and that rate ofextinction remained constant, the time to 75% species loss—that is, the sixthmass extinction—would be,240 to 540 years for those vertebrates shown herethat have been fully assessed (all but reptiles). CR: similarly, if all ‘criticallyendangered’ species became extinct in 100 years, the time to 75% species losswould be,890 to 2,270 years for these fully assessed terrestrial vertebrates.

REVIEW RESEARCH

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Macmillan Publishers Limited. All rights reserved©2011

Sexta extinção em massa

Introdução


Nível de organização Indivíduos / populações


interaçõesespaço / tempo nicho



Ecologia/Evolução Diversidade



comunidades / ecossistemas

Ecologia/Evolução Diversidade

Introdução


Levin, S. A. 1992. Ecology 73: 1943 - 1967

slide sem títuloecologia.ib.usp.br/guimaraes/aula/aula1_introducao.pdf · a organização da...

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