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Understanding global biodiversity gradients. Miguel B. Araújo Cátedra Rui Nabeiro – Biodiversidade, CIBIO, Universidade de Évora Museo Nacional de Ciências Naturales, CSIC, Madrid. Gulbenkian, Lisboa, Julho 2009. Causes of global biodiversity gradients. A debate with more than 160 years.

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Understanding global biodiversity gradients

Understanding global biodiversity gradients

Miguel B. Araújo

Cátedra Rui Nabeiro – Biodiversidade, CIBIO, Universidade de Évora

Museo Nacional de Ciências Naturales, CSIC, Madrid

Gulbenkian, Lisboa, Julho 2009



A debate with more than 160 years
A debate with more than 160 years

Alfred Russel Wallace

(1823-1913)

Alexander von Humboldt

(1769-1859)



Contemporary vs historical hypothesis
Contemporary vs. historical hypothesis

“We would challenge anyone who proposes an historical explanation for the contemporary patterns of species richness to derive the predictions of that explanation so that they may be tested”.

(Kerr & Currie, 1999)


Framing the evolutionary hypothesis
Framing the evolutionary hypothesis

Building of the species pool - Stability

Distribution of the species pool – Niche conservatism

Wiens & Donoghue (2004) TREE


Outline
Outline

  • Testing for differential building up of species pool

  • Testing for the effects of niche conservatism

  • Concluding remarks


Test of historic climate stability hypothesis with european reptiles and amphibians
Test of historic climate stability hypothesis with European reptiles and amphibians

Reptile species richness

Simultaneous autoregressive (SAR) models used to assess spatially corrected p values between species richness and contemporary and historical climate

Amphibian species richness

Araújo et al. 2008 Ecography


Test of historic climate stability hypothesis with european reptiles and amphibians1
Test of historic climate stability hypothesis with European reptiles and amphibians

Reptile species richness

Partial regression analysis to separate the unique contribution of the contemporary and historic climate variables

Amphibian species richness

Araújo et al. 2008 Ecography


Outline1
Outline reptiles and amphibians

  • Testing for differential building up of species pool

  • Testing for the effects of niche conservatism

  • Concluding remarks


Testing for the effects of niche conservatism example 1
Testing for the effects of niche conservatism reptiles and amphibians– example 1

  • If diversity gradients are not driven by niche conservatism,

  • then we would predict diversity gradients among clades originated in different periods to be similar.


Testing for the effects of niche conservatism example 11
Testing for the effects of niche conservatism reptiles and amphibians– example 1

  • If diversity gradients are driven by niche conservatism,

  • then we would predict diversity gradients among clades originated in different periods to be different.

  • Differences should reflect the ancestral climates shaping species niches.


Diversity of reptile families 74 of the world families dated with the fossil record
Diversity of reptile families – 74% of the World families dated with the fossil record

Families originated in the Cretaceous

Families originated in the Tertiary

Araújo et al. In preparation


Departure from a linear relationship
Departure from a linear relationship dated with the fossil record

r=0.74

More families in the Cretaceous

More families in the Tertiary

Araújo et al. In preparation


Testing for the effects of niche conservatism example 2
Testing for the effects of niche conservatism dated with the fossil record– example 2

  • If diversity patterns are not driven by niche conservatism,

  • then the slopes of the diversity gradients should not differ among species originated in different periods.


Testing for the effects of niche conservatism example 21
Testing for the effects of niche conservatism dated with the fossil record– example 2

  • If diversity patterns are driven by niche conservatism,

  • then the slopes of the diversity gradients should differ among species originated in different periods:

  • Diversity of species originated in warm periods should have steep slopes


Testing for the effects of niche conservatism example 22
Testing for the effects of niche conservatism dated with the fossil record– example 2

Slopes from 343 studies assessing contemporary gradients of diversity for a wide range of taxa and environments

Romdal, Araújo & Rahbek, In preparation


Outline2
Outline dated with the fossil record

  • Testing for differential building up of species pool

  • Testing for the effects of niche conservatism

  • Concluding remarks


Concluding remarks
Concluding remarks dated with the fossil record

  • Climate stability offers a parsimonious explanation for the differential building up of species pools (more stability less extinctions).

  • There is some evidence that niche conservatism at least partially drives the diversity gradients.

  • Evidence for niche conservatism does not contradict alternative hypotheses, but it highlights the need for more specific predictions that enable distinction among hypotheses.


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