understanding global biodiversity gradients
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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. - PowerPoint PPT PresentationTRANSCRIPT
Understanding global biodiversity gradients
Miguel B. AraújoCátedra 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
Alexander von Humboldt (1769-1859)
Alfred Russel Wallace (1823-1913)
125 Big Questions: What we don’t know?
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
Wiens & Donoghue (2004) TREE
Building of the species pool - Stability
Distribution of the species pool – Niche conservatism
Outline
1.Testing for differential building up of species pool
2.Testing for the effects of niche conservatism
3.Concluding remarks
Araújo et al. 2008 Ecography
Test of historic climate stability hypothesis with European reptiles and amphibians
Temperature PrecipitationHistoric climate stabilityReptiles 0.01 0.01
Amphibians 0.01 0.01
Contemporary climateReptiles 0.01 0.05Amphibians 0.01 ns
Reptile species richness
Amphibian species richness
Simultaneous autoregressive (SAR) models used to assess spatially corrected p values between species richness and contemporary and historical climate
Araújo et al. 2008 Ecography
Total a Total bHistoric climate stabilityReptiles 0.51 0.44Amphibians 0.38 0.26Contemporary climateReptiles 0.43 0.51Amphibians 0.26 0.40
Reptile species richness
Amphibian species richness
Partial regression analysis to separate the unique contribution of the contemporary and historic climate variables
Test of historic climate stability hypothesis with European reptiles and amphibians
Outline
1.Testing for differential building up of species pool
2.Testing for the effects of niche conservatism
3.Concluding remarks
• 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 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.
Testing for the effects of niche conservatism – example 1
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
More families in the Cretaceous
More families in the Tertiary Araújo et al. In preparation
r=0.74
• 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 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 2
7 132 10 13 3 36 43 14 78 1 15750 650 550 450 350 250 150 50 0my
Variation in slope5 categories
-0,5
0,5
1,5
2,5
Cold climate Warm climate
a)
Romdal, Araújo & Rahbek, In preparation
Slopes from 343 studies assessing
contemporary gradients of diversity for a wide
range of taxa and environments
Testing for the effects of niche conservatism – example 2
Outline
1.Testing for differential building up of species pool
2.Testing for the effects of niche conservatism
3.Concluding remarks
• 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.
Concluding remarks