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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 200

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 Presentation

Text of Understanding global biodiversity gradients

  • Understanding global biodiversity gradientsMiguel B. ArajoCtedra Rui Nabeiro Biodiversidade, CIBIO, Universidade de voraMuseo Nacional de Cincias Naturales, CSIC, MadridGulbenkian, Lisboa, Julho 2009

  • Causes of global biodiversity gradients

  • A debate with more than 160 yearsAlexander von Humboldt (1769-1859)Alfred Russel Wallace (1823-1913)

  • 125 Big Questions: What we dont know?

  • Contemporary vs. historical hypothesisWe 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 hypothesisWiens & Donoghue (2004) TREEBuilding of the species pool - Stability

    Distribution of the species pool Niche conservatism

  • OutlineTesting for differential building up of species poolTesting for the effects of niche conservatismConcluding remarks

  • Test of historic climate stability hypothesis with European reptiles and amphibiansArajo et al. 2008 EcographyReptile species richnessAmphibian species richnessSimultaneous autoregressive (SAR) models used to assess spatially corrected p values between species richness and contemporary and historical climate

  • Test of historic climate stability hypothesis with European reptiles and amphibiansArajo et al. 2008 EcographyReptile species richnessAmphibian species richnessPartial regression analysis to separate the unique contribution of the contemporary and historic climate variables

  • OutlineTesting for differential building up of species poolTesting for the effects of niche conservatismConcluding remarks

  • Testing for the effects of niche conservatism example 1If 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 1If 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 recordFamilies originated in the CretaceousFamilies originated in the TertiaryArajo et al. In preparation

  • Departure from a linear relationshipMore families in the Cretaceous More families in the TertiaryArajo et al. In preparationr=0.74

  • Testing for the effects of niche conservatism example 2If 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 2If 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 2Romdal, Arajo & Rahbek, In preparationSlopes from 343 studies assessing contemporary gradients of diversity for a wide range of taxa and environments

  • OutlineTesting for differential building up of species poolTesting for the effects of niche conservatismConcluding remarks

  • Concluding remarksClimate 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.

    However, the least we can say about these comparative tests is that they are incomplete because only qualitative or semi-qualitative estimates of past climates were investigated in contrast with the quantitative high resolution of contemporary climate variables. Used. If you compare species richness with a continuous variable for temperature and water you are bound to obtain a higher fit that what you would obtain with a dummy variable of zeros and ones. This analysis is biases to produce higher fits for contemporary climates. Here I will provide further comparative analyses of the contemporary and historical climate hypotheses using high resolution quantitative variables depicting historical climate. I will then use current distributions and the fossil record to test for the effects of the niche conservatism hypotheses. Ill finish by drawing some conclusions.

    Describe the maps on the left and then the results of SAREXPLAIN TABLE. Lets be Earnest. Reptiles and amphibians are bound to yield models where history plays a major role, because they are generally poor dispersers, thus being easily excluded from areas that become unsuitable, but needing lots of time to recolonise these areas as they become suitable again. Species with greater dispersal abilities might track climate changes more quickly in which case the signature of past climates on species richness is lost. This is why it is important to investigate what happens with species with different range sizes.Now I will move on to the second part of this talk and will provide some tests of the niche conservatism hypotheses as a mechanisms underlying global species richness patterns. I will present two analyses of work in progress.Testing for the effects of niche conservatism is not straightforward and requires that we use our best detective skills. Typically we have to do a lot of data mining, but if we want to make progress quickly we have to have clear hypotheses in mind when we dig in the data. In this particular example we make the following predictions: