Energy and temperature as contemporary and evolutionary determinants of the global biodiversity of birds.
Jetz, Walter*,1, 1 EBE Section, La Jolla, California, USA
ABSTRACT- The mechanisms that drive the broad-scale distribution of species and emerging patterns such as the latitudinal gradient in species richness are among the most highly debated and focal in ecology and evolution. Synthesis so far has been hindered by limitations from i) empirical evidence (scale usually only subcontinental, often excluding the tropics, perspective often purely latitudinal, only considering a subset of taxa), ii) methodology (spatial autocorrelation, spatial autoreplication, fixed-resolution grids) and iii) theory (approaches mostly correlative and statistical). The 'energy-richness theory' is a popular and prominent explanation for the broad patterns in species richness, but the presumed contemporary and evolutionary mechanisms that underpin it have only received limited theoretical and empirical scrutiny. Here I attempt a synthetic approach and develop simple models for the importance of temperature vs. energy availability as contemporary and past driver of biodiversity in endotherm vertebrates. The models make clear predictions about how temperature and energy availability should affect the summary pattern of species richness as opposed to that of the different clades which it is composed of. I test these models using a 100 km resolution database of the global distribution of all 9,900 species of extant birds. Clade level and phylogeny strongly affect the performance of environmental predictors, confirming model predictions and the role of productivity as contemporary constraint on species richness. I use these results to outline a more mechanistic approach to understanding the geographic patterns of species richness of endotherms at different levels of the phylogenetic tree.
Key words: biodiversity, energy - richness, global, birds
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