The role of the Neotropics as a source of world tetrapod biodiversity
Résumé
Aim: The Neotropics currently host outstanding levels of species richness, with onethird
of the global tetrapod species. The underlying causes of these extraordinary
levels of biodiversity are a topic debated in evolutionary ecology, but the main processes
at work remain elusive.
Location: Neotropics.
Time period: Cenozoic and Mesozoic.
Major taxa studied: Tetrapods.
Methods: Using global phylogenies for amphibians, birds, lepidosaurs and mammals,
biogeographical and time-variable (trait-dependent and trait-independent) diversification
models, we examined changes in speciation and extinction rates through time
in the Neotropics in relationship to other areas of the world, and estimated the time
of Neotropical colonizations.
Results: We found that from the origin of lepidosaurs and mammals until the Pliocene
(the Miocene for birds), diversification rates within the Neotropics were lower than
rates in other regions (i.e., turnover was high). Afterwards, extinction decreased
relative to speciation, and Neotropical diversification outpaced diversification in
other regions. Dispersal out of the Neotropics also increased after the Pliocene (the
Miocene for birds), exceeding into-the-Neotropics migrations. For amphibians, diversification
rates in the Neotropics have been higher than in other areas through time,
and dispersal out of the Neotropics decreased in the Cenozoic.
Main conclusions: The common view that the Neotropics are an ancient source of
world species diversity, with high in situ speciation, dispersal to other areas and low
extinction, might be true only for amphibians. For mammals, birds and lepidosaurs,
the Neotropics acted as a diversity sink from their origin until the Miocene–Pliocene
(i.e., diversification rates were lower and turnover higher than in other areas). Only
afterwards did the region turn into a diversity source. Our study highlights that models
accounting for rates of diversification that vary through time could improve our
capacity to assess evolutionary dynamics over long time-scales.
Domaines
Sciences du Vivant [q-bio]
Origine : Fichiers produits par l'(les) auteur(s)