Influence of Island Morphology on Micro-Endemic Biodiversity Distribution

Most islands host an endemic biota, i.e., present nowhere else on Earth like it is the case, for instance, of Madagascar. It has been shown that different populations of lemurs, endemic to the island, are mostly distributed along the watersheds surrounding the central plateau of Madagascar, creating a so-called micro-endemism, while the populations living on the central high-elevated watersheds are not showing this micro-endemism. Here we wish to address the question whether there exists a correlation between the evolution of the landforms (i.e., the morphology of the island) of Madagascar and the hybrid distribution of lemur populations? More broadly, how does the tectono-geomorphic evolution of an island influence the flourishing of micro-biodiversity?

To answer these questions in a quantitative manner, we combined a Landscape Evolution Model based on the Stream Power Law and taking into account Flexural Isostasy, with a Speciation Model. We first developed a morphometric index to differentiate between Π-islands with a central plateau surrounded by smaller basins, like Madagascar, from conical Λ-islands, like Sri Lanka. We then predicted patterns of biodiversity as a function of the index value and its time evolution. We show that the tectono-geomorphic evolution influences patterns of biodiversity and evaluate the influence of varying the values for model parameters, in particular the ones characterising dispersal and mutation. We finally used phylogenetic observations to constrain some of these parameters.