Insular biodiversity: colonization and diversification, legacy of a changing landscape
The equilibrium theory of island biogeography defines oceanic island species richness as a balance between immigration and extinction rates, influenced by area and isolation. Further developments extended this framework by incorporating island ontogeny, which changes island area and elevation to predict biodiversity. While these models focus on single islands, oceanic islands form clusters whose spatial configuration and area variations affect colonization and speciation.
Here, we aim to understand how the geo-environmental dynamics in an archipelago, i.e. the consecutive emergence and submergence of islands, and sea-level fluctuations, influence rates of immigration, speciation and extinction and if we can detect signatures of these processes in phylogenies. Using a neutral stochastic individual-based model, we find that phylogenetic tree shape vary following area and connectivity, and that the detection of geo-environmental signatures are modulated by the balance between inter-island speciation and mainland immigration.
Our work links population abundance to colonization success in archipelagos within a neutral framework. While empirical evidence supports that larger populations generally enhance colonization success through higher propagule pressure and genetic diversity, it remains unclear if the source population abundance advantage is maintained with environmental differences between the sourceand the colonized habitats. Our results show that the effect of population abundance on colonization success depends strongly on habitat similarity.
Overall, this work highlights the importance of integrating landscape dynamics into models to understand complex patterns incontemporary island phylogenies, and also this work show that neutral processes and priority effects may play a larger role than expected within archipelagos.