The influence of fragmented landscapes on speciation.

In the face of unprecedented global transformations, unravelling the intricate mechanisms governing biodiversity patterns is imperative for predicting and interpreting species responses. An important element in this interplay is fragmentation and the spatial mosaic or arrangement of suitable sites within the landscape. Beyond its well-documented impact on biodiversity loss, fragmented landscapes also influence the origin of biodiversity, by influencing speciation dynamics. This research employs a model that integrates spatial configuration and dispersal abilities of individuals to investigate the impact of landscape configuration on species' evolutionary trajectories. Specifically, we propose a microevolutionary model where individuals are characterized by their dispersal ability and a genome, allowing population evolution and diversification. Space is explicitly characterized by suitable and unsuitable sites that define fragmented landscapes. Our model demonstrates how intermediate dispersal abilities enhance diversification. However, simulations of more fragmented landscapes result in a lower total number of individuals and a lower percentage of occupied sites by individuals, particularly when species have limited dispersal abilities. Furthermore, we have found that intermediate levels of fragmentation can stimulate greater species richness, while higher levels of speciation and extinction events tend to occur under higher fragmentations. Our results also show a non-monotonic dependence of richness on dispersal, supporting the intermediate dispersal hypothesis as a promotor of diversification, demonstrating the synergistic effects of landscape configuration and species dispersal ability in the processes of speciation, extinction, and diversification. This impact of fragmentation poses a real challenge for biodiversity in the context of a dynamic world.
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