Contemporizing island biogeography theory with anthropogenic drivers of species richness

Human activity has greatly accelerated in the past century impacting biodiversity across the globe. To accurately explain contemporary patterns of biodiversity, classic ecological theory must be updated to incorporate the effects of this Great Acceleration on biodiversity. We contemporized island biogeographic theory (IBT) and its extension, the general dynamic model (GDM), to incorporate these effects. At their core, IBT and GDM predict positive relationships between island species richness and habitat diversity, and negative relationships between island species richness and isolation from source pools of species. Through the Great Acceleration, land development on islands has altered habitat diversity and the introduction of species through global trade has reduced island isolation. We contemporize IBT and GDM by conceptualizing trajectories of how species richness on islands will change given accelerations to land development and trade. Considering these contemporary trajectories, we provide expectations for the relationships of native, introduced, and total species richness with natural and anthropogenic metrics of habitat diversity (geographic and economic area, respectively) and isolation from source pools (geographic and economic isolation, respectively). We assessed the expectations across reptile and amphibian clades of the Caribbean islands. As expected by the contemporized theory, natural habitat diversity metrics exhibited positive relationships with both native and introduced species richness, strengthening total species richness-area relationships. Geographic isolation exhibited negative relationships with native and positive relationships with introduced species richness, weakening total species richness-isolation relationships. Economic area and isolation both exhibited negative relationships with native richness, but positive and negative relationships, respectively, with introduced richness. Total species richness relationships with economic area and isolation were also strongest in clades with many introduced species. As more species spread globally, the contemporary expectations we articulate here will increasingly predict island biogeography of the Anthropocene.