BIOTIC DISPERSAL AND DIVERSITY DYNAMICS IN DEEP TIME: THE CASE OF SOUTH AMERICAN MAMMAL EVOLUTION

Biotic dispersals have played a crucial role in shaping biodiversity dynamics in geologic time. However, the evolutionary processes underlying diversity changes in response to biotic dispersals are poorly understood. The South American mammals are characterized by a long evolutionary history where phases of biogeographic isolation were punctuated by dispersal events during the Cenozoic and followed by increased connectivity with the closure of the Panama Isthmus. Yet, significant challenges remain in evaluating diversity changes across mammalian clades through time due to substantial temporal and geographic sampling biases in the fossil record. Here, we use a novel method based on biodiversity simulations and deep learning to estimate the diversity trajectories of native and immigrant mammalian clades. To this aim, we compiled and analyzed a comprehensive dataset of fossil occurrence data encompassing 1600 species and 6000 occurrences spanning 66 million years. We found that two migration events, the Oligocene arrival of primates and caviomorphs from Africa and the migration of multiple North American lineages from the Early Miocene to the Pleistocene, consistently led to overall net increases in mammalian diversity in the continent. Yet, these migration events were also associated with the decline of the diversity of native lineages consistently through a process of clade competition and partial replacement. Our analyses reveal the complex interplay among speciation, extinction, and dispersal shaped mammalian communities in South America while accounting for spatial and temporal biases intrinsic to the fossil record.