However, recent studies suggest that marine predators may have followed a similar evolutionary path, diversifying elsewhere and subsequently arriving at the boundary of the Indian and Pacific oceans, where they then radiated. Much of this work focused on coastal plants or small marine animals with rich fossil records. Phylogenetic analysis and fossil evidence suggests that similar marine biodiversity hotspots were present near what is now southwest Europe during the Paleogene and that many of these species-groups present there immigrated into the current center of biodiversity during the Neogene. However, some of the lineages predate the formation of the biodiversity hotspot at the boundary of the Indian and Pacific oceans, suggesting these lineages immigrated to the region and then speciated. This region appears to have been a cradle of biodiversity, by facilitating speciation during the Neogene. There has been considerable interest in understanding the evolutionary and biogeographical processes that have shaped species diversity and composition in this region. The region at the boundary of the Indian and Pacific oceans represents a large marine biodiversity hotspot, housing a rich diversity of shallow-water marine and reef species. The assembly of diverse species communities in marine biodiversity hotspots has provided insights into the evolution of marine species and ecosystems. Geographical regions that contain a rich taxonomic diversity, across multiple taxonomically distant groups, with many endemic species are known as biodiversity hotspots. Our findings provide insights into the roles of marine biodiversity hotspots for higher-tropic level predators and the methods applied here can be used for additional studies of shark evolution. Conclusionsįrom this data we conclude that (1) center of carpet shark biodiversity has shifted during the last 100 million years, (2) carpet sharks have repeatedly dispersed to nascent habitat (including to their current center of diversity), and (3) the current center of carpet shark biodiversity conserves lineages that have been extirpated from this prehistoric range and is a source of new carpet shark species. Fossil evidence from sites in close geographic proximity to the current center of carpet shark diversity are generally restricted to younger geologic strata. We find that carpet sharks species richness was greatest in shallow seas connected to the Atlantic Ocean during the Late Cretaceous, but that there was a subsequent loss of biodiversity in Atlantic waters. We address the significance of this biodiversity hotspot in carpet shark evolution and speciation by leveraging a rich fossil record and molecular phylogenetics to examine the prehistoric distribution of carpet sharks. While a few carpet shark species are widespread, the majority of carpet shark species richness is contained within a biodiversity hotspot at the boundary of the Indian and Pacific oceans. In this study we focus on the evolutionary history of a group of small-to-medium sized sharks known as carpet sharks. There has been considerable interest in understanding the evolutionary processes that led to marine species richness being concentrated in specific geographical locations. The evolutionary processes that shape patterns of species richness in marine ecosystems are complex and may differ between organismal groups.
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