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Evolution of Chasmogenus: Tracking 70 million years of ecological and geological change in the Neotropics through an ancient water beetle lineage
Neff, Rachel Nicole
Neff, Rachel Nicole
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Abstract
While biogeographers have developed hypotheses to explain the immense biodiversity of the Neotropics since the time of Wallace and Darwin, many gaps in our understanding of Neotropical biogeography remain. Although Amazonia is relatively well-studied, biogeographic studies often employ distinct definitions and delineations to characterize this vast tropical forest area. Additionally, other Neotropical biomes such as savannas and wetlands make up a substantial part of the region but have received less attention in comparison to their tropical forest neighbors. Finally, our knowledge of certain taxonomic groups within the Neotropics remains scarce. Relative to vertebrate and plant lineages, fewer biogeographic studies have been performed on invertebrate taxa such as insects. Water scavenger beetles (Coleoptera: Hydrophilidae) have a high level of diversity and endemism in the Neotropics. Recently published studies have confirmed the genus Chasmogenus as an endemic Neotropical lineage. In order to understand the evolutionary history of this genus, a multigene dataset was used to construct maximum likelihood and Bayesian phylogenies that encapsulate the previously underestimated diversity of this ~70-million-year-old group. With an extensive geographic range and origins in the Cretaceous, Chasmogenus may serve as a useful model lineage for studying biogeographic patterns in the Neotropics during the late Mesozoic and Cenozoic eras. In particular, this study highlights how regional partitioning schemes that employ different definitions of “Amazonia” can affect the results of Neotropical biogeographic analyses. Ecological and geological perspectives are considered to reveal a pattern of geological constraint and biome conservatism. A single exception to the biome constraint within the genus can be found in Chasmogenus sapucay. While all other species of Chasmogenus inhabit tropical forests, C. sapucay is found exclusively in the relatively under-studied Neotropical savanna biome. Additionally, the lineage has an exceptionally large range from the northern reaches of South America to Argentina. Previous studies have suggested that savanna-dwelling species may have higher dispersal capabilities and lower levels of genetic structuring relative to forest-dwelling taxa. Ultra-conserved element data is utilized to assess whether or not substantial structuring exists within this lineage. Divergence time estimation is performed to explore how Chasmogenus can contribute to our understanding of Neotropical savannas’ landscape evolution as a whole. Specifically, we assess whether C. sapucay lends support to a young emergence of Neotropical savannas, and whether it reflects any pattern of connectivity within savannas.
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2022-08-31
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University of Kansas
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Keywords
Evolution & development, Entomology, Zoology, Beetles, Biogeography, Evolution, Neotropics, Savanna, South America