62.2 Saturday, Jan. 5 Biogeography and body size shuffling of aquatic salamander communities on a shifting refuge BONETT, RM*; TRUJANO-ALVAREZ, AL; WILLIAMS, MJ; TIMPE, EK; University of Tulsa; University of Tulsa; Louisiana State University; University of Connecticut firstname.lastname@example.org
The Southeastern Coastal Plain of North America is a refuge for many divergent lineages of freshwater vertebrates. However, this region was submerged by a marine transgression throughout the Eocene, so the modern Southeastern Coastal Plain and its communities are relatively young. Using the fossil record and a multi-locus nuclear phylogeny, we examine divergence times and body size evolution of aquatic salamanders from North American coastal plains since the Mesozoic. At least five salamander families occurred on the extensive Western Interior Coastal Plain, which existed from the Upper Cretaceous through the Eocene. Four of these families subsequently colonized the Southeastern Coastal Plain by the early Oligocene to late Miocene. The oldest divergences among extant species from Southeastern Coastal Plain endemic clades occurred during the Miocene, indicating that most of the current diversity arose from a single lineage of each family that colonized the Southeastern Coastal Plain after the Eocene marine regression. Body size is highly labile in these four families, which show at least one or more major size shifts since the early Cenozoic, including two recent size reversals in endemic Southeastern Coastal Plain clades. This has resulted in continuous shuffling of the size order of aquatic salamander lineages on this shifting refuge since the Late Cretaceous. Therefore, while the environmental niche parameters of these aquatic salamanders may be highly conserved, size related ecological factors (eg. trophic interactions) have likely been highly labile across space and time.