DISSERTATION RESEARCH: Species limits, hybrid zones, and systematics of the North American turtle genus Sternotherus

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Biodiversity is typically measured by counting the number of species in an area and the conservation status of species is assessed through periodic inventories to measure gain or loss of species over time. However modern science has discovered the prevalence of cryptic species. These are species that have few or no obvious morphological distinguishing features, which traditionally define species, but do not interbreed and therefore are separate biological species. New genetic technologies can identify cryptic species and provide important tools to more accurately measure biodiversity. The southeastern United States, especially Alabama, is a hotspot of aquatic biodiversity, especially for turtles. The North American turtle genus, Sternotherus, diversity has been under-described taxonomically relative to other turtle lineages due to morphological conservatism between and within species This project will investigate the morphology and genetics of Sternotherus to identify cryptic diversity and the evolutionary relationships among taxa. These data can be used to make evidence based conservation planning decisions which can optimize the use of funding to protect and conserve biodiversity. While accomplishing the project goals, undergraduate students will be mentored in a variety of biological sub-disciplines including field ecology, molecular biology, and bioinformatics. Effort will be made to include students underrepresented in STEM fields as well as Alabama natives.The research project will test species limits and infer relationships within a poorly resolved and imperiled turtle genus: Sternotherus. Sternotherus currently consists of four species for which past studies have presented conflicting relationships. This calls into question the taxonomic validity of some species and suggests that other populations are cryptic taxa. The researchers will collect samples from turtles across their entire distribution in the southeastern United States. These turtles will be measured for many morphological characters including shape and size. The researchers will perform genetic analyses using mtDNA and RAD-tag sequencing on the turtle DNA. This research takes an integrative approach considering gene history and hybridization for identifying species and species relationships within Sternotherus. These data will be used to test 1) genus wide species limits; 2) the role of hybridization between species; and, 3) species-level relationships within this group of turtles. This integrative analytical approach will resolve taxonomic relationships as well as identify incomplete lineage sorting, rapid radiations, and low level gene flow which confounded genetic signal in previous work