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The Ecological Context of Evolution

Because we are interested in the comparative evolutionary genomics in an ecologically-relevant context, some of the research in my lab investigates questions in population and ecological genetics, life history evolution and conservation biology following previous research (Lance et al. 1992, Valenzuela et al. 1997, Valenzuela 2000, Valenzuela 2001a,b,c, Valenzuela & Janzen 2001, Morjan & Valenzuela 2001, Valenzuela et al. 2003, 2004, Pearse et al. 2006). This component, which addresses basic questions in evolutionary ecology, provides a critical view of the ecological framework in which sex determining mechanisms evolve and their evolutionary potential in the face of climate change.

Turtles matingPopulation and ecological genetics of Neotropical turtles

We conducted a metapopulation genetic study of an endangered freshwater turtle (Podocnemis unifilis) inhabiting the Amazon and Orinoco river basins (Escalona et al. 2009). This study parallels a previous collaboration done on a sister taxon (P. expansa) (Pearse et al. 2006). This project was funded in part by the NSF DBI 0511958, and the Scott Neotropical Fund from the Cleveland Zoo.

Life History Evolution, Herpetology, and Conservation

Varying sizes of turtle eggsAnother important component of our research is the characterization of reptilian life histories, theoretical and empirical TSD thermal ecology, mating systems, and reproductive behavior. In particular, we study South American river turtles of the genus Podocnemis, the North American painted turtle (Chrysemys picta), softshell turtle (Apalone spinifera), and snapping turtle (Chelydra serpentina).

A recent study in Podocnemis unifilis test multple hypotheses to explain female nesting behavior and finds support for a social facilitation model rather than an adaptive nest site selection model (Escalona et al. 2009).

Turtle laying eggsReptiles are a very good taxon for study because TSD and GSD co-occur in this group. We use turtles as a model system to study the evolution of sex determining mechanisms, and compare both TSD and GSD species from the tropics and the temperate zone.

Many TSD reptiles are endangered. An important contribution to conservation is providing managers with essential biological information to design, evaluate, and enhance effective management programs. Part of our research is devoted to addressing basic questions that have conservation implications, such as the assessment of population structure, migratory and mating behavior with the use of molecular markers. The understanding of how TSD works in nature and under semi-natural or laboratory conditions is also important for conservation practices.