Laboratory of Evolutionary and Ecological Genomics

We are interested in studying how ecology affects genomic structure, genomic evolution, and genomic function, and how it mediates their role in the development and evolution of phenotypes.

Our work focuses on comparative evolutionary and ecological genomics related to the evolution of developmental pathways, particularly those that underlie the development of the sexual phenotype.

Using this approach we are addressing a fascinating evolutionary enigma in its own right (Valenzuela 2004a, b): Why do organisms vary so remarkably in the ways they produce some of the most conserved and consistent phenotypes – males and females ?

In most animals, sex is determined by genotypic mechanisms (GSD) such as by sex chromosomes. However, in some vertebrates sex is determined by environmental factors, such as temperature (TSD), as occurs commonly in reptiles (Valenzuela and Lance 2004).

The evolution of sex-determining mechanisms is marked by repeated transitions between systems that differ in their level of phenotypic plasticity (TSD) and developmental canalization (GSD). This framework permits us to examine how gene structure, genome compartmentalization, presence/absence of sex chromosomes (i.e. genomic structure) as well as gene and gene-network regulation, and epigenetics (i.e. genome function) affect sex determination and sexual dimorphism (i.e. the development and evolution of phenotypes). In turn, by using a multidisciplinary approach across levels of biological organization, we are able to examine how the level of phenotypic plasticity and genome organization themselves are driven by biotic factors such as sexual selection and sexual conflict, and abiotic influences such as thermal disturbances at contemporary (e.g. daily/seasonal/annual) and evolutionary (e.g. climate change over generations or millions of years) time scales. Notably, we approach this evolutionary frontier using non-model systems (reptiles), because an important component that is usually treated as noise in model systems, i.e. individual variation, constitutes the raw material upon which natural selection operates. Indeed, the effects of individual variation at the genomic level remain understudied. Therefore, one of our foci is understanding the nature, source, and consequences of individual variation, which is an essential part of building an integrative and comprehensive view of phenotypic evolution, using non-model organisms as an exemplar.

Another important component of the research in our lab relates to the evolution of life histories, population and ecological genetics, and tropical biology, particularly of reptiles. This component, which addresses basic questions in evolutionary ecology, provides a critical view to the ecological context in which genomes and sex determining mechanisms evolve, and is also the basis of our conservation component. Indeed, effective management strategies must be based on solid biological information about the target taxa, and our work provides knowledge to facilitate the conservation of endangered reptiles.

 

Temperature-dependent Sex Determination in Vertebrates

One of the most fascinating topics in evolutionary biology and conservation biology for decades, temperature- dependent sex determination (TSD) was discovered in the 1960's, yet no book has ever before been devoted entirely to the subject. Authored by many of the world's leaders on the subject, this is a comprehensive work that compiles, analyzes and integrates existing information about this field.

Distributed by NBN / Rowman & Littlefield
Available through book retailers.

Links TEMPERATURE DEPT SEX DETER