The Chavez Lab



Hybrid zones (red text) and intraspecific transects (blue text) in different environmental settings.

Genomics of Speciation and Adaptation

We are interested in the evolution of isolating barriers between diverging lineages and especially the role that ecology and divergent adaptations have in the formation of these barriers. We are addressing these questions with empirical research on taxa that are at different stages of divergence and in different environments and have focused largely in taxa that have formed hybrid zones and that occur along environmental gradients.

Our primary study system is the pine squirrel (Tamiasciurus). These squirrels primarily inhabit coniferous forests that span a wide range of abiotic and biotic conditions. We are interested in study local and parallel adaptation. Furthermore, T. douglasii (Douglas squirrel) and T. hudsonicus (red squirrel) form multiple hybrid zones in different kinds of environmental transitions In total, this study system provides plentiful opportunities to investigate how the environment has shaped divergent adaptations and reproductive isolation. We have generated de novo genome and transcriptome assemblies for this study system and are collecting population-level genomic and phenotypic data.

Ecology and Behavior of Reproductive Isolation

Ecological and behavioral interactions can play an integral role in the speciation process by shaping prezygotic and postzygotic mechanisms of reproductive isolation. Tamiasciurus tree squirrels are exemplar species for studies in behavioral ecology, life history evolution, and species interactions. We are conducting field studies in the North Cascades hybrid zone between the red squirrel (T. hudsonicus) and the Douglas squirrel (T. douglasii) to investigate the role of divergent behaviors and ecology in hybrid zone dynamics and reproductive isolation. We are interested in uncovering key ecological and behavioral factors (e.g., hybrid fitness, assortative mating, resource selection) that contribute to the maintenance of this hybrid zone.


Macroevolutionary Patterns of Color Variation

Color patterns are a key fitness trait in animals because they have important roles in visual signaling, concealment, and thermoregulation. The squirrel family has one of the greatest diversity of color patterns among mammal families. However, biologist know little about why squirrels, especially tree squirrels, possess such a range of color patterns. We are using comparative phylogenetic methods to study the relationship between color pattern variation and other key biotic and abiotic variables.

The Evolution of Venom in Shrews

Venom is known to have evolved in only a handful mammalian species, but our understanding of its origin and selective pressures is not well understood. We are collecting molecular data (genomics, transcriptomics, and proteomics) and using population genetic and phylogenetic approaches to study when and how venom genes have evolved. We are also beginning field studies to reveal the ecological significance of venom.