A central goal in evolutionary biology is to understand the processes that generate and maintain biodiversity. Insight into the process of speciation has traditionally been gained from both ends of the speciation continuum: from understanding the effects of geography on gene flow among populations across a landscape, to generating inferences about the evolution of complex traits at a macroevolutionary scale. Research in our lab has addressed these questions in a wide range of vertebrate taxa (including birds, skinks, and fish), both at the shallowest tips of the tree of life and among deeply diverged taxa.
Genomic techniques now allow us to attack long-standing questions about speciation in non-model organisms in ways that were previously impossible. For example, the combined use of genomic tools and detailed knowledge of geographic ranges and pre-mating isolation barriers (such as differences in male plumage pattern and song in birds), can provide powerful new insights into our understanding of speciation mechanisms.
Many current researchers in our lab are also particularly interested in the effects that gene flow may have on the speciation process: what are the consequences of gene flow during the evolution of reproductive isolation and what are the implications of gene flow during periods of secondary contact? For example, genes associated with reproductive barriers may not pass species limits, whereas those that are neutral or confer adaptive benefits could. Understanding the effects of gene flow and the patterns of divergence across different portions of the genome in recently diverged taxa is therefore directly relevant to elucidating the genetic basis of phenotypes relevant to speciation. Much of our ongoing research on speciation therefore addresses populations and species that are in the early stages of differentiation, using ‘big data’ genomic approaches that combine the tools of population genetics and phylogenetics.
Many of the current projects in our lab aim to understand avian diversification in the context of recent radiations, incipient species, hybrid zone dynamics and the maintenance of reproductive isolation. Examples of such ongoing projects (as of Fall 2014) based in our group include understanding the ecological and evolutionary dynamics of a hybrid zone between the Black-Capped Chickadees and Carolina Chickadees (postdoc Scott Taylor and collaborators), exploring patterns of gene flow and divergence in a rapid radiation of Neotropical Seedeaters (postdoc Leo Campagna and collaborators), understanding speciation and differentiation in the Yellow-rumped Warbler complex (postdoc David Toews and collaborators), studying the genetic basis of phenotypes that enable local adaptation to novel environments in Swamp sparrows (graduate student Petra Deane-Coe and collaborators), and exploring the genomic basis for local adaptation and range-wide differentiation in Horned Larks (graduate student Nick Mason).