Resolving mechanisms maintaining distinct Atlantic cod ecotypes in a hybrid zone

When interbreeding populations experience different selection pressures, there is a tension between divergent selection for local phenotypic optima and the homogenizing effects of gene flow. Reproductive isolation modulates this tension and is often used to define species.

Reproductive isolating barriers are categorized by whether they prevent hybrid formation (prezygotic) or impair hybrid fitness (postzygotic).

The relative importance of pre- and postzygotic barriers in early-stage (nascent) speciation is a long-standing, yet active, debate at the crux of how biodiversity evolves.

My overarching aim is to determine the origin and consequences of nascent speciation in light of environmental variation.

I will characterize the magnitude and target(s) of selection involved in mating and hybridization between recently diverged Atlantic cod ecotypes in a hybrid zone.

I will combine fine-scale acoustic telemetry data with high-throughput genomics in a multi-generational spawning experiment to quantify assortative mating, test for natural selection against ecotype hybrids, and identify the genomic basis of reproductive isolation between ecotypes. These data will be used to model ecotype persistence under environmental change.

Using an ecologically, economically, and culturally important fish, I will improve our understanding of the engines and brakes of evolution, the distribution and maintenance of biodiversity, and the consequences of a changing world for our oceans and society.