Meeting Abstract
Spatially varying selection could considerably limit the effective migrant exchange among ecologically distinct locations. In instances of “phenotype-environment” mismatch, genotypes selected to survive in one environment might be unfit to live in another. Here we use genome-wide genotyping (2bRAD) to test for evidence of spatially varying selection between proximate (< 20km apart) but environmentally distinct inshore, offshore, and deep reefs. We sampled juvenile (less than 2 years old) and adult individuals of the great star coral Montrastraea cavernosa and examined how allele frequencies change among age cohorts in differing habitats. Although genome-wide divergence (Fst) between populations was negligible, several dozen 2bRAD markers were highly divergent and formed a single cluster of linkage disequilibrium corresponding to a genomic region >100 kB in size, which is expected under very recent or ongoing selection. Moreover, these differences were less pronounced among juveniles compared to adults, indicating that spatially varying selection is ongoing and gradually removes migrants bearing “locally wrong” genotypes. These observations confirm that M. cavernosa is strongly affected by spatially varying selection across environmental gradients in the Florida Keys, reducing effective migration among habitats and limiting the capacity of coral populations to recover from disturbances.
