Dr Sarah Salisbury

Recently and repeatedly evolved intraspecific “morphs” offer a unique opportunity to detect the genes contributing to incipient phenotypic differentiation and reproductive isolation. Enter Arctic Charr (Salvelinus alpinus), a highly polymorphic Holarctic fish that has evolved multiple ecologically, phenotypically, and genetically differentiated morphs. Many of these charr morphs can be found in Labrador, Canada. Here, replicate pairs of sympatric small and large morphs as well as allopatric landlocked and anadromous populations paired by common drainage offer a unique opportunity to assess the genomic consistency underlying sympatric size differentiation and the loss of anadromy. Using an 87K SNP chip, strong genetic differentiation but limited overall genetic parallelism was detected among morph pairs. However, several functionally-relevant genes consistently differed between replicate morph pairs. For several genes, a different paralogous copy differentiated each replicate pair of morphs, suggesting parallelism at the level of the paralog. In addition, investigation of morph types across Labrador revealed that southern anadromous populations were more similar to landlocked populations in a genomic region that consistently differentiated paired landlocked and anadromous populations. This could indicate a genomic shift to a loss of anadromy in these southern anadromous populations, with potential implications for the local anadromous charr fishery. These results demonstrate the utility of investigating the genomic underpinnings of intraspecific morphs both for informing management decisions and for understanding the evolution of diversity.