CHROMOSOME LEVEL REFERENCE OF CUNNER Tautogolabrus adspersus AND LOW-DEPTH RESEQUENCING REVEAL EVIDENCE OF ECOLOGICAL ADAPTATION THROUGHOUT ATLANTIC CANADA

Cameron M. Nugent, Tony Kess*, Matthew K. Brachmann, Steven J. Duffy, Sarah J. Lehnert, Brendan F. Wringe, Ian R. Bradbury

Cunner (Tautogolabrus adspersus), a northern ranging species of Labridae, are being considered for use as a cleaner fish in North American salmonid aquaculture. Cunner genomics and population structure remain uncharacterized, and potential consequences of aquaculture escapees on the fitness and demography of wild populations are undefined.

To understand the existing genetic variation and evolutionary history of cunner, a 0.72Gbp reference genome spanning 24 chromosomes was constructed. Comparison to other Labridae reference genomes revealed 24 homologous chromosomes, suggesting a conserved genomic architecture. Whole genome resequencing of 749 individuals from 19 locations throughout Atlantic Canada identified 11 million genetic variants. Principal component analysis revealed four subpopulations in Atlantic Canada that were strongly associated with geography: Nova Scotia (NS), Northwest Newfoundland (NWNL), Northeast Newfoundland (NENL), and Southeast Newfoundland (SENL) (Figure 1A, 1B). Pairwise comparison of subpopulations via FST revealed strong signals of differentiation at specific regions in the genome and these regions overlapped with identified signatures of selection.

Genomic variation was also significantly correlated with environmental variation further suggesting that the spatial structure of cunner populations has partially stemmed from local adaptation. Observed patterns of genetic variation suggest that local adaptation to environmental differences across Atlantic Canada has resulted in genetically distinct and adaptively unique cunner subpopulations across the sampled range, these findings can inform future use of cunner within salmon aquaculture in Atlantic Canada.