Coregonus spp. opsin amplicon sequence alignments

Local adaptation can drive diversification of closely related species
across environmental gradients and promote convergence of distantly
related taxa that experience similar conditions. We examined a potential
case of adaptation to novel visual environments in a species flock (Great
Lakes salmonids, genus Coregonus) using a new amplicon genotyping protocol
on the Oxford Nanopore Flongle. Five visual opsin genes were sequenced for
individuals of C. artedi, C. hoyi, C. kiyi, and C. zenithicus. Comparisons
revealed species-specific differences in a key spectral tuning amino acid
in rhodopsin (Tyr261Phe substitution), suggesting local adaptation of C.
kiyi to the blue-shifted depths of Lake Superior. Ancestral state
reconstruction demonstrates that parallel evolution and “toggling” at this
amino acid residue has occurred several times across the fish tree of
life, resulting in identical changes to the visual systems of distantly
related taxa across replicated environmental gradients. Our results
suggest that ecological differences and local adaptation to distinct
visual environments are strong drivers of both evolutionary parallelism
and diversification.