Fin whale MDH‐1 and MPI allozyme variation is not reflected in the corresponding DNA sequences

• Published in: Ecology and evolution Vol. 4; no. 10; pp. 1787 - 1803
• Main Authors: Olsen, Morten Tange, Pampoulie, Christophe, Daníelsdóttir, Anna K., Lidh, Emmelie, Bérubé, Martine, Víkingsson, Gísli A., Palsbøll, Per J.
• Format: Journal Article
• Language: English
• Published: England John Wiley & Sons, Inc 01.05.2014; BlackWell Publishing Ltd
• Subjects: Adaptation; Aquatic mammals; Balaenoptera physalus; Deoxyribonucleic acid; Divergence; DNA; Exons; Gene flow; Gene sequencing; Genes; Genetic divergence; Genetic drift; Genetic structure; Loci; marine mammals; metabolic enzymes; Migration; Nucleotide sequence; Nucleotides; Nutrient deficiency; Original Research; outlier loci; Outliers (statistics); Phenotypic plasticity; Plastic foam; Plastic properties; Plasticity; Population; Population genetics; Population structure; Populations; selection; Studies; Whales & whaling; AN, North Atlantic; outlier loci; metabolic enzymes; population structure; selection; marine mammals; Adaptation
• ISSN: 2045-7758; 2045-7758
• DOI: 10.1002/ece3.1046

The appeal of genetic inference methods to assess population genetic structure and guide management efforts is grounded in the correlation between the genetic similarity and gene flow among populations. Effects of such gene flow are typically genomewide; however, some loci may appear as outliers, displaying above or below average genetic divergence relative to the genomewide level. Above average population, genetic divergence may be due to divergent selection as a result of local adaptation. Consequently, substantial efforts have been directed toward such outlying loci in order to identify traits subject to local adaptation. Here, we report the results of an investigation into the molecular basis of the substantial degree of genetic divergence previously reported at allozyme loci among North Atlantic fin whale (Balaenoptera physalus) populations. We sequenced the exons encoding for the two most divergent allozyme loci (MDH‐1 and MPI) and failed to detect any nonsynonymous substitutions. Following extensive error checking and analysis of additional bioinformatic and morphological data, we hypothesize that the observed allozyme polymorphisms may reflect phenotypic plasticity at the cellular level, perhaps as a response to nutritional stress. While such plasticity is intriguing in itself, and of fundamental evolutionary interest, our key finding is that the observed allozyme variation does not appear to be a result of genetic drift, migration, or selection on the MDH‐1 and MPI exons themselves, stressing the importance of interpreting allozyme data with caution. As for North Atlantic fin whale population structure, our findings support the low levels of differentiation found in previous analyses of DNA nucleotide loci. Studies of North Atlantic fin whale (Balaenoptera physalus) population structure have reported contrasting degrees of genetic differentiation in allozyme and nuclear markers. We sequenced the exons encoding for the two most divergent allozyme loci (MDH‐1 and MPI) and failed to detect mutations that could account for the reported levels of genetic variation at these markers. Thus, the reported allozyme variation does not appear to be a result of genetic drift, migration, or selection on the MDH‐1 and MPI exons themselves, stressing the importance of interpreting allozyme data with caution.