title: Fin whale MDH-1 and MPI allozyme variation is not reflected in the corresponding DNA sequences.
abstract: 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.
authors: Evolutionary Genetics Group, Department of Genetics, Microbiology, and Toxicology, Stockholm University Svante Arrhenius Väg 20C, S-106 91 Stockholm, Sweden.
authors: Morten Tange
authors: MT
authors: Olsen
authors: Marine Research Institute Skúlagata 4, IS-101 Reykjavík, Iceland.
authors: Christophe
authors: C
authors: Pampoulie
authors: Matís Vínlandsleið 12, IS-113 Reykjavík, Iceland.
authors: Anna K
authors: AK
authors: Daníelsdóttir
authors: Evolutionary Genetics Group, Department of Genetics, Microbiology, and Toxicology, Stockholm University Svante Arrhenius Väg 20C, S-106 91 Stockholm, Sweden.
authors: Emmelie
authors: E
authors: Lidh
authors: Evolutionary Genetics Group, Department of Genetics, Microbiology, and Toxicology, Stockholm University Svante Arrhenius Väg 20C, S-106 91 Stockholm, Sweden ; Marine Evolution and Conservation, Centre for Ecological and Evolutionary Studies, University of Groningen PO Box 11103, 9700 CC, Groningen, The Netherlands.
authors: Martine
authors: M
authors: Bérubé
authors: Marine Research Institute Skúlagata 4, IS-101 Reykjavík, Iceland.
authors: Gísli A
authors: GA
authors: Víkingsson
authors: Evolutionary Genetics Group, Department of Genetics, Microbiology, and Toxicology, Stockholm University Svante Arrhenius Väg 20C, S-106 91 Stockholm, Sweden ; Marine Evolution and Conservation, Centre for Ecological and Evolutionary Studies, University of Groningen PO Box 11103, 9700 CC, Groningen, The Netherlands.
authors: Per J
authors: PJ
authors: Palsbøll
keywords: Adaptation; marine mammals; metabolic enzymes; outlier loci; population structure; selection