Marine Biology

, Volume 160, Issue 5, pp 1065–1081

Strong population differentiation of softshell clams (Mya arenaria) sampled across seven biogeographic marine ecoregions: possible selection and isolation by distance

  • Philippe St-Onge
  • Jean-Marie Sévigny
  • Carly Strasser
  • Réjean Tremblay
Original Paper

DOI: 10.1007/s00227-012-2157-5

Cite this article as:
St-Onge, P., Sévigny, JM., Strasser, C. et al. Mar Biol (2013) 160: 1065. doi:10.1007/s00227-012-2157-5

Abstract

Twenty-two Mya arenaria samples spanning seven marine ecoregions mostly situated in the Cold Temperate Northwest Atlantic (CTNA) biogeographic province were collected between 2001 and 2010 and genotyped at seven highly polymorphic microsatellite loci to test for population differentiation. Results showed strong regional differentiation with six genetic clusters: (1) Northern Gulf of St. Lawrence (GSL), (2) Magdalen Archipelago, (3) Southern GSL, (4) Lower Atlantic Canada, (5) US Coasts and (6) Northern Europe. Population structure was supported no matter the statistical approach and generally does not reflect the geographical limits of marine ecoregions. A latitudinal cline in allelic richness provides evidence for a northward post-glacial expansion range for this species. While geographical distance explains the genetic variation detected in southern CTNA, increased heterogeneity observed in northern CTNA can be explained by isolation by distance, marine landscaping and presumable selective processes acting at the Mar5 locus. Exclusion of Mar5 from analyses resulted in the detection of three genetic clusters instead of six.

Supplementary material

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Supplementary material 1 (DOCX 36 kb)
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Online Resource 9 Assessment of the most probable number of clusters (K) explaining the genetic structure of M. arenaria individuals (N = 604) from 22 samples genotyped with seven microsatellite loci as detected with the ΔK graphical method developed by Evanno et al. (2005). a) Mean (±SD; N = 4) posterior probability of data; b) mean rate (±SD; N = 4) of change of the likelihood distribution; c) mean (±SD; N = 4) absolute values of the second-order rate of change of the likelihood distribution; d) ΔK. Arrows point to the greatest value of ΔK and the most probable number of clusters (K = 6) explaining the genetic structure in the dataset (DOCX 138 kb)
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Online Resource 10 Assessment of the most probable number of clusters (K) explaining the genetic structure of M. arenaria individuals (N = 604) from 22 samples genotyped with six microsatellite loci (all but Mar5) as detected with the ΔK graphical method developed by Evanno et al. (2005). a) Mean (±SD; N = 4) posterior probability of data; b) mean rate (±SD; N = 4) of change of the likelihood distribution; c) mean (±SD; N = 4) absolute values of the second-order rate of change of the likelihood distribution; d) ΔK. Arrows point to the greatest value of ΔK and the most probable number of clusters (K = 3) explaining the genetic structure in the dataset (DOCX 186 kb)
227_2012_2157_MOESM11_ESM.docx (22 kb)
Supplementary material 11 (DOCX 21 kb)

Copyright information

© Springer-Verlag Berlin Heidelberg 2013

Authors and Affiliations

  • Philippe St-Onge
    • 1
  • Jean-Marie Sévigny
    • 2
  • Carly Strasser
    • 3
  • Réjean Tremblay
    • 1
  1. 1.Institut des Sciences de la MerUniversité du Québec à RimouskiRimouskiCanada
  2. 2.Institut Maurice-LamontagnePêches et Océans CanadaMont-JoliCanada
  3. 3.UC Curation CenterUniversity of California Office of the PresidentOaklandUSA