Fine-Grained Spatial Genetic Structure in the Bivalve Gemma gemma from Maine and Virginia (USA), as Revealed by Inter-Simple Sequence Repeat Markers

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Environmental Studies


Gemma gemma is a small ovoviviparous bivalve distributed in shallow sand flats along the North American Atlantic and Gulf of Mexico coasts. Genetic variation in G. gemma was analysed by means of Inter-Simple Sequence Repeats (ISSRs) at the following levels: (i) between localities (Maine and Virginia), (ii) among 10-m-diameter patches within localities, and (iii) within patches. Thirty individuals/patch and three patches/locality were analysed. Individuals were genotyped for 67 ISSR polymorphic loci from five primers. The portion of the genetic variation found between localities (2%) was small compared to that found either among patches within localities (37%) or within patches (61%). ISSRs in G. gemma allowed the detection of significant differentiation at individual and patch levels. By contrast, a low degree of genetic variability was found between localities. The small-scale genetic heterogeneity does not follow a simple, consistent pattern. Our results contrast with the generally accepted rule that aplanic species are locally homogeneous and globally heterogeneous and teleplanic species are the inverse.


Original version is available from the publisher at: http://www.sciencedirect.com/science/article/pii/S002209810500208X



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