Loss of genetic variation in a strongly isolated Azorean population of the edible calm, Tapes decussatus
Jordaens, K.; De Wolf, H.; Willems, T.; Van Dongen, S.; Brito, C.; Martins, A.M.F.; Backeljau, T. (2000). Loss of genetic variation in a strongly isolated Azorean population of the edible calm, Tapes decussatus. J. Shellfish Res. 19(1): 29-34
In: Journal of Shellfish Research. National Shellfisheries Association: Duxbury. ISSN 0730-8000; e-ISSN 1943-6319
We used allozyme electrophoresis to compare the genetic variation of an introduced and strongly isolated population of the edible clam Tapes decussatus in the Azores (Lagoa de Santo Cristo, Sao Jorge) with populations from the main range of the species (Ria and Thau). Observed and expected heterozygosity values, number of polymorphic loci, and mean number of alleles per locus in the main-range populations fall within the limits reported for T. decussatus and other Venerid clams. In contrast to previous studies on Venerid clams, we observed no heterozygote deficiencies. In the introduced Lagoa population, we observed a strong reduction of allelic diversity and expected heterozygosities and an effective population size of only 5.30. The Lagoa population is only slightly differentiated from populations from the species' main range and may thus be of low "biological value." Exploitation of T. decussatus could therefore be allowed to continue but must follow strict collection guidelines, especially given that only 15% of the area is suitable for exploitation. Otherwise, a unique component of the Azorean fauna that also serves as a fishery resource may be lost.
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