Marked genetic divergence revealed by allozymes among populations of the guppy Poecilia reticulata (Poeciliidae), in Trinidad |
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Authors: | G. R. CARVALHO ,P. W. SHAW&dagger ,A. E. MAGURRAN&Dagger ,B. H. SEGHERS&Dagger |
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Affiliation: | *Department of Biology, Building 62, University of Southampton, Southampton 809 3TU;†School of Biological Sciences, University College of Swansea, Singleton Park, Swansea SA2 8PP;‡Department of Zoology, University of Oxford, South Parks Road, Oxford 0X1 3PS |
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Abstract: | Populations of the guppy Poecilia reticulata from six locations in N. Trinidad were examined by starch gel electrophoresis to estimate their degree of genetic divergence. Variability at seven enzyme-coding loci demonstrated that populations differed markedly in allele frequencies with some allelic substitution between sites (for 23 loci, Nei's mean genetic identity, Ī ranged from 0.869–1.00; the coefficient of gene differentiation, G ST= 0.086; and the absolute differentiation between populations, m= 0.044). There was a good correspondence between degree of physical isolation and extent of genetic differentiation, as exemplified by the partitioning of gene diversity (Nei's gene diversity analysis = 66% between river basins; 32% within river basins; 2% within rivers), though there was considerable variability in the contribution of individual loci. Most populations were in Hardy-Weinberg equilibrium, and any significant deviations were due exclusively to heterozygote deficiencies. The patterns of population differentiation are discussed in relation to probable past geological and historical events, and present-day evolutionary forces. Notable among these are previous continental land connections, periodic immigration from N.E. South America, and post-colonization events including differential predation, sexual selection, apparent restricted vagility and small effective population sizes. |
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Keywords: | Guppy Poecilia reticulata allozymes population differentiation polymorphism genetic distance gene diversity geographic variation |
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