Resumo

RODRIGUEZ ROMERO, F  e  TELLO CETINA, J. Geographic discontinuity and genetic variability in Crassostrea rhizophorae guilding in southeastern Mexico. Universidad y ciencia [online]. 2011, vol.27, n.1, pp.73-85. ISSN 0186-2979.

A study was carried out on the impact of habitat fragmentation on the genetic variability of two populations of Crassostrea rhizophorae Guilding 1828 in the estuarine system of Terminos lagoon, Campeche, Mexico, through the expression of isoenzymes of 10 enzyme systems and total protein. The software TFPGA 1.3 was used to analyse the genetic frequencies of the populations under study. Muscle samples of 50 organisms of each population were used to characterise the genotypic expression. The parameters determined were descriptive statistics, F statistic, genetic distance, Hardy-Weinberg equilibrium, UPGMA and the number of migrants as an indicator of gene flow. The protein polymorphism values were 36.35% (p95) and 90.90% (p99). The heterozygosis data were recorded between 0.2491 for Idh1 and 0.01 in Pt1, and the mean heterozygosity value was He = 0.1044. The averages of Fis = 0.1574 and Fit = 0.1727 indicated a heterozygote deficiency. The mean Fst = 0.0181 indicated that the genetic differences corresponded to an inter-population variation with a moderate endogamy. The number of migrants obtained by the Slatkin equation was 13.5621 per generation, indicated a certain degree of variability between populations, and is consistent with values of Nei genetic distance. It is concluded that both populations reflect a sensibility to the inter-population adaptive processes produced by the discontinuity of the geographical environment, with no affectation to their genetic variability, and do not reflect a fragility that subjects them to a process of formation of meta-populations.

Palavras-chave : Gene flow; Gulf of Mexico; isoenzymes; oysters; meta-populations.

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