Temporal stability in levels of genetic variation of the invasive bivalve Isognomon bicolor (C. B. Adams, 1845) (Bivalvia, Isognomonidae) at Praia de Itaipu, Niterói city, Rio de Janeiro state, southeastern Brazil.
We investigated the evolutionary genetics of the marine bioinvader bivalve Isognomon bicolor (C. B. Adams, 1845) by the allozyme electrophoresis method. For that, we collected individuals in 2005, 2009, and 2013 at Praia de Itaipu (Niterói city, Rio de Janeiro state, southeastern Brazil). Seven allozymic systems were interpreted as eleven loci. The observed heterozygosity ranged from 0.324 in 2013 to 0.534 in 2005, but such differences were not statistically significant. High levels of genetic variation in bioinvaders can be explained as being a consequence of the Wahlund effect, which results in significant deviations from the Hardy-Weinberg equilibrium as well as in linkage disequilibrium. However, we observed no evidence of linkage disequilibrium, and only two loci showed significant deviations from the Hardy-Weinberg equilibrium (Mdh in 2005 and α-Est-1 in 2013). Temporal stability in the levels of genetic variation of I. bicolor at Praia de Itaipu may be an indication that the studied population has already reached the climax stage of the bioinvasion evolutionary process. Probably, in a first moment the Wahlund effect may have contributed for the population to respond to ecological pressures in a way contrary to population decline and extinction. In a second moment, the population may have reached maturity and climax, thus finally reaching the Hardy-Weinberg equilibrium for most loci.