Frontiers in Marine Science (Dec 2015)
Genetic structure and effective population size through time: a tale on two coastal marine species with contrasting life-history patterns
Abstract
Species with dispersal mediated by planktonic larvae are expected to be more likely to show temporal genetic variation, due to differences in larval mortality and dispersal ability. The shanny Lipophrys pholis is a typical benthic rocky intertidal fish and its dispersion is limited to its long larval stage. In contrast, the sand-smelt Atherina presbyter has a very short planktonic life, small size and weak swimming capabilities, which translates into reduced dispersion potential. A total of 226 specimens of L. pholis (collected in 2003, 2013 and 2014) and 281 of A. presbyter (collected in 2005, 2012, 2013 and 2014) were screened for genetic variation using the mitochondrial control region. Only 12 (out of 171) and 25 (out of 155) haplotypes found were shared between sampling periods for the shanny and the sand smelt, respectively. For both species, haplotype networks showed a deep genealogy with multiple levels of diversification and no temporal structure. Interestingly, some of the previously inferred missing haplotypes were sampled in more recent years. The genetic diversity indices showed little variation among sampling periods and were generally high. For L. pholis significant genetic differentiation was detected between 2013 and 2014, while no significant differences were detected between sampling periods in A. presbyter. The shanny showed lower effective population size per generation when compared to the sand-smelt (which yielded lack of evidence for genetic drift for the first and second period of the study). These results highlight the fact that temporal changes in the gene pool composition need to be considered when evaluating population structure, especially for species with long pelagic larval dispersion, more vulnerable to fluctuations in the recruitment.
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