Abstract
Background: Species with planktonic larvae are 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 with its dispersion limited to a 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. Methods: A total of 226 shanny specimens (collected in 2003, 2013 and 2014) and 281 sand smelts (collected in 2005, 2012, 2013 and 2014) were screened for genetic variation using the mitochondrial control region. Genealogies, genetic diversities, temporal structures and contemporary effective population sizes were assessed. Results: Haplotype networks showed deep genealogies with multiple levels of diversification and no temporal structure. 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 two periods of the study). Conclusion: 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.
Highlights
In a context of climate change and anthropogenic influences on aquatic ecosystems, great importance is being given to the genetic biodiversity monitoring [1]
Concerning population genetic structure, and from a practical standpoint, it has often been assumed that the observed spatial patterns are stable over time [2,3]
A 380bp fragment of the control region (CR) of L. pholis was analyzed; 226 sequences were obtained corresponding to 171 haplotypes with a total of 108 polymorphic sites (Table S1)
Summary
In a context of climate change and anthropogenic influences on aquatic ecosystems, great importance is being given to the genetic biodiversity monitoring [1]. Assessments of changes in genetic diversity and their trajectories over time provide critical information for both fisheries and endangered-species management. Ne is defined as the number of breeding individuals of a population that has the same optimum amount of dispersion allele frequencies subject to random genetic drift [9]. This metric is sensitive to recent events and is related to the absolute size, calculated by census (N). By providing a measure of genetic diversity, contemporary or short-term Ne can be used to predict the adaptive potential of a population, as a function of its vulnerability to stochastic forces, i.e., to genetic drift [10]. The sand smelt Atherina presbyter has a very short planktonic life, small size and weak swimming capabilities, which translates into reduced dispersion potential
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