Demographic history, marker variability and genetic differentiation in sandy beach fauna: What is the meaning of low FST's?

Population genetics ofCerastoderma edulein Ria Formosa (southern Portugal): the challenge of understanding an intraspecific hotspot of genetic diversity

“…Our results provide evidence of genetic homogeneity of C. edule at a small geographic scale and the retention of new mutations (e.g. exclusive haplotypes) as an unequivocal support for rapid population expansion after a period of low effective population size (Avise et al, 1984;Stamatis et al, 2004;Bezuidenhout et al, 2014).…”

“…Sequences of a particular fragment of the mitochondrial COI have been employed in a number of studies to investigate genetic structuring and demographic history in populations of marine bivalve species, in which the observed values of haplotype diversity ( h ) and nucleotide diversity (π) were lower than those recorded for C. edule in the present study. For example, lower diversity values were recorded in other bivalve species: Amusium pleuronectes with h = 0.237, π = 0.0006 (Mahidol et al, 2007), Ruditapes decussatus at h = 0.486 and π = 0.011 (Gharbi et al , 2010), Scrobicularia plana with h = 0.52, π = 0.0016 (Santos et al , 2012), Donax serra with h = 0.30, π = 0.001 (Bezuidenhout et al , 2014), Crassostrea iredalei with h = 0.565, π = 0.0018 (Zainal Abidin et al , 2014) and Gemma gemma with values of h = 0.314, π = 0.0012 (Zhang et al , 2014). In our study of C. edule , estimates of haplotype and nucleotide diversity were higher than those recorded in these studies using marine samples.…”

“…It is also important to stress that although the work of Krakau et al (2012) was carried out in several localities at a large spatial scale showing high values of genetic diversity in the northern populations, comparisons among different lagoons and several localities inside each lagoon were not included; the authors did not consider the analysis of microgeographic genetic variation in C. edule, assuming genetic homogeneity inside each sampled coastal bay, estuary or lagoon Sequences of a particular fragment of the mitochondrial COI have been employed in a number of studies to investigate genetic structuring and demographic history in populations of marine bivalve species, in which the observed values of haplotype diversity (h) and nucleotide diversity (p) were lower than those recorded for C. edule in the present study. For example, lower diversity values were recorded in other bivalve species: Amusium pleuronectes with h ¼ 0.237, p ¼ 0.0006 (Mahidol et al, 2007), Ruditapes decussatus at h ¼ 0.486 and p ¼ 0.011 (Gharbi et al, 2010), Scrobicularia plana with h ¼ 0.52, p ¼ 0.0016 (Santos et al, 2012), Donax serra with h ¼ 0.30, p ¼ 0.001 (Bezuidenhout et al, 2014), Crassostrea iredalei with h ¼ 0.565, p ¼ 0.0018 (Zainal Abidin et al, 2014) and Gemma gemma with values of h ¼ 0.314, p ¼ 0.0012 (Zhang et al, 2014). In our study of C. edule, estimates of haplotype and nucleotide diversity were higher than those recorded in these studies using marine samples.…”

Genetic Diversity of the Atlantic Ghost Crab Ocypode quadrata (Decapoda: Ocypodidae) in Two Beaches With Different Anthropogenic Disturbance in the North Coast of Veracruz, Mexico

“…Worldwide, the increase of human population in coastlines has become a stressing factor on beaches at an unprecedented scale, resulting in significant alterations of ecological communities (Ocan˜a, Vega, & Co´rdova, 2012). In many of the beaches in urban areas worldwide, most of the dunes have been modified by a wide range of anthropogenic impacts, such as the construction of roads and buildings, pollution, damage to dune vegetation, and the impact caused by recreation and tourism (e.g., Bezuidenhout, Nel, & Hauser, 2014;Monteiro & Bemvenuti, 2006).…”

“…In this sense, the estimation of connectivity among populations through genetic techniques could be a method to assess the extent of fragmentation that may occur in an originally continuous distribution area. As such, this would involve the reduction in the exchange of individuals between locations and, thus, gene flow is expected to decrease (Bezuidenhout et al, 2014). Other consequences are also possible, such as the alteration of processes that allow the maintenance of genetic variability and an effect on biological adaptation and fitness of individuals (Freeland, 2005).…”