Implications of isolation and low genetic diversity in peripheral populations of an amphi‐Atlantic coral

Abstract

Limited dispersal and connectivity in marine organisms can have negative fitness effects in populations that are small and isolated, but reduced genetic exchange may also promote the potential for local adaptation. Here, we compare the levels of genetic diversity and connectivity in the coral Montastraea cavernosa among both central and peripheral populations throughout its range in the Atlantic. Genetic data from one mitochondrial and two nuclear loci in 191 individuals show that M. cavernosa is subdivided into three genetically distinct regions in the Atlantic: Caribbean-North Atlantic, Western South Atlantic (Brazil) and Eastern Tropical Atlantic (West Africa). Within each region, populations have similar allele frequencies and levels of genetic diversity; indeed, no significant differentiation was found between populations separated by as much as 3000 km, suggesting that this coral species has the ability to disperse over large distances. Gene flow within regions does not, however, translate into connectivity across the entire Atlantic. Instead, substantial differences in allele frequencies across regions suggest that genetic exchange is infrequent between the Caribbean, Brazil and West Africa. Furthermore, markedly lower levels of genetic diversity are observed in the Brazilian and West African populations. Genetic diversity and connectivity may contribute to the resilience of a coral population to disturbance. Isolated peripheral populations may be more vulnerable to human impacts, disease or climate change relative to those in the genetically diverse Caribbean-North Atlantic region.

Phylogeographical Analysis on Squalidus argentatus Recapitulates Historical Landscapes and Drainage Evolution on the Island of Taiwan and Mainland China

“…Compared with previous studies of freshwater fishes in southern China, the genetic diversity of cyt b sequences is similar to that of the other species [6,8–11]. Genetic diversity is reduced in peripheral populations in comparison with central and more pristine populations, which may result from a small founder population or genetic drift or inbreeding depression [27]. At the lineage scale, the genetic diversity of the lineage A was higher than that of lineage B, implying that lineage A might represent the center of distribution.…”

Long Distance Dispersal and Connectivity in Amphi-Atlantic Corals at Regional and Basin Scales

“…The four gamete test indicates that only a few recombination events have occurred at each locus for most species (Rm = 0–4), except for β-tubulin of S. siderea , where a minimum of 12 recombination events are inferred. Recombination has also been observed in β-tubulin1 and β-tubulin2 of M. cavernosa [20]. Every haplotype network had 1–5 haplotypes that were shared between two or more regions.…”

“…Due to the unusually low levels of genetic variation found in the mitochondrial DNA of corals [37], [38], only nuclear loci were used. The intron and exon of β-tubulin and the intron of the Pax-C gene, which have previously been shown to contain sufficient intraspecific variation in corals for population studies [20], [39], were amplified for all species studied, with the exception of P. astreoides , for which only β-tubulin could be amplified. For P. astreoides , the mitochondrial control region (thought to be one of the most variable regions of the coral mitochondrial genome) was amplified and sequenced for 32 individuals from Panamá and Brazil, but because all individuals contained identical nucleotide sequences at this locus, this marker was not used for further analysis.…”

“…Understanding the processes that limit or promote dispersal in coral species can provide insight into how and why populations persist and evolve. Although connectivity and dispersal have been explored for a number of co-distributed Pacific corals [18], [19], basin-scale connectivity among Atlantic corals has only been explored among populations of one scleractinian species [20] and one species of octocoral [21]. However, it is unclear whether the patterns observed in these two species can be generalized to all corals, or whether they are specific to the dispersal ability of these two organisms.…”

Correlation between pelagic larval duration and realised dispersal: long-distance genetic connectivity between northern New Zealand and the Kermadec Islands archipelago

“…Tracey et al 1975). However, recent research has provided examples of barriers to gene flow and population differentiation at scales of only a few kilometres, leading to the conclusion that marine populations may not be as ''open'' as previously thought (Bell and Okamura 2005;Wood and Gardner 2007;Nunes et al 2009;Crandall et al 2012;Wei et al 2013 and references therein).…”