Abstract
The spatial distribution and the amount of intraspecific genetic variation of marine organisms are strongly influenced by many biotic and abiotic factors. Comparing biological and genetic data characterizing species living in the same habitat can help to elucidate the processes driving these variation patterns. Here, we present a comparative multispecies population genetic study on seven mangrove crabs co-occurring in the West Indian Ocean characterized by planktotrophic larvae with similar pelagic larval duration. Our main aim was to investigate whether a suite of biological, behavioural and ecological traits could affect genetic diversities of the study species in combination with historical demographic parameters. As possible current explanatory factors, we used the intertidal micro-habitat colonised by adult populations, various parameters of individual and population fecundity, and the timing of larval release. As the genetic marker, we used partial sequences of cytochrome oxidase subunit I gene. Genetic and ecological data were collected by the authors and/or gathered from primary literature. Permutational multiple regression models and ANOVA tests showed that species density and their reproductive output in combination with historical demographic parameters could explain the intraspecific genetic variation indexes across the seven species. In particular, species producing consistently less eggs per spawning event showed higher values of haplotype diversity. Moreover, Tajima’s D parameters well explained the recorded values for haplotype diversity and average γst. We concluded that current intraspecific gene diversities in crabs inhabiting mangrove forests were affected by population fecundity as well as past demographic history. The results were also discussed in terms of management and conservation of fauna in the Western Indian Ocean mangroves.
Highlights
The genetic structure of populations in the marine realm is a complex process affected by both biotic and abiotic factors including biological, ecological, and behavioural traits of adults and larval stages [1, 2]
U. inversa, N. africanum P. guttatum are restricted to the east African coast and Madagascar Island [34,35,36], and they could not be collected in the Seychelles Islands (S1 Table)
The haplotype diversity index was found to be high in all species, except in U. occidentalis that only had 18 haplotypes recorded in more than 400 individuals (Table 1; Fig 2)
Summary
The genetic structure of populations in the marine realm is a complex process affected by both biotic and abiotic factors including biological, ecological, and behavioural traits of adults and larval stages [1, 2]. In addition to historical barriers, existing abiotic barriers include local currents and gyres, which favour retention of larvae in near-shore areas, and variations in seawater temperature and salinity, which are deleterious for larval survival or development [14]. The unpredictability of the connectivity in marine ecosystems is enhanced by the fact that even species with similar life-history traits and/or living in the same geographical area can show contrasting patterns of genetic variation (for a review see [17]). How can we uncover the mechanisms underpinning the differences in intraspecific genetic variation patterns that may be observed in the marine realm?
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