Isolation by Distance in Equilibrium and Nonequilibrium Populations of Four Talitrid Species in the Mediterranean Sea

Abstract

Allozymic variation at 21-23 loci was studied in 28 populations of Talitrus saltator, 23 populations of Orchestia montagui, 13 populations of O. stephenseni, and five populations of Platorchestia platensis from the Mediterranean Basin. Different levels of gene flow (Nmtheta) were detected within each species at the scale of the whole Mediterranean: O. montagui and P. platensis had low population structure, with levels of Nmtheta > or = 1, whereas the T. saltator and 0. stephenseni populations have values of Nmtheta < 1. The relationship between Nmtheta and geographic distance was analyzed to test for the presence of an isolation by distance pattern in the spatial genetic variation within each species. A model of isolation by distance is useful to describe the pattern of genetic structuring of study species at the scale of the whole Mediterranean: geographic distance explained from 28% to 70% of the variation in gene flow. In the Aegean area all species showed an island model of genetic structuring regardless of the levels of gene flow.

Mitochondrial DNA and microsatellites reveal significant divergence in the beachflea Orchestia montagui (Talitridae: Amphipoda)

“…More generally, previous allozyme-based studies on O. montagui revealed high or very high levels of gene flow at the scale of the Mediterranean Sea (De Matthaeis et al 2000a). Although our sampling was currently limited to a relatively low number of locations, it is worth noting that, whatever geographic scale is considered, we almost invariably retrieved a significant divergence among sampled populations.…”

“…The vast majority of them is based on allozymes (Angelini et al 1996;Cervelli et al 2006;De Matthaeis et al 1995, 2000a Here we present the first study that applies simultaneously mitochondrial and nuclear markers in a talitrids species in order to describe its population structure. Our study acts as a preliminary and exploratory research, seeking to address the interplay between population genetic structure and abiotic forces in the talitrid species O. montagui, by using markers with different evolutionary properties.…”

“…Different means of transportation have been hypothesized (i.e. birds or humans; Wildish 1988); nonetheless, the most presumable way of dispersing is still believed to be on floating wrack or wood (De Matthaeis et al 1995, 2000aPavesi et al 2011), a phenomenon known as rafting.…”

“…Talitrus saltator, Deshayesorchestia deshayesii) or dig into rotting logs (Macarorchestia remyi) (De Matthaeis et al 2000b;Pavesi et al 2011). On the other hand, species associated with heaps of decaying wrack on rocky shores seem to be genetically homogeneous, even over long distances (De Matthaeis et al 2000a). De Matthaeis et al (2000a, b) interpreted these contrasting patterns in the homogeneity of talitrid gene pools in terms of probabilities for the animals to be dragged away by sea currents and thus be dispersed passively.…”

Population structure and dynamics ofOrchestia montagui(Crustacea: Amphipoda) in the Bizerte lagoon (northern Tunisia)

“…However, previous studies based on allozymes have revealed a poor genetic structure of O. montagui populations (De Matthaeis et al 1995, 2000a, 2000bAngelini et al 1996;Cervelli et al 2006). More recent studies that were based on more variable and informative markers (cytochrome oxidase subunit I and microsatellites) showed signatures of local differentiation (Pavesi et al 2012(Pavesi et al , 2013 and differed from previous hypotheses.…”