Comparative phylogeography and population genetic structure of three widespread mollusc species in the Mediterranean and near Atlantic

Abstract

Although several studies have evaluated the genetic structure and phylogeographic patterns in many species of marine invertebrates, a general model that applies to all of them remains elusive. For example, some species present an admixture of populations with high gene flow, whereas others exhibit more complex patterns characterized by small‐scale unstructured genetic heterogeneity, even at a local scale. These differences are thought to be due to clear biological aspects such as direct versus indirect development, or the presence of lecithotrophic versus planktotrophic larvae, but few studies compare animals with similar distributions and life modes. Here, we explore the phylogeographic and genetic structure patterns in two chiton (Chiton olivaceus and Lepidopleurus cajetanus) and one abalone (Haliotis tuberculata) species co‐occurring in the same habitat. Samples were obtained from shallow rocky bottoms along the Iberian Peninsula (Atlantic and Mediterranean coasts), Italy, Croatia and Greece, and the mitochondrial markers COI and 16S rRNA gene were sequenced. Our data show evidence of admixture and population expansion in C. olivaceus and H. tuberculata, whereas L. cajetanus exhibited a ‘chaotic patchiness’ pattern defined by a high genetic variability with locality‐exclusive haplotypes, high genetic divergence, and a lack of geographic structure. Shared haplotypes were sampled in both coasts of Iberia (for H. tuberculata) and in the Western and Eastern Mediterranean (for C. olivaceus), potentially indicating high dispersal ability and a recent expansion. The processes underlying the fine‐scale structuring in L. cajetanus remain a mystery. These results are especially interesting because the reproductive mode of the two chitons is similar but differs from that of the abalone, with a veliger larva, while instead the genetic structure of C. olivaceus and H. tuberculata are similar, thus contrasting with predictions based on the life history of the three molluscs and showing that the genetic patterns of marine species may be shaped by many factors, including historical ones.

Evidence for rangewide panmixia despite multiple barriers to dispersal in a marine mussel

“…Evidence of panmixia has been previously provided for other species across some of the regions considered in this study (e. g. mitochondrial marker (D loop): fish species Diplodus sargus , Pagellus bogaraveo , Pagrus pagrus and Scomber japonicus 20 ; mitochondrial markers (Cox1 and 16S): abalone Haliotis tuberculata , chiton Chiton olivaceus 60 ). While we explain the genetic pattern of P .…”

“…Despite general evidence of panmixia across several taxa 20 , 60 , rangewide panmixia is extremely rare 9 , 61 . The panmitic genetic pattern described from northern Africa and southern Iberia strongly contrasts with the genetic pattern observed from South African populations of P .…”

“…perna in terms of life history traits and ecological variables, other panmitic genetic signatures have been explained as unlikely to be due to dispersal, but rather the result of fluctuations in populations size (i.e. extinction/colonization and migration) and historical demography 20 , 60 .…”

Commensal associations and benthic habitats shape macroevolution of the bivalve clade Galeommatoidea

“…However, case studies on galeommatoideans have shown that direct developers can have extensive geographical ranges [29,61] and that indirect developers can be geographically quite restricted [62]. It is known that molluscan species with similar developmental modes can show drastically different population structures [63]. Therefore, the impact of larval ecology on galeommatoidean speciation could be complex and is unlikely to be the major driver of the observed patterns.…”

Intraspecific genetic structure, divergence and high rates of clonality in an amphi‐Atlantic starfish

“…The particular life cycle of species, and the prevalence of one type of reproduction over the other (sexual vs. asexual), has a great influence on its demography, phylogeography and genetic diversity (Fern andez, Lemer, McIntyre, & Giribet, 2014;Kyle & Boulding, 2000;Sherman, Hunt, & Ayre, 2008;Uthicke, Schaffelke, & Byrne, 2009). As the rate of clonation affects the genetic structure of populations, it also has consequences on their evolutionary potential and their capacity to respond to environmental shifts (de Meeûs et al, 2007).…”