Phylogeography of the red coral (Corallium rubrum): inferences on the evolutionary history of a temperate gorgonian

Abstract

The red coral Corallium rubrum (Cnidaria, Octocorallia) is an exploited, long-lived sessile species from the Mediterranean Sea and the adjacent coastline in the Atlantic Ocean. Surveys of genetic variation using microsatellites have shown that populations of C. rubrum are characterized by strong differentiation at the local scale but a study of the phylogeography of this species was still lacking. Here, we used seven polymorphic microsatellite loci, together with sequence data from an intron of the elongation factor 1 (EF1) gene, to investigate the genetic structure of C. rubrum across its geographical range in the western Mediterranean Sea and in the Adriatic Sea. The EF1 sequences were also used to analyse the consequences of demographic fluctuations linked with past environmental change. Clustering analysis with microsatellite loci highlighted three to seven genetic groups with the distinction of North African and Adriatic populations; this distinction appeared significant with AMOVA and differentiation tests. Microsatellite and EF1 data extended the isolation by distance pattern previously observed for this species at the western Mediterranean scale. EF1 sequences confirmed the genetic differentiation observed between most samples with microsatellites. A statistical parsimony network of EF1 haplotypes provided no evidence of high sequence divergence among regions, suggesting no long-term isolation. Selective neutrality tests on microsatellites and EF1 were not significant but should be interpreted with caution in the case of EF1 because of the low sample sizes for this locus. Our results suggest that recent Quaternary environmental fluctuations had a limited impact on the genetic structure of C. rubrum.

Does historical harvesting affect colony size distribution and genetic diversity in Corallium rubrum (Linnaeus, 1758)? Evidences from the Southern Mediterranean commercial banks

“…These results contrast with genetic structuring in shallow water and deep-water populations in the Northwestern Mediterranean (Costantini et al, 2007a;Ledoux et al, 2010a;Costantini et al, 2013;. Low genetic structuring and high connectivity were found by Aurelle et al (2011) in a preliminary study on Algerian red coral, which seems to be a common feature of Southern Mediterranean populations.…”

Contrasted levels of genetic diversity in a benthic Mediterranean octocoral: Consequences of different demographic histories?

“…But these southern samples were also situated on the western side of the Almeria–Oran front which might contribute to this differentiation (Mokhtar‐Jamaï et al., 2011). For C. rubrum, northern samples appeared well separated from southern ones (Algeria and Morocco, including samples from the Atlantic side of the Almeria–Oran front; Aurelle et al., 2011). Conversely, the Algerian populations of E. singularis were partly related to northern samples of the French coasts (near Spain; Cataneo, 2011).…”

“…For E. cavolini , the marked differentiation between northern and southern populations could point to an alternative scenario: There could be a northern refugia more affected by climatic fluctuations than southern one. A higher diversity in southern compared to northern populations has not been observed for other octocoral populations, apart for E. singularis (Aurelle et al., 2011; Cataneo, 2011; Mokhtar‐Jamaï et al., 2011). This could suggest different responses of octocorals to climate fluctuations with a higher sensitivity of E. cavolini to past climatic variations.…”

“…These species present low dispersal abilities (Costantini, Fauvelot, & Abbiati, 2007a; Garrabou et al., 2009; Ledoux et al., 2010; but see Martínez‐Quintana, Bramanti, Viladrich, Rossi, & Guizien, 2015), and they could be more impacted by sea‐level and climatic fluctuations than species with higher dispersal. No clear past demographic fluctuations have been demonstrated for the red coral Corallium rubrum in the Mediterranean Sea (Aurelle et al., 2011; Ledoux et al., 2010) on the basis of tests of mutation–drift equilibrium, but other methods could be more informative (Girod et al., 2011). …”

Cryptic lineages and high population genetic structure in the exploited marine snail Hexaplex trunculus (Gastropoda: Muricidae)

“…A strong dispersal potential enhances genetic homogenization among populations throughout the distribution range of a species, whereas restricted dispersal (absence of larval phase or nektobenthic larvae, and sessile or sedentary adults) may lead to strong population differentiation and increased speciation rates (Kelly & Palumbi, 2010;Boissin et al, 2011b). Oceanographic barriers do not affect all marine species in the same way, and some species do not display deep phylogeographical breaks (Patarnello et al, 2007;Aurelle et al, 2011). The link between life-history traits and the impact of these barriers (Patarnello et al, 2007), as well as the correlation between potential dispersal and observed levels of genetic differentiation, are not straightforward (Selkoe & Toonen, 2011).…”