Interspecific Hybridization and Mitochondrial Introgression in Invasive Carcinus Shore Crabs

Abstract

Interspecific hybridization plays an important role in facilitating adaptive evolutionary change. More specifically, recent studies have demonstrated that hybridization may dramatically influence the establishment, spread, and impact of invasive populations. In Japan, previous genetic evidence for the presence of two non-native congeners, the European green crab Carcinus maenas and the Mediterranean green crab C. aestuarii, has raised questions regarding the possibility of hybridization between these sister species. Here I present analysis based on both nuclear microsatellites and the mitochondrial cytochrome C oxidase subunit I (COI) gene which unambiguously argues for a hybrid origin of Japanese Carcinus. Despite the presence of mitochondrial lineages derived from both C. maenas and C. aestuarii, the Japanese population is panmictic at nuclear loci and has achieved cytonuclear equilibrium throughout the sampled range in Japan. Furthermore, analysis of admixture at nuclear loci indicates dramatic introgression of the C. maenas mitochondrial genome into a predominantly C. aestuarii nuclear background. These patterns, along with inferences drawn from the observational record, argue for a hybridization event pre-dating the arrival of Carcinus in Japan. The clarification of both invasion history and evolutionary history afforded by genetic analysis provides information that may be critically important to future studies aimed at assessing risks posed by invasive Carcinus populations to Japan and the surrounding region.

RAD sequencing reveals genomewide divergence between independent invasions of the European green crab (Carcinus maenas) in the Northwest Atlantic

“…Previous studies have used COI sequence variation to study green crab population structure and to trace the invasion history (Darling, 2011; Darling et al., 2008, 2014; Roman, 2006). Overall, our SNP data were similar to COI in terms of resolving the current spatial structure of the invasions and suggests that patterns of divergence found in the mitochondria are widespread across the nuclear genome.…”

“…2002 from a Scotian Shelf population (Blakeslee et al., 2010). Green crab population structure has been investigated previously using traditional genetic markers, including mitochondrial DNA (16S, Geller, Walton, Grosholz, & Ruiz, 1997; COI, Darling, Bagley, Roman, Tepolt, & Geller, 2008; Roman & Palumbi, 2004; Roman, 2006) and microsatellites (Darling, 2011; Darling et al., 2008, 2014; Pascoal et al., 2009; Tepolt, Bagley, Geller, & Blum 2006). In their native range, green crab show distinct broadscale structuring of island populations (i.e., Faeroe Islands and Iceland) and northern and southern European populations (Roman & Palumbi, 2004) using COI sequence data and fine‐scale (~450 km) structuring has been reported using microsatellite loci (Pascoal et al., 2009).…”

Increase in density of genetically diverse invasive Asian shore crab (Hemigrapsus sanguineus) populations in the Gulf of Maine

“…Analyses using the maternally-derived mitochondrial cytochrome c oxidase subunit I gene have been widely utilized in crab population genetic studies, most notably to study the invasion history of the green crab along the northwest Atlantic coast (Roman 2006; Darling et al 2008, 2014; Blakeslee et al 2010; Darling 2011; Williams et al 2015). Only one study, however, has documented H. sanguineus COI genetic diversity, and this was conducted in its native range (Yoon et al 2011).…”

PopulationDynamics of Green Crabs (Carcinus maenas) -- A Review

“…Although there have been reports of an established population in Japan, the species is likely not C. maenas but its congener in the Mediterranean, C. aestuarii or a mixture and possible hybridization of the two species [5,29,48,56,57]. Based on suitable temperature regimes and depending on the European lineage, additional potential invasion sites have been identified where populations could be established, including coastal areas of Chile, China, Russia, Northern Japan, The Yellow Sea, Alaska, Namibia Uruguay, southern Brazil, and New Zealand [58].…”