Genomewide evidence of environmentally mediated secondary contact of European green crab (Carcinus maenas) lineages in eastern North America

Abstract

Genetic‐environment associations are increasingly revealed through population genomic data and can occur through a number of processes, including secondary contact, divergent natural selection, or isolation by distance. Here, we investigate the influence of the environment, including seasonal temperature and salinity, on the population structure of the invasive European green crab (Carcinus maenas) in eastern North America. Green crab populations in eastern North America are associated with two independent invasions, previously shown to consist of distinct northern and southern ecotypes, with a contact zone in southern Nova Scotia, Canada. Using a RAD‐seq panel of 9,137 genomewide SNPs, we detected 41 SNPs (0.49%) whose allele frequencies were highly correlated with environmental data. A principal components analysis of 25 environmental variables differentiated populations into northern, southern, and admixed sites in concordance with the observed genomic spatial structure. Furthermore, a spatial principal components analysis conducted on genomic and geographic data revealed a high degree of global structure (p < .0001) partitioning a northern and southern ecotype. Redundancy and partial redundancy analyses revealed that among the environmental variables tested, winter sea surface temperature had the strongest association with spatial structuring, suggesting that it is an important factor defining range and expansion limits of each ecotype. Understanding environmental thresholds associated with intraspecific diversity will facilitate the ability to manage current and predict future distributions of this aquatic invasive species.

Population genomics of the introduced and cultivated Pacific kelp Undaria pinnatifida: Marinas—not farms—drive regional connectivity and establishment in natural rocky reefs

“…4 (Loctudy) and the Men Guen Regarding sample Rb8, the hypothesis of a specific environmental feature is interesting to consider: this locality, where the species was reported for the first time 10 years ago, is exposed to strong waves, which is a rare habitat for U. pinnatifida. Further dedicated studies are needed, to characterize the fine-grained environmental conditions (e.g., wave exposure, nutrients availability, irradiance) using local autonomous data loggers in the areas colonized by U. pinnatifida and then examine genomic-environmental associations, as recently done in the invasive crab Carcinus maenas (Jeffery et al, 2018). In addition, a genome sequencing project is currently in progress (Yoon et al, pers.…”

Mitochondrial genotype influences the response to cold stress in the European green crab, Carcinus maenas

“…Further, the functional differences among mtDNA haplotypes imply that adaptation has played a key role in the limitation of the original C. maenas invasion to the Gulf of Maine, with the species' expansion into the Canadian Maritime provinces coming only after the introduction of presumably cold-adapted genetic variants (Roman, 2006). Assuming mtDNA differences and their likely co-adapted nuclear-encoded mitochondrial genes represent standing genetic variation originally shaped by the physical differences between northern and southern Europe in its native range over the last 500,000 years (Roman and Palumbi, 2004;Tepolt and Somero, 2014;Jeffery et al, 2018), then the success of C. maenas in North America and elsewhere may be related to pre-adaptation to specific thermal environments. Observational studies have suggested a role for mitochondrial preadaptation in invasion success in other systems, notably the bryozoan Watersipora subtorquata (Mackie et al, 2012), but ours presents the first mechanistic support for this possibility.…”

Twin introductions by independent invader mussel lineages are both associated with recent admixture with a native congener in Australia

“…Successive introductions of large numbers of larvae are likely to promote secondary contact and subsequent admixture between genetically differentiated lineages (Keller & Taylor, 2010;Rius & Darling, 2014). For example, differentiated lineages of the invasive European green crab, Carcinus maenas, have been independently introduced into eastern Northern America (Darling, Bagley, Roman, Tepolt, & Geller, 2008;Tepolt & Palumbi, 2015), and postintroduction admixture between warm-adapted and cold-adapted lineages has been proposed as a factor in the establishment of invasive genotypes beyond their previous range limits (Darling, Tsai, Blakeslee, & Roman, 2014;Jeffery et al, 2018;Tepolt & Somero, 2014). Our findings are in line with general perceptions that successful marine introductions are likely to involve propagules from multiple and potentially diverse sources (Lockwood, Cassey, & Blackburn, 2005;Rius et al, 2015).…”