Abstract
Genomic studies of invasive species can reveal both invasive pathways and functional differences underpinning patterns of colonization success. The European green crab (Carcinus maenas) was initially introduced to eastern North America nearly 200 years ago where it expanded northwards to eastern Nova Scotia. A subsequent invasion to Nova Scotia from a northern European source allowed further range expansion, providing a unique opportunity to study the invasion genomics of a species with multiple invasions. Here, we use restriction‐site‐associated DNA sequencing‐derived SNPs to explore fine‐scale genomewide differentiation between these two invasions. We identified 9137 loci from green crab sampled from 11 locations along eastern North America and compared spatial variation to mitochondrial COI sequence variation used previously to characterize these invasions. Overall spatial divergence among invasions was high (pairwise FST ~0.001 to 0.15) and spread across many loci, with a mean FST ~0.052 and 52% of loci examined characterized by FST values >0.05. The majority of the most divergent loci (i.e., outliers, ~1.2%) displayed latitudinal clines in allele frequency highlighting extensive genomic divergence among the invasions. Discriminant analysis of principal components (both neutral and outlier loci) clearly resolved the two invasions spatially and was highly correlated with mitochondrial divergence. Our results reveal extensive cryptic intraspecific genomic diversity associated with differing patterns of colonization success and demonstrates clear utility for genomic approaches to delineating the distribution and colonization success of aquatic invasive species.
Highlights
Global invasions of plants and animals are occurring at an increasing rate accelerated by human impacts and environmental change (Levings, Kieser, Jamieson, & Dudas, 2002; Mooney & Cleland, 2001; Ricciardi, 2006)
Our goals were to (i) quantify genomewide differentiation among samples encompassing both the invasions in eastern North America from northern and southern European source populations, (ii) describe the spatial distribution of these two invasions using a large number of genomewide SNPs, and (iii) compare spatial variation at both highly divergent and selectively neutral SNPs, as well as the mitochondrial cytochrome oxidase I (COI) gene to better understand the evolutionary dynamics associated with the recent invasion and northwards expansion of the species
The recent green crab range expansion in eastern North America appears to be driven by a second invasion from the northern region of their native range in Europe (Roman, 2006)
Summary
Global invasions of plants and animals are occurring at an increasing rate accelerated by human impacts and environmental change (Levings, Kieser, Jamieson, & Dudas, 2002; Mooney & Cleland, 2001; Ricciardi, 2006). Invasions can have significant ecological and evolutionary consequences at the species (McDonald, Parchman, Bower, Hubert, & Rahel, 2008), community Ecological impacts have been well studied in coastal marine habitats, which represent some of the most heavily invaded ecosystems due to human-mediated introductions from ship ballast and hull fouling, as well as the aquarium trade and aquaculture activities (Grosholz, 2002). A better understanding of the presence of intraspecific diversity within invasive species and how it correlates with variation in invasion success is necessary to successfully manage invaders and mitigate ecological and evolutionary impacts
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