A hitchhiker’s guide to the Maritimes: anthropogenic transport facilitates long‐distance dispersal of an invasive marine crab to Newfoundland

Abstract

Aim To determine timing, source and vector for the recent introduction of the European green crab, Carcinus maenas (Linnaeus, 1758), to Newfoundland using multiple lines of evidence.Location Founding populations in Placentia Bay, Newfoundland, Canada and potential source populations in the north‐west Atlantic (NWA) and Europe.Methods We analysed mitochondrial and microsatellite genetic data from European and NWA populations sampled during 1999–2002 to determine probable source locations and vectors for the Placentia Bay introduction discovered in 2007. We also analysed Placentia Bay demographic data and shipping records to look for congruent patterns with genetic analyses.Results Demographic data and surveys suggested that C. maenas populations are established and were in Placentia Bay for several years (c. 2002) prior to discovery. Genetic data corroboratively suggested central/western Scotian Shelf populations (e.g., Halifax) as the likely source area for the anthropogenic introduction. These Scotian Shelf populations were within an admixture zone made up of genotypes from both the earlier (early 1800s) and later (late 1900s) introductions of the crab to the NWA from Europe. Placentia Bay also exhibited this mixed ancestry. Probable introduction vectors included vessel traffic and shipping, especially vessels carrying ballast water.Main conclusions Carcinus maenas overcame considerable natural barriers (i.e., coastal and ocean currents) via anthropogenic transport to become established and abundant in Newfoundland. Our study thus demonstrates how non‐native populations can be important secondary sources of introduction especially when aided by human transport. Inference of source populations was possible owing to the existence of an admixture zone in central/western Nova Scotia made up of southern and northern genotypes corresponding with the crab’s two historical introductions. Coastal vessel traffic was found to be a likely vector for the crab’s spread to Newfoundland. Our study demonstrates that there is considerable risk for continued introduction or reintroduction of C. maenas throughout the NWA.

Master of all trades: thermal acclimation and adaptation of cardiac function in a broadly distributed marine invasive species, the European green crab,Carcinus maenas

“…Local adaptation in the native range in Europe may have contributed to the green crab's explosive expansion throughout the northern East Coast of North America. Our results support the hypothesis that secondary invasion from a northern source may have facilitated C. maenas' northward spread in the East Coast by introducing cold-adapted genotypes (Roman, 2006;Blakeslee et al, 2010). In a broader context, this example illustrates the potential importance of locally adapted populations in allowing a species to survive novel conditions.…”

“…This initial invasive population slowly spread north and south, to range between southern Nova Scotia and coastal Virginia (Carlton and Cohen, 2003). In the 1980s, the range of C. maenas rapidly advanced north through the Maritime Provinces of Canada, spreading to northern Nova Scotia, Prince Edward Island, and finally to Newfoundland in 2007 (Roman, 2006;Blakeslee et al, 2010). Genetic analysis revealed that this rapid northward expansion was concurrent with a second introduction of the species from northern Europe (Roman, 2006).…”

Asymmetric dispersal allows an upstream region to control population structure throughout a species’ range

“…This site has characteristics that predispose it to anthropogenic transport of Carcinus; the 2007 sampling was in a small fishing port where both bait transport and water discharge are potential vectors. Moreover, there is strong evidence that anthropogenic transport is responsible for the spread of Carcinus from Nova Scotia to eastern Newfoundland, suggesting that anthropogenic transport might also be important within our study area (27). Regardless of the mechanisms contributing to stochastic dispersal, its magnitude is likely to aid in the persistence of southern haplotypes in the population.…”

Revisiting recent history: records of occurrence and expansion of the European green crab across Prince Edward Island, Atlantic Canada

“…Initial records of green crab in North America date back to 1817 in the New Jersey/New York area, with the species spreading northward to Maine by the early 1900's, and to the Bay of Fundy over the following 50 years (Audet et al 2003;Klassen and Locke 2007). Genetic analyses have also indicated that a separate introduction occurred along the eastern Scotian shelf in the 1980's (Roman 2006;Blakeslee et al 2010) which has resulted in a mixing of northern and southern European green crab genotypes. Evidence suggests that this mixing may have widened the species' environmental tolerance locally, likely contributing to physiological and behavioural changes across subpopulations (Blakeslee et al 2010, Rossong et al 2012.…”

“…Genetic analyses have also indicated that a separate introduction occurred along the eastern Scotian shelf in the 1980's (Roman 2006;Blakeslee et al 2010) which has resulted in a mixing of northern and southern European green crab genotypes. Evidence suggests that this mixing may have widened the species' environmental tolerance locally, likely contributing to physiological and behavioural changes across subpopulations (Blakeslee et al 2010, Rossong et al 2012. It is also thought that this genetic mixing may have accelerated the species' eastward spread along the Nova Scotian coast (Blakeslee et al 2010) despite prevalent downstream current systems (Brickman 2014;Gharouni et al 2017).…”