Data from: Temporal dynamics of the genetic clines of invasive European green crab (Carcinus maenas) in eastern North America

Two genetically distinct lineages of European green crabs (Carcinus
maenas) were independently introduced to eastern North America, the first
in the early 19th century and the second in the late 20th century. These
lineages first came into secondary contact in southeastern Nova Scotia,
Canada (NS), where they hybridized, producing latitudinal genetic clines.
Previous studies have documented a persistent southward shift in the
clines of different marker types, consistent with existing dispersal and
recruitment pathways. We evaluated current clinal structure by quantifying
the distribution of lineages and fine-scale hybridization patterns across
the eastern North American range (25 locations, ~39-49°N) using
informative single nucleotide polymorphisms (SNPs; n=96). In addition,
temporal changes in the genetic clines were evaluated using mitochondrial
DNA and microsatellite loci (n=9-11) over a 15-year period (2000-2015).
Clinal structure was consistent with prior work demonstrating the
existence of both northern and southern lineages with a hybrid zone
occurring between southern New Brunswick (NB) and southern NS. Extensive
later generation hybrids were detected in this region and in southeastern
Newfoundland. Temporal genetic analysis confirmed the southward
progression of clines over time; however, the rate of this progression was
slower than predicted by forecasting models, and current clines for all
marker types deviated significantly from these predictions. Our results
suggest that neutral and selective processes contribute to cline dynamics,
and ultimately, highlight how selection, hybridization, and dispersal can
collectively influence invasion success.