Solving cryptogenic histories using host and parasite molecular genetics: the resolution of Littorina littorea's North American origin

Abstract

Even after decades of investigation using multiple sources of evidence, the natural histories of some species remain unclear (i.e. cryptogenic). A key example is Littorina littorea, the most abundant intertidal snail in northeastern North America. Native to Europe, the snail's ecological history in North America has been debated for over 100 years with no definitive resolution. To resolve its cryptogenic status, we used molecular genetics from a novel combination of the snail and a highly associated trematode parasite, Cryptocotyle lingua. Based on mitochondrial sequences of 370 L. littorea and 196 C. lingua individuals, our results demonstrate a significant reduction in genetic diversity in North America vs. Europe, North American haplotypes nested within European haplotypes, and mean divergence estimates of approxiamtely 500 years ago from Europe for both host and parasite--thus supporting a recent introduction of both host and parasite to North America from Europe. Our study therefore resolves not only a specific cryptogenic history, but it also demonstrates the success of our approach generally and could be used in resolving difficult invasion histories worldwide.

Large-Scale Spatial Distribution Patterns of Gastropod Assemblages in Rocky Shores

“…The richest families in the overall dataset in terms of number of species were the Trochidae and the Rissoidae with 32 and 30 species, respectively, followed by the Lottiidae (24 species), Littorinidae (22), Muricidae (21), Fissurellidae (17), Collumbellidae (16), Patellidae and Buccinidae (15 species each), Conidae (12), and Cerithiidae and Pyramidellidae (10 species each). None of the species found at each of the sites are listed as alien/invasive for their particular locality except for Littorina littorea which has been reported as an early introduced species in the Western North Atlantic [64]. In all LMEs, assemblages were dominated by few species and most other species were rare (Table 3).…”

Consistent Pattern of Local Adaptation during an Experimental Heat Wave in a Pipefish-Trematode Host-Parasite System

“…This generalist parasite shows a broad diversity of possible second intermediate hosts, but most of them are small coastal fishes [37]. Throughout European coastal waters C. lingua shows a high diversity where the majority of its European haplotypes can only be observed once [38]. Its larval cercarial stages penetrate the skin and lead to visible black spots (metacercariae).…”

Historical invasions of the intertidal zone of Atlantic North America associated with distinctive patterns of trade and emigration

“…DNA extractions of L. littorea and genetic analyses based on cytochrome b haplotypes followed published protocols (9). Previously unreported haplotypes have GenBank accession nos.…”

“…(n ϭ 8 haplotypes) and Nova Scotia as a whole (n ϭ 11 haplotypes) because of early reports (12,15) of L. littorea in these places. The other 14 North American haplotypes occur at low frequency (Dataset S1); statistical analysis predicts they are shared with yet undiscovered European haplotypes (9).…”