Background: The biodiversity and distributions of terrestrial snails at local and regional scales are influenced by their low vagility and microhabitat specificity. The accessibility of large-bodied species and their characteristically high levels of genetic polymorphism make them excellent ecological and evolutionary models for studies on the phylogeography, phylogenetics, and conservation of organisms in fragmented populations. This study aims to elucidate the biodiversity, systematics, and distributions of genetic lineages within the genus Oreohelix at the northern and western periphery of their range.Results: We found four mitochondrial clades, three of which are putative subspecies of Oreohelix subrudis. One clade was geographically widespread, occurring within numerous sites in Cypress Hills and in the Rocky Mountains, a second was geographically restricted to the Rocky Mountains in Alberta, and a third was restricted to the Cypress Hills region. A fourth clade was the small-bodied species, O. cooperi. ITS2 sequence and screening data revealed three genetic clusters, of which one was O. cooperi. Cluster 1 contained most individuals in COI clade X and some from clade B and cluster 2 was predominantly made up of individuals from COI clades B and B′ and a few from clade X. ITS2 alleles were shared in a narrow contact zone between two COI clades, suggestive of hybridization between the two.Conclusions: A sky island known as Cypress Hills, in southeastern Alberta, Canada, is a biodiversity hotspot for terrestrial land snails in the genus Oreohelix. The observed phylogeographic patterns likely reflect reproductive isolation during the Last Glacial Maximum, followed by secondary contact due to passive, long-range dispersal resulting from low vagility, local adaptation, and complex glacial history.

Parasite distributions are constantly changing due to climatechange, local and global movement of animals and humans, as well as landuse and habitat change. The trematode D. dendriticum is a relativelyrecent invader into Canada being first reported in Eastern Canada in the1930s and Western Canada in the 1970s. However, historical records arescarce and its emergence is poorly understood. The establishment of thisparasite in Canada provides an interesting opportunity to explore the useof population genetic approaches to help elucidate the invasion historyof a relatively recently established helminth parasite. In this study, wecompare the genetic diversity and population structure of a number of D.dendriticum populations from Western and Eastern Canada and compare thesewith much longer established European populations. Two independentgenetic marker systems were used; a microsatellite marker panel and aCOX1 mtDNA sequence marker. We found distinct differences in both geneticdiversity and population structure of the different Canadian populationsthat provide insights into their invasion histories when compared to theEuropean populations. Two populations from British Columbia - Salt Springand Vancouver Islands - are of low diversity, show evidence of apopulation bottleneck, and are closely related to each other suggesting ashared recent history of establishment. These west coast populations areotherwise most closely related to those from Eastern Canada and WesternEurope and in contrast are genetically divergent from those in CypressHills, Alberta. Although the Alberta parasite population is the mostrecently reported in Canada, being first identified there in the early1990s, it was the most genetically diverse of those examined and showed astrong pattern of admixture of genotypes present in western and EasternEurope. Overall, our results are consistent with a model in which WesternEurope is likely the source of flukes on the east coast of Canada whichwere then subsequently translocated to the west coast of Canada. The mostrecently reported D. dendriticum population in Canada appears to have adifferent history and likely has multiple origins.