Abstract:

Parasite distributions are constantly changing due to climate
change, local and global movement of animals and humans, as well as land
use and habitat change. The trematode D. dendriticum is a relatively
recent invader into Canada being first reported in Eastern Canada in the
1930s and Western Canada in the 1970s. However, historical records are
scarce and its emergence is poorly understood. The establishment of this
parasite in Canada provides an interesting opportunity to explore the use
of population genetic approaches to help elucidate the invasion history
of a relatively recently established helminth parasite. In this study, we
compare the genetic diversity and population structure of a number of D.
dendriticum populations from Western and Eastern Canada and compare these
with much longer established European populations. Two independent
genetic marker systems were used; a microsatellite marker panel and a
COX1 mtDNA sequence marker. We found distinct differences in both genetic
diversity and population structure of the different Canadian populations
that provide insights into their invasion histories when compared to the
European populations. Two populations from British Columbia - Salt Spring
and Vancouver Islands - are of low diversity, show evidence of a
population bottleneck, and are closely related to each other suggesting a
shared recent history of establishment. These west coast populations are
otherwise most closely related to those from Eastern Canada and Western
Europe and in contrast are genetically divergent from those in Cypress
Hills, Alberta. Although the Alberta parasite population is the most
recently reported in Canada, being first identified there in the early
1990s, it was the most genetically diverse of those examined and showed a
strong pattern of admixture of genotypes present in western and Eastern
Europe. Overall, our results are consistent with a model in which Western
Europe is likely the source of flukes on the east coast of Canada which
were then subsequently translocated to the west coast of Canada. The most
recently reported D. dendriticum population in Canada appears to have a
different history and likely has multiple origins.