Native parasite combating an invasive species: an oomycete vs. Echinogammarus ischnus
van Rensburg, Karla
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In the context of invasions in ecology, parasites can play an important role in mediating the outcomes of competition between the native and invasive species. For example, a native parasite in the upper St. Lawrence River area has been found infecting both native and non-native gammarid amphipods, Gammarus fasciatus and Echinogammarus ischnus, respectively. Usually when the non-native species invades an area, the native amphipod is rapidly replaced by the non-native species. However, in this specific region the native amphipod was not replaced by the non-native species, and the non-native species was observed to be infected by a parasite. To determine infection rates in the native and non-native hosts, DNA was extracted from both species of amphipods and specific primers for the 18S rRNA gene were created to generate quantitative analysis of the incidence of the parasite in the amphipods. These data indicate that the effect of the parasite on the native and non-native amphipods could be the mechanism preventing the dominance of the non-native species in this specific area for the past ten years, since the parasite was found to infect the non-native amphipod more frequently and at a higher level than the native amphipod.