Evolutionary ecology of parasite-host species interactions

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Evolutionary ecology of parasite-host species interactions: host species use, evolution of resistance, and parasite aggregation.****Much ink has been spilled about co-evolutionary interactions of parasites and their host species. That is, researchers are often interested in questions such as why some parasites and pathogen species are nasty, whereas others are relatively benign; or, why some parasites or pathogen species have broad host species ranges whereas others tend to be specialists, for a given stage of their life cycle. Parasites and pathogens are often seen as having the evolutionary upper hand over their hosts because of asymmetric selection. This is because parasites and pathogens often have shorter generation times than their hosts, have infective stages that are much more numerous than their hosts, and have an obligate dependence on host individuals for their growth, development and/or reproduction. *** However, this view belies the facts that parasites often share host resources with other species and also that many parasite species have several host species, even at single sites and over the same time frames. Concurrent multi-host, multi-parasite associations set the stage for diffuse ecological and evolutionary interactions amongst parasites and their hosts. Such diffuse interactions are likely common in nature, yet have received comparatively little attention.*** In this application, I will outline some of the more prominent hypotheses about intra- and interspecific variation in parasitism and host resistance and its relation to ecology of host species and host species range of parasitic organisms. My lab has a rich tradition in studying various species of dragonflies and their ectoparasitic mites to test such hypotheses. With my HQP, I will also address the evolutionary causes and importance of parasite aggregation on host species, which is deemed one of the general laws of ecological parasitology and which has implications for intra-and interspecific interactions among parasites.*** Tests and insights have become much stronger with the following: the advent of barcoding techniques, experimental approaches previously deemed difficult, geographical comparisons of species interactions, and equation-based models building on empirical results, all of which are proposed approaches for this grant cycle. Sample preparation and taxonomy is done in my lab; collaborators at Biodiversity Institute of Ontario and AgCan do barcoding. Experimental approaches are possible with CFI-funded Environmental Rooms and NSERC RTI-funded Zeiss microscope and Conviron incubators. We have sites chosen for the geographical studies and we have expertise with equation-based modeling. Students gain effective training from me, other HQP and collabotators with one to several experimental and statisitical techniques. ***(See CCV, Proposal and Attached Contributions for details).