Evolution and Phylogeny of Ciliated Protozoa

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I study the ciliated protozoa, common unicellular microorganisms found in lakes and oceans, in soils and forest litter, and in small ponds. Ciliates feed on bacteria and smaller protists. Ciliates are eaten by larval fish and small crustaceans, which may then be eaten by larger fish. Thus, ciliates are trophic links in food webs, and it is important to understand their overall diversity and their roles in these ecosystems. There may be over 30,000 species of ciliates, but the state of our knowledge of their species diversity and geographic distributions presents a barrier to understanding their ecological role. For example, different species may have very different ecological roles so correct species identification is a critical first step in any ecological study. Thus, a major goal of my research is to develop molecular methods, such as DNA barcodes, to enable us to operationally assess biodiversity and geographic distributions. I will focus study of genetic distributions on symbiotic ciliates found in the mantle cavities of clams and oysters, since these hosts have easily mapped distributions. An understanding of ciliate diversity leads to another major goal: reconstruction of both the evolutionary history of ciliates and establishment of a modern classification. Today phylogenetic analyses use gene sequences, such as ribosomal genes, which are highly conserved across all life forms. Species are related to each other by comparing these gene sequences, which are more similar to each other than the microscopic morphology of ciliates. Ribosomal genes however are not providing us with sufficient information, and so I will use multiple genes, derived from sampling the messenger RNA of selected species, to increase the character information and provide more robust conclusions. Since I am the only expert on these organisms in Canada and one of the few in the world, I often collaborate with colleagues around the world to describe new species.