Biology and evolution of the ascophyllum symbiosis

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This research program will investigate a complex symbiosis based around the brown seaweed, Ascophyllum nodosum. This species is the dominant photosynthetic organism of rocky intertidal shores of the cold-temperate North Atlantic Ocean, including large parts of coastal Atlantic Canada. The symbiosis includes: i) a mutualistic fungus (Mycophycias ascophylli), which is always present in the host tissues; ii) a common red alga that is an obligate epiphyte on Ascophyllum; iii) an obligate epiphytic brown alga (Elachista fucicola) that is often abundant on Ascophyllum; and iv) the most abundant marine insect yet described (Halocladius variabilis), that is largely restricted to Elachista. The research program will focus on the algal and fungal components of this symbiotic community using ecological, physiological and molecular tools to understand the nature of the interactions among these species. In addition, the molecular-evolutionary studies of the different components of the symbiotic community from throughout its distribution will provide important insights into the post-glacial biogeography of the North Atlantic and Arctic Oceans. Furthermore, since Ascophyllum is the basis of a major harvesting and processing industry in eastern Canada, it is possible that properties of the resulting products used in agricultural applications are derived from the fungal symbiont. This research program will help address this fundamental issue by collaborating with industry (Acadian Seaplants Ltd.) and making cultures available to them. Overall, this research program will provide new insights into intertidal ecology, and make Ascophyllum a major model system for marine symbioses.