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Community genetics

Marine ecology has provided many rich insights into the interactions between organisms and their environments. Despite a fairly deep mechanistic understanding of the benthic and pelagic processes shaping patterns of contemporary community structure on coral reefs and rocky shores, comparatively little is known about the long-term persistence, stability, and historical assembly of these communities.

As a factor affecting community composition and structure over geological timescales, climate change has received the most attention from biologists and paleontologists for two reasons.  Our lab has been conducting phylogeographic surveys in the northeastern Pacific to test several hypotheses about how late Pleistocene climate change has altered rocky-shore community composition.  These genetic data reveal that different species have responded differently to climate change in the past, creating new combinations of species.  The work has important implications for future global climate change, predicting that entire communities will not shift their geographic ranges en masse but that subsets of the community are expected to move out to higher latitudes and move in from lower latitudes. 

We are now using environmental DNA (eDNA) to study the community genetics of coral reefs.  This technique can be used to study the same historical questions described above but also provides an efficient complement to visual surveys for biomonitoring of threatened ecosystems. The analysis of eDNA, DNA sloughed or expelled from organisms into the environment, takes advantage of the fact that all organisms constantly shed DNA into the environment, leaving behind a genetic residue that can be detected and analyzed with molecular biology tools.  We have demonstrated that eDNA analysis provides a quick and cost-effective way to measure live coral “cover,” the amount of a coral reef occupied by living corals. Because corals facilitate the presence of many other species on a reef, coral cover is one of several important measuring sticks that scientists use to characterize the status of a reef, an urgent task on reefs that are declining worldwide as a consequence of global climate change.  We are currently applying what we have learned from this project to the most compelling applications of eDNA monitoring in communities that are much more difficult to visually assess, such as deep reefs that provide potential refuge from climate change for temperature-sensitive species. 

College of Natural Sciences, University of Hawai‘i at Mānoa, Honolulu, Hawai‘i  96822