Climate change and Community Genetic Analysis

1Over the past 40 years, rocky-shore marine ecology has provided many rich insights into the interactions between organisms and their environments, driving some of the most important conceptual advances in the field of community ecology. Despite there being a fairly deep mechanistic understanding of the benthic and pelagic processes shaping patterns of contemporary community structure on 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. First, there is a growing desire to predict the latitudinal responses of marine species and communities to increasing global temperatures. Second, because the composition of present-day cool-temperate marine communities are generally considered to have been assembled by recent range extensions from southern refugia, contemporary communities are thought to be dominated by species with high colonization capabilities and therefore may not represent truly ‘niche-assembled’ communities built through tens of thousands of years of colonization, extinction, and evolutionary change among interacting species.

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. A literature survey indicates that depleted genetic variation at high latitudes (evidence consistent with recent post-glacial re-colonization of the region) is more common among intertidal species that live relatively high on the shore, where exposure times to cold stress in air are longer than for species living lower on the shore. We are currently testing this hypothesis by examining patterns of population structure across entire guilds of intertidal organisms.

1 This work is supported by the National Science Foundation.

Marko, P. B., Hoffman, J. M., Emme, S. A., McGovern, T. M., Keever, C., & L. N. Cox. 2010. The expansion-contraction model of Pleistocene demography: rocky shores suffer a sea change?  Molecular Ecology 19:146-169. [PDF]

Marko, P. B. 2004. “What’s larvae got to do with it?” Contrasting patterns of post-glacial population structure in two benthic marine gastropods with identical larval dispersal capabilities. Molecular Ecology 13: 597-611. [PDF]


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