|J.A. Addison, B.Sc. (Dalhousie), Ph. D. (Dalhousie)
Population genetics and speciation in marine and freshwater invertebrates
The origin of new species remains the central and most elusive question in evolutionary biology. In aquatic environments, the problem of genetic divergence and speciation is especially complex, because the barriers to genetic exchange that are generally essential for allowing divergence to occur are much more subtle than in terrestrial systems. Nevertheless, species can and do form rapidly in aquatic environments.
Research in my lab uses a multi-species approach to compare patterns of population genetic structure, in the context of life history variation and biogeographic history, to identify the features that lead to population divergence within a species, and that promote (or retard) the evolution of reproductive isolation between species. I use both frequency-based and coalescent-based analyses of mitochondrial and nuclear DNA sequences to draw strong inferences about historical demography, population growth histories, and the patterns of gene flow between both populations and species of aquatic organisms. Current projects include the population genetics of marine amphipods (Corophium volutator) throughout the Bay of Fundy, and freshwater insects throughout Atlantic Canada. This research will provide key insights into the history of the aquatic community assemblages of eastern North America by linking the maintenance of present-day community structure to historic and contemporary patterns of dispersal.
I also investigate the mechanisms that drive reproductive isolation among closely related species of Strongylocentrotus sea urchins. I use a variety of molecular techniques to assess the diversity in allopatric populations and to characterize the genetics interactions between species in sympatry. By studying the formation and maintenance of barriers to gene flow among strongylocentrotid sea urchins, this research aims to specifically test the predictions of allopatric and sympatric models of speciation to draw broader conclusions about the patterns and processes of speciation in the sea.
Keever, C, C., J. Sunday, J. B. Puritz, J. A. Addison, R. J. Toonen, R. K. Grosberg, M. W. Hart. 2009. Discordant distribution of populations and genetic variation in a sea star with high dispersal potential. Evolution, 63: 3214-3227.
Addison, J. A., and G. H. Pogson. 2009. Multiple gene genealogies reveal asymmetric hybridization and introgression among strongylocentrotid sea urchins. Molecular Ecology 18: 1239-1251.
Addison, J. A., B. S. Ort, K. A. Mesa, and G. H. Pogson. 2008. Range-wide genetic homogeneity in the California sea Mussel (Mytilus californianus): a comparison of allozyme, nuclear DNA markers, and mitochondrial DNA sequences. Molecular Ecology, 17:4222-4232.
Harper, F. M., J. A. Addison, and M. W. Hart. 2007. Introgression versus immigration in hybridizing high-dispersal Echinoderms. Evolution 61:2410-2418.
Addison, J. A. 2007. Simultaneous cloning of multiple nuclear genes by pooling PCR products of variable size: a cost effective method of improving efficiency in large-scale genetic analyses. Molecular Ecology Notes 7:389-392.
Addison, J. A., and M. W. Hart. 2005. Spawning, copulation and inbreeding coefficients in marine invertebrates. Biology Letters 1:450-453.
Addison, J. A., and M. W. Hart. 2005. Colonization, dispersal, and hybridization influence phylogeography of north Atlantic sea urchins Strongylocentrotus droebachiensis. Evolution 59:532-543.
Hart, M. W., S. L. Johnson, J. A. Addison, and M. Byrne. 2004. Strong character incongruence between life history traits and nucleotides in asterinid sea star phylogeny. Invertebrate Biology 123:343-356.Addison, J. A., and M. W. Hart. 2004. Analysis of population genetic structure of the green sea urchin (Strongylocentrotus droebachiensis) using microsatellites. Marine Biology 144:243-251.
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Last Update: 09 March 2010
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