Phylogeography & Population Genetics

Mountain Pine Beetle (Dendroctonus ponderosae)

Understanding spatial genetic patterns and their relationship to environment is a key part of my research. I am currently working on the Mountain Pine Beetle (MPB). The MPB is a native bark beetle that can infest most pine species in its range. The MPB mass attack trees (mediated by pheromones), overwhelming the trees defenses. It plays an important role in maintaining healthy ecosystem and under normal conditions will attack older and weaker trees. However, during eruptive seasons its numbers can get high enough that it can cause massive die backs in healthy trees. I have been leading a project to look at how their population genetic structure is influenced by their Neo X/Y system and how this impacts MPB environmental adaptation.

Dowle, E.J., R.R. Bracewell, M.E. Pfrender, K.E. Mock, B.J. Bentz, G.J. Ragland, Reproductive isolation and environmental adaptation shape the phylogeography of mountain pine beetle (Dendroctonus ponderosae). Molecular Ecology, 2017 DOI: 10.1111/mec.14342

Placostylus Snails

During my PhD research, I examined the relationship between shell shape, environment and genetics in a giant edible land snail of New Caledonia. New Caledonia is a small pacific island with high levels of animal and plant diversity. Placostylus snails are large and endemic, it was thought that much of their genetic diversity was driven by allopatric speciation and that shell shape was uninformative and arbitrary.




This land snail was previously described using its shell shape which is known to differ depending on the environmental conditions at a site. Using detailed morphometric analysis, I quantified the shell shape variation in the Placostylus snails. Coupling this with a detailed SNP (ddRAD) and environmental dataset I was able to show that shell shape was the result of adaptation to local environmental conditions. The SNP data showed that different lineages under the similar environmental conditions were almost indistinguishable by shell shape but still maintained their distinct genetic clusters. Suggesting that diversity in the snails was not the result of allopatric speciation but rather was driven by independent adaptation to environmental conditions across the island.

For more details see:

Dowle, E.J., M. Morgan-Richards, F. Brescia, and S.A. Trewick, Correlation between shell phenotype and local environment suggests a role for natural selection in the evolution of Placostylus snails. Molecular Ecology, 2015. 24(16): p. 4205-4221.