Co-diversification of Plants and Insects
Perhaps the most striking evolutionary pattern is the extraordinary diversity of life, and the remarkable predominance of a few groups of organisms. With over 250,000 described species, the angiosperms, although geologically young, comprise approximately 20% of all living organisms. The insects are even more diverse, with at least a million described species. A frequently advanced hypothesis to explain the extraordinary diversity of these two groups is that interactions between plants and insects, such as herbivory and pollination, have promoted adaptive radiations in each group. Our lab uses phylogenetic, ecological, and population genetic tools to test this hypothesis on a variety of scales in diverse plant and insect groups.
Pollination Biology of Joshua Trees
A major research focus in our lab is on the pollination biology of yuccas, and in particular that of the Joshua tree (Yucca brevifolia). Like all yuccas, Joshua trees are pollinated exclusively by yucca moths, that in turn reproduce by laying their eggs in the yucca flower. Across their range, Joshua trees are associated with two distinct, sister species of moth, and populations of trees associated with each moth are both morphologically and genetically distinct. Our lab is examining the role of coevolution between the Joshua tree and its pollinators in producing the differences between the two tree types, and in mediating reproductive isolation between them. We use a variety of tools and approaches to address these questions, from observational studies and ecological experiments, to phylogenetics and population genomics. We are currently developing transcriptome data and SNP libraries for the trees and their pollinators. These tools will eventually allow us to quantify genomic signatures of selection acting on genes associated with co-adaptation between plants and pollinators.
Population genetic tools offer many opportunities to answer important questions in conservation biology. Our lab is currently engaged in a number of conservation genetics projects, including determining the species status of the Asian Great Bustard, reconstructing the introduction and spread of the invasive eastern grey squirrel in the Pacific Northwest, and the effects of climate change on population growth in Joshua trees.