How do ecological interactions evolve over short timescales?
Our group is interested in the rapid evolution of distribution and abundance on human timescales, particularly in invasive species that are colonizing new locations, as well as in native species responding to environmental change. We are working to understand how genetic and environmental variation in these species translate into phenotypic diversity, adaptation, and changes in ecologically important traits. Colonization events are fundamental parts of the evolution and ecological interactions of all organisms: they shape species distributions, provide opportunities for population differentiation and adaptation, and can initiate the formation of new species. The study of rapid evolutionary responses to environmental variation can therefore inform both applied conservation questions about the fate of invasive or threatened species, and fundamental research into how biological diversity itself evolves.
In general, our approach can be thought of as making connections from changes in genotype to changes in phenotype to consequences for distribution and abundance in species encountering new environments.
We use the tools of field ecology, quantitative genetics, genomics, and bioinformatics to ask specific questions about how traits are evolving, how genetic variation is distributed geographically, how ecological interactions differ among genotypes, and how genetic differences translate into changes in population dynamics and species distributions.
Rapid evolution of ecologically important traits
The rapid adaptation of species to human-altered environments is arguably one of the most important discoveries made in ecology over the last few decades. Much of the evidence for rapid evolution has come from the study of introduced species, making these outstanding systems in which to investigate the genomic features that facilitate rapid response to selection. ‘Next-generation’ genomic tools are providing the opportunities to make connections between phenotypic evolution and its molecular genetic basis in non-model organisms. We are leveraging these tools to map the genetic basis of evolving traits, to track the sources of adaptive alleles, and to infer the ecological functions and genetic trade-offs that might be under selection during colonization events.
Often cited at one of the ‘10 Worst Weeds of the West’, yellow starthistle (Centaurea solstitialis) is a highly invasive plant introduced to the Americas from Europe, and now the primary study system in our lab. We have shown that invading genotypes have evolved a novel increase in growth and acceleration of flowering time, which may be a source of increased fitness in these invasions. We are currently investigating a potential negative trade-off between growth and immune function, together with collaborators David Baltrus and Sarah Swope. To understand the timing, source, and ecological consequences of these trait changes, we are studying loci underlying their evolution in invading populations (funding USDA #2015–67013–23000; NSF #1750280).
Distribution of genomic variation and adaptive variants
It is a simple truism that evolution requires genetic variation. For rapidly evolving populations, the source(s) of individuals and genes that contribute to a population will determine its raw material for future evolution. Genetic bottlenecks are often expected during colonization events, but mixing of material from different source locations and hybridization with related species are also sources of novel genetic variation that are hypothesized to enhance adaptation and ecological success. We are working to shed light on the potential sources of evolutionary change in rapidly evolving populations.
We are investigating the distribution of genetic variants in a variety of study systems. In yellow starthistle and one of its biocontrol agents (hairy weevil, Eustenopus villosus), we are currently studying aspects of phylogeography, current and historical demography, distribution of loci under selection, and the distribution of genome size, transposable element, and plant-associated microbiome variation. We are also inferring the distribution of variation at loci under selection, and potential demographic impacts of responses to climate change in two systems with extremely well-studied ecological interactions and demography: the native alpine plant moss campion (Silene acaulis; in collaboration with Dan Doak, Bill Morris, and Cynthia Hays), and the native Sonoran desert winter annual Pectocarya recurvata (in collaboration with Larry Venable and Monica Ge).
Gene expression variation across environments
Together with collaborator Mike Barker (University of Arizona), we have launched a major initiative to identify the connections between gene expression and demographic success in response to environmental variation. In particular, we are conducting comparative work among sets of diploid, polyploid, and invasive plant species that co-occur in a community. This work leverages the National Ecological Observatory Network (NEON), with a goal of understanding how the genetic and plastic variation that shape the most basic aspect of phenotype (gene expression) can predict differences in distribution and abundance across environments (funding NSF #1550838). See more at our project page here.