Research interests

Our research is focused on three main areas:


1. The genetic basis of local adaptation

2. The role of genetic drift in limiting adaptation, and increased risk of extinction

3. The maintenance of outcrossing in predominantly selfing species


We are also begining to investigate freezing tolerance, and tradeoffs between abiotic stress tolerance, pathogen resistance, and yeild in winter wheat in collaboration with Mohsen Mohammadi in the Agronomy Department at Purdue.


We have worked on a variety of plant species, and use a combination of traditional crossing designs, field and greenhouse experiments, and molecular genetic approaches.



1. The genetic basis of local adaptation.

A major goal of evolutionary biology is to understand the factors contributing to the origin and maintenance of biological diversity. Genetic tradeoffs, where adaptation to one environment comes at a fitness cost in an alternate environment, are an intuitive explanation for the ubiquity of adaptive diversification. My research addresses this fundamental hypothesis by investigating the genetic basis of local adaptation and adaptive traits, particularly those that result in fitness trade-offs across environments.


Despite the importance of understanding of the genetic basis of adaptation and fitness tradeoffs, relatively few studies have mapped the genetic basis of fitness, and underlying adaptive traits using reciprocally adapted populations. To better understand the genetic basis of local adaptation and fitness tradeoffs, I combine genetic and genomic tools available in the model plant Arabidopsis thaliana with field and growth chamber studies using genotypes from intact natural populations. This work is part of a collaboration with Jon Ågren (Uppsala University), Mike Thomashow (MSU), John McKay (CSU), and Doug Schemske (MSU). A multi-year reciprocal transplant study between populations near the northern (Sweden) and southern (Italy) edge of the native range demonstrating strong local adaptation forms the foundation for this work.


We have used a large recombinant inbred line (RIL) mapping population to identify quantitative trait loci (QTL) for fitness in the native sites for going on seven years (> 100,000 total plants, and > 1 million total fruits counted!). One key result from the first three years of data (Ågren et al. 2013) was that genetic tradeoffs, QTL where the local allele had higher fitness in both environments, are quite common. I subsequently identified large effect QTL for freezing tolerance (Oakley et al. 2014) that colocalize with genetic tradeoff QTL, suggesting that freezing tolerance is the mechanism of some genetic tradeoffs. The casual gene (CBF2) for the largest effect freezing tolerance QTL has been identified and functionally validated (Gehan et al. 2015), and now we am using CRISPR mutants to examine effects on patterns of gene and trait expression and fitness in contrasting environments. At the same time, we am using fine mapping approaches with near isogenic lines to identify the causal genes at the other freezing tolerance QTL. We are also addressing questions about parallel evolution by examining the genetic basis of freezing tolerance across different latitudinal and elevational gradients.



2. The role of genetic drift in limiting adaptation, and increased risk of extinction


under construction ...


3. The maintenance of outcrossing in predominantly selfing species


under construction ...