Comparison of additive genetic variance in native and introduced populations
When plants are introduced to a novel location, their environmental context is altered. How some introduced species manage to survive and thrive, occasionally to the point of becoming invasive, is an interesting and pressing question in evolutionary ecology. Increasingly, researchers recognize that evolutionary factors play an important role in invasions, and many of the best documented examples of rapid adaptation are in invasive species.
Genetic diversity is a prerequisite for any adaptation to occur. Most traits that will be under selection in a new environment will be quantitative. In order to compare their evolutionary potential, I am quantifying additive genetic variance in introduced and native populations of Ambrosia artemisiifolia (ragweed).
Local adaptation in introduced Arabidopsis thaliana: Do early flowering lines have higher fitness in dry winters?
Optimizing flowering time is critical for plant species, as it will directly affect the number of seeds they can produce, and the climate their flowers and fruits will experience at their critical reproductive stage (Simpson and Dean 2002). As it is such an important life history trait, adaptation in flowering time could be crucial for the success of introduced plant populations (Barrett et al. 2008, Montague et al. 2008).
Research on Arabidopsis thaliana in its native European range has found clinal patterns and evidence of adaptation to climatic conditions (e.g., Stinchcombe et al. 2004, Caicedo et al. 2004, Rutter and Fenster 2007, Samis et al. 2008, Hancock et al. 2011, Fournier-Level et al. 2011). Despite its recent colonization (~200 years ago (Jørgensen and Mauricio 2004)), preliminary evidence for adaptive evolution in North American A. thaliana has been found (Samis et al. 2012). Samis et al. observed a longitudinal flowering time cline, which was parallel to that previously described in Europe and was robust to the inclusion of population structure — evidence that the cline reflects local adaptation. Winter precipitation best explained the geographic variation in flowering time. To examine this putative cause of the observed cline on flowering traits and fitness, Amanda Stock and I completed a manipulative chamber experiment. We asked the following questions: Do early flowering lines have higher fitness in dry winters? How consistent is flowering time order when the same accessions are grown in simulated versus natural winter conditions?
You can read about our results here.