Plasticity and Invasiveness
We are intensively studying the non-native annual Polygonum cespitosum to assess the role of plasticity in the species invasion process. This project involves documenting genotypic norms of reaction for functional and life-history traits in contrasting light and moisture conditions for a broad sample of populations in the species’ introduced range. These glasshouse data will reveal patterns of genetic variation for adaptive plasticity as well as evolutionary potential within and among populations of this invasive plant. Comparisons with populations from the native range will provide further insights regarding the dynamics of this species invasion in relation to plasticity. In addition to glasshouse norm of reaction experiments, the project includes environmental, demographic, and microsatellite studies to characterize the species’ ecological distribution and population structure in its introduced range.
Rapid evolution of plasticity in a newly invasive species
During the past 10-15 years, the introduced shade annual Polygonum cespitosum has begun to colonize open habitats in Northeastern North America for the first time; at the same time it has become invasive in the region. Do these changes in ecological distribution and behavior reflect recent evolution in this species? Does rapid evolution of adaptive phenotypic plasticity occur during the lag phase of a species invasion? We are using resurrection protocols to test whether individual plasticity patterns have rapidly evolved within the introduced range of P. cespitosum. In a suite of greenhouse studies, we are comparing responses to contrasting light and moisture conditions by genotypes collected from the same local populations at time points that are several generations apart. We are also studying how genotypes evolving in the species’ introduced range express adaptive traits in simulated future environments, in a manipulative field experiment at the University of Illinois Free Air Co2 Enrichment site (SoyFACE) where conditions include high light and diurnal heat, drought stress, and elevated carbon dioxide concentration.
Transgenerational plasticity: inherited, non-genetic adaptation
In addition to developmental, physiological, and life-history plasticity, we study transgenerational plasticity: the ways that plants subjected to environmental stresses alter the size, structure, and specific growth traits of their offspring. Of particular interest is the capacity for adaptive transgenerational responses, which comprise a non-genetic yet inherited influence on offspring phenotype that can have important fitness and ecological consequences. Previous work has identified adaptive transgenerational effects of parental drought, shade and nutrient stress in the moisture generalist Polygonum persicaria. A comparative study revealed that the closely related but ecologically restricted congener P. hydropiper lacks this mode of adaptive plasticity. P. hydropiper plants also express distinct transgenerational responses to shade depending on the architectural position of seeds on the parent plant. Our current studies aim to determine the persistence across generations of adaptive transgenerational plasticity in P. persicaria. We are investigating methylation as a potential mechanism for this plasticity.
Lab Funding: National Science Foundation Population Biology Panel; U.S. Department of Agriculture Weedy and Invasive Plants Program; Andrew Mellon Foundation Program in Conservation and the Environment; Mathers Charitable Trust; Eppley Foundation; New Phytologist Trust; European Commission Marie Curie Program.