OOS 10-6
Genetic differentiation, transcriptome variation, and adaptation of prairie grass Andropogon gerardii along a climate gradient
My talk will focus on the genetic, molecular and ecological mechanisms involved in response of the prairie grass big bluestem Andropogon gerardii to diverse and changing climates of the Great Plains. Big bluestem is an ecologically dominant grass in Central US grasslands. With wide distribution across a precipitation gradient (400-1200mm yr-1), we expect ecotypic variation in drought tolerance and local adaptation. Understanding ecotypic variation will help predict how a dominant prairie grass may respond to current and predicted future climate change. We investigated phenotypic variation, genetic diversity and transcriptional variation using reciprocal gardens across the Midwest gradient (wet to dry) in Carbondale, Illinois, Manhattan and Hays KS and a site in Colby, KS (to test tolerance in even drier areas). Three ecotypes (each comprised of seeds collected from populations in Central KS, Eastern KS, and Illinois) were reciprocally planted in seeded communities (with competitors). We measured phenotypic variation in drought tolerance across ecotypes and sites. Because genetic diversity may be critical for predicting a species’ ability to adjust to climate change, we assessed genetic diversity and population differentiation of 12 source populations used in the reciprocal gardens.
Results/Conclusions
A phenotypic cline in drought tolerance of ecotypes was observed with establishment and cover showing significant ecotype, site, and interaction effects. The Central KS ecotype had greater cover in Hays and Colby relative to Illinois and Eastern KS ecotypes, indicating local adaptation. Eleven ecotype-specific loci under diversifying selection were identified and related to climate. We used NGS to compare transcriptional variation of Central KS and Illinois ecotypes growing under abiotic stress in xeric Colby KS. The Illinois ecotype mounted a weaker transcriptional response, primarily consisting of genes involved in abiotic stress as an inducible, short-term stress strategy. In contrast, the Central KS ecotype shows a stronger, more varied transcriptional response that matched its higher photosynthetic rates, increased nitrogen metabolism, and competitiveness under drought. Our results provide insights about the extent to which a dominant prairie grass may respond to current and future climates, via plasticity or genetic adaptive variation and may also guide prairie restoration strategies.