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ARS Home » Plains Area » Temple, Texas » Grassland Soil and Water Research Laboratory » Research » Publications at this Location » Publication #314527
Title: Intraspecific variation in precipitation responses of a widespread C4 grass depends on site water limitation

Author
item ASPINWALL, MICHAEL - Western Sydney University
item Fay, Philip
item HAWKES, CHRISTINE - University Of Texas
item LOWRY, DAVID - Michigan State University
item KHASANOVA, ALBINA - University Of Texas
item BONNETTE, JASON - University Of Texas
item WHITAKER, BRIANA - University Of Texas
item JOHNSON, NICHOLAS - University Of Texas
item JUENGER, THOMAS - University Of Texas

Submitted to: Journal of Plant Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/23/2016
Publication Date: 6/13/2016
Publication URL: https://handle.nal.usda.gov/10113/5695365
Citation: Aspinwall, M.J., Fay, P.A., Hawkes, C.V., Lowry, D.B., Khasanova, A., Bonnette, J., Whitaker, B.K., Johnson, N., Juenger, T.E. 2016. Intraspecific variation in precipitation responses of a widespread C4 grass depends on site water limitation. Journal Of Plant Ecology. 10(2):310-321. doi:10.1093/jpe/rtw040.

Interpretive Summary: Switchgrass is a native warm-season grass found throughout much of the continental U.S. and highly promising as source of bioenergy. Switchgrass occurs in two main genetic forms and also occurs in distinct genotypes within each of these forms. These genotypes differ in drought tolerance, but there have been few rigorous experimental demonstrations of drought tolerance in switchgrass genotypes from different geographic origins. We planted over 900 plants of 10 genotypes from the two genetic forms of switchgrass on deep and shallow soils and watered them in amounts spanning the driest to the wettest years in central Texas. Both genetic forms experienced similar decreases in biomass production in the driest treatment, but one of the forms gained twice as much as the other form when rainfall was abundant, suggesting that plants of this form may be better adapted to prosper when wet years occur.

Technical Abstract: 1. Changes in precipitation expected with climate change have important implications for plant growth and fitness, as well as species genetic diversity and ecological distributions. Intraspecific variation in phenotypic plasticity – the ability of a genotype to alter its phenotype in response to environmental change, could influence how species respond to changes in precipitation. Despite this, little is known about the pattern and magnitude of variation in plasticity to variable precipitation, and whether genotype responses to precipitation change across contrasting local environments. 2. Here, we exposed five tetraploid and four octoploid Panicum virgatum genotypes representing diverse climatic origins to six precipitation treatments at two sites varying in water limitation. We measured flowering time, aboveground net primary productivity (ANPP), tiller production, and leaf area index (LAI), and hypothesized that tetraploid genotypes would be more responsive to precipitation than octoploid genotypes, and across ploidy types, that phenotypic plasticity of genotypes will correlate with their climate of origin. 3. At the less water-limited site tetraploids showed higher ANPP and growth (e.g., tiller mass) plasticity than octoploids, and across ploidy types, genotypes showed substantial variation in ANPP and growth plasticity. At the more water-limited site, ploidy type and genotype variation in growth plasticity was limited. Across both ploidy levels, genotypes from relatively cool, moist environments were more responsive to changes in precipitation. 4. We propose that ploidy type differences in growth responses to precipitation are related to ecotypic differentiation, and across ploidy levels, genotype growth plasticity is associated with climatic adaptation. However, importantly, our results demonstrate that the expression of genetic variation in growth responses to precipitation may be constrained when water limitation is severe. 5. Our results highlight the complexity of genotype responses to climate change across variable local environments, and the need to integrate such complexity into predictions of populations and species responses to climate change.