Abstract
Plant response to climate depends on a species’ adaptive potential. To address this, we used reciprocal gardens to detect genetic and environmental plasticity effects on phenotypic variation and combined with genetic analyses. Four reciprocal garden sites were planted with three regional ecotypes of Andropogon gerardii, a dominant Great Plains prairie grass, using dry, mesic, and wet ecotypes originating from western KS to Illinois that span 500–1,200 mm rainfall/year. We aimed to answer: (a) What is the relative role of genetic constraints and phenotypic plasticity in controlling phenotypes? (b) When planted in the homesite, is there a trait syndrome for each ecotype? (c) How are genotypes and phenotypes structured by climate? and (d) What are implications of these results for response to climate change and use of ecotypes for restoration? Surprisingly, we did not detect consistent local adaptation. Rather, we detected co‐gradient variation primarily for most vegetative responses. All ecotypes were stunted in western KS. Eastward, the wet ecotype was increasingly robust relative to other ecotypes. In contrast, fitness showed evidence for local adaptation in wet and dry ecotypes with wet and mesic ecotypes producing little seed in western KS. Earlier flowering time in the dry ecotype suggests adaptation to end of season drought. Considering ecotype traits in homesite, the dry ecotype was characterized by reduced canopy area and diameter, short plants, and low vegetative biomass and putatively adapted to water limitation. The wet ecotype was robust, tall with high biomass, and wide leaves putatively adapted for the highly competitive, light‐limited Eastern Great Plains. Ecotype differentiation was supported by random forest classification and PCA. We detected genetic differentiation and outlier genes associated with primarily precipitation. We identified candidate gene GA1 for which allele frequency associated with plant height. Sourcing of climate adapted ecotypes should be considered for restoration.
Highlights
Plant response to current and changing climate depends on adaptive potential within species (Des Roches et al, 2017; Etterson, 2004; Hufford & Mazer, 2003; Nicotra et al, 2010; Shaw & Etterson, 2012)
We focus on phenotypic variation in ecotypes of big bluestem (Andropogon gerardii Vitman), a long-lived dominant perennial and clonal C4 grass (Weaver & Fitzpatrick, 1932; Epstein, Lauenroth, & Burke, 1997; Knapp, Briggs, Harnett, & Collins, 1998), in response to a precipitation gradient
(4) What are the implications for climate change and restoration? To answer these questions and test hypotheses, we present results of vegetative performance and fitness measurements of A. gerardii in reciprocal gardens and in their homesite garden
Summary
Plant response to current and changing climate depends on adaptive potential within species (Des Roches et al, 2017; Etterson, 2004; Hufford & Mazer, 2003; Nicotra et al, 2010; Shaw & Etterson, 2012). Environment refers to the different planting sites (S) Another possibility is that ecotype and site both exert separate and independent main effects on phenotype (S, E, i.e., no interaction, Figure 1c). Andropogon gerardii comprises up to 80% of biomass in tallgrass prairies (Knapp et al, 1998) and has wide natural distribution across the eastern United States (http://plants.usda.gov) This species is planted widely in the 3 million ha of Conservation Reserve grassland restoration throughout the Great Plains. Understanding natural variation in genetic versus phenotypic plasticity across the precipitation gradient of a dominant grassland species is timely in the face of climate change.
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