Nursery seed origin and admixture alter traits but not performance responses to soil moisture extremes in Chamaecrista fasciculata

Abstract Introduction Climate change may complicate local restoration seed sourcing approaches (i.e. “local is best” strategies) by shifting target site environments farther away from historical conditions. Therefore, it may be increasingly difficult to select nursery‐sourced seeds from single or multiple suppliers without understanding potential phenotypic and performance responses to climate change. Objectives We explored how different strategies of seed sourcing for restoration (e.g. choice of seed origin, single‐source vs. mixed‐source) impacts plant traits and performance and their responses to soil moisture extremes, simulating the precipitation extremes (droughts and highly wet conditions) forecasted under climate change. Methods We assessed how eight nursery‐sourced “populations” of the annual legume Chamaecrista fasciculata differed in their responses to an experimental gradient of soil moisture extremes. We then considered how crossing source populations (i.e. to mimic intraspecific admixture) altered performance relative to plants from a single‐source population. Results We found that seed source and crossing (i.e. single‐ or mixed‐source) influenced plant phenotypes under different soil moisture conditions. Single‐source populations differed in specific leaf area, leaf dry matter content, and height responses to soil moisture availability, while cross‐populations varied in their flowering phenology between treatments. The geography and climate of the source population(s) explained some of these phenotypic differences. In contrast, performance responses to water availability were independent of population effects for both single‐ and mixed‐source plants. Conclusions Nursery seed sourcing approaches can impact plant traits and performance in restorations broadly, but particularly in the broader context of climate change.