Large-scale restoration is occurring in many areas of the western United States and the use of genetically appropriate native plant seed is expected to increase the success of restoration efforts. Thus, determining intraspecific variation among populations and its driving forces are the first steps in successful seed sourcing. Here, we examine intraspecific variation of characters expressed in early life history stages of Cleome lutea var. lutea, an annual forb native to the western United States that has attracted increasing attention as a restoration species because it provisions diverse pollinators. We conducted a common garden experiment comprised of 9 populations sourced from across the Intermountain West in a climate-controlled growth chamber. We measured 10 life history and morphological traits and found significant among-population differences for 9 of them, including seed germination requirements and flowering status. With the exception of seed germination, this variation was not effectively captured by broad ecoregion delineations, nor was it significantly explained by source site climatic differences or geographic distance between sites. However, flowering status was significantly explained by latitude of the source population (P = 0.033), suggesting that among-population variation reflects divergent adaptation to photoperiod. The variation in life history traits that differentiates our study populations indicates that informed seed sourcing will be necessary when using C. lutea var. lutea for restoration. More comprehensive spatial sampling that stratifies both environmental and geographic variates is needed to determine the drivers of population differentiation and the scale of local adaptation in this species. Such sampling can be used to better inform appropriate seed sourcing decisions. Until then, a cautious approach to sourcing this species for use in restoration is indicated.
ASJC Scopus subject areas
- Ecology, Evolution, Behavior and Systematics