Phenotype and QTL mapping data from: Genetic trade-offs underlie divergent life history strategies for local adaptation in white clover

Local adaptation is common in plants, yet characterization of its
underlying genetic basis is rare in herbaceous perennials. Moreover, while
many plant species exhibit intraspecific chemical defense polymorphisms,
their importance for local adaptation remains poorly understood. We
examined the genetic architecture of local adaptation in a perennial,
obligately outcrossing herbaceous legume, white clover (Trifolium
repens). This widespread species displays a well-studied chemical
defense polymorphism for cyanogenesis (HCN release following tissue
damage) and has evolved climate-associated cyanogenesis clines throughout
its range. Two biparental F2 mapping populations, derived from
three parents collected in environments spanning the U.S. latitudinal
species range (Duluth, MN, St. Louis, MO, and Gainesville, FL), were grown
in triplicate for two years in reciprocal common garden experiments in the
parental environments (6,012 total plants). Vegetative growth and
reproductive fitness traits displayed trade-offs across reciprocal
environments, indicating local adaptation. Genetic mapping of fitness
traits revealed a genetic architecture characterized by allelic trade-offs
between environments, with 100% and 80% of fitness QTL in the two mapping
populations showing significant QTL X E interactions, consistent with
antagonistic pleiotropy. Across the genome, there were three hotspots of
QTL co-localization. Unexpectedly, we found little evidence that the
cyanogenesis polymorphism contributes to local adaptation. Instead,
divergent life history strategies in reciprocal environments were major
fitness determinants: selection favored early investment in flowering at
the cost of multi-year survival in the southernmost site vs. delayed
flowering and multi-year persistence in the northern environments. Our
findings demonstrate that multi-locus genetic tradeoffs contribute to
contrasting life history characteristics that allow for local adaptation
in this outcrossing herbaceous perennial.