UC Santa Barbara

The main objective of this study was to identify traits involved in serpentine adaptation in Aquilegia eximia and to test whether serpentine tolerance has a simple genetic basis in this species. I assessed seedling survival and growth and measured trichome type frequencies of hybrid crosses between A. eximia (serpentine specialist) and Aquilegia formosa (soil generalist, and presumed progenitor of A. eximia) on field collected serpentine and non-serpentine soil. Seedling growth experiments revealed that A. eximia has smaller seeds, smaller seedlings at germination, as well as reduced total seedling biomass after 4 weeks of growth compared to A. formosa in nutrient rich non-serpentine soil. Chi2 tests compared frequencies of seedling survival and growth phenotypes of parent species, F1 and F2 reciprocal cross types on serpentine and non-serpentine soil to test whether any traits follow expected Mendelian ratios for a single locus trait. Serpentine tolerance appears to have a generally dominant inheritance pattern for seedling survival and growth in the F1 and F2 hybrid crosses. Phenotypic frequencies of seedling survival and seedling growth rate on serpentine soil, as well as trichome type appear to segregate in Mendelian ratios in the hybrid mapping populations, suggesting a potentially simple genetic basis for these traits. In contrast, total biomass at harvest of seedlings grown on serpentine soil does not follow expected Mendelian ratios in the hybrid mapping populations, and therefore appears to be a more complex polygenic trait.