UC Santa Cruz

Floral volatiles are often used by plants to attract the subset of floral visitors that are mostly likely to contribute to pollination. Consequently, the composition and complexity of floral scents differ greatly among plant species. Recent studies of woodland stars, Lithophragma (Saxifragaceae), have found that species in this genus often have scents composed of an unusually large number of compounds, and even populations of the same species can differ extremely in the composition of scents. Here, I assess how the composition and complexity of floral scents change when closely related species of woodland stars hybridize. I evaluated floral scent in experimentally produced hybrids between two sister taxa, L. parviflorum and L. affine. Most F1 and F2 hybrids produced scents that were intermediate mixtures of the two parental species, but the scents of hybrids were often novel in the relative proportions of compounds they produced. Moreover, some hybrids produced scents with either fewer or more compounds than found in any parental individual. Alteration of the mix and complexity of monoterpenes contributed greatly to the variation among hybrid individuals, but most individuals produced scents composed of compounds arising from at least several biochemical pathways. Hence, the chemical profiles of these hybrids suggest the possibility of transgressive segregation of this complex floral trait. These results suggest that natural hybridization in woodland stars would produce novel scent combination that could alter the interactions with their coevolved Greya moth pollinators and other visiting insects. Because the distributions of many plant species are rapidly changing, altered interactions with pollinators through novel scent combinations in hybrids could become common in many species-rich taxa capable of hybridization.