GEOGRAPHIC DIVERGENCE IN FLORAL MORPHOLOGY AND SCENT IN LINANTHUS DICHOTOMUS (POLEMONIACEAE)

Floral reproductive morphology and scent are of primary importance to pollinators in guiding foraging decisions. We compared the floral scent and reproductive morphology between two subspecies of Linathus dichotomus (Polemoniaceae) that are taxonomically distinguished by geography and flowering time: the vespertine L. dichotmus subsp. dichotomus and diurnal L. dichotomus subsp. meridannus. Disparity in flowering time between the two subspecies is accompained by differences in flower visitors. We collected floral volatiles using dynamic headspace methods analyzed them using gas chromatography and mass spectroscopy. Together, the subspecies produced a total of 39 floral scent compounds. Subspecies differ in the quantiative pattern of volatiles that attract noctuid month (e.g., lilac aldchydes) vs. a more general suite of visitors (e.g., phenylacctaldehyde), but not in overall scent emission rates. A discriminat function analysis correctly distinguished between the two subspecies based on scent sample 86% of the time. We measured seven reproductive morphological traits: a discriminant function analysis distinguished between the two subspecies based on morphological samples 81% of the time. We found significant differences between subspecies in scent but not individual morphological traits. The evidence presented here is most consistent with a hypothesis of pollinator-mediated selection.