Chess, Sally K. R. , Raguso, Robert A. , LeBuhn, Gretchen .
Evidence for pollinator mediated selection in Linanthus dichotomus.
Linanthus dichotomus (Polemoniaceae) contains two subspecies that are taxonomically distinguished solely by the time of day that they flower. Linanthus dichotomus meridianus is the only taxon in Linanthus sect. Linanthus that blooms diurnally; it is restricted to a subset of counties in northern California. In contrast, Linanthus dichotomus dichotomus is night-blooming and is found throughout central and southern California, Arizona, and Nevada. Difference in flowering time between the two subspecies is accompanied by differences in suites of insects visiting them. We documented only moths visiting L. dichotomus dichotomus but bees, flies, butterflies, and moths all visited L. dichotomus meridianus. Depending upon the frequency and efficiency of pollination, diurnal pollinators could affect selective pressure on reproductive traits (e.g., scent and morphology) in L. dichotomus meridianus. We grew wild seed from five different populations of each subspecies in a common garden, and we collected floral scent from intact flowers of potted plants using dynamic headspace analysis. We separated chemicals using GC-MS to determine floral scent composition. The monoterpene trans-B-ocimene and benzenoids such as benzaldehyde, phenylacetaldehyde, methyl salicylate, and methyl benzoate are dominant chemicals in both subspecies. Preliminary data indicate that scent emission rates produced by L. dichotomus meridianus are lower than rates of L. dichotomus dichotomus. A discriminant function analysis distinguishes the two subspecies based on seven reproductive morphological traits.
1 - San Francisco State University, Department of Biology, 1600 Holloway Ave., San Francisco, California, 94132, USA
2 - University of South Carolina, Department of Biological Sciences, Coker Life Sciences Building, 700 Sumter St., Columbia, South Carolina, 29208, USA
Presentation Type: Paper
Location: Wasatch (Cliff Lodge)
Date: Monday, August 2nd, 2004
Time: 3:00 PM