Lambrecht, Susan .
Floral and physiological trait correlations differ among populations of Leptosiphon (Polemoniaceae) with contrasting moisture availability.
INTRASPECIFIC floral variation arises from multiple, interacting biotic and abiotic factors. My objective was to investigate how environment may contribute to that variation by examining floral traits in relation to leaf traits and moisture availability for two closely-related species of Leptosiphon. Both species (L. bicolor and L. androsaceous) were sampled in multiple populations across a naturally occurring precipitation gradient in California. These Leptosiphon are insect-pollinated, but may also autogamously self-fertilize. Measured traits included parameters of floral size (such as petal lobe width, corolla diameter, floral tube length), leaf size (leaf length, leaf lobe number, leaf area), plant size (leaf number, flower number, height), and leaf physiology (water-use efficiency or WUE, inferred from δ13C). Soil moisture and microclimate were also measured in each population. Flowers were larger for both species at sites with greater soil moisture (0.0001 < P < 0.002). However, length of the floral tube, which relates to pollinator tongue length, was similar across the sites (0.35 < P < 0.61). The differences in floral traits observed with moisture were independent of plant and leaf size (-0.08 < r < 0.50). Floral traits were, however, related to leaf physiology. For both species, floral size was positively correlated with δ13C in populations with low moisture availability (r > 0.65, P < 0.01). That is, plants with larger flowers had greater WUE. But, floral size was independent of δ13C in populations with high moisture availability (r < 0.32). Overall, variation in δ13C was more strongly related to floral size than to moisture availability. These results demonstrate a relationship between floral and physiological traits that is modified by environment. Therefore, floral size may vary with moisture due to functional relationships with other plant traits. Ongoing studies are examining the heritability of and causal relationships among these trait correlations.
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1 - San Jose State University, Department of Biological Sciences, San Jose, California, 95192-0100, USA
Presentation Type: Oral Paper:Papers for Sections
Date: Wednesday, August 2nd, 2006
Time: 10:15 AM