PS 36-34 - Age-related changes in pitcher characteristics and prey capture of seasonal cohorts of Sarracenia alata

Wednesday, August 10, 2011
Exhibit Hall 3, Austin Convention Center
John D. Horner1, Julie Cross Steele2, Chris Underwood2 and Daniel Lingamfelter2, (1)Department of Biology, TCU, Fort Worth, TX, (2)Biology, TCU, Fort Worth, TX

The characteristics associated with prey attraction and capture in pitcher plants are not well understood.  Because of physiological constraints, pitcher characteristics should vary among seasonal cohorts of pitchers and with pitcher age.  We measured age-related changes in characteristics (funnel diameter, extrafloral nectar guides, and extrafloral nectar concentration) and in prey capture of early- and mid-season cohorts of Sarracenia alata pitchers. 


Pitchers achieved their mature height before opening, and pitchers of the mid-season cohort were smaller than those produced early in the growing season.  In both cohorts, extrafloral nectar concentration on the lip of the pitcher and the number of “secondary nectar guides” (an indication of hood coloration) were highest approximately three weeks after pitchers opened.   The rate of insect capture in both cohorts was highest approximately three weeks after pitchers opened, corresponding with the peak in nectar concentration and number of secondary nectar guides.  At the population level, the mass of insects captured was positively related to nectar concentration.  Prey capture per unit size per unit time was higher in the mid-season cohort even though nectar concentration was not significantly different between pitchers of similar physiological age in the two cohorts. The results of this study show that characteristics of pitchers and their effect on prey capture vary between seasonal cohorts and with pitcher age.  Nectar concentration appears to be an important attractant, and foraging insects may be attracted by nectar, coloration, or most likely by some combination of these and other characteristics.  The physiological constraints and evolutionary pressures leading to these differences require additional study.

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