Investment in Carnivory in Drosera capillaris: Effects of Varying Light Levels on Trichome Density

Abstract

In this study I examined Drosera capillaris, which is a plant common in the southeastern Gulf Coastal Plain’s pitcher plant bogs. Investment in carnivory has been examined in other groups of carnivorous plants but very little investigation has been done in members of the genus Drosera. I considered trichome density as a potential indicator of investment in carnivory in Drosera capillaris. Since it can be assumed that reducing light reduces photosynthesis and subsequently can reduce the benefits gained from carnivory, I observed the effects of varying light levels on these plants. Two non-field experiments were conducted. In one, plants were placed in a greenhouse to determine the effects of varying light levels on trichome number and trichome density in a controlled setting. Results for this experiment were not conclusive, most likely due to a combination of small sample size and high plant mortality. In a second non-field experiment conducted in the lab, I examined rates of prey escape in Drosera capillaris to determine if reducing trichome density affected the plants’ ability to retain prey. Prey escape trials using Drosophila sp. did not show a statistically significant trend toward higher prey escape rates for plants with reduced numbers of trichomes. The lack of significant results were most likely due to small sample size as well as the fact that Drosophila sp. are larger than prey normally captured by Drosera capillaris. In the field, I clipped surrounding vegetation and created plots in which light levels were greater to determine the effects of light level on trichome number and trichome density. In 2009 in TNC and Big Bog and in Lottie Bog in 2010, I found that increasing the amount of available light did not lead to a significant increase in trichome density. However, data collected from Lottie Bog in 2009 showed a significant increase in trichome density in plants which had more available light. By changing the amount of light available to some plants within a population, I have been able to demonstrate that Drosera capillaris can respond to changes in the environment within a given season and population through alteration of investment in carnivory as measured by trichome density.