THE ROLE OF CARNIVORY IN THE GROWTH AND REPRODUCTION OF DROSERA-FILIFORMIS AND D-ROTUNDIFOLIA

A greenhouse experiment determined the effects of differential feeding treatments on the growth and reproduction of two North American species of sundew, Drosera filiformis Raf. and D. rotundifolia L. Plants were fed 0, 5, 10, or 20 fruit flies (Drosophila melanogaster) per week for 7 or 8 weeks during the growing season. For both species feeding enhanced growth during the feeding period. In the growing season following the feeding treatments, D. rotundifolia showed carryover of the effect of feeding treatment on growth; D. filiformis did not. Effects of feeding were more pronounced for reproduction than for growth. Plants that had been fed 10 or 20 flies per week produced more flower stalks than unfed plants. Feeding also increased the number of flowers and reproductive dry weight. Effects of feeding treatment on percent reproductive effort were not significant, perhaps because of high variability and limited sample size. Carnivory is of immediate benefit in low-nutrient environments and can also have longer term effects on both growth and reproduction. Controlled experimental feeding may be applied to future questions of carnivorous plant performance under interspecific competition.