PS 39-69 - Effects of population size on the survival and reproduction of a rare carnivorous plant (Drosera rotundifolia)

Abstract: Forty percent of the world’s flowering plants are categorized as rare and of conservation priority. Carnivorous plants in particular are threatened and sensitive to environmental changes and hence can play a key ecological role in ecosystems, however, remain largely understudied. Drosera rotundifolia is classified as rare throughout North America, particularly in Southern Appalachia with only four known populations in Tennessee. Surprisingly, information on this species’ life history, survival and reproductive strategies is lacking, which limits conservation action. This project aims to fill these knowledge gaps by evaluating spatial variation, and in particular the effect of population size, in determining D. rotundifolia’s survival and reproductive strategies. This information is urgently needed to aid in the preservation of this species. I evaluated variation in germination rate, plant size, prey capture rate, flowering phenology, and mating strategies of D. rotundifolia across eight populations in Southern Appalachia and how this may be affected by population size and elevation. We recorded flower production, prey capture per individual, and plant size for all individuals in up to12 plots per population. We evaluated the degree of selfing, outcrossing and autonomous self-pollination for each population under greenhouse conditions.

Approximately 3050 individual plants were observed across all sites with an average size of 26.29 mm ± 9.71mm but with large differences across populations (6.2 mm – 45.84 mm). Average daily prey capture rate was 9.88 insects across all populations but range between 0 insects – 90 insects observed per visit. Elevation seems to have no effect on flowering phenology (time of peak flowering). We found a significant effect of population size on prey capture rate, but it did not affect peak flowering or plant size. Plant size did not affect prey capture rate. Evaluation of reproductive strategies is ongoing. It has been shown that population size plays a key role in mediating reproductive success and genetic diversity within plant populations. Our results however suggest that population size may also play a key role in nutrient acquisition in Carnivorous species, which is key for their survival. Population size and elevation however did not affect flowering phenology or plant size. Larger plants were also no more successful at obtaining prey compared to smaller plants suggesting other important mechanisms are at play. Our results, although preliminary, can have important practical applications for conservation and management efforts in this species.