The role of predispersal seed predators and their parasitoids for Ruellia humilis reproduction

Abstract

Plant reproductive success is greatly affected by predispersal seed predators and their parasitoids. Ruellia humilis is an herbaceous plant with a dimorphic flowering system in which individual plants can produce both open showy flowers (chasmogamous, CH) and closed flowers (cleistogamous, CL) that can only self-fertilize.  The objectives of this study were to (1) determine the extent of among population variation in R. humilis-seed predator-parasitoid interactions and (2) determine whether seed predation and parasitoid rates vary between CL and CH fruits of R. humilis.  We found considerable among population variation in seed predation and parasitism rate.  Additionally, we found that the seed predator, Tripudia rectangula, preferentially attacked CH fruits.  In contrast, the wasp parasitoids of the seed predator preferentially attacked seed predators in CL fruits.  Our findings indicate that while parasitoids have been found to influence seed predation rates by the seed predator, the parasitoids themselves do not drastically affect the reproductive success of R. humilis. Given the preference of the seed predators for CH fruits, this ecological interaction may be a potent selective force for reproductive traits of R. humilis.