Commensalism or competition: how are the larval inhabitats found in Sarracenia purpurea pitcher leaves interacting?

Abstract

The composition and abundance of species in a community can be largely affected by both interspecific and intraspecific interactions. Three dipteran species, Wyeomyia smithii (Culicidae), Metriocnemus knabi (Chironomidae), and Blaesoxipha fletcheri (Sarcophagidae), inhabit the pitcher fluid of the purple pitcher plant, Sarracenia purpurea. These larvae constitute a simplified community that can elucidae interactions among and between trophic levels. The frequency and density of these three species along with the types of associations that occur amongst them were surveyed in a natural population in Emmet County, MI. Wyeomyia smithii was found to be the most prevalent of the three species sampled (63%). Many different associations between the three species were found living in the pitcher plant leaves, with the association between Metriocnemus knabi and Wyeomyia smithii the most common of those sampled (36%) frequency. When Metriocnemus knabi and Wyeomyia smithii occurred together, decreased size of Metriocnemus knabi seemed to give the implication that interspecific competition may be taking place. Intraspecific competition amongst individuals of Wyeomyia smithii seemed to exist as well. Reducing the level of competition may be a driving force in the life strategies of these organisms.