Microbial Communities Hosted By Carnivorous Pitcher Plants: Diversity, Recruitment, Functions and Succession in Sarracenia Purpurea Microbiomes

Abstract

The pitcher plant Sarracenia purpurea supplements nutrient acquisition through carnivory, capturing insect prey which are digested by a food web community of eukaryotes and bacteria. Analysis of both bacterial and eukaryotic diversity, and an understanding of bacterial recruitment into pitchers and succession of bacterial and eukaryotic communities over time have not been well explored. This thesis presents three studies designed to address these gaps using field sampling and manipulative greenhouse experiments. Study I compared bacterial and eukaryotic composition and diversity of pitcher communities within and between populations of plants in two distinct wetland habitats. Genetic sequence analysis revealed an underappreciated eukaryotic diversity of ciliates, mites, and fungi. Significant differences in bacterial composition were observed between the two populations which experience differences in habitat and eukaryotic visitation. Study II examined sources of bacteria for recruitment, how the host plant affects microbial community development, and contrasts between established and assembling communities. An important source of bacterial input was air, contributing many dominant taxa. Distinct communities in artificial pitchers confirmed an important influence of host plant tissue on community development, possibly mediated via nutrients. Established communities with higher initial diversity showed more stability over time. Community functions were examined as hydrolytic enzyme activities showed that insect prey additions result in rapid nutrient transformation. Study III examined succession of the eukaryotic and bacterial community in field pitchers from opening until senescence. Bacterial diversity in