Date of Award

December 2021

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Department

Biological Sciences

First Advisor

Erica B Young

Committee Members

John A Berges, Charles F Wimpee, Filipe A Alberto, Gyaneshwar Prasad

Keywords

Bioinformatics, Carnivorous plant, Ecology, Eukaryotes, Microbes, Sarracenia

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 <40 mL pitchers was shown to rival that of larger aquatic communities (such as Lake Michigan). In field succession pitchers, eukaryotic composition was often dominated by a few eukaryotic taxa which had greater variation among replicate pitchers than bacterial composition which showed greater richness over time. Succession showed clear early and late stages for microbial composition and functions. Within 14-28 days early succession showed high compositional and functional changes and after day 28, communities were more stable. These studies broadly suggest that early stochastic bacterial recruitment, prey capture and colonization by eukaryotes drives microbial food web composition over the 1-2 year lifespan of a pitcher.

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