DISSERTATION RESEARCH: Exploring convergence within pitcher plant microcosms

Harvard University, Cambridge MA

Investigators

Abstract

Understanding the factors driving community formation within a host or habitat has implications for global climate change, human health, and microbial ecology. As host species shift location, can other symbionts substitute for those from the original habitat? Pitcher plants have modified leaves that collect water and microbes, and trap insects that are digested for nutrients. These pitchers can be thought of as plant analogs to the human gut, and studying how their microbial communities form, interact with each other, and assist with host digestion could inform our understanding of our own gut inhabitants. The project will involve training opportunities for American and Malaysian students, and will foster cooperation and networking with scientists in Malaysian Borneo. The researchers will work collaboratively to create educational exhibits for the Malaysian research center, and the complex ecology of pitcher plants will be shared with children and adults through a Harvard Museum of Natural History family program. Convergence of form and function is common in all domains of life, because similar selective forces in geographically distant locations shape evolutionary change. Pitchers of carnivorous plants are exquisite examples of convergent evolution: pitcher plant morphology and function has evolved separately in three distant plant lineages in different biogeographic regions. This study investigates whether the organisms associated with pitchers show similar patterns of convergence in the nature of their ecological interactions. It will compare community pattern and function across four different kingdoms, within convergent hosts. With two genera of pitcher plants, Sarracenia in North America and Nepenthes in Southeast Asia, the microbial community composition across different pitcher plant species and collecting sites will be determined by DNA sequencing of the fungal, bacterial, and protist inhabitants. The ability of pitcher plant insects and microbes to colonize a convergently evolved host will be investigated by placing Nepenthes plants in a Sarracenia habitat, along with artificial controls, to see if and how insects and microbes colonize unfamiliar hosts. A laboratory experiment will compare native and convergently evolved microbial communities in facilitating the nutrient-limited pitcher plants in nitrogen uptake from prey. Finally, to determine if community patterns of inhabitants are similar across convergent hosts the similarity of taxa, community patterns, and factors structuring communities in Sarracenia and Nepenthes insect and microbial associates will be tested using metagenomic analyses to examine community functional capacity within convergent pitcher plant hosts by statistical and phylogenetic analyses, and with null models.