DISSERTATION RESEARCH: A next-generation sequencing framework for understanding trait evolution across multiple scales in the Viburnum lentago clade

Yale University, New Haven CT

Investigators

Abstract

Many plant species are extremely variable. Even within a population, plants of the same species can differ from one another in characteristics such as leaf shape or flower color. However, almost all broad-scale studies of trait evolution ignore such variation within species and instead assign a single value to each species. Partially for this we know little about how variation within species relates to evolutionary differentiation over longer timescales. This project focuses on six closely related species of shrubs that are native to the Eastern United States. The goal is to quantify different types of variation within species and to relate the observed patterns to how these species evolved over the past 5-20 million years. Special emphasis will be placed on describing variation in a set of leaf characteristics (size, shape, leaf margins) within individual plants, within populations, across populations spanning a latitudinal gradient in growing conditions, and across species. These data will allow a better prediction of which traits are most likely to evolve and how plant species might respond to future climate change. This project uses a new next-generation molecular method to generate phylogenetic and phylogeographic data for the Lentago lineage within the flowering plant clade Viburnum. RAD (Restriction site Associated DNA) markers will be sequenced for over 30 individuals per species to create a high-resolution phylogeny that spans across levels of divergence, linking populations that diverged only several hundred years ago to speciation events in the Miocene. This phylogenetic framework will resolve species relationships, determine the extent of hybridization within the clade, and enable the researchers to reconstruct the phylogeographic (population-level) history of each species. The resulting detailed understanding of common ancestry and migration history will provide new insight into how adaptation and gene flow generate and maintain trait variation within and among species. The project will improve understanding of the genesis of variation in morphological traits, of how types of variation translate across levels of organization, and of the emergence of the traits that mark deeper branches in the tree of life.