Date of Award

Fall 10-1-2021

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Ecology and Evolutionary Biology

First Advisor

Edwards, Erika

Abstract

Plants exhibit extensive variation in leaf form, but the evolutionary drivers of this variation are not well understood. This dissertation leverages the wide diversity of leaf form and instances of leaf syndrome convergence in Viburnum to investigate trends in leaf trait evolution across the group. First, I explore how changes in chromosome number and genome size influence leaf characters of ecophysiological importance. It appears that even with extensive variation in chromosome number and genome size across Viburnum, nucleotypic changes largely do not constrain leaf traits related to ecophysiological function. I then look into a case of convergent evolution for leaf syndromes in a radiation of Central and South American cloud forest species. First, I studied whether or not different species with the same leaf syndromes occupied similar climatic niches and found that though all leaf syndromes occupied largely overlapping climatic zones, some leaf syndromes do seem to sort by a couple select climate variables. I then uncover hybridization between two Mexican species with different leaf syndromes and use this underlying genetic diversity to identify genetic markers associated with leaf trait differences. I find that some leaf traits are associated with many genomic regions while others are associated with only a few and that some significant regions are associated with multiple traits. Overall, there are many factors, from genetic to environmental, shaping the evolution of leaf form in Viburnum.

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