Functional Traits in an Evolutionary Radiation: The Role of the Environment in the Diversification of Protea (L.)

Evolutionary radiations are responsible for much of the diversity on Earth, but the mechanisms leading to rapid lineage diversification and expansive morphological diversity are not always clear. Diversification may be the result of neutral processes, such as drift, or adaptive processes like adaptation to the abiotic or biotic environment. Flowering plants represent an extreme example of a radiation, and radiations at the tips of the angiosperm phylogeny are ideal places to examine the evolutionary relationships between plant traits and environmental factors. These relationships help us to understand the role of abiotic factors in driving the evolution of plant form. This dissertation uses the radiation of the flowering shrub genus Protea, a diverse group predominantly found in the Cape Floristic Region of South Africa, a biodiversity hotspot, to examine the relationships between functional traits (those with presumed consequences for survival) and the environments in which traits are found across different scales. Chapter 1 uses field-collected plant traits and databased climatic variables to compare trait-environment relationships between Protea and a parallel radiation in the genus Pelargonium. In these two distinct lineages, there is support for some associations in the same direction, while there is evidence for conflict in others. Chapter 2 provides a new phylogeny for Protea using a targeted-capture approach to sequence almost 500 nuclear genes. Species-level relationships are well-resolved, with differences between input gene trees and resultant species trees mostly due to a lack of information associated with short branch lengths. Chapter 3 uses the phylogeny from Chapter 2 to examine the joint evolutionary history of traits and environments in Protea, and finds that most associations are consistent across contemporary and evolutionary scales, with no strong evidence for either in situ adaptation or environmental filtering driving current patterns. Chapter 4 provides evidence for trait-environment relationships at the microgeographic scale in two closely-related species of Protea and tests these patterns in a controlled greenhouse experiment on seedlings. Although there are detectable relationships at the microgeographic scale, they are not found in the greenhouse, implying that plasticity may be driving associations at the micro-scale