Abstract
This dissertation marries two aspects of biogeography at numerous temporal scales. The first two chapters explore the evolution and geographic distributions of fire adaptations. The 3rd and 4th explore the phylogeographic history of a maritime alpine disjunct conifer and three coastal disjunct rainforest understory plant species. Briefly, in the first chapter, we used a variety of phylogenetic comparative methods and diversification analyses to determine when and how many times fire adaptations evolved in conifers, if there were any climates particularly associated with fire adaptations, and if possession of fire adaptations were associated with increased diversification rates in conifer clades. We found multiple convergent evolutionary events for fire adaptations across the phylogeny. Also, fire traits were associated with climates experiencing a marked dry period, with Mediterranean-type climates being particularly correlated. However, with the possible exception of the Pinus subsections Australes and Ponderosae, we do not see evidence for fire-associated increased diversification rates in conifers. In Chapter 2 we looked at fire related community phylogeographic processes behind adaptations as well the geographic distribution of fire traits in North America. We found that metrics of species richness along with measures of phylogenetic overdispersion and clustering were latitudinally stratified. We also see that fire adaptations and fire regimes themselves are latitudinally stratified, with traits like resprouting and the seedling grass stage occurring only in more southern conifer communities. Chapter 3 and 4 explore the phylogeographic history of Larix lyallii (Chapter 3) and the coastal disjunct species Lysichiton americanus, Oplopanax horridus, and Asarum caudatum (Chapter 4). In short, we find that the population structure of Larix lyalllii is very old with breaks between major clades dating back over 1 million years. For the three coastal disjunct species we see similar topologies in all three species. All three appear to have migrated north through the Cascade Mountains and British Columbia Coast, with two dispersal / separation events into the interior. However, the timing of major population divergences differ by millions of years when comparing the three species. We see support for populations surviving in the interior rainforest during glaciation in Lysichition americanus and Oplopanax horridus, with a strictly recent dispersal history in Asarum caudatum.