UBC Theses and Dissertations
Major features of macroevolution : how phylogenies vary across time, clades, and environmental gradients Henao Diaz, Luis Francisco
For centuries, biologists have been captivated by the vast disparity in species richness between different groups of organisms. Variation in diversity is widely attributed to differences between groups in how fast they speciate or go extinct, due to changes in their evolutionary history. Evolutionary dynamics operating across deep time leave footprints in the shapes of phylogenetic trees. For the last several decades, researchers have used increasingly large and robust phylogenies to study the evolutionary history of individual clades and to investigate the causes of the glaring disparities in diversity among groups. While typically not the focal point of individual clade-level studies, many researchers have remarked on recurrent patterns that have been observed across many different groups and at many different time scales. In this thesis, I explore the general patterns in macroevolution by using phylogenies to understand diversity changes through time, clades, and environmental gradients. In Chapter 2, I collate and analyze over 90 phylogenetic trees and fossil times-series to estimate diversification rates. With the intention of explaining variation in rates among a wide range of multicellular organisms I document that diversification rates inferred from phylogenies and fossils have a negative time-dependency. Expanding on this, in Chapter 3, I explore and describe other general patterns in phylogenetic trees from a macroevolutionary perspective. I try to recapitulate earlier findings on tree topologies with recently published megaphylogenies and expand the suite of patterns into a more comprehensive catalogue. Finally in Chapter 4, I investigate whether the time required to attain secondary sympatry after two lineages have diverged varies with elevation and other ecological and geographical predictors. This avenue of investigation is rooted in theoretical and empirical evidence that the time to secondary sympatry could be a major rate limiting step in the process of diversification. As such, understanding the drivers behind species coexistence sheds light on how elevational gradients are formed. Overall, my thesis expands our understanding of the patterns in the Tree of Life, and the evolutionary dynamics that take place along biogeographical gradients.
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