Doctor of Philosophy (PhD)
The factors that influence how species form is of fundamental interest to biology. Under the framework of the speciation cycle, the process begins by population subdivision creating structured populations that then diverge until two new species form. Following speciation, however, continued divergence is necessary for these new species to be able to coexist without adverse interactions, known as the transition to secondary sympatry. At this point the speciation cycle is complete and the process can begin anew. Many of the factors influencing these processes remain poorly understood. Here, I explore the factors that influence speciation and community assembly in Neotropical birds, at three stages of the speciation cycle. First, I use genome-wide molecular data to estimate relationships between species and populations in a poorly known genus of Neotropical birds, the Epinecrophylla antwrens (Aves: Thamnophilidae). I uncovered novel phylogenetic relationships and proposed a revised taxonomic treatment for the group. Next, I use comprehensive population sampling and genome-wide molecular markers to ask whether habitat association predicts population genetic structure, a proxy for dispersal ability, across 66 species. I found strong support for this relationship, and showed that habitat association, especially proximity to dynamic riverine environments, decreases population genetic structure. Finally, I compiled and analyzed species-level genetic, distributional, and morphological data from over a thousand bird species to ask how long it takes for the transition to secondary sympatry to occur, and which traits mediate that process. I found that secondary sympatry following speciation is extremely protracted and is influenced by many morphological traits depending on the scale of sympatry and avian family.
Johnson, Oscar, "Genetic Structuring and Community Assembly in Neotropical Birds" (2021). LSU Doctoral Dissertations. 5677.
Brumfield, Robb T.