April 19 2019

2:00 pm LSB 2320

Ian McFadden
University of California, Los Angeles

Separating the Effects of Multiple Processes on Diversity Patterns in an Amazonian Tree Community and the New World Flora


Doctoral Dissertation Seminar

What controls diversity? The high diversity of many tropical taxa and the decline in diversity away from the Equator has inspired many theories and much debate. Unfortunately, the testing of these theories has been hampered by a lack of data and a limited ability to separate the effects of multiple processes on observed patterns. In this thesis, I use novel datasets and recent advances in functional, spatial and phylogenetic methods to parse the contributions of multiple processes shaping patterns of diversity at both local and macro scales.

At the local scale, I use spatial point process and null models to identify trait-based drivers of dispersal limitation and environmental filtering in a hyper-diverse tree community in the Ecuadorian Amazon. At the macro scale, I ask if a proximate cause of the latitudinal diversity gradient is a gradient in the turnover of assemblages or beta diversity. To test this hypothesis I map the taxonomic and phylogenetic beta diversity of the New World flora and identify key climatic drivers of turnover. The results of this thesis suggest multiple processes combine and interact to create diversity patterns at both local and macro scales.

Committee: Nathan Kraft (Advisor), Steven Hubbell, Lawren Sack, Matthew Fitzpatrick

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