Diversification describes how a single ancestral lineage gives rise to multiple descendant species that differ in morphology, behavior, and ecology. In my work, this process is studied at the intersection of ecological filtering, macroevolutionary dynamics, and statistical model behavior.
The Intersection of Macroecology and Macroevolution
Global paleobotanical and palynological records indicate that the K-Pg Chicxulub impact triggered widespread forest collapse. In Field et al. 2018, Current Biology, we proposed that this ecological disruption filtered against strongly arboreal lineages, producing a predominantly non-arboreal post-extinction fauna. Under this framework, Mesozoic adaptation to arboreality predicts macroecological patterns of Cenozoic diversification.
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My first paper on this topic focused on ecological filtering in Mesozoic arboreal birds; cover art was prepared by paleoartist Phillip Krzeminski.
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Comparative Extensions
We later evaluated the same hypothesis in mammals and found similar, though more ambiguous, patterns. As part of that study, I developed tools for analyzing ancestral-state transitions from stochastic character maps.
I am currently extending these questions to Cenozoic diversification in frogs.
Modeling Diversification Through Simulation
Statistical models of speciation and extinction have transformed macroevolutionary inference, but model assumptions can also drive misleading conclusions. In ongoing work, I use simulations to test when diversification models may infer predetermined outcomes under biologically unrealistic scenarios, particularly when time-heterogeneous molecular evolution is ignored. These analyses indicate that some broad global patterns reported across taxa may be methodological artifacts.