macroevolution & comparative biology

Macroevolution asks how and why biodiversity changes across geological time, through origination, extinction, and morphological evolution of lineages. The Swain Lab approaches these questions using a combination of fossil data, phylogenetic comparative methods, and Bayesian rate estimation, asking what drives variation in diversification rates and morphological disparity across the tree of life. A unifying interest across these projects is in how ecological opportunity, diversity dependence, and environmental change interact to shape the long-term trajectories of lineages, and whether the patterns we observe in the fossil record reflect general macroevolutionary principles or the contingencies of particular evolutionary histories.

Much of our published work has focused on insect and plant diversification. A central finding has been that the drivers of herbivore diversity are more complex than previously appreciated, decoupled across ecological and evolutionary timescales in ways that challenge simple narratives of plant-driven insect radiation. The discovery of an exceptionally diverse Early Pennsylvanian ecosystem, preserved in a Lagerstätte with remarkable fidelity, has expanded our understanding of early insect ecological diversification. Work on ant diversification has shown that diversity-dependent effects likely played an important role in shaping the trajectories of species-rich crown subfamilies across the Cenozoic, suggesting that ecological limits on diversity are a general feature of macroevolutionary dynamics rather than an exception. Work on avian morphological evolution has demonstrated that niche pre-emption — the prior occupation of morphological space by existing lineages — acts as a significant constraint on subsequent evolutionary diversification in passerine birds, connecting macroevolutionary pattern to community-level ecological processes.The lab is actively expanding this comparative framework into new taxonomic systems — including body size evolution in cetaceans, wing morphology evolution in Odonata, and the macroevolutionary dimensions of plant–insect co-diversification across the Mesozoic — using the deep fossil records of these groups to ask broader questions about the tempo and mode of morphological and taxonomic macroevolution.