Macroevolutionary dynamics

I am also interested in the evolution of body size in mammals and the role of constraints on minimum and maximum size over the last 65 Ma. I was a co-PI on an NSF-RCN grant with Felisa Smith and Morgan Ernest that focused on the role of life history characteristics, ecology and phylogeny on the evolution of body size in mammals. We evaluated patterns in the maximum size of mammals for all orders across the Cenozoic (Smith et al., 2010, Evans et al., 2012).  We show that on each continent the maximum size of mammals leveled off after 40 Ma and remained relatively constant thereafter.  Moreover, there was a remarkable similarity in the rate, trajectory and upper limit of body size diversification on the different continents, across orders and across trophic groups.  This suggests that the evolution of large size in mammals was primarily driven by diversification to fill ecological niches. Currently we are examining body size distributions of mammalian communities across the Cenozoic and finding remarkable consistency in the shapes of these distributions suggesting that body size play a similar role in community assembly for both modern and archaic mammal groups (Lyons et al., in prep).


With Peter Wagner, I have been examining the relationship between macroecological success and macroevolutionary success. Many speciation models predict that species with large geographic ranges are more likely to give rise to daughter species because of the greater potential for barriers to divide the range and allow for allopatric speciation. Thus, macroecological success (high occupancy) should be correlated with macroevolutionary success (high richness). We tested this idea using marine invertebrates across the last 600 million years by examining the geographic occupancy of genera across time. We find that macroecological and macroevolutionary success are decoupled suggesting that the traits that lead to a broad niche reduce the potential of for daughter taxa (Wagner et al. 2018).