Species distribution model for plains zebra during the Holocene
Modern giraffe at the Smithsonian National Museum of Natural History
Skull of the giant saber-tooth cat Homotherium from Hadar
Climatic influences on mammal distributions
Temporal turnover (origination and extinction) and range shifts (immigration and extirpation) in the mammalian and hominin fossil record are often causally linked to climatic or habitat change. However, drawing causal links between environmental change and species turnover, as is commonly done, assumes that mammal species are constrained in their environmental niches. This is an assumption that remains to be tested. Lack of a well-defined environmental niche (i.e., species are more flexible than assumed) implies that biotic interactions are likely to be a more important modulator of mammal species turnover than environmental ones.
I use modern mammal species and their associations with climate, habitat, and ecosystem-level data to assess the degree to which mammal species distributions and community composition are a product of climate and environments. These methods primarily focus on species distribution models, among others.
Plio-Pleistocene ruminant evolution
I am especially interested in the evolution of African artiodactyls (e.g., bovids, giraffids, hippopotamids, and suids) and ruminants (bovids and giraffids) in particular. Artiodactyls are the cornerstone of mammal communities in eastern African savannas – they are the most diverse and abundant herbivores, making them the primary liaison between plant productivity and the higher trophic levels. Documenting their past diversity through time and space is a critical step to understanding paleo-ecosystems and the history of those today.
Emergence of modern mammal communities
The modern mammal communities and herbivore and carnivore guilds in eastern Africa are both taxonomically and functionally depauperate compared to those of the Plio-Pleistocene. Plio-Pleistocene herbivore guilds were characterized by a great diversity of megaherbivores (several giraffid, hippopotamid, and proboscidean species co-existing) and much richer mesoherbivore communities than those today. Machairodontine felids (primarily Dinofelis, Homotherium, and Megantereon) were apex predators and co-existed with several medium to large felid (Panthera, Acinonyx), hyaenid (Chasmaporthetes, Crocuta, Hyaena, Ikelohyaena), and mustelid (Enhydriodon) genera, and rarely giant bears (Agriotherium), in the carnivore guild. Although both the herbivore and carnivore guilds winnow in diversity through time, the exact sequence and rate of this diversity loss and its underlying causes remain unclear.