Evolution and ecology of eastern Africa's mammals and ecosystems
I am broadly interested in the evolution and ecology of African mammals and eastern African ecosystems that host large herbivore and carnivore guilds. I study how taxonomic and phylogenetic composition, species’ ecologies, and community and guild structure of eastern Africa mammal assemblages have changed over time. This work spans the early Neogene when savanna-like ecosystems first emerged until the present day.
Emergence of modern mammal communities and guilds
Mammal communities and large herbivore and carnivore guilds of present-day eastern Africa today are both taxonomically and functionally depauperate compared to those of the Neogene and Quaternary. 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. Likewise, the broader ecological consequences of these losses for species interactions (e.g., predator-prey relationships) and ecosystem functioning are essentially unknown. I use a variety of methods, including functional trait community structure, food web network analyses, and simulations of faunal turnover to address these questions.
Climatic and environmental influences on mammalian evolution
Temporal turnover (origination and extinction) and range shifts (immigration and extirpation) in the mammalian and fossil record are often causally linked to climatic or habitat change. Drawing such causal links between environmental change and species turnover, however, assumes that mammal species are constrained in their environmental niches. I use modern mammal species and their associations with climate, habitat, and ecosystem variables 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 and estimations of realized and fundamental abiotic niches, among others.
Taxonomy, systematics, and paleo- ecology and biology of African artiodactyls
I am especially interested in the evolution of African artiodactyls (even-toed ungulates) and ruminants (e.g., 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 higher trophic levels. Documenting their past diversity through time and space is a critical step to understanding modern and paleo- ecosystems and the history of those today. I am currently involved in taxonomic, systematic, and paleoecological studies of fossil antelopes, camels, and giraffes.
Evolution and ecology of early hominins
I study the paleoecology of early fossil hominins (human ancestors) in eastern Africa using a variety of methods, including stable isotopes of herbivore tooth enamel, dental wear (microwear, mesowear), ecomorphology, and community structure analyses. This work provides a critical contextual and comparative framework for interpreting the hominin fossil record and the role of different drivers in shaping hominin paleobiology and behavioral and cultural innovations.
I am an active participant in two paleontological field projects in Ethiopia, both of which focus on hominin-bearing Plio-Pleistocene outcrops. Ledi-Geraru Research Project I have been working with the Ledi-Geraru Research Project (LGRP) since I came to ASU in 2012. The project is directed by Kaye Reed and others and includes a diverse array of paleoanthropologists, paleontologists, geologists, and archaeologists. LGRP fieldwork is concentrated on the poorly known interval of the late Pliocene (3-2.6 Ma) during the origin of Homo, Paranthropus, and Oldowan stone tool technologies. Thus far, late Pliocene sediments in the LGRP area have yielded the earliest known specimen of the genus Homo (specimen LD 350-1, ~ 2.8 Ma) along with an associated fauna, most of which is unpublished at present. My contribution to the project is primarily as a specialist in ruminant fossils (giraffids and bovids) and paleoenvironmental analyses. [Project Website]
Omo Group Research Expedition I joined the Omo Group Research Expedition (OGRE) in 2016 for fieldwork and have been studying the Shungura Formation giraffids. The OGRE initiated fieldwork in the mid-2000s under the direction of Jean-Renaud Boisserie. This recent work in the Shungura Formation, the most continuous sequence of Plio-Pleistocene mammal evolution in eastern Africa, has produced an abundance of new fossil remains and has clarified the stratigraphy and location of the older International Omo Research Expedition (1960s-1970s) collections. The Shungura Formation has yielded an exceptionally large collection (>1000 specimens) of fossil giraffids, all of which are unpublished at present. These specimens offer critical insights into the evolution of Giraffidae in Africa and the past diversity of the family. [Project Website]