We use genetic and genomic tools to shed light on behavioral and evolutionary questions. Our projects primarily focus on populations for which we can combine genetic analysis with data on the behavior, life history, and environmental milieu of known individuals. This approach allows us to connect behavioral and environmental effects on trait variation in individuals, to evolutionary outcomes on the level of populations and species.
It also gives us the opportunity to study the role of gene regulation in explaining social environmental effects on fertility, health, and survival across the life course, in primate models for human health.
Although we also work on other systems (especially rhesus macaques), the bulk of the research in the lab focuses on a population of baboons in the Amboseli ecosystem of Kenya, which has been the subject of research by the Amboseli Baboon Research Project for over 44 years. Check out the ABRP's webpage and Facebook page!
Epigenetic consequences of environmental variation across the life course
Social and environmental adversity can have long-lasting impacts on both fitness and health. For instance, low social status and social isolation in early life have been linked to elevated rates of cardiovascular disease later in life, even when status differences are erased. At the same time, traits that are influenced by social conditions early in life remain responsive to later life environmental conditions. Epigenetic mechanisms have been hypothesized to mediate these effects, but little is known about social, behavioral, and environmental epigenetics in natural populations.
We are taking advantage of the extensive longitudinal data on the Amboseli baboon population--including information on social relationships, social status, resource availability, and life history--to investigate the epigenetic consequences of naturally occurring environmental variation. We are interested in the timing, magnitude, and reversibility of epigenetic effects; the locations in the genome that are most sensitive to environmental conditions; and the impact of epigenetic changes on downstream phenotypes. The results of our research will shed light on the role of epigenetics in linking environmental conditions to fitness-related traits, including health-related outcomes.
We collaborate on aspects this research with Susan Alberts (Duke University) and Xiang Zhou (University of Michigan). This work is supported in part through NIH grant R21AG049935-01 and NSF BCS-1455808.
The impact of social adversity on gene regulation
Socially induced stress is strongly correlated with disease susceptibility and mortality risk in humans, and recent studies show similar patterns in nonhuman primates. Rhesus macaques in captivity present the opportunity to study social environmental effects on gene regulation in a controlled setting, and potentially to establish causality. We take advantage of the ability to manipulate social status and social group composition to test the effects of these variables on gene regulation.
Our studies are revealing the role of different cell types in the response to social status-mediated stress, the plasticity of these effects when social status changes, and the degree to which social status affects an animal's ability to respond to other environmental challenges. This work is a collaboration with Luis Barreiro (University of Montreal) and Mark Wilson (Emory University), and funded through NIH grant 5R01GM102562.
We have also begun complementing our work in captive primates with studies in the Amboseli baboons. There, we are testing whether the demographic characteristics and social history of individual baboons predict variation in gene regulation, including in response to ex vivo immune stimulation. This work is a collaboration with Elizabeth Archie (University of Notre Dame) and the Institute of Primate Research in Kenya, and funded in part through NSF BCS-1455808 and the Leakey Foundation.
New methods for genomic analysis of noninvasive samples
Noninvasive samples are often the only type of biological sample available for natural populations, especially in endangered or threatened species. However, they yield small quantities of low-quality DNA, making genetic analysis challenging. Noninvasive genetic analysis techniques, though revolutionary twenty years ago, have changed little since that time. The genomic revolution is still yet to arrive for species in which only noninvasive samples are available.
New methods, both lab and computational, are crucial for moving the field forward. We are tackling this problem by developing such methods, which focus on enriching DNA yield from noninvasive samples to a level appropriate for genomic analysis, and developing software to analyze the resulting data. We are validating our approaches against high quality samples and pedigree data from the Amboseli baboons.
The causes and consequences of hybridization in baboons
Hybridization and admixture are processes that have been deeply important in primate evolutionary history. The Amboseli baboon population is located in an active hybrid zone: while the dominant baboon species in Amboseli is the yellow baboon (Papio cynocephalus), observers at the ABRP have observed periodic immigration of anubis (P. anubis) or hybrid baboons into the basin since 1982. From this vantage point, we have the rare opportunity to investigate both the causes and consequences of admixture between two closely related primates. We are particularly interested in behavioral correlates of ancestry, social and behavioral factors that facilitate (or inhibit) admixture, and the signature of hybridization in the genome.
Our work has revealed that anubis ancestry is associated with earlier maturation and a mating advantage to males. Despite no obvious phenotypic costs ot admixture, however, the hybrid zone appears to be narrow, transitioning quickly between phenotypically anubis animals and phenotypically yellow animals. These observations present a puzzle that we aim to solve, using a combination of behavioral, demographic, and genomic data.
Anubis baboons, Samburu, Kenya
Yellow baboons, Tsavo, Kenya
Photo Credit: Noah Snyder-Mackler
A freezer of noninvasively collected baboon samples
Attainment and stability of macaque dominance ranks over time (each line shows Elo-based rank for an individual female)
An infant baboon in Amboseli rides jockey style on her mother's back
With Elizabeth Archie (University of Notre Dame), Jeanne Altmann (Princeton), and Susan Alberts (Duke), we are investigating how multiple sources of early life adversity combine to impact later life health and survival.
With Elizabeth Archie (University of Notre Dame), Ran Blekhman (University of Minnesota), and Luis Barreiro (University of Montreal), we are investigating the signature of social structure and social interactions on the gut microbiome in the Amboseli baboons (supported in part through NIH/NICHD 2P2C-HD065563-06).
With James Higham (NYU), we are studying the gene regulatory signature of dispersal in free-ranging rhesus macaques on the island of Cayo Santiago.
Other projects in the lab
Baboons on the savanna, Amboseli, Kenya