As a scientist, I am captivated by the diversity of pathogens that persist in wild animal populations, and my research concerns the ecological and genetic interactions between hosts and parasites. I use a combination of field studies, experiments, models and comparative approaches to understand variation in epidemiological patterns within and among populations. For the past 15 years, I have studied monarch butterfly migration, ecology, and interactions with a protozoan parasite, asking how seasonal migration of these butterflies affects parasite transmission. I have also collaborated with other scientists to study the diversity and characteristics of infectious diseases in wild mammals. Other work on infectious diseases in wild songbirds has examined how seasonality and urban land use influence avian-pathogen dynamics. Collectively, this work has practical significance for mitigating disease risks in animal populations in the face of anthropogenic pressures and climate-induced changes. Below you will find a summary of my research projects (including funding sources and collaborations).

1) Monarch butterfly ecology and interactions with a protozoan parasite

Dormant spores (smaller objects) of the protozoan parasite O. elektroscirrha form around the developing scales of monarch butterflies. Adults emerge covered with parasites on the outside of their bodies, particularly on the abdomen.

For the past 15 years I’ve maintained a strong interest in the population biology of monarch butterflies, with a particular focus on their interactions with an obligate protozoan parasite, Ophryocystis elektroscirrha.

Monarchs inhabit islands and continents worldwide, and in parts of the world they undergo a spectacular annual migration. Parasite prevalence, pathogen virulence, and host susceptibility to infection are all lower in migratory populations as opposed to those that are resident breeders.

My work with monarchs has focused on two main areas – the ecological and evolutionary consequences of long-distance migration for host-parasite interactions, and geographic variation among monarch butterflies in different parts of their worldwide range. In addition, a graduate student in my lab (Elizabeth Lindsey) explored the environmental and genetic determinants of monarch butterfly resistance to O. elekstroscirrha. A second graduate student (Catherine Bradley) completed a project examining the effects of parasite infection on flight ability in captive butterflies. A postdoctoral researcher (Jaap de Roode) examined evolutionary determinants of parasite virulence within and among populations. Finally, together with Andy Davis and other and researchers in my lab, I examined geographic variation in wing morphology (size, shape and color), host plant use (female preference and larval development), and response to thermal stress among monarch butterfly populations within North America.

Link for this project: Monarch Parasites on the web, and the Monarch Health science project!

2) Ecology and evolution of infectious diseases in mammalian mating and social systems

In collaboration with Charlie Nunn (at the Max Planck Institute for Evolutionary Anthropology and UC Berkeley) and scientists from 7 different institutions, I studied the association between behavioral and ecological traits of mammals and the diversity and characteristics of their parasites and infectious diseases. Questions we have examined with large comparative databases and theoretical models of disease spread include: How does the diversity of parasites and infectious diseases vary among mammals in relation to their social behavior, life histories, diet, and habitat use? Do pathogen characteristics, such as specificity and transmission mode, covary with host social and mating systems? Under what conditions will pathogens influence the evolution of host social behavior, and vice versa? Do the diversity and characteristics of parasites differ between threatened and non-threatened mammal species?

Browse our searchable online data sets : Global Mammal Parasite Database

Charlie Nunn and I coordinated working groups at the National Center for Ecological Analysis and Synthesis (NCEAS) in Santa Barbara, California, and at Conservation International in Washington, D.C. Together with project participants, we tested predictions from epidemiological models against the characteristics of hundreds of parasites and pathogens from a wide range of primates, carnivores, and ungulates. This research has been funded by NCEAS, the National Science Foundation and the Center for Applied Biodiversity Science at Conservation International. This project offers exciting opportunities for graduate students and undergraduates interested in pursuing components of this study.

3) Ecology of songbird-parasite interactions

From 2001-2005, I was involved in a collaborative project centered at the Cornell Laboratory of Ornithology to investigate the spread of mycoplasmal conjunctivitis, an emerging bacterial eye disease infecting North American house finches. This study was funded in part through an NIH/NSF "Ecology of Infectious Disease" award to Dr. Andre Dhondt at Cornell University . My main interests focused on factors driving spatial and temporal variation in prevalence, particularly the regular seasonal outbreaks of disease . Because disease prevalence peaks during the winter months when finches form flocks and depend heavily on bird feeders, we examined the interactions between seasonal changes in host age structure, behavior, immune function, condition, and susceptibility to conjunctivitis. More recently, graduate student Cat Bradley has investigated the role of urbanization in the transmission and fitness effects of multiple parasites in their wild songbird hosts.