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| RESEARCH |
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| To
me, life histories synthesize what I find fascinating about biology:
behavior, evolution, ecology, and physiology. All these components of
the biology of an organism must be integrated. Studying life histories
becomes a study of tradeoffs among competing demands and an integration
of the biotic and abiotic. In particular, I study evolutionary
tradeoffs at the interface between behavior and physiology. I am using four study systems: (1) Cavity-nesting birds (2) Field crickets (3) Color-banded individually-marked birds at feeders (4) Captive Zebra Finches |
| Current Research Projects: |
| Evolution of clutch size
in Tachycineta swallows:
This NSF-funded research is done in collaboration with David
Winkler
and others at Cornell University. The support for the research comes
through the NSF-PIRE (Partnership in International Research and
Education) program. Our central research question is to test
hypotheses explaining latitudinal variation in clutch size in the genus
Tachycineta,
which shows marked
among and within-species variation in clutch size. Over five
years, teams of US and
International students will conduct experiments and monitor nests at
multiple sites, while developing their own
independent research projects. |
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Geographic variation in life history tradeoffs: In addition to the NSF-PIRE, I serve as US Coordinator of Golondrinas, a network of swallow biologists across the Western Hemisphere stretching from Alaska to Tierra del Fuego. My role is to coordinate research collaboration among sites. With collaborators across the Hemisphere, I plan to build upon my dissertation research, which compared three populations of tree swallows: Alaska, New York and Tennessee. I found that swallows in Alaska show a different set of life history tradeoffs than do swallows in Tennessee, such as greater investment in offspring, different levels of immune activity, different nestling development trajectories (left), and different incubation patterns. |
| Role of Environmental Variation in Driving Life History: Levels of parental investment can be determined by and thus constrained by environmental conditions. Avian incubation is an excellent model system for examining the influence of environmental conditions on parental investment, as the maintenance of proper temperatures during embryonic development is costly and incubation can have consequences on current and future reproductive bouts. In collaboration with Ethan Clotfelter, we have been experimentally manipulating nest temperatures during incubation using Peltier thermoelectric heating/cooling devices. I have testing two main questions: (1) individual variation in incubation investment, with particular attention to egg temperature, and (2) tradeoffs across life history stages by examining direct and indirect effects of temperature manipulations on offspring. |  |
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Integrating Behavior and Physiology in Life History Evolution of Crickets: I’ve started a new study system in my research: field crickets (Gryllus and Acheta). Crickets are an excellent model for studying life history evolution because they are strongly influenced by environmental conditions and it is possible to precisely quantify lifetime reproduction. I'll be asking three main questions: (1) tradeoffs between reproduction and immunity, (2) effect of environmental conditions on mating behavior, and (3) tradeoffs between constitutive pathogen defenses and performance. |
| Factors affecting over-winter survival in feeder birds: I’ve started a long-term banding effort in backyards near campus to investigate factors predicting over-winter survival in common feeder birds. In addition, a color-banded population is an excellent resource for use in teaching and student research. It will be used extensively in Bio 373 Behavioral Ecology. |  |
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Ecological Immunology:
Ecoimmunology seeks to address why we see variation in immune responses
among individuals and across species. An ecoimmunological approach
takes an explicitly evolutionary perspective by hypothesizing that
immunity is costly (e.g. energetically expensive) and therefore subject
to tradeoffs. Under certain conditions it may be more adaptive to
invest less in immunity and more in reproduction. Conversely, if
pathogen pressure is high, animals may need to increase investment in
immunity at the expense of reproduction. Thus patterns of investment in
immunity are life history traits and should be viewed as evolving in a
whole organism context. I study immune activity within the framework of
how organisms interact with their environment and ask two main kinds of
questions: (1) how does immune activity tradeoff with other life
history traits? (2) What tradeoffs drive variation in immune responses
at three levels of organization: among species, among individuals
within a species, and within individuals. Currently, we are undertaking a study of tradeoffs among arms of the immune system in captive zebra finches (left and below). |
| Sexual Selection and Color: Color displays in animals serve a variety of functions, including sexual displays, pathogen defense and camouflage. I’ve been studying how colorful displays tradeoff with other life history traits, particular immune response. Working with Kevin McGraw, we’ve tested two key assumptions of sexual selection theory: (1) that carotenoid displays are honest in revealing enhanced physiological function and (2) that high levels of testosterone affect individuals differently. Recently, in collaboration with Ethan Clotfelter we found tradeoffs between allocation of carotenoids to display color and immunity in the Siamese Fighting Fish Betta splendens. My students and I will be examining tradeoffs between color and dominance in captive zebra finches (right). |  |