Current Research

I am working on three projects, all related to mutualism. I find it nice to be able to switch among mathematical modelling, field work, and lab experiments!

Since I will use these terms in most of the sections below, here are a couple of definitions:
Mutualism: exchange of resources or services between individuals of two (or more) species resulting in a net benefit for each individual.
Exploitation: use of resources/services offered by a mutualist partner without reciprocation resulting in a net cost for the partner; exploiters may be individuals of a mutualistic species or of a separate species and may switch between mutualistic and exploitative behaviors.

Coevolutionary dynamics between pollinators and exploiters in the yucca/yucca moth mutualism

Exploiters are common in mutualisms and, in at least some systems, appear to have coexisted with mutualists for long periods of time. I'm interested in the way that exploiters coevolve with mutualists and what ecological factors might be important in enabling the evolutionary persistence of mutualists and exploiters.
Right now I'm using an adaptive dynamics model of pollinator/exploiter coevolution in the yucca/yucca moth mutualism (there is more natural history about this system in the section below). With this model, I have been investigating the effects of intraspecific competition on the evolutionary dynamics of the system. Soon, though, I'll be moving on to my next model!

Yucca moth larval competition

In the yucca/yucca moth mutualism, moths actively pollinate the flowers of the yucca plant and then lay their eggs inside the ovary of the flower. As the fruit develops, so do the larvae, which eat some of the seeds before exiting to pupate in the ground. In this case, the mutualism is an exchange a service (pollination) for a resource (food for larvae). Most yucca/yucca moth systems are exploited by other moths which do not pollinate, but are still seed parasites. However, there is a conflict even between the pollinator and plant over how many seeds the larvae eat. Competition between larvae may be an important factor in regulating how many seeds are consumed.
To test whether larval competition does actually reduce seed consumption, I am collecting and dissecting fruits of Yucca schottii from southeastern Arizona. This yucca species has two pollinator species, Tegeticula yuccasella and Parategeticula pollenifera, which differ in both their pollination and egg laying behaviors. Thus, I can compare how these different strategies affect levels of competition and seed consumption.

Pollinator foraging response to predation risk

Pollinators are attracted to flowers offering the best rewards (in terms of nectar and pollen quality and quantity) - but so are their predators. Pollinators also avoid their predators, so what will a forager do when the most attractive flowers are also the most dangerous? In addition to being interested in the behavior itself, I want to learn more about how predators can alter selection on mutualistic traits (such as investment in pollinator attraction) by exploiting the mutualism.
In my lab experiments, I simulate predator attacks on foragers of the bumble bee Bombus impatiens and observe their subsequent foraging behavior. I'm planning to incorporate my results into an individual based model to explore selection on floral traits.

Previous Research

Chimera formation by two social amoebae

As an undergraduate, I worked in the lab of Joan Strassman and Dave Queller on the interaction between Dictyostelium discoideum and Dictyostelium purpureum. These two species of social amoebae form chimeras, which is exciting... and still mysterious. Social amoebae are unicellular eukaryotes which aggregate together when they run out of food (bacteria) in the area. The aggregation then acts like a multicellular organism by migrating towards the soil surface and differentiating into two cell types: stalk and spores. The stalk cells die, while the spores cells on top of the stalk get a chance to escape to a new place with more food. Consequently, social amoebae are a good study organism for the evolution of social behavior, multicellularity, cell differentiation, etc. We also found it an interesting system to study species interactions - but, at least at the time that I graduated, it was not clear what the true nature of the interaction was (cooperation, exploitation, commensalism).