erol akçay -- research

My work so far focused on two general areas: behavioral ecology, specifically reproductive social behavior, and interspecific mutualisms. I develop models of how particular systems function, and then ask how this way of functioning can evolve.

I am working with Joan Roughgarden on developing a new theory of reproductive social behavior, and evaluating existing empirical evidence.

Below are short descriptions of my recent projects.

rhizobium-legume mutualism

Following an interest that I picked up as an undergrad, I modeled how the interaction between nitrogen-fixing rhizobium bacteria and legume plants proceeds. The question there was how the two partners could reach a stable and mutually beneficial exchange of materials, without having any kind of neural system, and thus memory, etc.. I showed that these were in fact, unnecessary: a very simple negotiation dynamics, based on random fluctuations and a war-of-attrition type game resulted in a mutually beneficial exchange between the rhizobium nodule and the plant. The outcome of the interaction was the so-called Nash Bargaining Solution, which maximized the product of the growth rates of the nodule and the plant. Now I am interested in how negotiations would evolve, including in the context of multiple nodules, and how that affects the generation and maintenance of mutualist diversity in this system. Below is the reference.

Akçay, E. and J. Roughgarden. 2007. 'Negotiation of mutualism: rhizobia and legumes.' Proc. R. Soc. B; 274:25 - 32.

extra-pair paternity in birds

Birds were once thought to be the epitome of monogamy, but now it is old news that extra-pair copulations, i.e. copulations of females with males that they are not paired with, are quite common. Evolutionarily, this is interesting, since the partners of females who have extra-pair copulations end up providing care for offspring that are not their own (this is called extra-pair paternity). Most theorizing about this phenomenon assumes that the females simply "cheat" on their social males, and try to copulate with genetically superior males behind their backs. Two forms of this genetic benefits hypothesis (good genes, compatible genes) have been tested extensively for the last two decades now, and we evaluated the results of these studies using a literature survey and a meta-analysis. We found that the support from genetic benefits is not strong at all.

To try and develop an alternative, we turned to the theory of human marriages and hypothesized that extra-pair paternity might be the result of an agreement between males. This can be modeled using a cooperative game, and it turns out that such a model correctly predicts well-established patterns of extra-pair paternity. It also provides explanations for data that has been seen as problematic before. Our model, and another newcomer to this literature, the sexual conflict hypothesis, seem to be the hypotheses that hold the most promise to explain extra-pair paternity. References to our papers on this phenomenon are below:

Akçay, E. and J. Roughgarden. in press. 'Extra-pair parentage: a new theory based on transactions in a cooperative game.' Evolutionary Ecology Research

Akçay, E and J. Roughgarden. 2007. 'Extra-pair paternity in birds: Review of the genetic benefits.' Evolutionary Ecology Research; 9:855-868

parental care

I have been developing a simple model of biparental care that is geared towards explaining the results from manipulation experiments in birds. These experiments were designed to test one salient prediction from models of biparental care, namely the so-called partial compensation. However, the results in the literature are mixed, and do not support the clear prediction from the models. The partial compensation prediction basically stems from the assumption that parents are in conflict with each other. So, I dropped that assumption to see what the models would yield then. This model also incorporates two different components of parental care, nest defense and provisioning. It allows for much more variation in the responses of the parents to each other. The manuscript describing this work is in review.

evolution of mutual regard

This is more recent work I am doing with Jeremy Van Cleve. We are developing a model where behavioral dynamics happen separately from the evolutinary dynamics. With this two-tier approach, we have obtained some interesting results. For example, even if the two individuals are in total payoff conflict with each other, it is easy for non-selfish play to evolve. In analyzing this game, we built a general framework that can be extended to many interesting directions and applications. We are currently working on that.