Current Research Projects
Disease, Movement and the Evolution of Cannibalism
Cannibalism is an extremely widespread behavior among animals. It is of particular interest in the fields of behavioral and evolutionary ecology, because it is perhaps the supreme example of a non-altruistic, or selfish, behavior. Cannibalism can have strong positive effects on Darwinian fitness of the cannibal, because it provides high-quality meals and simultaneously eliminates competitors. However, cannibalism can also have strong negative fitness effects if the cannibal accidentally eats a close relative or contracts a virulent pathogen from its victim. Given these strong costs, how does cannibalistic behavior evolve?
This project is In collaboration with Jay Rosenheim (University of California, Davis) and Moshe Coll (Hebrew University of Jerusalem, Rehovot). Its overarching goal is to develop a synthetic theory (using evolutionary agent-based models, which represent individuals foraging and reproducing in a simulated spatial environment) to explore how cannibalism evolves. We hypothesize that permissive pathways to the evolution of cannibalism may be created by behavioral traits that decouple the costs of cannibalism from its benefits. To ground the model in real biology, and to test important assumptions underlying the model, the project integrates modeling work with observational and experimental studies of the cannibalistic big-eyed bug, Geocoris pallens.
We have discovered recently in Geocoris what appears to be the first known case of a pathogen that triggers a strong increase in its host’s expression of cannibalism: cannibalism jumps from ca. 5% to >90% for infected individuals. We propose to characterize further this cannibalism-eliciting pathogen and to develop theory for the influence of pathogens on the expression and the evolution of cannibalism. Early observations in the field suggest that Geocoris populations appear to be crashing in some areas of its range. We are trying to decipher the potential contributing roles of cannibalism and the virus as drivers. Geocoris is an important biological control agent and an influential player in the arthropod communities of many annual crops. Therefore, this work has important implications for agriculture.
Papers published thus far from this project:
- Sadeh A, Northfield TD, Rosenheim JA (2016) The epidemiology and evolution of parasite transmission through cannibalism. Ecology 97(8):2003-2011 [PDF] [journal link]
- Sadeh A, Rosenheim JA (2016) Cannibalism amplifies the spread of vertically-transmitted pathogens. Ecology 97(8):1994-2002 [PDF] [journal link]