I am broadly interested in the ecology and evolution of species interactions. My current research focuses on understanding how cooperation between species can persist. Mutualisms are present nearly everywhere. For example, many plants need pollinators to reproduce, and many animals (including humans) need gut bacteria to take up nutrients. But why would individuals from different species provide costly benefits to each other? What prevents partners from turning into cheaters that reap the benefits of the interaction without paying the costs? My research explores these, and other questions related to the ecology and evolution of mutualisms.
In my doctoral research I asked how cheating is limited in the mutualism between fig trees and their tiny pollinating wasps. Fig wasps develop inside fig fruits, and transfer pollen from the fruit in which they are born to a different, flowering, fig tree. Most fig wasp species actively collect pollen with their front legs, carry it in special pollen pockets on their thorax, and then again use their front legs to actively deposit the pollen onto fig flowers. Some wasp individuals fail to carry pollen, and can therefore not perform the pollination service for the tree. The vast majority of wasps, however, do pick up and deposit pollen. Why do they do this? Through field experiments my collaborator and I demonstrated that fig trees are able to impose host sanctions that lower the fitness of wasps that do not pollinate. These sanctions vary in strength across fig species, and pollen-free wasps are least common in the species with strong sanctions, where costs of not cooperating are high. Ongoing projects include exploring critical aspects of fig sanctions and wasp behaviour, and the effects of other interactors on this mutualism. In my work I combine field and lab experiments with molecular methods and mathematical modelling.
The picture on top shows A pollinator fig wasp about to enter a fig of Ficus maxima. Once inside, the female wasp can lay her eggs and pollinate the flowers inside the fig. Photo by C. Ziegler.
Jandér, K.C. and Herre, E.A. 2010. Host sanctions and pollinator cheating in the fig tree – fig wasp mutualism. Proceedings of the Royal Society B, 277:1481-1488.
Herre, E.A., Jandér, K.C., Machado, C.A. 2008. Evolutionary ecology of figs and their associates: Recent progress and outstanding puzzles, Annual Review of Ecology, Evolution and Systematics, 39: 439-458.