Behavioral ecology

There is a long history of conceptually linking foraging behavior of predators and parasitoids with subsequent predator-prey population dynamics. However, most of what we know about parasitoid behavior is at the scales of centimeters and minutes in the laboratory. Therefore there is still a lot to learn about the connection between individual behavior and population dynamics.

We approach spatial and temporal aspects of parasitoid foraging by observing foraging parasitoids and hyperparasitoids in the lab, field, and in a large (26 x 32 meter) outdoor cage, in experiments lasting hours to weeks. In conjunction with our knowledge of the large-scale distribution and dynamics of the species in Åland we attept to link what individuals due to larger scale consequences.

The hyperparasitoid Mesochorus sp. cf stigmanticus probing in an M. cinxia caterpillar for a host parasitoid larvae

 

Detecting visits to host egg cluster by RFID labeled parasitoid wasp
photo: W. Reschka

 

 

 

 

 

Spatial memory and landmark use by H. horticola

The parasitoid H. horticola searches for its host egg clusters during the weeks before the eggs are vulnerable to parasitism returning by following memorized visual landmarks. This "anticipatory foraging" and use of visual landmarks allows it to efficiently use a host that is suseptable for a very short time.

van Nouhuys, S. & R. Kaartinen 2008. A parasitoid wasp uses landmarks while monitoring potential resources. Proceedings of the Royal Society B, 275: 377-385

van Nouhuys, S, & J. Ehrnsten 2004. Parasitoid behavior that leads to uniform parasitism of a host available only a few hours per year. Behavioral Ecology, 15: 661-665

Strong intraspecific competition in H. horticola

Couchoux, C., Seppä, P., van Nouhuys, S. 2015. Effectiveness of deterrent marking by a parasitoid wasp: Behavioral and genetic approaches. Behaviour, DOI:10.1163/1568539X-00003277

Couchoux, C. and van Nouhuys, S. 2014. Effects of intraspecific competition and host-parasitoid developmental timing on foraging behaviour of a parasitoid wasp, Journal of Insect behavior, 27:283–301

Maintenance of submaximal resource use by H. horticola

When there is conspicuous under-exploitation of a limited resource it is worth asking, what mechanism makes it beneficial to leave presumably valuable resources unused? Evolutionary biologists have generated a wide range of hypotheses to explain this, ranging from interdemic group selection to selfishly prudent individual restraint. We consider a situation in which, in spite of high intraspecific competition, individuals leave most of a key resource unexploited. The parasitic wasp that does this finds virtually all host egg clusters in a landscape, but parasitize only about a third of the eggs in each.  We first test, and reject, a series of system-specific simple constraints that might limit full host exploitation, such as asynchronous maturation of host eggs.  We then consider classical hypotheses for the evolution of restraint. Prudent predation and bet-hedging fail as explanations because the wasp lives as a large well-mixed population. Also, we find no individual benefits to the parasitoid of developing in a sparsely parasitized host nest. However an optimal foraging model, including empirically measured cost of superparasitism and risk of hyperparasitism, can explain through individual selection, both the consistently low rate of parasitism and marking.

Montovan, K. J., Couchoux, C., Jones, L. E., Reeve, H. K., van Nouhuys, S. 2015. The puzzle of partial resource use by a parasitoid wasp.  The American Naturalist, 185: 538–550

Behavioral ecology of other parasitoid species

Kraft, T. S. and van Nouhuys, S. 2013. The effect of multi-species host density on superparasitism and sex ratio in a gregarious parasitoid. Ecological Entomology 38: 138-146

Corley, J. C., Villacide, J. M., van Nouhuys, S. 2010. Patch time allocation by a parasitoid: the influence of con-specifics, host abundance and distance to the patch Journal of Insect Behavior, 23: 431-440