Parasitoid foraging
behavior at a landscape scale
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.
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The hyperparasitoid Mesochorus sp. cf stigmanticus probing
in an M. cinxia caterpillar for a host parasitoid larvae
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Drawing by Zdravko Kolev
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Over the last few years
we have approached spatial and temporal aspects of parasitoid foraging
by observing foraging parasitoids and hyperparasitoids in the field and
in a large (26 x 32 meter) outdoor cage, in experiments lasting days
to weeks. In conjunction with our knowledge of the large-scale distribution
and dynamics the species in Åland this work is unique and has yielded
very interesting results. Over the next few years we will continue to
study several aspects of parasitoid foraging. |
Navigation, spatial memory and anticipatory foraging by Hyposoter horticola
The parasitoid H. horticola copes with a host that is available for
parasitism for an extremely short period of time by searching for the host
during
the weeks before it is susceptible, and returning by following memorized
visual
landmarks. This “anticipatory
foraging” has only once before been
documented in insects, and ours is the first record of visual landmark
use by a parasitoid.
van
Nouhuys, S. & R. Kaartinen 2008. A parasitoid wasp uses
landmarks while monitoring potential resources. Proceedings of the
Royal Society
B, 275: 377-385 PDF
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 PDF
What
are the important aspects of parasitoid foraging?
a) contrasting foraging constraints:
The number
of progeny produced by a parasitoid is generally thought of as limited by
the number of eggs produced, or by the
amount
of time available
for foraging. Both of these may be constraints for
the hyperparasitoid M. stigmaticus ,
but the wasp H. horticola may instead be most
constrained by competition among foraging females.
Currently
we are assessing the competition among female H. horticola in
field experiments. We are also conducting experiments
to estimate the the area over which individual female M.
stigmaticus forage, the number of
females
that use a single
host nest, and the time budget involved in foraging.
van
Nouhuys, S. & R.
Kaartinen 2008. A parasitoid wasp uses landmarks while monitoring
potential resources. Proceedings of the Royal
Society B, 275: 377-385 PDF
Kankare,
M., van Nouhuys, S., Gaggiotti, O., Hanski, I. 2005. Metapopulation
genetic structure of two coexisting parasitoids of the Glanville fritillary
butterfly. Oecologia,
143: 77-84 PDF
b) The relationship
between foraging cues and rate of parasitism
Parasitoids
use a a range of host associated cues to find their hosts. Many of these
cues are related to the host substrate (such as the food plant). Cues
perceived by parasitoids can be identified in laboratory experiments, but
their use
by the parasitoids, as well as
the reliability
importance of particular cues are difficult to pin down, and must be
addressed in relatively realistic foraging environments, at appropriate
temporal
scales.
Furthermore,
relating perception of cues to actual foraging can be difficult because
host finding is not a limiting factor for some parasitoids. Similarly attracting
parasitoids does
not
significantly
reduce
herbivory
on
some plants.
Under
these conditions, we may expect a weak match between
signals produced by plants and cues received by parasitoids.
Castelo,
M. K., van Nouhuy, S. &. Corley, J. C. Foraging
cues for a parasitoid that uses hosts as larvae but searches fro them as
eggs, in review