Geoscience Reference
In-Depth Information
Host-parasitoid interactions have a long history of use in the study of
behaviour as foraging and reproduction are directly linked in these networks,
as opposed to predator-prey interactions where reproduction is indirectly
mediated through energy transfer (
Cook and Hubbard, 1977; Hubbard
and Cook, 1978
). Patch time allocation, the length of time that a forager
spends utilising a particular patch of resources, controls the distribution
of individuals within their habitat according to available resources and
has been studied with parasitoids as model organisms (
Hubbard and Cook,
1978; Wajnberg, 2006
). The importance of individual behaviour upon popu-
lation level processes, such as the impact of patch time allocation on popula-
tion distribution, has been suggested to be an important aspect in
understanding the structure of trophic networks (
Abrams, 2010;
Valdovinos et al., 2010
), although little work has been done on foraging
behaviour in a multi-species environment.
D. The Aims of This Review
Keeping in mind the impending focus upon studies that consider multiple
network types within the same ecosystem, it is important that host-
parasitoid networks are well understood to promote collaboration and the
development of better-integrated ecological network theory (
Ings et al.,
2009
). Recently, studies aimed at providing a mechanistic understanding of
the way in which interactions are structured within food webs and mutualis-
tic networks have focused on the role of body size as a predictor of which
species pairs interact with each other (
Arim et al., 2010; Brose et al., 2006;
Petchey et al., 2008; Stang et al., 2009
). The next section will cover, in brief,
what is meant by network structure and how optimal foraging theory has
been used to predict it in food webs according to species characteristics. We
then discuss the applicability of these studies to host-parasitoid networks
and suggest a general framework for understanding the mechanisms that
determine 'who eats whom' in host-parasitoid networks, based on how
parasitoid life-history characteristics, such as those defined in
Table 1
,con-
strain or facilitate parasitoid-host interactions.
II. THE STRUCTURING OF TROPHIC NETWORKS
A. What is Network Structure and How is it Determined?
Globally, not all species are capable of interacting directly as there are
numerous barriers that prevent species from coming into contact with one
another. These barriers, which may be spatial, temporal, morphological or a
