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quality, in terms of composition of different species, in a range of parasitoids,
could clearly help to characterise what determines parasitoid realised niches
in host-parasitoid networks.
D. The Optimal Foraging Strategy
The previous sections have discussed two foraging strategies by which para-
sitoids can maximise individual fitness: optimising host encounter rate or
optimising host quality (and by proxy offspring fitness). These two strategies
consist of multiple decisions made by parasitoid foragers as to whether to
utilise an available host or to forego the available host in favour of finding
one of higher quality; optimal foraging theory predicts that parasitoids will
make the decision that best profits their fitness (
Figure 6
A). When foregoing
an available host in favour of finding a more suitable host increases the
fitness of an individual more than using the available host, we would suggest
that the forager will be highly elective and exhibit the second of the two
strategies. This should result in a network that is structured according to the
characteristics of the available host species (
Figure 4
B), and not by the
relative abundance of each host species within the ecosystem.
This section has considered how host characteristics change the relative
profitabilities of each host (summarised in
Figure 6
B); the next section
A
B
Utilise available host
Forego available host
Increasing host quality
Profit from finding new host
Profit from finding a new host
Figure 6
Diagrams considering the effect of the relative profit of a host, where host
profitability is the benefit to individual fitness minus the costs of different foraging
decisions, according to predictions made by optimal foraging theory: (A) The effects
of the costs and benefits associated with finding hosts and utilising them related to
attacking or foregoing an available host. (B) The effects of host characteristics on the
profitability of hosts and how this affects optimal foraging decisions. When the profit
to using a host is greater than the profit associated with finding another host, optimal
foraging theory predicts that the parasitoid will utilise the available host. This concept
has been applied to all further profit comparison diagrams.
