Geoscience Reference
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applicable positive relationship between size and fecundity in insects (
Honˇk,
1993
). Unlike consumers in food webs, offspring body size in parasitoids is
determined by the amount of nutrition available from a single consumption
event during the larval stage, rather than from multiple meals integrated over
a far longer period of feeding events (
Jervis et al., 2008
). Because of the
limitations associated with the single consumption event, the nutritional
value of the host plays a highly significant role in determining offspring
characteristics, which determine fitness (
Cohen et al., 2005; Morris and
Fellowes, 2002; Nakamatsu et al., 2009; Ode et al., 2005
). Primarily, larger
hosts have been shown, over a range of parasitoid and host species, to
produce larger, fitter offspring; owing to a greater biomass availability
(
Cohen et al., 2005; Jervis et al., 2008; Lacoume et al., 2006; Luo and Liu,
2011; Ode et al., 2005; Sequeira and Mackauer, 1992; Sidney et al., 2010
).
Empirical evidence involving parasitoid choice experiments in the laboratory
have shown categorically, over a range of parasitoid and host species, that
some parasitoid foragers preferentially attack certain host species over others
(
Brotodjojo and Walter, 2006; Buitenhuis et al., 2004; Morris and Fellowes,
2002; Ode et al., 2005; Sidney et al., 2010
).
There are some problems associated with using size as a measure of host
quality. In order to eclose, tissue feeding koinobiont parasitoids, such as
Hyposoter didymator, must consume all host biomass, which imposes a
maximum limit upon the size of hosts from which offspring can successfully
complete development; although in the original study, host size was positive-
ly correlated with offspring fitness and survival when excluding the largest
groups of available hosts (
Reudler Talsma et al., 2007
). Similarly, survival
rates of offspring developing within different species may not be directly
related to host size. For example, female Aphidius colemani, a wasp that
parasitizes a range of aphid species, were more likely to reject available oat
aphid, Rhopalosiphum padi, hosts because, even though the species is of an
average size, successful eclosion rates were much lower in that host species
compared to the others available (
Ode et al., 2005
). Further, host character-
istics can impose restrictions on the maximum oviposition rate of parasitoid
foragers by altering handling times. For example, aggressive host defensive
behaviour has been suggested to affect optimal host utilisation, where, for
example, the smaller host subspecies Uroleucon jaceae spp. jaceae was pref-
erentially attacked by Aphidius funebris as it was less capable to defending
against attacks than the larger U. jaceae spp. henrichi (Stadler, 1989 in
Mackauer and Volkl (1993)
). However, these exceptions aside, we can gen-
erally assume that host species present different opportunities for parasitoids
to maximise their fitness and that size is a good proxy for host quality.
To the best of our knowledge, no studies have considered the effect of
patches differentially composed of host species of different quality and PAT.
An experiment testing the co-variant effects of host patch density and
