Geoscience Reference
In-Depth Information
Intriguingly,
Brose et al. (2008b)
illustrated that the size-related feeding
properties of predatory beetles and spiders mediate, not only functional
responses but also the energy flux through feeding links. Such a view has
been widely applied to species-based food-web models by relating body size
to population dynamics based on biologically plausible energetics and the
allometric scaling of metabolism (
Arim et al., 2011; Brose, 2010; Brose et al.,
2006b; Emmerson and Raffaelli, 2004; Weitz and Levin, 2006
; for pioneering
work, also see
Brown et al., 2004; Yodzis and Innes, 1992
). These studies
have illustrated that species body size critically affects key dynamic features
of food webs (e.g. variability and persistence) and, moreover, realistic food
webs are likely to be stable. However, the effects of intraspecific variations
have not been considered in these studies. An exceptional study is that by
Rudolf and Lafferty (2011)
, which showed that ontogenetic niche shifts
reduce the robustness of multispecies communities. For a better understand-
ing of size-structured food webs, the species-based allometric model and the
size-based spectrum model should be reconciled using the information
provided by this study on predator-prey interactions.
C. Food-Web Modelling
The integration of species-based and size-based approaches would potential-
ly improve our understanding of size-structured food webs. There are two
possible approaches: one using the species-based model and one using the
size-based community-spectrum model.
The first approach would require the incorporation of intraspecific size/
stage variation into species-based allometric food-web models. Obviously,
this makes the model structure more complex, the number of parameters
larger, and the food-web modelling more technically difficult. However,
mathematical techniques have been proposed to reduce the complexity and
make this approach feasible. For example,
De Roos et al. (2008)
presented an
analytical method to convert a physiologically structured (i.e. size-
structured) population model to an easy-to-handle stage-structured biomass
model.
Rossberg and Farnsworth (2011)
devised a numerical method to
approximately describe the complex dynamics of stage-structured multispe-
cies models. However, those techniques are based on specific, and often
mutually contradicting, assumptions, such as constant body size (i.e. no
growth) after maturation (
De Roos et al., 2008
) and constant growth rates
throughout life history (
Rossberg and Farnsworth, 2011
), which makes the
unification of these different methodologies difficult. More sophisticated
mathematical techniques are still necessary to appropriately simplify size/
stage-structured food-web models. Another difficulty in adopting this
approach is that the determinants of species-based PPMRs (species-averaged
