Geoscience Reference
In-Depth Information
Dynamical and structural food web models, which describe the interactions
between multiple species, have often focused on the relationship between
complexity and stability in ecological communities, and this approach has a
long history (e.g. MacArthur, 1955; May, 1972; McCann, 2000; McCann et al.,
1998, Tilman and Downing, 1994 ). They have the potential to increase our
understanding of the effects of perturbations on the structure and functioning
of ecosystems and can be used as predictive tools in ecosystem management,
but only recently have such models ceased to be based on networks that are
randomly ordered and parameterized ( Brose et al., 2008; Otto et al., 2007 ).
Traditionally, food webs are illustrated by a food web graph and described by
various statistical foodwebmetrics (such as average food chain length, number/
fraction of basal, intermediate and top species, etc.). These are used to capture
the trophic complexity of these webs and, as such, they are useful, but they also
have limitations. First of all, these tools may capture important aspects of
trophic structure but might reveal little about the functioning of the system.
For example, how robust is the food web to disturbances and what is the
contribution of individual species to community robustness? To address this
issue, species characteristics that affect community-level properties need to be
identified, and the distribution of these characteristics among the constituent
species needs to be described and analyzed. This calls for augmenting tradition-
al food web descriptions with additional information on species characteristics
that affect community-level properties. There are now growing efforts to
incorporate data on organismal traits into food web analyses. Recent
approaches include the trivariate or so-called MN-web (a food web with data
on body sizes, M, and abundance, N,ofspecies;after Brown et al., 2011; Cohen
et al., 2003; Jonsson et al., 2005; Layer et al., 2010, 2011; McLaughlin et al.,
2010; Mulder et al., 2011; O'Gorman et al., 2010 ), the trophochemical web (a
food web with stoichiometric data on species, Sterner and Elser, 2002 )anda
growing awareness of the importance of body size for many species traits and,
by extension, food web attributes (e.g. Brose et al., 2006a,b; Riede et al., 2011;
Woodward et al., 2005 ). Several size-based approaches to estimate trophic
interaction strengths and to parameterize food web models have also recently
been developed (e.g. Berg et al., 2011; Brose et al., 2008; O'Gorman and
Emmerson, 2010; Otto et al., 2007 ) as well as new techniques to analyse
community viability ( Ebenman and Jonsson, 2005 ) and the contribution of
every species to community robustness ( Berg et al., 2011 ). Taken together, these
new developments in food web ecology have the potential for yielding an
improved understanding of controls on food web structure, as well as elucidat-
ing the ways in which perturbations may affect natural ecosystems ( Woodward
et al., 2010a ). Much of this work is still in its infancy, and the possible insights
gained from these approaches have only started to be explored. We assume that
the functional characteristics of the species that make up a food web (i.e.
foraging behaviour and feeding strategy) will affect the properties of the entire
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