Geoscience Reference
In-Depth Information
usually by focusing on taxonomy or body size, but rarely both. The analogy of
the ''entangled bank'' was first coined by Darwin in The Origin of Species
(
Darwin, 1859
), and modern ecology has unveiled evermore complex networks
of interactions since
Camerano's (1880)
first depiction of a recognisable food
web over a century ago. Traditionally, food web ecology has focused on
structural patterns (e.g. connectance) and dynamic processes (e.g. network
stability) from a species-centric perspective, reflecting the field's roots in com-
munity ecology. More recently, the role of body size in influencing both these
properties has come to the fore (e.g.
Berlow et al., 2009; Brose et al., 2006b;
Cohen et al., 2003; Layer et al., 2010b, 2011; Loeuille and Loreau, 2005;
McLaughlin et al., 2010; O'Gorman and Emmerson, 2010; Petchey et al.,
2008; Reuman and Cohen, 2005; Reuman et al., 2009; Woodward et al.,
2005a,b
). In parallel, a range of size-based approaches to understanding
multispecies systems that are independent of taxonomy have been used in
applied disciplines, such as commercial fisheries science (
Jennings et al.,
2002, 2007
), and these too have been very successful at capturing a large
amount of ecological information in a single dimension: individual body size
(
Petchey and Belgrano, 2010
). However, both size- and species-based
approaches have rarely been applied to the same system simultaneously (but
see
Brown et al., 2011; Layer et al., 2010b
) and fewer still have done so from an
individual-based perspective, as we do here (but see
Woodward et al., 2010
),
despite the fact that interactions among organisms happen at this level of
organisation.
A. The Allometry of Trophic Relations
The size range of all living organisms spans more than 23 orders of magnitude,
with the blue whale and giant sequoia weighingmore than 10
8
g and the smallest
phytoplankton weighing less than 10
15
g(
Barnes et al., 2010; McMahon and
Bonner, 1983; Peters, 1983
). Within-species size variation can also be consider-
able (
Ebenman and Persson, 1988; Hartvig et al., 2011; Werner and Gilliam,
1984; Woodward andWarren, 2007
). For instance, in fishes and reptiles, where
growth is continuous, individuals pass through a wide spectrum of sizes, possi-
blymore than four orders of magnitude, during the independent part of their life
cycle (
Werner and Gilliam, 1984
). Given that the size of an organism is corre-
lated with many of its fundamental ecological properties (
Brown et al., 2004;
Peters, 1983
), it should come as no surprise that an individual's size affects the
type of prey it can consume andwhat predatorswill attack it. The large variation
in body size within and among species can therefore be expected to have
profound consequences for the trophic organisation of ecological communities
(
Ebenman and Persson, 1988; Elton, 1927; Hardy, 1924; Hartvig et al., 2011;
Hildrew and Townsend, 2007; Petchey et al., 2008; Woodward et al., 2005a,b,c,
2010; Yvon-Durocher et al., 2011
).
