The Role of Body Size in Complex Food Webs: A Cold Case - Advances in Ecological Research - page 201

be useful to understand how ratios of consumer and resource body sizes are
correlated to network structure, interaction strength patterns and food web
robustness, especially, with respect to predatory types (i.e. benthic predators/
scavengers) where the proposed positive relationship between body mass and
trophic level does not hold true ( Riede et al., 2011 ). Future research involving
the relationships between functional traits and ecosystem functioning, in
combination with size-based analyses (e.g. Gilljam et al., 2011; Woodward
et al., 2010b ), should aim to focus on the role of different predatory types,
however simple the classification might seem, as this information appears to
provide meaningful additional insights into network structure beyond those
simply related to size per se.
Here, as in the vast majority of food web studies to date, we considered a
summary food web (cf. webs listed in Ings et al., 2009 ), ignoring potential
seasonal changes and differences among ontogenetic stages as well. It is
clear that intraspecific variation related to ontogeny, body size
( Cianciaruso et al., 2009 )ordietbreadth( Bolnick et al., 2003 ) could
comprise a major part of a species trophic role ( Gilljam et al., 2011;
Meli´n et al., 2011; Woodward et al., 2010b ). Further, because it can
facilitate frequency-dependent interactions that can affect a population's
stability, the amount of intraspecific competition, fitness-function shapes
and the populations' capacity to diversify and to specialize rapidly may be
key to understanding network structure and dynamics ( Bolnick et al., 2003,
Yvon-Durocher et al., 2011 ). Future research involving different ontoge-
netic stages, for example, larval and adult fish, as well as incorporating
information on seasonal differences in food web structure and functioning,
is clearly needed. Incorporating ontogenetic stages in the Weddell Sea data
set would definitely add to the complexity observed, whereas taking into
account, seasonal changes have a smaller impact on the overall structure,
all herbivores depend on phytodetritus all year round, a slight change will
include marine mammals and some seabirds which use the Weddell Sea only
in summer as feeding grounds ( Jarre-Teichmann et al., 1997 ) although the
task is logistically challenging: the results of the current chapter nonetheless
represent an important first step before we can move towards these more
highly resolved approaches.
C. Extinction Scenarios the Robustness of the Weddell
Sea Food Web
The influence of extinction risk on trophic vulnerability and species life
histories are both complex and specific to the source of the threat ( Purvis
et al., 2000 ). Further, such relationships depend on the species sensitivity to a
stress that intensifies through time, such as a gradual change in salinity or