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species near the base of the food web that provide and channel energy for the
many larger species of this system.
Our results also reinforce the findings of other studies regarding the
importance of the highly connected species for robustness (
Dunne et al.,
2002; Ekl
ยจ
f and Ebenman, 2006; Petchey et al., 2008
), with both in- and
out-links being important. The suddenness of the collapse when removing
the most vulnerable species (only approximately 25 primary removals within
this sequence were required for the system to collapse to half of its size)
reiterates the importance of detritus and planktonic copepods (the two most
vulnerable species) for the Antarctic food web. It is also interesting that there
is no positive relationship between generality and body mass, unlike as has
often been observed in other systems (e.g.
Woodward et al., 2005
). As has
been found in some other studies (e.g.
Digel et al., 2011
), the Weddell Sea
web is perhaps rendered more susceptible to the loss of generalist predators,
at least when undergoing a topological-based extinction simulation, and then
would be expected in webs with a stronger generality allometry, where
the loss of larger more specialized species causes more trophic cascades
(
Myers et al., 2007
).
V. CONCLUSION
Assuming that the emergent behaviour of an ecosystem is, at least partly,
dependent on the properties and behaviour of the species it is composed of,
we looked into different properties and how they are distributed within the
overall ecosystem structure. We only focused on a small number of traits and
simple predatory classifications and, although the total number of traits in
marine consumers is potentially almost infinite, our data analyzed here and
results clearly reflect the generalist trophic ecology of most species in the
Weddell Sea.
An understanding of the relations between species functional roles and
ecosystem structure is an indispensable step towards the comprehension of
change in Antarctic or any other food web structure due to global change and
subsequent biodiversity loss and gain (
Woodward et al., 2010a
). This paves
the road towards understanding the role of the functional and life-history
traits of species, and the many services provided by ecosystems, the relation-
ship between functional traits and to species taxonomy, ecological network
structure, functioning and dynamics.
Our study clearly emphasizes that species body size and species classifica-
tion in terms of trophic or functional roles are one key to understanding why
certain species are abundant while others are rare, and how species functional
roles may change in response to species loss.
