Geoscience Reference
In-Depth Information
A
Parasitoid A
Host
1
2
3
4
B
Parasitoid B
Host
1
2
3
4
Figure 4
Hypothetical quantitative networks illustrating relative interaction
strengths between two different parasitoid species and their hosts. Widths of the
boxes indicate abundance of the species within the ecosystem, and width of the
interaction arrows at the base indicates the proportion of the parasitoid population
that is derived from each respective host species; wider arrows indicate a stronger
interaction between the parasitoid and that host species. (A) Parasitoid species A
attacks every viable host it encounters; resultantly, the relative strengths of each host-
parasitoid interaction have been determined by the relative abundances of each host
species. (B) Parasitoid species B preferentially attacks hosts according to their char-
acteristics, resulting in interaction strengths determined by these characteristics.
The most important characteristics determining a species' realised niche
are those that dictate how it interacts with other species (
McGill et al., 2006
).
However, the relative importance of different characteristics in determining
network structure can be expected to differ among network types. Body-size
is often an important trait-pairing characteristic in mutualistic networks and
food webs and determines ecological network structure directly as well as
through indirect interactions with other characteristics (
Vazquez et al., 2009;
Woodward et al., 2005
).
B. Body Size as a Determinant of Food-Web Structure
In food webs, the size of an individual typically correlates closely with life
history and ecology, which affect how individuals interact. For example,
larger organisms exhibit a greater scale of movement and bigger home-ranges
