Geoscience Reference
In-Depth Information
250
200
150
100
Random
Mass up
Mass down
Gen up
Gen down
Vul up
Vul down
50
0
0
50
100
150
200
250
Number of primary extinctionns
Figure 6
The relationship between the number of species removed and the cumula-
tive number of extinctions (both removals and species which went secondary extinct).
The dashed lines indicate the point at which half of the original species richness is
reached. The different colours indicate the different extinction orders. Gen stands for
generality and Vul for vulnerability. Up stands for removing the species with the
lowest value of the trait to the highest. Down stands for removing the species with the
highest value of the trait to the lowest.
to analyse this food web complexity by regressing body size of species
against food web parameters (trophic height) and found that when we
separated the data according to our classification system, that is, when
we added additional traits to the information on body size, stronger food
web patterns emerged.
Our extinction simulations have shown that it has been the removal of
small to medium-sized, and not large, organisms that caused a cascade of
secondary extinctions. It appears that larger-bodied species can be lost
without causing a direct collapse of the network topology that will affect
other species. This finding is surprising given that large species are assumed
and have been proven to cause trophic cascades (
Raffaelli, 2007
).
