This can be compared with distributions of observed overlap in diets of desert lizards
from 28 sites on three continents (Fig. 9.13). Those in the Kalahari desert of south-
ern Africa showed the greatest degree of overlap (because one food type, termites,
comprised a large amount of the diet), and those in Australia the least. In no case
were observed distributions similar to the random distributions: there were far more
148 Chapter 9
100
80
60
40
20
0
100
80
60
40
20
0
Grasses Herbs Shrubs
Food type
(b)
Winter habitat
Shallow Silty Stony hill
Habitat type
% of habitat
% of diet
(a)
Diet
Elk
Mule deer
Pronghorn
Bison
Fig. 9.11(a) Diet and
(b) winter habitat use
of elk, mule deer,
pronghorn, and bison
in Wind Cave National
Park, South Dakota.
Where habitat choice is
similar there are major
differences in diet.
(Data from Wydeven
and Dahlgren 1985.)
15
10
5
0
0 0.5 1.0
Niche overlap
Frequency (%)
Fig. 9.12Frequency
distribution of niche
overlaps in 100
randomly constructed
communities with 15
species and five equally
abundant resource
states. (After Pianka
et al. 1979.)