untitled

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.)