Biology Reference
In-Depth Information
(a)
(b)
(c)
(d)
(e)
Ideal free - all fish equal
Fig. 5.5
An illustration of how in theory it is difficult to distinguish between a
numerical distribution based on the simple ideal free distribution with equal competitors
(e) and a distribution with unequal competitors (a-d). The left-hand patch has twice the
input rate of that on the right, so the ideal free distribution (e) of 12 equal competitors is
8:4. To illustrate unequal competitors, we imagine that six of the fish (drawn as twice
the size) are capable of eating twice as many prey per unit time than the other six. There
are now four possible ways of distributing the 12 fish so that the average intake at the
two ends is equal (a-d). However, the number of different possible combinations of
individuals which achieves each of these distributions varies. Imagine each fish has a
name. The 12 fish can be arranged in only one pattern to achieve distribution (a).
However, for (b), (c) and (d), there are many ways of arranging the individual fish to
achieve the distribution; the numbers of ways are 90, 225 and 20. In short, by chance
alone, (c) is the most likely to be observed. Note that it has the same numerical pattern
as (e). After Milinski and Parker (1991).
