Biology Reference
In-Depth Information
Figure 8.4. A null-model analysis was conducted using ectoparasite communities of
45 species of marine fish. Little evidence for nonrandom occurrence patterns was
found. One example is illustrated here. Histograms of SES (standardized effect sizes)
of the number of species pairs forming checkerboard distributions are shown. Each
observation is an SES for a different host-parasite presence-absence matrix. (for
details see Gotelli and Rohde
2002
). The broken vertical lines indicate
รพ
2 and
2
standard deviations, the approximate boundaries for statistically significant patterns.
The null-hypothesis is that the observed distribution does not differ significantly from
a mean of 0. 0. The asterisk indicates the tail of the distribution for which species
co-occurrence would be less than expected by chance, indicating competitive (?)
structuring. (a) Fixed-fixed null-model algorithm; (b) fixed-equiprobable
null-model algorithm. From Gotelli and Rohde (
2002
). Reprinted by permission of
Blackwell Science Ltd.
