Measuring Tailing's 'element of chance in pond populations'

SUMMARY. 1. A series of small seasonal pools on a freshwater marsh was used to estimate the element of chance in animal community patterns.
2. The pools were artificially created in 1963. They were all the same age, size, shape, depth and had the same substrate. Other physico-chemical parameters, and the faunas, were sampled. Community assemblages were analysed using multivariate classification and ordination (TWINSPAN and DECORANA). and related to physico-chemical characteristics. Communities correlated with distance of pools from permanent water and annual drying/flooding regimes.
3. TWINSPAN analysis in 1987 was used to identify co-occurring groups of animals and the sets of ponds with which each group was associated. The presence or absence of a taxon from a pool within a set in which it otherwise commonly occurred was used as a measure of the element of chance.
4. The mean occurrence of taxa in pools in which they were expected was 79.6.16.2%. The mean occurrence in pools in which they were not expected was 10.9.10.5% ( n =80).