Resolution of spatial complexity in a field sample of singing crickets Teleogryllus commodus (Walker) (Gryllidae): a nearest-neighbour analysis

Abstract

The nearest-neighbour distances for a sample of singing crickets were analysed for spatial pattern using a goodness-of-fit test. There was an excess of individuals in the lower and upper tails of the distribution, indicating aggregation of some crickets, and a spacing out of thers. Regularity within the aggregated component was also demonstrated, using the Pielou (1962, J. Ecol., 50, 357–367) test for competition. Thus, to obtain an overall analysis of spatial pattern of the sample, both tests were required. The presence of aggregation together with regularity in a population results in a loss of sensitivity of the Clark & Evans test (1954, Ecology, 35 445–453) and the Thompson test (1956, Ecology, 37, 391–394) because for these single-component tests the effects of opposing deviations from randomness can cancel out. This was illustrated by applying the tests to a synthetic sample, and to the sample of singing crickets. A computer program NN-TESTS was used for the analyses. The behavioural significance of the spacing in crickets is discussed.