Detecting regular spacing in patchy environments and estimating its density using nearest-neighbour graphical analysis.

Organisms can aggregate to form patches or clusters interspersed with interstices of unoccupied space for behavioural or ecological reasons. Territorial spacing in the clusters could follow, resulting in regularity. In these circumstances an analysis of spatial pattern in a sample area defined by a boundary enclosing the clusters might reveal the aggregation but not the regularity. To demonstrate the occurrence of regularity, spacing trends and an estimate of density based on a nearest-neighbour graphical analysis can be used. The method is independent of boundaries and the presence of interstices. The basis of the method, and its strengths and limitations, are examined. A re-analysis of acorn woodpecker data, which has generated some controversy in the past, illustrates its potential for revealing "hidden" regularity.