SREL Reprint #2607

Nearest-neighbor contingency table analysis of spatial segregation for several species

Philip M. Dixon

Savannah River Ecology Laboratory, Drawer E, Aiken, South Carolina 29802,USA

Abstract: Spatial segregation of species occurs when a species is more likely to be located in the vicinity of conspecifics. This can be investigated by mapping and identifying all locations in a study area, then analyzing the nearest-neighhbor contingency table, where each location is classified by its species and the species of its nearest neighbor. Nearest-neighbor contingency tables for two species can be analyzed using the methods in Dixon (1994). Here, I present methods to analyze contingency tables for any number of species. Calculation and interpretation of the multispecies contingency table are illustrated by two examples: spatial segregation of species in a swamp forest, with five types of points (Fraxinus caroliniana, Nyssa sylvatica, Nyssa aquatica, Taxodium disticum, and "other species"), and spatial segregation in the gamodioecious tree Nyssa aquatica, with three types of points (male, female, and juvenile). Two issues that affect the results and their interpretation are the choice of randomization (random labelling or toroidal rotation) and the choice of test (pairwise or multispecies).

Keywords: spatial pattern, point process, dioecious plant, toroidal rotation, random labelling

SREL Reprint #2607

Dixon, P. M. 2002. Nearest-neighbor contingency table analysis of spatial segregation for several species. Ecoscience 9:142-151.

This information was provided by the University of Georgia's Savannah River Ecology Laboratory (srel.uga.edu).