Measurement of Niche Breadth and Overlap: The Colwell‐Futuyma Method

Abstract

The Colwell—Futuyma niche metrics are examined by means of data on microgeographic distribution of 25 species of drosophilid flies. Niche metrics based on a variety of weighting factors (circular, non—circular, absolute, and relative) are highly positively correlated. Unweighted metrics are highly correlated with all weighted metrics. The niche breadth and overlap values with drosophilids as weighting factors are highly positively correlated to metrics using drosophilids matched with co—occurring plants, even though the weights are slightly negatively correlated. Increasing the number of species in the resource matrix (species X resource states table) decreases the variation in weights of resource states and they approach uniform distinctness. Most drosophilid species are broad niched for all calculation methods used. Samplig error may account for some skewing of breadth values because flies might be attracted into otherwise unfavorable environments by the baits.