Null models for null hypotheses in taxonomy: a test using Scyphozoa

Abstract

Although molecular tools are becoming more important in the delineation of scyphozoan species there is, perforce, a need to substantiate new species definitions using morphological data. Access to type material is often difficult and detailed, raw morphometric data are rarely provided in older type descriptions, which makes comparisons of new with old challenging. Here, we use null models based on simple measures of central tendency to generate morphometric data sets for four species of Aurelia, three species of Chrysaora and two species of Crambionella. The results of PERMANOVA and CAP analyses indicate no significant differences between random and real data within species, but significant differences between congeneric species (null or real), suggesting that this multivariate approach may be a useful tool for defining species when comparative data are scant.