How useful are male genitalia as taxonomic characters in the genus Pseudochazara de Lesse, 1951 (Lepidoptera: Satyridae)?

Abstract

Useful taxonomic characters are those that help group individuals into species. In Lepidoptera, scent-producing male androconial scales and genitalia can be particularly useful in the taxonomy of closely related species. As these structures are closely linked to reproduction, differences in their morphology are probably good indicators of the specific status that would be revealed by observation of breeding ecology. However, genitalia are sometimes not used to their full potential as taxonomic characteristics of Lepidoptera species. A more rigorous objective approach based on precise measurement and statistical analysis would produce a more reliable assessment of how genitalia may help in the classification of a particular insect, than the tendency to identify anecdotal differences solely on visual comparison of morphology, often represented by photographs or diagrams. But one of the disadvantages of statistical analysis is that it requires sufficient specimens to make the analysis mathematically meaningful. In some cases, a 'good' species may be genuinely rare and this raises ethical questions about collecting large numbers of specimens. In other cases a 'species' may be too rare to provide sufficient data for analysis because it is in fact not a distinct species, but rather a localised or seasonal variant, or a rare hybrid such as Erebia serotina Descimon & de Lesse, 1953 (Higgins & Riley, 1980). In the absence of sufficiently large samples, statistical analysis may produce a statistically significant correlation which has no true biological interpretation or fails to produce statistically significant difference where there is, in fact, biological difference (Zar, 1984).
Evolution by natural selection is a dynamic process and by definition must be resulting in the development of new species, subspecies and intermediate groupings. Attempts by taxonomists to neatly classify every specimen into a group are therefore difficult. Data which can be statistically analysed have a great advantage over anecdotal observations in that they can be used to reveal reliable groupings within an otherwise inexplicable continuum of biological variation. Where sufficient data are available, statistical analysis should be applied.
Statistical analysis has been used to assist classification in the genus Agrodiaetus Hübner (Lepidoptera: Lycaenidae) by Brown (1976a) and Wakeham-Dawson & Spurdens (1994), although in the latter case analysis could have been improved by logarithmic transformation and use of ratios (e.g. valve length divided by valve breadth) which measure proportion (shape) and so allow for variation in specimen size within species (Dr T. Tolman, pers. comm.). The present paper uses analysis of variance (ANOVA) and multivariate discriminant analysis to investigate the usefulness of male genitalia in the taxonomy of nine species of the genus Pseudochazara, which is notorious for showing very little variation in the structure of male or female genitalia between species when subjected to anecdotal comparisons (Brown, 1976b; Coutsis, 1990).