Morphometry as a tool in species identification: a study with special reference to species of the genus Mycalesis (Lepidoptera: Nymphalidae)

Abstract

Morphological variability among four species of Mycalesis in Sri Lanka that are difficult to discriminate due to their morphological similarity was investigated to identify characters that distinguish species more accurately. Using traditional morphometrics, 90 variables from the wing, forelegs and genitalia of M. perseus typhlus, M. mineus polydecta, M. subdita and M. rama were measured and analysed. A set of 19 characters of the wing, male genitalia and forelegs were identified to discriminate species. Results of the analysis showed that male specimens were discriminated with nine wing characters and five characters of genitalia. Females could be discriminated with three wing characters and two foreleg characters. Male specimens of M. p. typhlus and M. m. polydecta showed the greatest morphological differentiation, while females of M. subdita and M. rama were the most similar species. These results were used to improve the currently available identification key. Two instances of possible hybridisation were discovered: one between M. p. typhlus and M. m. polydecta and the other between M. p. typhlus and M. subdita. Hence, the species of Mycalesis, particularly M. p. typhlus, M. m. polydecta and M. subdita may not be strictly reproductively isolated in Sri Lanka. Preliminary comparisons of M. p. typhlus in Sri Lanka with M. p. tabitha of India indicated that the Sri Lankan subspecies is unlikely to be a synonym.