Patterns in the pond: the role of colour, pattern and texture in species delimitation of polymorphic froglet species of south-western Australia

Faced with the threatening processes of land clearing, a warming climate, and spread of disease, accurate monitoring of frog populations is crucial. To achieve this, frogs often require in situ identification or identification from photographs, which is difficult when closely related species exhibit few diagnostic characteristics and/or are polymorphic. By understanding colour, pattern, and texture within and among species and sexes, we can draw clearer species boundaries and aid identification. We used standardised photography to analyse dorsal colouration, ventral colouration, colour patterning, and skin texture within and among four species of Crinia froglets in south-western Australia: C. insignifera, C. pseudinsignifera, C. glauerti, and C. subinsignifera. We found minor, but significant, differences among species, such as a higher frequency of the striped morph pattern in C. insignifera populations. We also found significant differences among sexes and populations within species, such as in the extent of black on the throat and belly. Variation in colour and pattern among- and within-species align with our expectations regarding apostatic selection and background matching, which may explain some of the observed trends. Further research covering additional populations and species will help clarify our understanding of this polymorphic frog genus.