Intraspecies differentiation of winter fur colouring of Pteromys volans (Sciuridae, Mammalia) within its range

Abstract

Pteromys volans (Siberian flying squirrel) inhabits major part of temperate forests in Eurasia. The species is represented by 10 subspecies within its range. To distinguish the subspecies, such a morphological indicator as the skin colouring is used. This article represents the peculiarities of the Siberian flying squirrel's fur colouring in different areas of the species range taking into account the intraspecific fur differentiation.The latter is determined using the original author's methodics. We propose to use objective colourimetric parameters («whiteness» and «shade of red colour») as diagnostic indicators for describing the fur cover. It can be quantified using RGB values (values of red, green and blue filtres) in almost any graphic editor. Whiteness is the arithmetic mean of the R, G and B values, while the shade of red colour is the ratio of R to whiteness. The fur of subspecies individuals inhabiting coastal regions with a warmer and more humid climate is characterised by the lowest whiteness. Subspecies individuals from the continental regions characterising by a more continental climate have generally greater whiteness and the highest values of whiteness are recorded in areas located at more northern latitudes. The value of the shade of red colour was higher in the colouration among the P. volans subspecies living near the Pacific Ocean coast. The dispersion analysis of the climatic factor effects (humidity and temperature) showed that the degree of humidity influence was maximal in both colour indicators, and it amounts 29.1% for whiteness and 20.5% for a shade of red colour. The temperature effect was less than humidity effect; it accounted for 18.7% for whiteness and 1.3% for a shade of red colour. The combined effect of these climatic factors on the whiteness and shade of red colour was 14.5% and 12.0%, respectively. Besides of environmental factors, the intraspecific differentiation of the P. volans fur colour could also be explained by the peculiarities of its subspecies phylogeography. In general, we have demonstrated that the used colourimetric fur indicators, being determined by the proposed method, were estimated to be statistically adequate and representative to distinguish the subspecies of P. volans.

Keywords

• graphic editor
• red data book
• shade of red colour
• subspecies
• whiteness