abstract |
Sciurus vulgaris is a widespread and highly variable species by fur colour. Up to 40 subspecies are distinguished, although their nature has not been sufficiently studied. It is believed that coat colouration of the squirrel is determined by several genes, and such environmental factors as the type of forest and altitude above sea level affect the work of these genes; however, the purely adaptive nature of the differences may also be important. According to the analysed sources, the author hypothesised that different colour phases of squirrels can differ in cranial features, which may refute a purely adaptive hypothesis. Previous studies by the author revealed that several color phases of squirrels are widespread in Ukraine, the main of which are black, brown, red, and ginger, with a high level of variability within each. In the mountainous area (Carpathians), the coexistence of several color phases is observed, which are widespread at different altitudes, with the dominance of black and brown forms in the mountains, red in the lowlands, and ginger on the lowland, mainly in the anthropogenic zone. In the rest of Ukraine, only light-coloured squirrels (red and ginger) are widespread within the natural range. The study showed that color phases of squirrels differ by craniometric features: black and red forms, based on the Tst and CD criteria, differ in two craniometric features of the neurocranium; the red and ginger red forms differ in four features, two of which are related to the neurocranium, one to the upper and one to the lower jaw. The black (with brown) and red forms differ significantly in nine features: these are mainly the measurements of the upper jaw and the neurocranium. According to discriminant analysis, three groups can be distinguished with a small (up to 10%) overlap. In this case, red and black squirrels are located side by side, and red ones occupy a mixed intermediate position from both of them. It is possible to assume further colour and morphological differentiation of colour phases, especially the black form, taking into account the aspect that dark-colored squirrels in the Carpathian region are confined to mountainous and high-altitude areas and are relatively isolated from the other colour phases. |
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