Morphological variation in brown frogs from the Caucasus and the taxonomy of the Rana macrocnemis group

Multivariate analysis of body proportions, skin texture, and coloration cha racteristics of brown frogs (Rana macrocnemis and R. camerani) from 14 Geor gian populations confirms the existence of two, geographically distinct gro ups of populations Frogs in the first group (R. macrocnemis) are characteri zed by a smooth skin, a pale spotted pattern, absence of a mid-dorsal strip e, and a small inner metatarsal tubercle. Frogs in the second group (known as R. camerani) possess a rugose skin, a conspicuous pattern of dorsal spot s, a mid-dorsal stripe with contrasting borders, and a large metatarsal tub ercle. The first group occurs in the uplands of the Cleat Caucasus and othe r forested areas while the second group occurs in the treeless uplands of t he Near East, A stepped dine exists between them, with parallel variation i n eight morphological characters. Other characters analyzed vary independen tly of the dine. Fully diagnostic (fixed) morphological characters separati ng the groups were not observed. Some characters previously used for taxono mic purposes are shown to be associated with local ecological conditions. W e conclude that R, macrocnemis is a single, though polytypic, species compo sed of two interbreeding evolutionary lineages.