Multivariate analysis of the population systematics of the ringed snake, Natrix natrix (L)

Abstract

The racial affinities of the widely distributed (palearctic) ringed snake, Natrix natrix were assessed using a large number of phenotypic characters from a wide range of features. These characters show a considerable amount of complex geographic variation which is further complicated by geographic variation in the extent of their sexual, ontogenetic and local variation. Nevertheless, extensive analysis of the data using univariate statistics, numerical taxonomy and a wide range of multivariate statistics allowed the primary patterns of ‘racial’ differentiation to be elucidated.The dominant feature of the racial affinities is the division of the majority of the complex into distinct eastern and western forms which meet along a ‘hybrid zone’. The nature of this zone is analysed in detail and discussed in relation to aspects of evolutionary theory such as gene flow. The island populations of Corsica and Sardinia are also extremely divergent. The evolution and taxonomy of the four primary subdivisions of the complex (east, west, Corsica, Sardinia) are discussed in relation to Pleistocene history, evolutionary theory, species concepts (phenetic and biological) and subspecies concepts, etc. These four subdivisions border on the species rank and may be regarded by some as semispecies. They are formally recognised as subspecies. Attention is drawn to the difficulties of intraspecific taxonomy and the arbitrary nature of the four taxa given formal recognition.