A brief review of morphological variation in Natrix tessellata in Israel: between sides, among individuals, between sexes, and among regions


Abstract: After introducing the distribution and biology of Natrix tessellata in Israel, on the southern edge of its range, we address its intraspecific variation from the literature and examination of 262 museum specimens. Head pholidosis showed no significant directional asymmetry, but asymmetry in infralabial plates was significantly correlated with frequency of injured tails. Variation in body size showed no clear seasonal growth, presumably due to climatic fluctuations. The variation in number of ventrals (in males, 159-173, mode 165) was not geographical. Females attained 750-800 mm (head and body; mode 600-650) and males 700-750 (mode 500-600) mm. Females had significantly greater relative head length, and males significantly greater eye size relative to head length, counts of ventrals and of subcaudals, and relative tail length. The sexual dimorphism in relative tail length was evident also in juveniles. The sexual dimorphism varied geographically within Israel: that of head size was stronger in the south, that of relative tail length and number of subcaudals stronger in the north. Trunk coloration commonly comprised 6 rows of blackish spots of equal or different size. Head coloration in some individuals extraordinarily resembled that of Natrix natrix. We discuss some methodological problems and compare variation within Israel and with Anatolia.

Keywords: Feeding behaviour, directional asymmetry, sexual dimorphism, normal variation, geographic variation, caudal injury, Natrix natrix, character displacement

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