Lacerta agilis and L.strigata are broadly sympatric across the eastern Caucasus and often coexist in the same habitats. To quantitatively compare the patterns and extents of individual and geographic variation in these two related species, 524 specimens of L. agilis. (ssp. L.a.boemica) and 425 specimens of L. strigata from 5 localities of their syntopic occurrence within eastern North Caucasus were investigated biometrically. Eight meristic and fourteen multi-state scalation characters were used, and univariate and multivariate (principal component analysis, computation of Euclidean distances between local populations) procedures were performed.
The most interesting finding confirmed by the both multivariate analyses on the both character sets was a clear difference in extent of geographic variation; it was higher in L. agilis. than in sympatric L. strigata. Two factors potentially responsible for this difference are proposed. 1. Gene flow among the populations may have been more intense in L. strigata as it is more widely distributed and, in general, more abundant in the study area than L. agilis. 2. Developmental homeostasis, also known to impede phenetic divergence (Mayr, 1970), should be higher in L. strigata judging from the following: (a) a lower level of individual variability for nearly all meristics studied; (b) a lower level of fluctuating asymmetry of bilateral characters; and (c) lower frequency of irregular deviations from the typical scalation pattern as compared with L. agilis.
The two species also differ in the extent to which subspecies are recognized. While L. strigata has no trinomials, L. agilis has nine subspecies of which three are within the area of sympatry with L. strigata. The fact that lower extent of phenetic differentiation of L. strigata is manifested at both the micro- and the macro-geographical levels appears to argue in favour of the intrinsic (developmental) explanation of this phenomenon.