Multivariate analysis of geographic variation in Darevskia clarkorum (Darevsky & Vedmederja, 1977), correlation with geographic and climatic parameters, and true status of Darevskia dryada (Darevsky & Tuniyev, 1997)

Abstract

All the Turkish populations studied, both those previously assigned to D. dryada (Subaşı and Yoldere villages, near Hopa) and those attributed to D. clarkorum (the largest sample studied so far, 177 specimens in total), are indistinguishable from each other and therefore must all be ascribed to the natural variability of a monotypic D. clarkorum. The Georgian specimens from the Type Locality of D. dryada (Charnaly river gorge, Chevachauri district) are clearly different, so that taxon cannot be considered a simple synonym for D. clarkorum, but as a valid taxon, although its proper status (more probably as a subspecies of D. clarkorum), is yet to be clarified. It is a highly threatened population, so studies should be done in vivo or with as low intrusiveness as possible.                 Darevskia dryada is clearly larger (SVL) than any D. clarkorum studied, with strongly longer heads and pilei in adult males (and hence more teeth in dentary bone), and higher dorsalia counts. There also seem to be (but need to be studied in a larger sample) more longitudinal rows of temporal scales between tympanic and parietal plates, a tendency to have more supralabial scales; comparatively smaller values for longitudinal rows of scales on the ventral surface of the thigh between the femoral pores and the outer row of enlarged scales, and higher collaria, and circumanalia scales. Other differences in femoralia and gularia are also reflected in Darevsky & Tuniyev’s (1997) tables and should also be investigated with more Georgian specimens.                 Two supposed discriminant characters, the frontonasal index and the presence of developed masseteric, are not valid. The frontonasal index does not discriminate both taxa; D dryada specimens fall inside the variation of D. clarkorum for this character. Also the presence of a developed masseteric plate is supposed to be rare if at all in D. clarkorum but always present in D. dryada; however, it appears in nearly 75% of D. clarkorum studied and in all D. dyada, so is also no longer valid for taxa discrimination.                 Although very similar, D. clarkorum and D. dryada are morphologically different, and genetic studies (as the unpublished results mentioned by Fu, 1999) do not make the provenance of the specimens clear, and hence the correct identification of the supposed specimens of D. dryada used.                 There are no geographical clines in D. clarkorum. However, as stated by Schmidtler et al. (2002), there is an inverse relationship between altitude and dorsalia values in D. clarkorum. Both the general differentiation between populations and the scalation (dorsalia) appear statistically correlated with the altitude and also with latitude (being both factors not strictly the same). The correlation seems to be stronger with morphology in general (multiple scalation characters and head biometry) than only with dorsalia. In the case of the general differentiation among samples, it is also significantly correlated with temperatures during the activity period (April-September) and with precipitation during incubation (July-August). As these climatic parameters of temperature and precipitation are not directly correlated with the dorsalia variation, the relation with altitude (and perhaps latitude) must be linked to some other climatic parameter not studied here, perhaps solar radiation or evapotranspiration.