Lack of recombination in parthenogenetic organisms limits their ability to adapt to changing environments by natural selection. However, some obligatory parthenogens, such as rock lizards of the genus Darevskia, could survive for millions of years across multiple Pleistocene glaciations. There are different explanations for this phenomenon. Analysis of phenotypic variation may shed further light on the high adaptability of the parthenogenetic lizards. We compared the genetic and phenotypic variability of 186 individuals of the parthenogenetic Darevskia dahli and 54 individuals of its sexually reproducing paternal species, D. portschinskii, whose ranges almost coincide in Georgia (the Caucasus). The analysis showed that, despite the higher genetic variability of the individuals and metapopulations of D. portschinskii, phenotypic variability (as measured by KW dispersion and the normalized effective number of individuals per metapopulation), based on the nominal traits, was almost equal in the two species. Moreover, phenotypes of the parthenogen correlated with the distances among the localities, and with the annual rainfall level at a locality. The latter species also had more outlier phenotypes. Phenotypic plasticity may be a strategy for adaptation of parthenogenetic rock lizards, to a certain extent, compensating for the lack of genetic diversity.
Tarkhnishvili et al. (Wed,) studied this question.