Natural history of Valentin’s rock lizard(Darevskia valentini) in Armenia

Valentin's rock lizard (Darevskia valentini) is suggested to be the pare nt for several parthenoge netic species (e.g., D. armeniaca, D. bendimahiensis, D. sapphirina, and D. unisexualis) that evolved through hybridization. Complex evolutionary processes (ineluding reticulate evolution) are occurring within the areas where Valentin' s rock lizard coexists with these and other rock lizards. Hence, a detailed biological specification of this species is important for understanding how vertebrates evolve. Valentin's rock lizard is a longlived (up to 9 years), small diurnal lizard with larger females than males, which is unlike other species of the genus. Their relatively large eggs and early reproducti on period, which occurs just after emerge nee from winter shelters, are adaptatio ns for living in a high elevation climate (higher than 2 000 m a.s.l.). Their body temperatures (31 -32℃) are comparable to body temperatures of rock lizards living in milder climates, though female body temperature is more depe ndent on substrate temperature and basking due to their lower activity than that found in males. Population density fluctuates from several individuals to several hundred per hectare and is not affected by parthenogen coexistenee, although hybrids do occur in sexually biased populations where males are more common than females. The male home range is larger than that of females, though these home ranges broadly overlap. Prey is not limited in the mountain meadows and Valentin's rock lizards feed on a great variety of arthropods. Infan ticide occurs in high-de nsity populati ons.

Evolution of parthenogenetic reproduction in Caucasian rock lizards:A review

Despite numerous works devoted to hybrid origin of parthenogenesis in reptiles,the causes of hybridization between different species,resulting in the origin of parthenogenetic forms,remain uncertain.Recent studies demonstrate that sexual species considered parental to parthenogenetic rock lizards(Darevskia spp.)avoid interspecific mating in the secondary overlap areas.A specific combination of environmental factors during last glaciation period was critical for ectotherms,which led to a change in their distribution and sex ratio.Biased population structure(e.g.,male bias)and limited available distributional range favored the deviation of reproductive behavior when species switched to interspecific mates.To date,at least 7 diploid parthenogenetic species of rock lizards(Darevskia,Lacertidae)originated through interspecific hybridization in the past.The cytogenetic specifics of meiosis,in particular the weak checkpoints of prophase l,may have allowed the formation of hybrid karyotypes in rock lizards.Hybridization and polyploidization are 2 important evolutionary forces in the genus Darevskia.At present,throughout backcrossing between parthenogenetic and parental species,the triploid and tetraploid hybrid individuals appear annually,but no triploid species found among Darevskia spp.on current stage of evolution.The speciation by hybridization with the long-term stage of diploid parthenogenetic species,non-distorted meiosis,together with the high ecological plasticity of Caucasian rock lizards provide us with a new model for considering the pathways and persistence of the evolution of parthenogenesis in vertebrates.

Does reproductive mode affect sexually-selected coloration?Evaluating UV-blue spots in parthenogenetic and bisexual lizards of the genus Darevskia

Sexual selection often leads to evolution of conspicuous signals,raising the chances of attracting not only potential mates,but also predators.In lacertid lizards,ultraviolet(UV)-blue spots on flanks and shoulders represent such a trait.Some level of correlation between male and female ornamen-tation is also known to exist.Therefore,the phenotype of females may change in the absence of sexual selection.We tested this hypothesis on a complex of parthenogenetic and bisexual lizards of the genus Darevskia.We evaluated area,counts,and chromatic properties(UV opponency,sat-uration)of UV-blue spots and compared the values between the clones and their bisexual progeni-tor species.We found a fair heterogeneity between the parthenogenetic species,but no general tendency toward higher crypsis or conspicuousness.Values of the parthenogens were not signifi-cantly different from the values of sexual females.A possible explanation is that the changes in se-lective forces associated with parthenogenetic reproduction are too small to affect the resulting pattern of selective pressures on the studied traits,or that the phenotypes of the parthenogens re-sult from the unique combination of parental genomes and are conserved by clonal reproduction.