Blue-tongued skinks of the genus Tiliqua (Scincidae) are characterized by their large blue melanin-pigmented tongues, often displayed during open-mouth threats, when the animal feels endangered. It is not clear whether this unusual coloration is a direct anti-predation adaptation or it may rather serve intraspecific communication, as ultraviolet-blue color is a frequent visual signal in a number of lizard species. We used spectrophotometry and visual modeling to compare blue tongues of Tiliqua gigas with tongues and skin coloration of other lizard species, and to examine their appearance through the eyes of both the conspecifics and avian predators. Our results show that (1) the tongue coloration is probably not substantially influenced by the amount of melanin in the skin, (2) lingual and oral tissues are UV-reflective in general, with blue colored tongues having chromatic qualities similar to UV-blue skin patches of other lizard species, (3) UV-blue tongues are more conspicuous than pink tongues, especially in the visual model of conspecifics. We hypothesize that blue tongues may possibly serve as a semantic (honest) signal analogous to UV-blue skin patches of other lizard species due to greater UV-bias in the vision of diurnal lizards. Regarding the social behavior and high aggressiveness in Tiliqua and their relatives, such signal might serve, e.g., in intraspecific long-distance communication between conspecifics in order to avoid aggression, and its anti-predation effect may only be a secondary function (exaptation).

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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 ornamentation 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, saturation) of UV–blue spots and compared the values between the clones and their bisexual progenitor 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 significantly different from the values of sexual females. A possible explanation is that the changes in selective 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 result from the unique combination of parental genomes and are conserved by clonal reproduction.

Parthenogenetic species are usually considered to be short‐lived due to the accumulation of adverse mutations, lack of genetic variability, and inability to adapt to changing environment. If so, one may expect that the phenotype of clonal organisms may reflect such genetic and/or environmental stress. To test this hypothesis, we compared the developmental stability of bisexual and parthenogenetic lizards of the genus Darevskia. We assessed asymmetries in three meristic traits: ventral, preanal, and supratemporal scales. Our results suggest that the amount of ventral and preanal asymmetries is significantly higher in clones compared with their maternal, but not paternal, progenitor species. However, it is questionable, whether this is a consequence of clonality, as it may be considered a mild form of outbreeding depression as well. Moreover, most ventral asymmetries were found in the bisexual species Darevskia valentini. We suggest that greater differences in asymmetry levels among bisexuals may be, for instance, a consequence of the population size: the smaller the population, the higher the inbreeding and the developmental instability. On the basis of the traits examined in this study, the parthenogens do not seem to be of significantly poorer quality.