In many animals, females choose males for mating in relation to their conspicuous coloration, but males can also select females by display traits. In a lizard species in which females show red tail ...coloration during the mating season, tail color was experimentally manipulated and males preferred red versus white adult females for courtship. Red coloration makes females more sexually attractive in this lizard species, possibly because it indicates sexual maturity and a pre-ovulatory reproductive status.
Abstract
Female mate choice for male display traits is widely observed across animal taxa and is a well-established mechanism of evolution. However, males are increasingly seen to exhibit mate choice for female display traits, even in species with traditional sex roles, although this continues to be an understudied aspect of sexual selection. We evaluated the role of female coloration on male mate choice decisions in the spiny-footed lizard (Acanthodactylus erythrurus), a species in which adult females show red coloration as a retained juvenile trait. Although both sexes show red tails as juveniles and subadults, only females maintain red colored tails when becoming adult; moreover, this coloration is only present at the beginning of female adulthood and becomes white after ovulation, suggesting a mating-related function. Male courtship preferences were investigated through an experimental approach, where they were offered pairs of females that differed in size (adult/subadult) and tail coloration (red/white). Male lizards preferred adult females using both visual and chemical cues and, when adult female coloration could be chosen, they preferred red females. These results suggest that red coloration is a sexual signal involved in male mate selection. We hypothesize that red coloration in adult females might indicate sexual maturity and a pre-ovulatory reproductive status. Being a juvenile trait retained until the beginning of adulthood, we also suggest that it might indicate reduced risk of sperm competition. This study highlights the role of a juvenile trait for sexual selection and adds to the understanding of the evolution of male mate choice.
Hybridisation is increasingly recognised as an important cause of diversification and adaptation. Here, we show how divergence in male secondary sexual characters between two lineages of the common ...wall lizard (Podarcis muralis) gives rise to strong asymmetries in male competitive ability and mating success, resulting in asymmetric hybridisation upon secondary contact. Combined with no negative effects of hybridisation on survival or reproductive characters in F1‐hybrids, these results suggest that introgression should be asymmetric, resulting in the displacement of sexual characters of the sub‐dominant lineage. This prediction was confirmed in two types of secondary contact, across a natural contact zone and in two introduced populations. Our study illustrates how divergence in sexually selected traits via male competition can determine the direction and extent of introgression, contributing to geographic patterns of genetic and phenotypic diversity.
The decoy or deflection hypothesis, which states that conspicuous colouration is present in non-vital parts of the body to divert attacks from head and trunk, thus increasing survival probability, is ...a possible explanation for the presence of such colouration in juveniles of non-aposematic species. To test this hypothesis we made plasticine and plaster lizard models of two colour morphs, red or dark-and-light striped tails, based on the colouration of spiny-footed lizard (Acanthodactylus erythrurus) hatchlings, which naturally show a dark-and-light striped dorsal pattern and red tail. Lizard models were placed in the field and also presented to captive common kestrels (Falco tinnunculus), a common avian lizard predator. The number of attacks and the body part attacked (tail or rest-of-body) were recorded, as well as the latency to attack. Our results suggest that models of both colour morphs were recognized as prey and attacked at a similar rate, but in the field, red-tailed models were detected, and thus attacked, sooner than striped-tailed. Despite this increase in detection rate by predators, red-tailed models effectively diverted attacks to the tail from the more vulnerable body parts, thus supporting the decoy hypothesis. Greater fitness benefits of attack diversion to the tail compared to the costs of increased detection rate by predators would explain the evolution and maintenance of red tail colouration in lizards.
Successful establishment and range expansion of non-native species often require rapid accommodation of novel environments. Here, we use common-garden experiments to demonstrate parallel adaptive ...evolutionary response to a cool climate in populations of wall lizards (Podarcis muralis) introduced from southern Europe into England. Low soil temperatures in the introduced range delay hatching, which generates directional selection for a shorter incubation period. Non-native lizards from two separate lineages have responded to this selection by retaining their embryos for longer before oviposition—hence reducing the time needed to complete embryogenesis in the nest—and by an increased developmental rate at low temperatures. This divergence mirrors local adaptation across latitudes and altitudes within widely distributed species and suggests that evolutionary responses to climate can be very rapid. When extrapolated to soil temperatures encountered in nests within the introduced range, embryo retention and faster developmental rate result in one to several weeks earlier emergence compared with the ancestral state. We show that this difference translates into substantial survival benefits for offspring. This should promote short- and long-term persistence of non-native populations, and ultimately enable expansion into areas that would be unattainable with incubation duration representative of the native range.
Ontogenetic colour changes in animals generally involve cryptic juveniles developing conspicuous coloration when they achieve sexual maturity. However, there are several species in which juveniles ...develop conspicuously coloured tails that become cryptic in adults. In lizards, colourful tails may act as an antipredator mechanism, either by diverting predator attacks from vital body parts to the expendable tail (decoy hypothesis) or, when associated with tail movements, by signalling to the potential predator that it has been spotted and an attack will probably not succeed (pursuit deterrent hypothesis). In both cases, the antipredator function would allow lizards with colourful tails to show more risk-taking behaviours. The aim of this study was to test whether conspicuous coloration was related to risk behaviours in spiny-footed lizards, Acanthodactylus erythrurus, a species with red-tailed juveniles. Behaviour was recorded in free-ranging lizards and several risk-related behavioural indices were calculated. As predicted, risk behaviour and tail coloration were found to be related, as redder (less orange) lizards stayed further from refuge, maybe because redder coloration was associated with a perception of lower predation risk. Coloration was not related to any other behavioural index, including tail displays, but the level of activity was negatively related to lizard size, suggesting a change towards less active behaviour associated with growth, probably because energy and thermoregulatory requirements depend on body size. In conclusion, the link between red coloration and risk-taking behaviour in spiny-footed lizards supports the antipredator function of this coloration that enables more colourful lizards to take more risks when necessary. Moreover, the nonsignificant association between coloration and tail displays is not consistent with the pursuit deterrent hypothesis, thus making the decoy hypothesis more probable.
•Behaviour was recorded in free-ranging lizards of different age classes.•Redder (less orange) lizards took more risks by staying further from refuge.•This is consistent with red coloration being an antipredator mechanism.•Rate of tail and limb display was not significantly related to coloration.•This is not consistent with red coloration having a pursuit deterrent function.
In many animal taxa, coloration is a visual signal used for communication among conspecifics, for example between age classes. Juvenile coloration has been hypothesized to reduce aggression from ...adults in some species, in what is called the aggression avoidance hypothesis. Spiny-footed lizards are good subjects for testing this hypothesis, as juveniles develop conspicuous red coloration on their hind limbs and tails that fades in adulthood. To test the influence of juvenile coloration on adult aggressiveness, we conducted videotaped encounters in captivity between adults of both sexes and juveniles with their natural red coloration, or experimentally painted either red or white on their natural red parts. Then we recorded the number of times juveniles were bitten and attacked. In unpainted juveniles, no significant relationship was found between juvenile coloration (brightness, red chroma or hue) and adult aggressiveness. However, juveniles painted red were bitten less than those painted white when number of times bitten was controlled for number of times attacked. This result supports the aggression avoidance hypothesis, as an escalation from low-intensity (attacking) to high-intensity aggression (biting) was less probable towards red juveniles. The presence of red coloration in juveniles caused the reduction in adult aggression, while small natural variations in this red colour did not seem to have any further effect. Juvenile red coloration in this species might indicate age or sexual immaturity to adults.
•Coloration was experimentally manipulated in juveniles of a lizard species.•Adult aggression towards juveniles was recorded in staged encounters.•Natural juvenile coloration was not significantly related to adult aggression.•Once attacked, juveniles painted red were bitten less than those painted white.•Red coloration in juveniles of this species reduces adult aggression.
Abstract
Breeding coloration of females often signals aspects of their reproductive status, suggesting a link between color and sex steroid hormones. In this study, we examined the relationships ...between 2 sex steroid hormones (progesterone and β-estradiol) and reproductive coloration in female spiny-footed lizards Acanthodactylus erythrurus. We first explored natural variation in female plasma hormone levels and coloration during their reproductive cycle. β-estradiol was negatively related to brightness and positively related to red saturation, whereas progesterone was not significantly related to coloration. After identifying key relationships, plasma hormone concentrations were manipulated by creating 3 experimental female groups (β-estradiol-treated, progesterone-treated, and control), and the effects on coloration were monitored. β-estradiol-treated females, in which there was a rise in both β-estradiol and progesterone levels, lost their red coloration earlier than females in the other 2 experimental groups, whereas progesterone treatment had no significant effect on female coloration. Our results suggest that high levels of either β-estradiol alone or β-estradiol together with progesterone trigger the loss of red coloration in female spiny-footed lizards, and that progesterone alone does not affect coloration. We hypothesize that changes in female breeding color might be regulated by β-estradiol in species in which conspicuous coloration is displayed before ovulation, and by progesterone in species in which this color is displayed during gravidity.
In many animal taxa, coloration is a visual signal used for communication among conspecifics, for example between age classes. Juvenile coloration has been hypothesized to reduce aggression from ...adults in some species, in what is called the aggression avoidance hypothesis. Spiny-footed lizards are good subjects for testing this hypothesis, as juveniles develop conspicuous red coloration on their hind limbs and tails that fades in adulthood. To test the influence of juvenile coloration on adult aggressiveness, we conducted videotaped encounters in captivity between adults of both sexes and juveniles with their natural red coloration, or experimentally painted either red or white on their natural red parts. Then we recorded the number of times juveniles were bitten and attacked. In unpainted juveniles, no significant relationship was found between juvenile coloration (brightness, red chroma or hue) and adult aggressiveness. However, juveniles painted red were bitten less than those painted white when number of times bitten was controlled for number of times attacked. This result supports the aggression avoidance hypothesis, as an escalation from low-intensity (attacking) to high-intensity aggression (biting) was less probable towards red juveniles. The presence of red coloration in juveniles caused the reduction in adult aggression, while small natural variations in this red colour did not seem to have any further effect. Juvenile red coloration in this species might indicate age or sexual immaturity to adults.
Successful establishment and range expansion of non-native species often require rapid accommodation of novel environments. Here, we use commongarden experiments to demonstrate parallel adaptive ...evolutionary response to a cool climate in populations of wall lizards (Podareis muralis) introduced from southern Europe into England. Low soil temperatures in the introduced range delay hatching, which generates directional selection for a shorter incubation period. Non-native lizards from two separate lineages have responded to this selection by retaining their embryos for longer before oviposition—hence reducing the time needed to complete embryogenesis in the nest—and by an increased developmental rate at low temperatures. This divergence mirrors local adaptation across latitudes and altitudes within widely distributed species and suggests that evolutionary responses to climate can be very rapid. When extrapolated to soil temperatures encountered in nests within the introduced range, embryo retention and faster developmental rate result in one to several weeks earlier emergence compared with the ancestral state.We show that this difference translates into substantial survival benefits for offspring. This should promote short-and long-term persistence of nonnative populations, and ultimately enable expansión into areas that would be unattainable with incubation duration representative of the native range.
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