Evolutionary theory proposes that signals used in sexual selection can only be stable if they are honest and
condition dependent. However, despite the fact that chemical signals are used by many animals, empirical
research has mainly focused on visual and acoustic signals. Vitamin D is an essential nutrient for lizards,
but in some lizards its precursor (cholesta-5,7-dien-3-olZprovitamin D) is found in femoral gland
secretions, which males use for scent marking and intraspecific communication. By allocating provitamin
D to secretions, males might need to divert vitamin D from metabolism. This might be costly and
condition dependent. We tested whether diet quality affected chemical signals of male Iberian rock lizards
(Lacerta monticola) and its consequences for sexual selection. After experimental supplementation of
dietary vitamin D, males increased the proportion of provitamin D in femoral secretions. Further
experiments showed that females detected these changes in males’ signals by chemosensory cues, and
discriminated provitamin D, and changes in its concentration, from similar steroids (i.e. cholesterol) found
in secretions. Moreover, females preferred areas scent marked by males with more provitamin D in their
secretions. This mechanism would confer honesty to chemical signals of male lizards, and, thus, females
may rely on it to select high-quality males. We suggest that the allocation of vitamins and other essential
nutrients to either visual (e.g. carotenoids) or chemical ornaments might be the common basis of honest
sexual displays in many animals.
Evolutionary theory proposes that signals used in sexual selection can only be stable if they are honest and
condition dependent. However, despite the fact that chemical signals are used by many animals, empirical
research has mainly focused on visual and acoustic signals. Vitamin D is an essential nutrient for lizards,
but in some lizards its precursor (cholesta-5,7-dien-3-olZprovitamin D) is found in femoral gland
secretions, which males use for scent marking and intraspecific communication. By allocating provitamin
D to secretions, males might need to divert vitamin D from metabolism. This might be costly and
condition dependent. We tested whether diet quality affected chemical signals of male Iberian rock lizards
(Lacerta monticola) and its consequences for sexual selection. After experimental supplementation of
dietary vitamin D, males increased the proportion of provitamin D in femoral secretions. Further
experiments showed that females detected these changes in males’ signals by chemosensory cues, and
discriminated provitamin D, and changes in its concentration, from similar steroids (i.e. cholesterol) found
in secretions. Moreover, females preferred areas scent marked by males with more provitamin D in their
secretions. This mechanism would confer honesty to chemical signals of male lizards, and, thus, females
may rely on it to select high-quality males. We suggest that the allocation of vitamins and other essential
nutrients to either visual (e.g. carotenoids) or chemical ornaments might be the common basis of honest
sexual displays in many animals.
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