UV-Induced Fluorescence in the Balance: Mate Choice and Predation Risk in the Female Ornamented Jumping Spiders.

The adaptive significance of female ornamentation remains a central question in evolutionary biology, with ultraviolet (UV)-induced fluorescence emerging as a key area of interest. This study investigates the potential adaptive advantages of female-specific UV-induced fluorescence in male mate choice and predation risk, as fitness costs, using two species of ornate jumping spiders Phintella vittata and Ph. bifurcilinea. In these species, the palps of adult females exhibit UV-induced fluorescence, offering a compelling model to explore the interplay of sexual and natural selection acting on female ornamentation. In male mate-choice trials, males were presented with a choice between a fluorescent (F+, UV-visible) and a non-fluorescent (F-, UV-blocked) female. Males showed pronounced mate preference for F+ females over F- females, that is, spending significantly more time interacting with F+ females, suggesting that fluorescence serves as a sexually selected signal. To assess the potential costs of fluorescence, we tested its effect on predation risk using the spider-eating jumping spider Portia xishan as a predator under F+ and F- conditions. Predation rates were significantly higher for F+ females than for F- females, indicating that UV-induced fluorescence increases detectability by predators. These findings provide empirical evidence of a trade-off: While fluorescence enhances male mate preference, it also increases predation risk. This study is the first to demonstrate the dual roles of fluorescence in sexual signaling and predation in female jumping spiders, challenging traditional male-centric perspectives on mate choice. By integrating behavioral and ecological approaches, this work offers new insights into the evolutionary trade-offs associated with female sexually selected traits.