Sexual selection drives rapid phenotypic diversification of mating traits. However, we know little about the causative genes underlying divergence in sexually selected traits. Here, we investigate the genetic basis of male mating trait diversification in the medaka fishes (genus Oryzias) from Sulawesi, Indonesia. Using linkage mapping, transcriptome analysis, and genome editing, we identify csf1 as a causative gene for red pectoral fins that are unique to male Oryzias woworae. A cis-regulatory mutation enables androgen-induced expression of csf1 in male fins. csf1-knockout males have reduced red coloration and require longer for mating, suggesting that coloration can contribute to male reproductive success. Contrary to expectations, non-red males are more attractive to a predatory fish than are red males. Our results demonstrate that integrating genomics with genome editing enables us to identify causative genes underlying sexually selected traits and provides a new avenue for testing theories of sexual selection.

The diversity of aposematic signals is one of the most difficult phenomena for understanding the evolution of such signals because aposematic animals are most effectively protected when they are common. Theoretical and experimental studies predict that a combination of local selection pressures could maintain variation in aposematic signals. However, the application of this hypothesis to large-scale geographic variation in aposematic signals, other than mimicry systems, is yet to be tested empirically. I investigated geographic variation in morphological and behavioural aposematic signals of the newts, Cynops pyrrhogaster, and in predation pressures on them in populations ranging over 800 km of latitude. Field experiments demonstrated that local differences in predation pressures explain well the island-mainland variation in the aposematic colouration and behaviour of newts. Furthermore, I found a latitudinal gradient in aposematic colouration but not in behaviour, independent of predation pressures. The results suggested that islandmainland variation in aposematic signals resulting from local differences in predation pressures might also be shaped by several factors, such as temperature, body size variation, and genetic differences, and such factors might act on each aposematic trait differently.

Aposematic animals advertise their unprofitability to potential predators with conspicuous coloration, occasionally in combination with other life-history traits. Theory posits that selection on functionally interrelated aposematic characters promotes the unidirectional evolution of these characters, resulting in an increase or decrease in the effectiveness of the signal. To test whether this prediction applies on a microevolutionary scale, the intra-and interpopulational variations in aposematic coloration, behaviour (which enhances the effectiveness of the coloration) and body size of newts, Cynops pyrrhogaster (Urodela: Salamandridae), were investigated. A parallel geographical mosaic of variation in aposematic coloration and behaviour among populations, independent of body size, was found. Newts on islands displayed more conspicuous aposematic traits than those on the mainland, both morphologically and behaviourally. There was no significant relationship between variation in coloration and behaviour within populations. Male newts displayed more conspicuous coloration than females. Surveys of potential predators suggest that variable natural selection at a local scale, such as predation pressure, may primarily be responsible for the microevolution of variable aposematic traits in newts.

The influence of sympatric large animals on the sleeping behavior of primates in the wild is still largely unknown. In this study, we observed behaviors of wild Japanese macaques (Macaca fuscata yakui) at their sleeping sites, using a highly sensitive video camera. We found evidence of nocturnal interspecific interactions, such as agonistic interactions, between Japanese macaques and sika deer (Cervus nippon yakushimae). Deer approached sleeping clusters of macaques, which slept on the ground, to eat their feces or unidentified materials near the sleeping clusters, and as a result, the macaques were often quickly displaced from their sleeping site. There was a significant difference in the occurrence of macaque-deer agonistic interactions between seasons. Our results suggested that the size of the sleeping cluster, the number of adult macaques in the cluster, and the existence of adult males in the cluster did not influence the occurrence of the agonistic interactions. Finally, we discuss the influence of this interaction on macaques and speculate on the influential factors leading to nocturnal coprophagy of macaques' feces by deer.