I'm sexy and I glow it: female ornamentation in a nocturnal capital breeder

In many species, males rely on sexual ornaments to attract females. Females, by contrast, rarely produce ornaments. The glow-worm (Lampyris noctiluca) is an exception where wingless females glow to attract males that fly in search of females. However, little is known about the factors that promote the evolution of female ornaments in a sexual selection context. Here, we investigated if the female ornament of the glow-worm is a signal of fecundity used in male mate choice. In support of this, we found brightness to correlate with female fecundity, and males to prefer brighter dummy females. Thus, the glow emitted by females is a reliable sexual signal of female fecundity. It is likely that male preference for the fecundity-indicating ornament has evolved because of large variation among females in fecundity, and because nocturnal males cannot directly assess female size and fecundity. These results indicate that female ornamentation may evolve in capital breeders (i.e. those in which stored resources are invested in reproduction) when females vary significantly in fecundity and this variation cannot be assessed directly by males.     

What is driving male mate preference evolution in Jamaican field crickets?

Male mating preferences are often a neglected aspect of studies on sexual selection. Male mating preferences may evolve if they provide males with direct‐fitness benefits such as increased opportunity to fertilize more eggs or indirect‐fitness benefits such as enhanced offspring survival. We tested these ideas using Jamaican field crickets, Gryllus assimilis, previously shown to exhibit male mating preferences. We randomly mated males to either their preferred or non‐preferred potential mates and then asked whether mating treatment influenced egg oviposition or offspring viability. Preferred females were not significantly more fecund and did not produce more viable eggs or offspring than non‐preferred females. Male mate preferences were therefore inconsistent with both the direct‐ and indirect‐fitness benefits hypotheses under the conditions of our experiment. Our null results leave us with an open question about what is driving the evolution of mating preferences in male crickets. Future research should explore the whether the offspring of preferred females are more attractive, have stronger immune systems, and/or experience higher adult longevity.     

Sexes of a monomorphic species differ in preference for mates with a novel trait

We investigated the different roles of the sexes in the originationof novel traits in the sexually monomorphic Javanese mannikinLonchura leucogastroides. We introduced a red feather as anevolutionarily novel trait in both sexes and tested their preferencesfor prospective mates with this trait. Males rejected femalesbearing the red feather and preferred to court unadorned females.In contrast, females partly preferred adorned males. Specifically,previously unattractive males gained in attractiveness and could increasetheir reproductive success when bearing the ornament, whereas previouslyattractive males lost in attractiveness, but this did not affect theirreproductive success. We introduced two other novel traits inmales and investigated the females' response to these in matechoice tests. Each of the three new traits interacted with thenatural attractiveness of males. The more attractive a malewas before ornamentation, the more it lost in attractiveness afterornamentation and vice versa. Thus, the position of the traitdid not affect the interaction. Because males rejected adornedfemales and females partly preferred adorned males, novel traitsmight evolve by intersexual selection in males rather than infemales. This can lead to a sexual dimorphism with conspicuoustraits in males. Our study reveals a new insight into the mechanismof the evolution from monomorphism to dimorphism with ornamentaltraits in males.