Nuptial gifts and female fecundity in the neotropical katydid Conocephalus ictus (Orthoptera: Tettigonidae)

Potential strategic allocation of nuptial gift proteins of the neotropical katydid Conocephalus ictus (Orthoptera Tettigoniidae)

In many katydids, the male feeds his mate with a large gelatinous spermatophore. While providing large spermatophores can increase female fecundity and lifespan, it may also decrease their sexual receptivity, benefiting male fitness. Allocating resources to these edible gifts may entail a lower apportionment of them to other functions, generating a trade-off between somatic and reproductive functions. Despite their effect on male and female fitness, little is known of the compounds associated with katydid spermatophores. Our study found 177 different putative proteins in the spermatophore of Conocephalus ictus, with no correlation between male body size with spermatophore mass, number, concentration and mass of proteins. However, we did observe a negative relationship between male forewing length and protein concentration, and a negative relationship between the mass of the spermatophore transferred to the females and their body size, suggesting a resource allocation trade-off in males, but also strategic transference of resources based on female quality.

Correlated sexual selection on male genitalia, copulatory performance and nuptial gifts in a bushcricket (Orthoptera: Tettigoniidae) indicated by allometric scaling

We adopt an allometric framework of scaling relationships for comparison between mating-related traits in the middle European bushcricket Roeseliana roeselii (Hagenbach, 1822). Eight characters, covering ontogenetic fitness (size traits; fixed at final moult), male condition (mass traits) and mating motivation (reproductive behaviours), were analysed in unrestricted matings and in matings involving genital manipulation. Shortening the male titillators had no effect on mating-related traits in males. However, titillators, known to be under sexual selection, scale hyperallometrically, with larger males possessing proportionally longer titillators, performing more titillator movements and exhibiting a reduced duration of copulation. Scaling was also hyperallometric for spermatophore mass, with larger males being heavier and transferring heavier nuptial gifts. Both titillator length and spermatophore mass might be condition-dependent indicators, because their variances were nearly twice as large those of body size or body mass. Mass traits were also dynamic, increasing by 11% for male body mass and 17% for spermatophore mass between the first and second matings. Sexual selection by female choice seems to favour larger trait size in the bushcricket R. roeselii, acting in concert on titillator length, intensity of titillator movements and spermatophore mass.

Fighting and aggressive sound determines larger male to win male-male competition in a bark beetle

Intrasexual selection occurs in male-male competition over access to females and usually results in the larger male winning. While much research has documented that size matters, little is known about how the larger male wins. Dendroctonus valens is an aggregating monogamous bark beetle in which males have large variation in body size and display intense competition over females. Behavioral observation showed two males fight each other within the gallery by pushing/shoving and stridulated more when two males encountered each other. Experiments using two different-sized males synchronously competing showed that larger males won 95% of contests. Reciprocal displacement experiments using muted and intact males of different or equal size were used to simulate male-male competition. Larger males displaced the smaller resident male in 90% of contests, while smaller males prevailed over larger residents in 6.7% of contests. With both males silenced, larger males displaced smaller males in 80% of contests, while smaller males prevailed in 8% of contests. Further experiments using equal-sized males showed aggressive sound-emitting males displaced muted males in 67% of contests, yet intact males displaced other intact males in only 37.5% of contests. Sound analysis showed sound pressure level is an honest signal of body size and males chose soft sounds over loud aggressive sounds in assays. Therefore, D. valens males have evolved dual behaviors, fighting and aggressive sounds associated with body size, to assess rivals to compete for a partner, gaining insights in male-male competition for this species and for other animals.

Males Become Choosier in Response to Manipulations of Female Wing Ornaments in Dry Season Bicyclus anynana Butterflies

Male investment towards reproduction is substantial in some species, and this leads to the evolution of choosy males. Male choice is often directed towards female phenotypes that are good indicators of fecundity such as body size, age, or virgin status, and often acts in the same direction as fecundity selection. In insects, only a few examples exist where male choice is directed towards female ornaments as proxies Butler of female quality. Here, we use dry season males of the sex-role reversed butterfly species Bicyclus anynana to test for differences in male choosiness and investment towards females of varying attractiveness using ornament-manipulations. Male reproductive investment in this species is in the form of a nuptial gift, a spermatophore, given to females upon mating. Males were placed in cages with either wild-type ornamented females or with nonornamented females (center of the dorsal forewing eyespots painted over), and time to mating, duration of mating, and longevity of males and females after a single mating were measured. Ornament manipulations consisted of blocking the UV-reflective scales in the center of the dorsal forewing eyespots of females, a known sexual ornament. Males displayed lower latency to mate and longer mating durations with ornamented females. The longer mating duration did not, however, translate in the transfer of a nuptial gift that increased female longevity or reduced male longevity. Instead, we propose that longer mating durations with ornamented females may represent increased mate guarding behavior or increased sperm transfer.

Macronutrient intake regulates sexual conflict in decorated crickets

Sexual conflict results in a diversity of sex-specific adaptations, including chemical additions to ejaculates. Male decorated crickets (Gryllodes sigillatus) produce a gelatinous nuptial gift (the spermatophylax) that varies in size and free amino acid composition, which influences a female's willingness to fully consume this gift. Complete consumption of this gift maximizes sperm transfer through increased retention of the sperm-containing ampulla, but hinders post-copulatory mate choice. Here, we examine the effects of protein (P) and carbohydrate (C) intake on the weight and amino acid composition of the spermatophylax that describes its gustatory appeal to the female, as well as the ability of this gift to regulate sexual conflict via ampulla attachment time. Nutrient intake had similar effects on the expression of these traits with each maximized at a high intake of nutrients with a P : C ratio of 1 : 1.3. Under dietary choice, males actively regulated their nutrient intake but this regulation did not coincide with the peak of the nutritional landscape for any trait. Our results therefore demonstrate that a balanced intake of nutrients is central to regulating sexual conflict in G. sigillatus, but males are constrained from reaching the optima needed to bias the outcome of this conflict in their favour.