Interpopulation variation in female remating is attributable to female and male effects in Callosobruchus chinensis

The evolution of female multiple mating is best understood by consideration of male and female reproductive perspectives. Females should usually be selected to remate at their optimum frequencies whereas males should be selected to manipulate female remating to their advantage. Female remating behavior may therefore be changed by variation of male and female traits. In this study, our objective was to separate the effects of female and male strains on female remating for the adzuki bean beetle, Callosobruchus chinensis, for which there is interstrain variation in female remating frequency. We found that interstrain variation in female remating is primarily attributable to female traits, suggesting genetic variation in female receptivity to remating in C. chinensis. Some interstrain variation in female remating propensity was attributable to an interaction between female and male strains, however, with the males of some strains being good at inducing nonreceptivity in females from one high-remating strain whereas others were good at inducing copulation in nonvirgin females from the high-remating strain. There is, therefore, interstrain variation in male ability to deter females from remating and in male ability to mate successfully with nonvirgin females. These results suggest that mating traits have evolved along different trajectories in different strains of C. chinensis.</p

Data from Receptive females mitigate costs of sexual conflict

data of three experiments: comparison of (1) remating receptivity, (2) costs of male exposure, and (3) costs of mating between females from selection lines

Data from Harano & Kutsukake 2018 J Evol Biol

Posterior observations for each parameter (θ0, the trait value for the most recent common ancestor; μ0, the baseline evolutionary rate; and drsl, the effect of consistent directional selection in a specific branch) of five independent MCMC chains

Data from: Directional selection in the evolution of elongated upper canines in clouded leopards and sabre-toothed cats

Extremely developed or specialised traits such as the elongated upper canines of extinct sabre-toothed cats are often not analogous to those of any extant species, which limits our understanding of their evolutionary cause. However, an extant species may have undergone directional selection for a similar extreme phenotype. Among living felids, the clouded leopard, Neofelis nebulosa, has exceptionally long upper canines for its body size. We hypothesised that directional selection generated the elongated upper canines of clouded leopards in a manner similar to the process in extinct sabre-toothed cats. To test this, we developed an approach that compared the effect of directional selection among lineages in a phylogeny using a simulation of trait evolution and approximate Bayesian computation. This approach was applied to analyse the evolution of upper canine length in the Felidae phylogeny. Our analyses consistently showed directional selection favouring longer upper canines in the clouded leopard lineage and a lineage leading to the sabre-toothed cat with the longest upper canines, Smilodon. Most of our analyses detected an effect of directional selection for longer upper canines in the lineage leading to another sabre-toothed cat, Homotherium, although this selection may have occurred exclusively in the primitive species. In all the analyses, the clouded leopard and Smilodon lineages showed comparable directional selection. This implies that clouded leopards share a selection advantage with sabre-toothed cats in having elongated upper canines

Revisiting the evolutionary trend toward the mammalian lower jaw in non-mammalian synapsids in a phylogenetic context

The mammalian lower jaw comprises a single bone, the dentary, which is a unique feature among vertebrates. The lower jaws of extinct non-mammalian synapsids were composed of the dentary and several postdentary bones. Synapsid fossils exhibit variation in the dentary size relative to the overall lower jaw. An evolutionary trend toward dentary enlargement and postdentary reduction in non-mammalian synapsids has long been documented but has not been established using modern phylogenetic comparative methods. In this study, we examine the evolutionary pattern of dentary size relative to the lower jaw through phylogenetic analyses of measurements in a broad range of non-mammalian synapsid taxa. Our analyses revealed an evolutionary trend toward dentary area enlargement relative to the overall lower jaw in the lateral view across all non-mammalian synapsids. This trend is likely due to vertical expansion of the dentary given that the same trend is not evident when looking at anterior to posterior measurements of the dentary relative to the lower jaw as a whole in lateral view. Ancestral character reconstructions revealed that the evolution of the measurements was not unidirectional in non-mammalian synapsids. Our results provide no evidence of an evolutionary trend toward the dentary enlargement at the expense of postdentary bones across non-mammalian synapsids. This implies that the evolutionary origin of the mammalian lower jaw is not adequately explained by the evolutionary trend of dentary enlargement throughout non-mammalian synapsids. Instead, selection that occurred during the transition from non-mammalian cynodonts to early mammals may have produced the mammalian lower jaw

Inbreeding depression in development, survival, and reproduction in the adzuki bean beetle (Callosobruchus chinensis)

Inbreeding depression of an aspect of fitness is observed in many insects, but the traits that are of importance for inbreeding depression of fitness remain poorly understood. Here the magnitude of inbreeding depression of fitness-related traits in the development and adult stages was measured in a captive population of the adzuki bean beetle, Callosobruchus chinensis (Coleoptera: Bruchidae). Beetles produced by full-sib matings had 8% lower survival in the development stage than did beetles produced by unrelated matings. Although inbred and outbred offspring did not differ in body size after emergence, inbred offspring took 2-3% longer to develop to emergence. This indicates inbreeding depression of growth rate. At the adult stage, inbreeding had no significant effect on longevity, however lifetime offspring production was reduced by 11%. Thus, the magnitude of inbreeding depression was relatively large for offspring production. This suggests inbreeding depression of fitness manifests, to a particularly significant extent, in reduced productivity. This study shows the C. chinensis population, which has been in captivity for more than 100 generations, harbors genetic loads

Water Availability Affects Female Remating in the Seed Beetle, Callosobruchus chinensis

Benefits of multiple mating to females may come from the acquisition of water in male ejaculates. This hypothesis seems plausible in species in which males provide females with large ejaculates and has been tested with the prediction that females mate more frequently when an external source of water is unavailable. My study observed that females deprived of water were more likely to remate than females given water in the adzuki bean beetle, Callosobruchus chinensis. This result suggests that females may absorb the water in male ejaculates and thus change their remating receptivity according to the need for additional water. However, compared with related species, the ejaculate size is smaller, so ejaculatory hydration benefits are expected to be small in this species. There were no significant differences in lifetime fecundity and longevity between females that were allowed to receive one ejaculate from remating and females that were not allowed to do so when water was unavailable. This provides no evidence that receiving an additional ejaculate enhances female fitness. Thus, obtaining water from male ejaculates may partly compensate the costs of remating to females, although it alone would be insufficient to explain polyandry in C. chinensis. Increased mating frequency in water-deprived females would not necessarily support the hypothesis that females remate for ejaculatory hydration benefits

Female seed beetles, Callosobruchus chinensis, remate more readily after mating with relatives

Mate relatedness can have an impact on fitness and inbreeding avoidance is a potential factor shaping mating behaviour. When females are unable to avoid mating with kin, they may exploit postcopulatory mechanisms as an alternative means to avoid inbreeding. If females increase their remating propensity after incestuous matings, they could reduce the likelihood of kin siring their offspring. We investigated the effects of male relatedness on the probabilities of female first mating and remating in the adzuki bean beetle, Callosobruchus chinensis. Females showed no precopulatory discrimination against brothers at their first or second mating. In contrast, females mated first with brothers were more willing to remate than females mated first with unrelated males. We found no evidence that males transfer fewer sperm when mating with sisters. This study suggests that C. chinensis does not avoid inbreeding before and during copulation. Instead, females that mated with related males adapted their subsequent mating behaviour to avoid the potential costs of inbreeding. Polyandry in this species may be the result of females attempting to prevent genetic incompatibility by remating after having mated to a relative

No genetic correlation between the sexes in mating frequency in the bean beetle, Callosobruchus chinensis

Female multiple mating, which is common in animals, may have evolved not in response to fitness advantages to females but as a genetic corollary to selection on males to mate frequently. This nonadaptive hypothesis assumes a genetic correlation between females and males in mating frequency, which has received a few empirical investigations. We tested this hypothesis by observing the correlated response in male mating frequency in the adzuki bean beetle, Callosobruchus chinensis to artificial selection on female propensity to remate. Compared to control females, females from lines selected for increased or decreased female propensity to remate had, respectively, higher or lower mating frequency measured by the number of mating within a given period. This indicates that female receptivity to remating is genetically correlated with female mating frequency, and thus the artificial selection for female propensity to remate influenced female mating frequency. In contrast, males from the selected lines that diverged in female mating frequency did not vary significantly in their mating frequency. These results indicate that there is no genetic correlation between the sexes in mating frequency in C. chinensis. This study shows that the reason why females in C. chinensis remate despite suffering fitness costs cannot be explained by indirect selection resulting from selection on males to mate multiple times