Playfulness in Adults Revisited: The Signal Theory in German Speakers.

The Effect of Sexual Selection on Offspring Fitness Depends on the Nature of Genetic Variation

Creativity offers both survival and reproductive benefits, being a desirable trait in potential mates and linked to fertility and sexuality. We investigated whether viewing attractive faces of potential short-term or long-term partners in a simulated dating portal enhances participants’ creativity. We also explored possible mediators (arousal, mood, sexual arousal, motivation, and attraction) and moderators (relationship status, satisfaction, mate value, and sociosexual orientation). In Study 1, 483 participants (Mage = 30.06, SD = 6.37; 242 women, 241 men) viewed either four attractive or four unattractive opposite-sex potential partners and wrote self-promotional bios. No significant creativity differences were found between the attractive and unattractive groups. However, men were more flexible and produced more original ideas than women, while women showed greater fluency and self-creativity promotion. In Study 2, 494 participants (Mage = 30.84, SD = 6.06; 258 women, 236 men) viewed profiles of attractive potential partners for either short-term or long-term inclined relationships. Women's fluency and originality were higher in the long-term condition, but sexual arousal negatively impacted both fluency and originality when choosing an attractive partner for a long-term relationship, particularly when a real date desirability with the mate was high. Overall, the results suggest that creativity is influenced by the mating context, though the effects were modest. Future studies should increase sample sizes, geographic diversity, and experimental settings.

Measuring mate preferences: Absolute and comparative evaluation of potential partners

BackgroundDespite its short-term costs, behaviour that appears altruistic can increase an individual’s inclusive fitness by earning direct (selfish) and/or indirect (kin-selected) benefits. An evolved preference for other-regarding or helping behaviour in potential mates has been proposed as an additional mechanism by which these behaviours can yield direct fitness benefits in humans.ResultsWe asked 32 heterosexual women and 35 heterosexual men to rate the attractiveness of members of the opposite sex in the presence and the absence of information about helping behaviours. Reports of helping behaviour were associated with a significant increase in the attractiveness of both men and women as potential long-term sexual partners. Altruism also increased the attractiveness of men as potential partners for short-term flings, but to a lesser extent than when the same men were being considered for long-term relationships. Altruism did not affect the attractiveness of women as partners for short-term flings.ConclusionsOur results unite two important areas of evolutionary theory – social evolution and sexual selection – and extend the list of means by which helping behaviours, which appear at first glance to be costly to the actor, can in fact earn direct fitness benefits. Helping behaviours may be attractive because they signal ‘good genes’ and/or because they are perceived as a signal of likely provision of non-genetic benefits (e.g. parental care). Exactly why helping behaviours in a non-mating context might be attractive to potential mates, and whether they are honest signals of mate quality, remains to be elucidated.

With the advent of QTL mapping in the late 1980s, evolutionary geneticists have actively dissected the genetic basis of adaptive phenotypes. In recent times, advances in whole genome sequencing have allowed for finer scale mapping of traits that have diverged due to natural selection. These relatively inexpensive sequencing technologies have also greatly facilitated adaptive trait dissection in non-model species that exhibit especially interesting patterns of adaptation. One class of trait that has largely escaped the attention of the next generation ecological and evolutionary genomics research programme, are sexually-selected traits. Sexual selection is a strong form of directional selection in nature and is thought to be responsible for the evolution of elaborate sexual ornaments and armaments. However we still know comparatively little of the genetic basis of such traits. The cuticular hydrocarbons (CHCs) of Drosophila serrata provide an opportunity for dissecting the divergence of sexually selected traits. Populations along the eastern Australian coast exhibit latitudinal variation in these traits in association with climatic factors and consistent with the action of divergent natural selection. Under experimental settings, divergent sexual as well as natural selection has been implicated in the evolution of CHCs. Natural populations of D. serrata along the northern part of the Eastern Australian coast have recently been observed to exhibit a polymorphism in three of their CHC compounds representing the shortest carbon chains; 5,9-tetracosadiene (5,9-C24), 5,9-pentacosadiene (5,9-C25) and 9-pentacosene (9-C25). One class of phenotype only expresses these three compounds in trace amounts (‘low’ phenotype) whereas the other has normal levels (‘high’ phenotype). These short-chained CHCs also exhibit strong genetically-based latitudinal clines up to, but not beyond, 20 degrees south of the equator. Based on both traditional QTL and modern sequence-based genomic mapping approaches, the aim of this study was to dissect the genetic basis of the polymorphism in D. serrata CHCs and to examine its adaptive significance within the context of sexual and natural selection. Through F2 QTL mapping based on a cross between two inbred lines, from the opposite ends of the D. serrata CHC cline, one a ‘low’ phenotype and the other a ‘high’ phenotype, the genetic basis of all CHCs in this species was mapped to twenty two overlapping QTLs on chromosomes 2 and 3. The short-chain CHC polymorphism was traced to two major effect recessive QTLs on the right arm of chromosome 3, which including their interaction, accounted for more than 70% of the variance in the polymorphism (Chapter 2). Fine mapping of this major polymorphism was then conducted using next generation DNA sequencing and bulk segregant analysis of an advanced F60 cross of the same founding lines. Bulk segregant analysis revealed a single peak of genetic differentiation on chromosome 3R (~20kb), harbouring three adjacent fatty acyl-CoA reductase genes (Chapter 3). Other candidate genes already reported in the literature as underlying CHC variation in Drosophila were also detected nearby the reductases but appear unlikely responsible for the polymorphism. An analysis of genome sequences for nine independent wild-derived inbred lines, fixed for either the ‘low’ or ‘high’ phenotype, replicated the results of the bulk segregant analysis and uncovered a hotspot of fixed nucleotide differences within three adjacent reductase genes, particularly in gene CG17560. This gene has recently been confirmed to be expressed in D. serrata oenocytes in both CTN42 and FORS4 lines (Chapter 4). In an attempt to identify the likely sources of natural and sexual selection acting on and maintaining this polymorphism, I assayed desiccation resistance and heat stress survival on multiple lines of contrasting phenotype from a single population of flies in Cooktown, far north Queensland. I also assayed male and female mate choice on the same lines (Chapter 5). The fitness effects of the polymorphism appeared sex-specific. Natural selection seemed to operate on this polymorphism through females, with ‘low’ individuals being superior to ‘high’ ones in their survival to desiccation. By contrast, the effect of sexual selection on this polymorphism was evident in males but not females. ‘Low’ males were half as likely to succeed in copulation as their ‘high’ counterparts. This is the first study to trace the genetic basis of CHC variation to gene level in D. serrata and exposes a small genomic region where a polymorphism may be maintained by an antagonistic relationship between natural and sexual selection. Although complex traits are generally polygenic, mutations within specific segments of a biosynthetic pathway may have a pervasive effect on trait divergence if targeted by selection. Further tissue–specific gene expression analysis is likely to pinpoint the gene and ultimately the actual causal mutation(s) underlying this polymorphism. Combining traditional QTL and modern genomic approaches may greatly accelerate the fine-scale genetic dissection of adaptive trait divergence in non-model species.

Iridescent polychromatism in a female hummingbird: is it related to feeding strategies?

Second CISM-IFToMM international symposium on theory and practice on robots and manipulators

We welcome the comment by Urbach and Cotton (2008) on our exploratory analysis of the consequences of sexual selection for fisheries-induced evolution (Hutchings and Rowe 2008). Two primary conclusions emerged from our work. First, irrespective of the underlying cause, fisheries-induced evolution of traits linked to reproductive success may lead to unanticipated consequences regarding the rate and direction of genetic change. Secondly, if reproductive success increases with body size, and if the variability in body size declines with increased fishing pressure, the strength of selection for smaller body size may be comparatively rapid. While accepting these conclusions, Urbach and Cotton (2008) proffer the legitimate argument that an increase in reproductive success with body size need not always be a consequence of sexual selection. With regard to our analysis, they suggest that (i) our example might represent natural selection rather than sexual selection and (ii) the consequences of sexual selection to fisheries-induced evolution may be more complicated than our analyses might have indicated. We agree entirely with the second point. Regarding the first point, the authors argue that increased reproductive success with increasing body size in Atlantic cod need not be a consequence of sexual selection. Rather, given the curvilinear increase, for example, in fecundity with female body size characteristic of most fishes, such a relationship may be more appropriately described as being a consequence of natural selection. In response, we might initially caution against drawing a finer distinction between sexual and natural selection than may be warranted. Nonetheless, Urbach and Cotton (2008) draw attention to what constitutes an appropriate null model for the question at hand. Within this context, one means of addressing the issue (for females) is to compare the slope of the regression relating fecundity to female body size with that of the regression relating reproductive success to female body size. If the slopes are equal, then the argument could be made that our exploratory analysis dealt with an element of natural, rather than sexual, selection. Alternatively, if the slope of the reproductive success:body size regression exceeds that of the fecundity:body size regression (indicating that success increased at a faster rate with body size than that predicted by the rate of increase in egg number with body size), the argument could be made that our paper dealt with sexual, rather than (or, more appropriately, in conjunction with) natural selection. Estimates of the slopes of fecundity:length regressions have been reported for Atlantic cod in the same geographical region from which our experimental cod were obtained. Fitting egg number and body length data to the same exponential function that Hutchings and Rowe (2008) used to estimate reproductive success as a function of length, McIntyre and Hutchings (2003) reported slopes of 0.044 and 0.052 for cod inhabiting the Southern Gulf of St Lawrence and Georges Bank, respectively. These are lower than the slope of the regression between body length and offspring number for females (0.071) in the data set used by Hutchings and Rowe (2008). Based on this comparison, and based on the highly skewed relationships that have been documented between male body size and reproductive success in Atlantic cod (Rowe et al. 2008), we suggest that it may be premature to discount the possibility that sexual selection is partially responsible for the increased reproductive success concomitant with increases in body size modelled by Hutchings and Rowe (2008). We concur with Urbach and Cotton's (2008) recommendation that the effects of sexual selection on fisheries-induced evolution warrant considerably more research than has been undertaken to date. By articulating several predictions and various points for consideration, they have contributed to the development of a theoretical framework within which one might assess the influence of sexual selection on the strength, rate and direction of evolutionary change generated by exploitation.

The (mis)concept of species recognition

Natural selection is considered a major force shaping brain size evolution in vertebrates, whereas the influence of sexual selection remains controversial. On one hand, sexual selection could promote brain enlargement by enhancing cognitive skills needed to compete for mates. On the other hand, sexual selection could favour brain size reduction due to trade-offs between investing in brain tissue and in sexually selected traits. These opposed predictions are mirrored in contradictory relationships between sexual selection proxies and brain size relative to body size. Here, we report a phylogenetic comparative analysis that highlights potential flaws in interpreting relative brain size-mating system associations as effects of sexual selection on brain size in shorebirds (Charadriiformes), a taxonomic group with an outstanding diversity in breeding systems. Considering many ecological effects, relative brain size was not significantly correlated with testis size. In polyandrous species, however, relative brain sizes of males and females were smaller than in monogamous species, and females had smaller brain size than males. Although these findings are consistent with sexual selection reducing brain size, they could also be due to females deserting parental care, which is a common feature of polyandrous species. Furthermore, our analyses suggested that body size evolved faster than brain size, and thus the evolution of body size may be confounding the effect of the mating system on relative brain size. The brain size-mating system association in shorebirds is thus not only due to sexual selection on brain size but rather, to body size evolution and other multiple simultaneous effects.

Sexual selection can be an engine of divergent evolution between closely related lineages, as a result of idiosyncratic coevolution of male and female reproductive traits. The possibility that this can contribute to speciation has ample support from comparative studies but very few experimental evolution studies have addressed the role of sexual selection in very early stages of divergent evolution. Here, we use experimental evolution to study divergent evolution between replicate lines of the seed beetle Acanthoscelides obtectus evolving under strong or weak sexual selection for>190 generations. We first confirm that the experimental regimes employed resulted in marked differences in the strength of sexual selection. We then indirectly assess the degree of divergent evolution of those male and female traits that affect postmating sexual selection, by crossing replicate lines. We find that lines evolving under strong sexual selection are more divergent in reproductive traits, as evidenced by a stronger male×female interaction for male sperm competition success. Finally, we assess the degree of divergent evolution in the expression of candidate genes for male seminal fluid proteins and female reproductive proteins. We find that lines evolving under strong sexual selection are more divergent in the expression of reproductive proteins, providing a possible causal mechanism contributing to the results seen in the reproductive phenotype. Our findings provide evidence for more divergent evolution of reproductive traits under stronger sexual selection, in line with the tenet that sexual selection may promote divergence even in the absence of environmental differences between populations.

Sexual selection can be defined in terms of mating preferences which favour particular genotypes or phenotypes and which are expressed at the same level in all females without any degree of assortment in the matings. In this paper, population genetic models are analysed in which assortative mating is combined with sexual selection. If separate mating preferences for each of three genotypes at a locus give rise to sexual selection and if each genotype may also mate assortatively, then a wide range of conditions entails the establishment of a unique, globally stable equilibrium which coincides with the equilibrium for assortative mating alone. Under certain other conditions, however, one of two different stable equilibria will be established dependent on the parameters of both sexual selection and assortative mating. This multiplicity of equilibria cannot arise in models involving either sexual selection or assortative mating alone. If females prefer either dominant or recessive phenotypes, then the advent of sexual selection prohibits the fixation that would occur by assortative mating alone: the effect of sexual selection is to ensure that a globally stable equilibrium will be established. In the combined model, therefore, sexual selection for a dominant trait exerts a greater effect on the final outcome than assortative mating. However, in contradistinction to the model with dominance, assortative mating usually determines the outcome when genotypes are preferred and assort separately.

Explosive speciation rates and unusual species richness in haplochromine cichlid fishes: Effects of sexual selection

Sexual selection has had profound effects at the copulatory and postcopulatory levels, upon the evolution of reproductive anatomy, physiology, and patterns of mating behavior. This review deals with the effects of sexual selection upon the evolution of relative testes sizes, sperm morphology, seminal vesicular function, penile morphology, and copulatory behavior in the Order Primates. The concept of cryptic female choice is also discussed, and its potential value in understanding how co-evolution of genital morphologies may have occurred in primates and inother animals.

7 - Mating Conflicts and Sperm Competition in Simultaneous Hermaphrodites