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Attractiveness data distribution and means errors etc

The seemingly transparent wings of many insects have recently been found to display dramatic structural coloration. These structural colours (wing interference patterns: WIPs) may be involved in species recognition and mate choice, yet little is known about the evolutionary processes that shape them. Additionally, existing research has been restricted by analysing WIPs without due consideration of how they are actually perceived by the viewers’ colour vision. Here, we use multispectral digital imaging and a model ofDrosophilavision to compare WIPs of male and femaleDrosophila simulansfrom replicate populations forced to evolve with or without sexual selection for 68 generations. We show for the first time that WIPs modelled inDrosophilavision evolve in response to sexual selection, and confirm that WIPs correlate with male sexual attractiveness. These findings add a new element to the otherwise well describedDrosophilacourtship display and confirm that wing colours evolve through sexual selection.

The seemingly transparent wings of many insects have recently been found to display unexpected structural coloration. These structural colours (wing interference patterns: WIPs) may be involved in species recognition and mate choice, yet little is known about the evolutionary processes that shape them. Furthermore, to date investigations of WIPs have not fully considered how they are actually perceived by the viewers' colour vision. Here, we use multispectral digital imaging and a model ofDrosophilavision to compare WIPs of male and femaleDrosophila simulansfrom replicate populations forced to evolve with or without sexual selection for 68 generations. We show that WIPs modelled inDrosophilavision evolve in response to sexual selection and provide evidence that WIPs correlate with male sexual attractiveness. These findings add a new element to the otherwise well-describedDrosophilacourtship display and confirm that wing colours evolve through sexual selection.

Genotype-by-environment interactions (G × Es) describe genetic variation for phenotypic plasticity. Recent interest in the role of these interactions in sexual selection has identified G × Es across a diverse range of species and sexual traits. Additionally, theoretical work predicts that G × Es in sexual traits could help to maintain genetic variation, but could also disrupt the reliability of these traits as signals of mate quality. However, empirical tests of these theoretical predictions are scarce. We reared iso-female lines of Drosophila simulans across two axes of environmental variation (diet and temperature) in a fully factorial design and tested for G × Es in the expression of cuticular hydrocarbons (CHCs), a multivariate sexual trait in this species. We find sex-specific environmental, genetic and G × E effects on CHC expression, with G × Es for diet in both male and female CHC profile and a G × E for temperature in females. We also find some evidence for ecological crossover in these G × Es, and by quantifying variance components, genetic correlations and heritabilities, we show the potential for these G × Es to help maintain genetic variation and cause sexual signal unreliability in D. simulans CHC profiles.

Supplementary methods and results

Sexual selection is responsible for the evolution of many elaborate traits, but sexual trait evolution could be influenced by opposing natural selection as well as genetic constraints. As such, the evolution of sexual traits could depend heavily on the environment if trait expression and attractiveness vary between environments. Here, male Drosophila simulans were reared across a range of diets and temperatures, and we examined differences between these environments in terms of (i) the expression of male cuticular hydrocarbons (CHCs) and (ii) which male CHC profiles were most attractive to females. Temperature had a strong effect on male CHC expression, whereas the effect of diet was weaker. Male CHCs were subject to complex patterns of directional, quadratic and correlational sexual selection, and we found differences between environments in the combination of male CHCs that were most attractive to females, with clearer differences between diets than between temperatures. We also show that genetic covariance between environments is likely to cause a constraint on independent CHC evolution between environments. Our results demonstrate that even across the narrow range of environmental variation studied here, predicting the outcome of sexual selection can be extremely complicated, suggesting that studies ignoring multiple traits or environments may provide an over-simplified view of the evolution of sexual traits.

TheBAallele of theDrosophilacytochrome P450 geneCyp6g1confers resistance to a range of insecticides. It is also subject to intralocus sexual conflict when introgressed into theCanton-Sbackground, whose collection predates the widespread use of insecticides. In this genetic background, the allele confers a pleiotropic fitness benefit to females but a cost to males, and exhibits little sexual dimorphism in conferred insecticide resistance. It is unclear whether these sexually antagonistic effects also exist in current populations that have naturally evolved with insecticides, where genetic modifiers that offset male costs might be expected to evolve. Here, we explore these issues usingDrosophila melanogastercaught recently from an Australian population in which theBAallele naturally segregates. While we find increased fecundity in insecticide-resistantBAfemales and no consistent evidence of fitness costs in males, experimental evolution indicates balancing selection at the locus. We suggest that this apparent discrepancy may be due to reduced investment in reproduction in resistant males. Our results at the population level are consistent with previous work, and suggest that individual-level fitness assays do not always capture sexually antagonistic fitness effects that emerge in a population context.

Metallographic, X ray diffraction, and microhardness studies on an alloy of 2.35 wt pct nitrogen, balance iron are reported. This alloy is analogous to the eutectoid iron-carbon alloy with respect to transformation to “pearlitic” and “martensitic” structures. Isothermal transformation at all temperatures is slower in the nitrogen alloy, and the nitrogen austenite is far more stable with respect to transformation to martensite.

Changes in hardness, tensile properties, microstructure, electrical resistance, and X-ray diffraction effects indicate that lattice strains are necessary for the embrittlement of ferritic stainless steels when heated for relatively short times at 475°C (885°F). It is suggested that 475°C (885°F) embrittlement is due to the accelerated formation of an intermediate stage in the formation of σ under the influence of these strains.