Signalling components of the house mouse mate recognition system

Subspecies-specific mate recognition may represent significant barrier to gene flow between diverged genomes potentially leading to speciation. In the house mouse, assortative mating involves the coevolution of several signals and receptors. We compared signalling ability of bedding material, faeces, urine, saliva, salivary androgen binding proteins (ABP) and combinations of urine with saliva and urine with ABP in mate choice in two wild-derived inbred strains (one of Mus musculus musculus and one of Mus musculus domesticus origin). We observed high levels of variation in assortative preferences between the two strains and sexes. The strongest preferences were observed in M. m. musculus-derived individuals in tests where urine was present either alone or as part of a composite signal target. M. m. domesticus-derived mice displayed strain-specific preferences for faeces. Saliva was the least preferred stimulus in both strains and sexes. No effect of two-compound cues was detected. We conclude that there is divergence across both the stimulus and preference parts of the recognition system for both house mouse strains. Of the tested stimuli, those that have the capacity to carry a signal for extended periods under natural conditions (such as urine and faeces) seem to be the most important substances in strain-specific recognition.     

Do female fruit flies (Drosophila serrata) copy the mate choice of others?

Female mate-choice copying is a social learning phenomenon whereby a female's observation of a successful sexual interaction between a male and another female increases her likelihood of subsequently preferring that male. Although mate-choice copying has been documented in several vertebrate species, to our knowledge it has not yet been investigated in insects. Here, we investigated whether female mate-choice copying occurs in the fruit fly Drosophila serrata, a model system for the study of mate preferences and the sexual selection they generate. We used two complementary experiments in which focal females were given a choice between two males that differed in either their apparent (as determined visually by the focal female) or actual recent mating success. Mate-choice copying was evaluated by testing whether focal females mated more frequently with the ‘preferred’ male as opposed to the other male. In both experiments, however, we found no evidence for mate-choice copying. We discuss possible reasons for the apparent absence of mate-choice copying in this species.     

Structural Information, Resolution, and Noise in High-Resolution Atomic Force Microscopy Topographs

AFM has developed into a powerful tool in structural biology, providing topographs of proteins under close-to-native conditions and featuring an outstanding signal/noise ratio. However, the imaging mechanism exhibits particularities: fast and slow scan axis represent two independent image acquisition axes. Additionally, unknown tip geometry and tip-sample interaction render the contrast transfer function nondefinable. Hence, the interpretation of AFM topographs remained difficult. How can noise and distortions present in AFM images be quantified? How does the number of molecule topographs merged influence the structural information provided by averages? What is the resolution of topographs? Here, we find that in high-resolution AFM topographs, many molecule images are only slightly disturbed by noise, distortions, and tip-sample interactions. To identify these high-quality particles, we propose a selection criterion based on the internal symmetry of the imaged protein. We introduce a novel feature-based resolution analysis and show that AFM topographs of different proteins contain structural information beginning at different resolution thresholds: 10 Å (AqpZ), 12 Å (AQP0), 13 Å (AQP2), and 20 Å (light-harvesting-complex-2). Importantly, we highlight that the best single-molecule images are more accurate molecular representations than ensemble averages, because averaging downsizes the z-dimension and “blurs” structural details.Abbreviations: 2D, two-dimensional; 3D, three-dimensional; ACV, auto-correlation value; AFM, atomic force microscopy; AQP0, aquaporin-0; AQP2, aquaporin-2; AqpZ, aquaporin-Z; bR, bacteriorhodopsin; CCV, cross-correlation value; CTF, contrast transfer function; DPR, differential phase residual; EM, electron microscopy; FRC, Fourier ring correlation; FSC, Fourier shell correlation; IS, internal symmetry; LH2, light-harvesting-complex 2; RMSD, root mean-square deviation; SD, standard deviation; SNR, signal/noise ratio; SSNR, spectral signal/noise ratio     

杂色藻类硅藻和金藻的77K荧光特性

实验测定了7种杂色藻包括:4种硅藻三角褐指藻(Phaeodactylum tricornutum)、牟氏角毛藻(Cheatoceros mulleri)、中肋骨条藻(Skeletonema costatum)、尖刺拟菱形藻(Pseudo-nitzschia pungens)和3种金藻湛江等鞭金藻(Isochrysis zhanjiangensis)、绿色巴夫藻(Pavlova viridis)、球形棕囊藻(Phaeocystisglobosa)的77 K荧光光谱,并与其它杂色藻以及高等植物菠菜进行了比较。结果表明,4种硅藻和3种金藻的77 K低温荧光发射光谱相似,只有一个明显的荧光发射主峰位于684~686 nm,类囊体膜的荧光光谱中在700 nm附近有个不明显的肩峰,它们均没有高等植物作为PSⅠ特征的730 nm长波荧光发射峰,这个结果与杂色藻类褐藻的荧光特性一致。说明,杂色藻类PSⅠ缺少730 nm长波荧光峰可能具有其普遍性,预示杂色藻类在PSⅠ结构以及能量传递等方面与高等植物具有很大的差异。     

Does competitive divergence occur if assortative mating is costly?

Most models of sympatric speciation have assumed that assortative mating has no costs. A few studies, however, have shown that the costs for being choosy can prevent such speciation. Here, we investigate the role of the strength of assortment and of the costs for being choosy for a simple genetic model of a single ('magic') trait that mediates both intraspecific competition for a continuum of resources and assortative mating, which is induced by choosy females who preferentially mate with males of similar phenotype. Choosiness may be costly if it is difficult to find a mating partner. Such magic trait models are considered to be most conducive of sympatric speciation. We consider a sexually reproducing population of haploid individuals that is density regulated. The trait is determined by a single locus with multiple alleles. The strength of stabilizing selection (caused by a unimodal resource distribution), the strength of competition, the degree of assortment and the costs for being choosy are independent parameters. We investigate analytically and numerically how these parameters determine the equilibrium and stability structure. In particular, we identify conditions under which no polymorphism at all is maintained as well as conditions under which strong competitive divergence occurs, or the population even splits into two reproductively isolated classes of highly diverse phenotypes. If costs are absent or moderate, genetic variability tends to be minimized at intermediate strengths of assortment, and reproductively isolated classes of phenotypes are a likely result of evolution only for intermediate or strong competition and for very strong assortment. The likelihood of divergence depends relatively weakly on the costs as long as they are not high. With high costs, however, increasingly strong assortment rapidly depletes all genetic variation, and strong competitive divergence is prevented.     

Self-poisoning of the mind

Rational-choice theory tries to explain behaviour on the assumption that individuals optimize. Some forms of irrational behaviour can be explained by assuming that the individual is subject to hedonic, pleasure-seeking mechanisms, such as wishful thinking or adaptive preference formation. In this paper, I draw attention to psychic mechanisms, originating in the individual, which make her worse off. I first consider the ideas of counterwishful thinking and of counteradaptive preference formation and then, drawing heavily on Proust, the self-poisoning of the mind that occurs through the operation of amour-propre.     

Z LINKAGE OF FEMALE PROMISCUITY GENES IN THE MOTH UTETHEISA ORNATRIX: SUPPORT FOR THE SEXY‐SPERM HYPOTHESIS?

Female preference genes for large males in the highly promiscuous moth Utetheisa ornatrix (Lepidoptera: Arctiidae) have previously been shown to be mostly Z‐linked, in accordance with the hypothesis that ZZ–ZW sex chromosome systems should facilitate Fisherian sexual selection. We determined the heritability of both female and male promiscuity in the highly promiscuous moth U. ornatrix (Lepidoptera: Arctiidae) through parent–offspring and grandparent–offspring regression analyses. Our data show that male promiscuity is not sex‐limited and either autosomal or sex‐linked whereas female promiscuity is primarily determined by sex‐limited, Z‐linked genes. These data are consistent with the “sexy‐sperm hypothesis,” which posits that multiple‐mating and sperm competitiveness coevolve through a Fisherian‐like process in which female promiscuity is a kind of mate choice in which sperm‐competitiveness is the trait favored in males. Such a Fisherian process should also be more potent when female preferences are Z‐linked and sex‐limited than when autosomal or not limited.     

CONVERGENT EVOLUTION OF RED CAROTENOID COLORATION IN WIDOWBIRDS AND BISHOPS (EUPLECTES SPP.)

Avian carotenoid‐based signals are classic examples of sexually selected, condition‐dependent threat displays or mate choice cues. In many species, male dominance or mating success is associated with redder (i.e., longer wavelength) color hues, suggesting that red colors are either more efficient or more reliable signals than yellow colors. Few studies, however, have investigated selection for redness in a macroevolutionary context. Here, we phylogenetically reconstruct the evolution of carotenoid coloration in the African widowbirds and bishops (Euplectes spp.), for which agonistic selection for redder hues, as well as pigmentary mechanisms, is well documented. Using reflectance spectrometry for objective color quantification, and accounting for phylogenetic uncertainty, we find that yellow plumage color is a retained ancestral state in Euplectes, and that red color hues have convergently evolved two or three times. Results are discussed in relation to a known diversity in pigment mechanisms, supporting independent origins of red color, and suggesting that agonistic selection and physiological constraints have interacted to generate color diversity in Euplectes.