X-linked meiotic drive can boost population size and persistence

X-linked meiotic drivers cause X-bearing sperm to be produced in excess by male carriers, leading to female-biased sex ratios. Here, we find general conditions for the spread and fixation of X-linked alleles. Our conditions show that the spread of X-linked alleles depends on sex-specific selection and transmission rather than the time spent in each sex. Applying this logic to meiotic drive, we show that polymorphism is heavily dependent on sperm competition induced both by female and male mating behavior and the degree of compensation to gamete loss in the ejaculate size of drive males. We extend these evolutionary models to investigate the demographic consequences of biased sex ratios. Our results suggest driving X-alleles that invade and reach polymorphism (or fix and do not bias segregation excessively) will boost population size and persistence time by increasing population productivity, demonstrating the potential for selfish genetic elements to move sex ratios closer to the population-level optimum. However, when the spread of drive causes strong sex-ratio bias, it can lead to populations with so few males that females remain unmated, cannot produce offspring, and go extinct. This outcome is exacerbated when the male mating rate is low. We suggest that researchers should consider the potential for ecologically beneficial side effects of selfish genetic elements, especially in light of proposals to use meiotic drive for biological control.     

Physical interactions facilitate sex change in the protogynous orange-spotted grouper,Epinephelus coioides

Sex change in teleost fishes is commonly regulated by social factors. In species that exhibit protogynous sex change, such as the orange-spotted grouper Epinephelus coioides, when the dominant males are removed from the social group, the most dominant female initiates sex change. The aim of this study was to determine the regulatory mechanisms of socially controlled sex change in E. coioides. We investigated the seasonal variation in social behaviours and sex change throughout the reproductive cycle of E. coioides, and defined the behaviour pattern of this fish during the establishment of a dominance hierarchy. The social behaviours and sex change in this fish were affected by season, and only occurred during the prebreeding season and breeding season. Therefore, a series of sensory isolation experiments was conducted during the breeding season to determine the role of physical, visual and olfactory cues in mediating socially controlled sex change. The results demonstrated that physical interactions between individuals in the social groups were crucial for the initiation and completion of sex change, whereas visual and olfactory cues alone were insufficient in stimulating sex change in dominant females. In addition, we propose that the steroid hormones 11-ketotestosterone and cortisol are involved in regulating the initiation of socially controlled sex change.     

The rates of introgression and barriers to genetic exchange between hybridizing species: sex chromosomes vs autosomes

Interspecific crossing experiments have shown that sex chromosomes play a major role in reproductive isolation between many pairs of species. However, their ability to act as reproductive barriers, which hamper interspecific genetic exchange, has rarely been evaluated quantitatively compared to Autosomes. This genome-wide limitation of gene flow is essential for understanding the complete separation of species, and thus speciation. Here, we develop a mainland-island model of secondary contact between hybridizing species of an XY (or ZW) sexual system. We obtain theoretical predictions for the frequency of introgressed alleles, and the strength of the barrier to neutral gene flow for the two types of chromosomes carrying multiple interspecific barrier loci. Theoretical predictions are obtained for scenarios where introgressed alleles are rare. We show that the same analytical expressions apply for sex chromosomes and autosomes, but with different sex-averaged effective parameters. The specific features of sex chromosomes (hemizygosity and absence of recombination in the heterogametic sex) lead to reduced levels of introgression on the X (or Z) compared to autosomes. This effect can be enhanced by certain types of sex-biased forces, but it remains overall small (except when alleles causing incompatibilities are recessive). We discuss these predictions in the light of empirical data comprising model-based tests of introgression and cline surveys in various biological systems.     

A new linkage group involved in sex determination in haplotilapiine cichlids

The high diversity of sex chromosomes and sex determination systems among haplotilapiines suggests that this large cichlid clade is a good model for investigating the evolution of genetics of sex determination. Nonetheless, information about sex determination in this clade remains sparse. The present study reports a microsatellite marker that is closely associated with sex in Xenotilapia rotundiventralis from Lake Tanganyika, Africa. This study is the first to suggest the role of linkage group 17 in sex determination in haplotilapiine cichlids.     

男性内源性性激素水平与冠心病范围及左心室射血分数的相关性

摘要 目的：探究男性内源性性激素水平与冠心病范围及左心室射血分数（LVEF）的相关性。方法：将2018年6月至2020年6月于我院接受治疗的96例经冠状动脉造影术（CAG）确诊为冠心病的96例患者纳入研究,按照临床分型将其区分为稳定型心绞痛（SAP,30例）、不稳定型心绞痛（UAP,30例）、急性心肌梗死（AMI,36例）,另选同期CAG检测结果提示冠状动脉管腔直径狭窄率<50 %的50例个体为对照组,检测入组对象的睾酮（Ts）、雌二醇（E₂）水平,评估计算入组对象的Gensini积分以及LVEF,对比不同组别之间Ts、E₂、Gensini积分以及LVEF差异,Spearman相关分析探究Ts、E₂与Gensini积分、LVEF的相关性,最后将患者按照Genisini评分区分为狭窄轻型组与严重组,Logistic回归分析影响冠脉狭窄的危险因素。结果：（1）比较显示,冠心病各组间Ts、E₂、Gensini积分以及LVEF差异明显,以AMI组患者Ts、E₂和LVEF水平最低,Gensini积分最高（P<0.05）;（2）Spearman相关性分析显示,Ts、E₂均与Gensini积分呈负相关,与LVEF呈正相关（P<0.05）;（3）多因素Logistic回归分析显示Ts、E₂水平是影响冠脉狭窄程度的独立危险因素（P<0.05）。结论：男性内源性性激素水平同其冠心病范围和LVEF呈现密切相关性,是影响冠脉狭窄程度的独立危险因素,可以考虑将其应用于临床冠脉狭窄的诊断与鉴别中。     

Seasonal changes in cuticular hydrocarbons in response to polyphenism in the host-alternating aphid Prociphilus oriens

In most terrestrial arthropods, cuticular hydrocarbons (CHCs) function to assist in desiccation tolerance and chemical communications. However, few studies have clarified whether CHC profiles change among developmental stages or among different morphs in non-social insects. In the present study, we evaluated how CHC profiles change in accordance with polyphenism in the host-alternating aphid Prociphilus oriens, which exhibits a complex life cycle and five distinct morphs. These morphs are sexual or asexual and adapt to different host plants. We found that all generations of P. oriens shared high proportions of n-alkanes, but its composition varied among morphs. Three morphs that are attended by ants were characterized by relatively high proportions of n-C25 to n-C27, whereas two morphs that are not attended by ants had higher proportions of longer-chain n-alkanes, such as n-C27 and n-C29. The CHC profiles of sexual females were largely different from those of males. Considering that sexual females of Prociphilus spp. lack organs that secrete sex pheromones (scent plaques), the CHCs of sexual females are likely to function as a sex attractant. High proportions of methyl-branched alkanes were detected in the long and flocculent waxy substances of autumnal migrants. These methyl-branched alkanes are considered a cue to recognize conspecifics. We concluded that the functions and components of CHCs differ among morphs, and that those of sexual females differ from those of males and asexual generations because of their function in sexual communication.     

Selection against immigrants in wild seabird populations

Immigration is a major demographic parameter shaping population dynamics and is an important driver of eco‐evolutionary patterns, but the fitness consequences for individuals following their settlement to a new population (immigrants) remain poorly tested in wild animal populations, particularly among long‐lived species. Here we show that immigrants have a lower fitness than residents in three wild seabird populations (wandering albatross Diomedea exulans, southern fulmar Fulmarus glacialoides, snow petrel Pagodroma nivea). Across all species and during a 32‐year period, immigrants made on average ?9 to 29% fewer breeding attempts, had 5–31% fewer fledglings, had 2–16% lower breeding success and produced 6–46% fewer recruits. Female immigration and male residency were also favored through differences in breeding performance. We provide evidence for selection against immigrants in wild populations of long‐lived species and our results are consistent with female‐biased dispersal in birds being driven by asymmetric limiting resources and the competitive ability of dispersers vs. non‐dispersers.     

When to estimate sex ratio in natural populations of insects? A study on sex ratio variations of gall midges within a generation

Precise estimation of arthropods' sex ratio is an important issue in a wide range of ecological studies and biological control programs. Although, in many cases changes in arthropods' sex ratio may be under the control of parents or some symbiotic microorganisms, biased sex ratios in some other species are caused by some extrinsic factors, neglect of which may lead to under/overestimation of true sex ratio. In this paper, we pursued those factors that cause false estimation of sex ratio in insects' species. We studied the predatory gall midge, Aphidoletes aphidimyza Rondani (Diptera: Cecidomyiidae), an important biological control agent of aphids, that shows protandry (i.e. early male emergence), differential lifespan of sexes, and differential distribution of sexes across habitat. Ten populations of A. aphidimyza were released separately in transparent cages and their sex ratio variations were recorded every 12 hours. The primary sex ratio in this species seems to be slightly male‐biased (52.41% males), however early emergence of males biases the sex ratio up to 72% males in a few hours after emergence. Shortly after the emergence of females, the sex ratio reaches its primary situation, but as a result of male‐biased mortality after mating, the proportion of females increases gradually to 97% by the fourth and fifth days after emergence. These results explicitly suggest that direct estimation of sex ratio in natural populations may be affected by some secondary factors such as differential mortality of sexes, protandry, and differential distribution of males and females over time and/or across habitat.