Extraordinary flux in sex ratio

The ratio of males to females in a species is often considered to be relatively constant, at least over ecological time. Hamilton noted that the spread of "selfish" sex ratio-distorting elements could be rapid and produce a switch to highly biased population sex ratios. Selection against a highly skewed sex ratio should promote the spread of mutations that suppress the sex ratio distortion. We show that in the butterfly Hypolimnas bolina the suppression of sex biases occurs extremely fast, with a switch from a 100:1 population sex ratio to 1:1 occurring in fewer than 10 generations.     

Radiation and the sex ratio in man

An analysis of new data concerning the sex of children born to the survivors of the atomic bombings of Hiroshima and Nagasaki, together with a reanalysis of the data previously presented by Neel and Schull (9), reveals significant changes in the sex ratio of these children, changes in the direction to be expected if exposure had resulted in the induction of sex-linked lethal mutations (16).     

满江红三膘亚属种及种间杂种雄性育性初步研究

报道满江红三膘亚属(Euazolla)4个种——蕨状满江红(Azolla filiculoides)、小叶满江红(A.microphylla)、墨西哥满江红(A.mexicana)和卡洲满江红(A.Caroliniana)小孢子育性特点；卡洲满江红2个品种，其它3个种及种间杂种F1代小孢子育性特点。影响小孢子育性的两个主要因素是外界环境条件和遗传因素。讨论了小孢子育性研究对满江红物种划分的意义。     

Queen control of sex ratio in fire ants

The haplodiploid sex-determination system of ants gives rise to conflict between queens and workers over colony sex ratios, and the female-biased allocation ratios seen in many species suggest that workers often prevail in this conflict. We exchanged queens between male- and female-specialist colonies of the fire ant Solenopsis invicta. These exchanges quickly reversed the sex-ratio biases of adopting colonies. The sex ratio of queen-laid eggs differed strongly between male- and female-specialist colonies. These findings suggest that queens can force workers to raise male sexuals by limiting the number of female brood and help to explain why sex investment ratios lie between the queen and worker equilibria in this and many other ant species.     

Constraints in the evolution of sex ratio adjustment

When the relative fitness of male and female offspring varies with environmental conditions, evolutionary theory predicts that parents should adjust the sex of their offspring accordingly. Qualitative and even quantitative support for this prediction is striking in some taxa but much less convincing in others. Explaining such variation across taxa in the fit of sex ratio theory remains a major challenge. We use meta-analysis to test the role of two constraints in the evolution of sex ratios. Based on analysis of sex ratio skews in birds and wasps, we show that (i) mechanisms of sex determination do not necessarily constrain the evolution of sex ratio adjustment, and (ii) parental ability to predict their offsprings' environment influences the evolution of sex ratio patterns across taxa. More generally, our results show that multiple constraints may determine the precision of adaptation.     

竹柏种群生命表与性比分析

为更好地指导竹柏的引种、种群保护和优良种源筛选,采用空间代时间方法和匀滑技术编制竹柏种群生命表,并分析其性比的地形分异规律。结果表明:竹柏种群龄级结构属于增长型。竹柏种群的死亡率和损失率的三个峰值分别出现在第3、5和7龄级,存活曲线属于Deevey-Ⅱ型。生存分析结果表明,竹柏种群具有前期衰退,中后期稳定的特点。竹柏种群雄性个体在不同坡位上表现为上坡位>中坡位>下坡位,在不同立地质量等级上表现为Ⅱ类地<Ⅲ类地<Ⅳ类地;雌性个体在不同坡位和立地质量等级上的分布规律与雄性个体呈相反趋势。     

花马杂交鹿茸化学成分的测定

通过对花马杂交鹿茸常规成分(灰分、蛋白质、脂肪分别采用重量法、凯氏定氮法、索氏提取法)、氨基酸(高效液相色谱法)、钙(高锰酸钾滴定法)、磷(钼黄比色法)、微量元素(火焰原子吸收法)进行测定,结果表明:花马杂交鹿茸中灰分含量为28.32%;粗蛋白质含量为56.74%;粗脂肪含量为3.34%;氨基酸总量为45.20%;钙、磷含量分别为3.59%和2.02%,钙磷比为1.78 : 1;微量元素铁、锌、铜、锰、镍、钴的含量分别为3.677 0、0.687 6、0.077 4、0.028 2、0.061 6、0.070 8 mg/g.     

湘南丘岗红壤地区土壤肥力质量指标的空间变异特征

采用地理信息系统(GIS)和地统计学方法研究了湘南丘岗红壤地区土壤表层(0～20 cm)pH值、有机质、碱解氮、有效磷、速效钾、全氮、全磷、全钾8项土壤肥力指标的空间变异特征.结果表明:土壤pH、有效磷、全氮和全钾的理论模型为球状模型,有机质、碱解氮和速效钾的理论模型为指数模型,全磷的理论模型为高斯模型;碱解氮和全磷的基底效应分别为13.6％、19.0％,表现出强烈的空间相关性,土壤pH、有机质、有效磷、速效钾、全氮和全钾的基底效应分别为28.7％、29.9％、54.7％、53.1％、55.6％、73.0％,具有中等的空间相关性;研究区域的书林寺村南部和官山坪村北部以石灰岩风化物母质为主,土壤肥力较高,属Ⅰ～Ⅲ级,幸福桥村区域以板岩风化物母质为主,土壤肥力为Ⅳ级,官山坪村南部以第四纪红土母质为主,土壤肥力属Ⅴ级,应重视第四纪红土母质地区土壤退化防治和肥力恢复调控.     

濒危马麝的有效取香率分析

【目的】研究圈养雄性马麝(Moschus sifanicus)有效取香率(有成熟麝香生成的雄麝占参与采香雄麝的比例)的变动规律及影响因素。【方法】在1997-2009年,于甘肃兴隆山马麝繁育场进行人工取香,通过识别参与取香的马麝个体,收集产香数据,计算年度及特定亚群的有效取香率,研究圈养马麝来源(野捕、驯养繁殖)、父母来源、取香时间(繁殖季节前和繁殖季节后)及年龄对有效取香率的影响。【结果】甘肃兴隆山圈养马麝的总体有效取香率为90.30%(n=732);因年度间驯养管理方式的差异,圈养马麝的有效取香率存在显著的年度间差异(P<0.05)。马麝个体来源影响其有效取香率,野捕圈养雄麝的有效取香率(93.75%,n=272)极显著高于驯养繁殖雄麝(88.26%,n=460),但雄麝的父母来源对其有效取香率影响不显著(P>0.05)。繁殖季节前取香的有效取香率(90.43%,n=208)与繁殖后取香的有效取香率(94.83%,n=312)无显著差异(P>0.05)。圈养马麝的年龄显著影响其有效取香率(P<0.05),1.5岁龄雄麝开始分泌麝香,有效取香率为87.5%(n=96);4.5岁龄雄麝几乎都能产香,有效取香率约为100%(n=100);高峰取香年龄段为1.5～8.5岁龄;9.5岁龄雄麝有效取香率为71.43%(n=28)。【结论】驯养雄性马麝的有效取香率与个体来源、年龄和饲养管理有关,父母来源和取香时间对有效取香率无显著影响。     

西北马鹿群体遗传多样性及系统地位

【目的】揭示西北马鹿(Cervus elaphus)群体的遗传多样性及系统地位,为科学地保护和利用我国西北地区马鹿资源提供基础研究材料。【方法】对塔里木马鹿、阿尔泰马鹿、天山马鹿、甘肃马鹿及阿拉善马鹿5个群体108个个体的D-loop全序列进行扩增、测序,分析其碱基组成及变异,构建系统发育树,研究西北马鹿群体遗传结构、群体遗传多样性及其系统地位。【结果】共检测到40个单倍型,平均单倍型多样度(Hd)为0.998±0.006,平均核苷酸多样度(Pi)为0.041±0.005,平均核苷酸差异数(K)为36.08。构建NJ和MP分子系统发育树发现,塔里木马鹿与其他马鹿遗传距离较远,分属于不同的类群;阿尔泰马鹿、天山马鹿及甘肃马鹿之间均存在基因交流,可能是群体间引种杂交所致。【结论】西北地区马鹿整体遗传多样性丰富;中国马鹿可能起源于欧洲;部分马鹿群体间存在基因交流情况。     

遗传和温度因素对鱼类性别分化相关基因表达及性别比例的影响

鱼类的性别决定机制较为复杂,是遗传和环境共同作用的结果,具有很大的可塑性。随着分子生物技术的不断更新,对鱼类性别决定及分化相关基因的鉴定和研究有了新的进展,环境因子如温度、光照、p H、低氧、水压等均能影响大多数鱼类的性别决定和分化过程。本研究中,阐述了鱼类遗传型性别决定(GSD)和温度依赖型性别决定(TSD)方式,并对TSD与遗传型性别加温度影响(GSD+TE)性别决定机制下,性别决定相关基因在雌雄异型中的表达及结合温度诱导性逆转进行概述,分析了温度对鱼类性别比例的影响,并提出今后应加强对性别决定基因的鉴定、解析和基因功能研究,为科学制定鱼类繁殖计划提供指导。     

遗传和温度因素对鱼类性别分化相关基因表达及性别比例的影响

鱼类的性别决定机制较为复杂,是遗传和环境共同作用的结果,具有很大的可塑性。随着分子生物技术的不断更新,对鱼类性别决定及分化相关基因的鉴定和研究有了新的进展,环境因子如温度、光照、p H、低氧、水压等均能影响大多数鱼类的性别决定和分化过程。本研究中,阐述了鱼类遗传型性别决定(GSD)和温度依赖型性别决定(TSD)方式,并对TSD与遗传型性别加温度影响(GSD+TE)性别决定机制下,性别决定相关基因在雌雄异型中的表达及结合温度诱导性逆转进行概述,分析了温度对鱼类性别比例的影响,并提出今后应加强对性别决定基因的鉴定、解析和基因功能研究,为科学制定鱼类繁殖计划提供指导。     

桑树种质资源及杂交组合性比调查

[目的]调查桑树种质资源及杂交组合性比的规律,为广西桑树育种提供参考.[方法]2011～2012年对收集保存的1000多份桑种质资源及人工授粉组配的165份杂交组合F1代的性比进行田间调查,研究不同材料植株的性比特点.[结果]在199份广西地方品种资源中,雌、雄性植株分别占50.3％、41.7％,雌雄同株占5.0％,6份为不明花性.在474份四倍体桑种质资源中,雌、雄性植株分别占59.3％、31.0％,雌雄同株占8.0％,雌雄同穗1.7％.在173份四倍体杂交F1代材料中,雌、雄性植株分别占42.2％、49.7％,雌雄同株占8.1％.在67份鲁桑、白桑与广东类型桑杂交选育的中间类型桑树种质资源中,雌、雄性植株分别占28.3％、64.2％,雌雄同株占7.5％.2011～2012年对165份杂交组合的调查结果显示,不同杂交组合中雄株占57.7％～58.5％,雌株占39.8％～41.8％,雌雄同株占0.5％～1.7％.广西常规种植的桑树二倍体超高产杂交组合沙2×伦109的雄株比率（约60.0％）明显高于雌株（低于20.0％）,桂桑优12与桂桑优62的雄株比率略高于雌株;桑特优1号、桑特优2号、桑特优3号3个三倍体的雌株比率（高于60.0％）明显高于雄株比率.[结论]不同类型桑树种质资源之间的性比表现不同,同一类型种质资源的性比相对稳定;不同年份组配的同一杂交组合的性比较稳定,不受组配时间和调查年份的明显影响.     

An instability in neutron stars at birth

Calculations with a two-dimensional hydrodynamic simulation show that a generic Raleigh-Taylor-like instability occurs in the mantles of nascent neutron stars, that it is possibly violent, and that the standard spherically symmetric models of neutron star birth and supemova explosion may be inadequate. Whether this "convective" instability is pivotal to the supemova mechanism, pulsar magnetic fields, or a host of other important issues that attend stellar collapse remains to be seen, but its existence promises to modify all questions concerning this most energetic of astronomical phenomena.     

Evolution of a balanced sex ratio by frequency-dependent selection in a fish

Balanced (1 to 1) sex ratios are thought to evolve by a process known as frequency- dependent selection of the minority sex. Five populations of a fish with genetically based variation in temperature-dependent sex determination were maintained for 5 to 6 years in artificial constant-temperature environments that initially caused the sex ratio to be highly skewed. Increases in the proportion of the minority sex occurred in subsequent generations until a balanced sex ratio was established, thus confirming a central premise underlying the theory of sex-ratio evolution.     

Postpartum psychiatric reactions: time of onset and sex ratio of newborns

There is no predominance of male infants born to women who develop schizophrenic symptomns with in 1 month after delivery. Moreover, there is no difference in the sex ratio of infants born to schizophrenic women whose onset of symptoms occurred within the first 10 days postpartum, which is the period of rapid hormonal changes that is most likely to reflect postnatal influences of fetal sex.