云斑天牛对补充营养寄主的选择性

通过林间调查和室内选择性试验,研究云斑天牛Batocera horsfieldi(Hope)成虫在补充营养阶段对多种寄主植物的选择性。林间调查结果表明,云斑天牛成虫对法国冬青(V.awabuki)和光皮桦(B.luninifera)有较强的嗜食性,林间最高取食选择率分别为100%和92.4%。利用"Y"型嗅觉仪测定云斑天牛成虫对法国冬青、核桃(Jugians regia L.)、光皮桦和杨树(Populus tomentosa)等寄主挥发物的行为反应,生测结果与林间调查及室内选择结果一致,法国冬青和光皮桦的挥发物对云斑天牛引诱效果明显,并且枝条挥发物引诱力高于叶片挥发物,引诱效果最佳的组合为:采用蒸馏法,用二氯甲烷提取的冬青枝叶粗提物;采用浸提法,用乙醚提取的冬青和光皮桦枝叶粗提物和二氯甲烷分别提取的冬青枝和叶的粗提物。     

辽东山地古石河冰缘地貌森林生态系统苔藓物种多样性研究

基于9个20 m×30 m森林群落样地的调查数据,采用物种丰富度、α和β多样性指数,对辽东山地古石河冰缘地貌不同林型石生、树生苔藓植物物种多样性进行定量研究,采用皮尔逊相关分析方法对其影响因素进行分析。结果显示,古石河冰缘地貌苔藓植物共有26科46属59种;不同林型石生、树生苔藓植物物种丰富度和α多样性指数均为:暗针叶林针阔混交林落叶阔叶林;石生苔藓植物β多样性指数最高为落叶阔叶林-针阔混交林间(0.44),最低为落叶阔叶林-暗针叶林间(0.33);树生苔藓植物β多样性指数最高为针阔混交林-暗针叶林间(0.40),最低为落叶阔叶林-暗针叶林间(0.25);分析表明,林冠层郁闭度、海拔高度是影响辽东山地古石河冰缘地貌森林生态系统苔藓物种多样性的重要因子。     

思茅松毛虫幼虫空间格局与抽样技术的初步研究

采用聚集度指标法和回归分析法,对思茅松毛虫幼虫在林间的空间格局进行测定,并用刀切法对聚集度指标进行估计和检验,结果表明,思茅松毛虫幼虫在林间呈聚集分布,分布的基本成份为个体群．并计算了林间调查的理论抽样数,列出序贯抽样分析表。     

人尿及汗液中几种化合物对黄脊竹蝗的引诱活性

黄脊竹蝗Ceracris kiangsu Tsai成虫对发酵人尿及汗液有明显的趋向行为。利用昆虫触角EAG反应和林间诱蝗试验对氯化钠、碳酸氢氨及乙醇3种主要的人尿、汗液化合物的诱蝗活性进行测定。结果表明:3种物质均能明显激发黄脊竹蝗雌、雄成虫的触角电位反应,激发活性的强弱次序为乙醇>碳酸氢氨>氯化钠。3种化合物对雌蝗触角的刺激作用强于雄蝗。在林间,氯化钠、碳酸氢氨及乙醇及其混合物对竹蝗的引诱效果不明显,化合物浓度及药剂种类是影响竹蝗引诱量的因子之一。     

萧氏松茎象幼虫的空间分布型和抽样技术

萧氏松茎象Hylobitelus xiaoi Zhang是我国近年来发现的危害松林的新害虫。该文利用1wao等7种方法对萧氏松茎象幼虫的空间分布型进行了测定。结果表明,萧氏松茎象幼虫在林间呈聚集分布,且符合负二项分布,由此得出了林间理论抽样数公式,其抽样方式以对角线最佳;其有虫株率与平均虫口密度之间的关系可用冥函数曲线方程：Y=2．916X^0.887来进行描述。     

受害兴安落叶松挥发物混合物对林间昆虫的诱集

植株释放的挥发物能够调节寄主、害虫及天敌三者关系,是植物与害虫协同进化的产物。兴安落叶松挥发物种类虽已确定,但这些物质,特别是受害植株所释放的挥发物对林间昆虫的影响尚不清楚。本研究在3种林龄林分内设置携带受害兴安落叶松枝叶挥发物的诱捕器以考察其对林间昆虫的影响。结果表明挥发物混合物对昆虫诱集效果良好,特别是对天牛类及叶甲类。林龄并未对挥发物的引诱效果造成显著影响,可能与本研究年龄组的划分标准有关。文章指出应将诱集昆虫群落进一步细化,并对关键种或类群进行电生理方面的深入探讨。本文也指出了受害兴安落叶松挥发物混合物发展为植物源农药的前景。     

荒漠草原区柠条林平茬和牧草补播对地面节肢动物群落的影响

以荒漠草原区25年龄柠条林为研究对象,通过调查未平茬未补播、补播、平茬和既平茬又补播牧草的柠条林地中地面节肢动物群落特征,分析了补播和平茬及其交互作用对柠条林间和林下地面节肢动物个体数和类群数分布的影响.结果表明:在未平茬未补播牧草的林地中,林间地面节肢动物个体数和类群数均显著低于林下.与未平茬未补播牧草林地相比,补播、平茬和既平茬又补播牧草均显著增加柠条林间地面节肢动物个体数和类群数,而对柠条林下地面节肢动物个体数和类群数分布无显著影响,经过不同管理措施处理后,柠条林下与林间的地面节肢动物分布无显著差异.平茬和补播对柠条灌丛内外地面节肢动物分布影响具有类同效应,而且相互之间存在缓冲作用,补播与平茬处理、平茬与既平茬又补播处理、补播与既平茬又补播处理之间,林间和林下地面节肢动物的分布均无显著差异.在荒漠草原区柠条人工林中,平茬、补播和既平茬又补播牧草均可以显著提高柠条林地特别是林间地面节肢动物多样性,有利于退化草地生物多样性保护、生态系统恢复和柠条人工林的有效管理.     

球孢白僵菌种群在松林中的寄主转移及遗传多样性对松毛虫持续控制的影响

通过林间接种式放菌及其后一周年的野外调查,从林间采集到30种寄主昆虫及从土壤、落叶和气流中分离到119株球孢白僵菌.酯酶同工酶分析表明,它们属于32个不同酯酶型,呈现出丰富的遗传多样性.释放菌株所属的酯酶型02包括从11种昆虫上分离出的18个菌株,表明林间释放的菌株已成功地在不同寄主昆虫种群中宿存下来,并以常发的地方病状态存在于松毛虫及松灰象甲等12种昆虫种群之中;当林间目标寄主缺乏时,其它寄主可将食物链维系下去.其它酯酶型分别包括1～23个菌株.一周年内的寄主转移动态结果表明,球孢白僵菌在松林生态系统中不同寄主间可转移寄生.每个酯酶型中的菌株对松毛虫的毒力相差很大.表明球孢白僵菌在松林中的延续和扩散流行不是1条路线,每个酯酶型至少代表食物网上的1条支链.有些环节的寄主连接了不同的酯酶型,使松林中食物网变得十分复杂.另外,从土壤、枯枝落叶层、林冠层和空气中分离到的球孢白僵菌分属于不同的酯酶型,表明松林中还存在着复杂的腐生食物链,有利于松毛虫及其它害虫的持续控制.     

外引迪氏跳小蜂与本地粉蚧长索跳小蜂的竞争比较

初步研究了美国引进的迪氏跳小蜂Zarhopalus debarri与本地粉蚧长索跳小蜂Anagyrus dactylotpii(Howard)竞争的情况,结果表明,即使在种群数量占优的情况下,在竞争中迪氏跳小蜂仍处于明显的劣势,而且两种寄生蜂在混合种群中相互排斥的.在林间释放迪氏跳小蜂,也未能在林间找到子代蜂推测林间存在的本地蜂是影响外引蜂的定居与繁殖因素之一.     

三种植物乙醇粗提物对松梢螟幼虫的生物活性研究

在室内测定了垂序商陆全草、柚果皮、博落回全草乙醇粗提物对松梢螟幼虫的生物活性,并测定了其林间防效。结果显示,不同浓度3种植物乙醇粗提物对松梢螟幼虫都有一定的生物活性,且浓度越高作用效果越强。柚皮粗提物对松梢螟幼虫的生物活性最强,100 mg/m L的柚皮粗提物对松梢螟幼虫的最高毒杀校正死亡率、拒食率、生长抑制率分别为80.00%、99.28%和96.32%,同时其林间防治效果为55.70%,与对照药剂噻虫啉的防治效果在同一显著水平。垂序商陆粗提物对松梢螟幼虫的生物活性最弱,但其高浓度粗提物校正死亡率仍在70%以上,拒食率以及生长抑制率也在90%以上。     

Conflict over condition‐dependent sex allocation can lead to mixed sex‐determination systems

Theory suggests that genetic conflicts drive turnovers between sex‐determining mechanisms, yet these studies only apply to cases where sex allocation is independent of environment or condition. Here, we model parent–offspring conflict in the presence of condition‐dependent sex allocation, where the environment has sex‐specific fitness consequences. Additionally, one sex is assumed to be more costly to produce than the other, which leads offspring to favor a sex ratio less biased toward the cheaper sex in comparison to the sex ratio favored by mothers. The scope for parent–offspring conflict depends on the relative frequency of both environments: when one environment is less common than the other, parent–offspring conflict can be reduced or even entirely absent, despite a biased population sex ratio. The model shows that conflict‐driven invasions of condition‐independent sex factors (e.g., sex chromosomes) result either in the loss of condition‐dependent sex allocation, or, interestingly, lead to stable mixtures of condition‐dependent and condition‐independent sex factors. The latter outcome corresponds to empirical observations in which sex chromosomes are present in organisms with environment‐dependent sex determination. Finally, conflict can also favor errors in environmental perception, potentially resulting in the loss of condition‐dependent sex allocation without genetic changes to sex‐determining loci.     

A predictive relationship between population and genetic sex ratios in clonal species

Sexual reproduction depends on mate availability that is reflected by local sex ratios. In species where both sexes can clonally expand, the population sex ratio describes the proportion of males, including clonally derived individuals (ramets) in addition to sexually produced individuals (genets). In contrast to population sex ratio that accounts for the overall abundance of the sexes, the genetic sex ratio reflects the relative abundance of genetically unique mates, which is critical in predicting effective population size but is difficult to estimate in the field. While an intuitive positive relationship between population (ramet) sex ratio and genetic (genet) sex ratio is expected, an explicit relationship is unknown. In this study, we determined a mathematical expression in the form of a hyperbola that encompasses a linear to a nonlinear positive relationship between ramet and genet sex ratios. As expected when both sexes clonally have equal number of ramets per genet both sex ratios are identical, and thus ramet sex ratio becomes a linear function of genet sex ratio. Conversely, if sex differences in ramet number occur, this mathematical relationship becomes nonlinear and a discrepancy between the sex ratios amplifies from extreme sex ratios values towards intermediate values. We evaluated our predictions with empirical data that simultaneously quantified ramet and genet sex ratios in populations of several species. We found that the data support the predicted positive nonlinear relationship, indicating sex differences in ramet number across populations. However, some data may also fit the null model, which suggests that sex differences in ramet number were not extensive, or the number of populations was too small to capture the curvature of the nonlinear relationship. Data with lack of fit suggest the presence of factors capable of weakening the positive relationship between the sex ratios. Advantages of this model include predicting genet sex ratio using population sex ratios given known sex differences in ramet number, and detecting sex differences in ramet number among populations.     

Phylogeny of sex‐determining mechanisms in squamate reptiles: are sex chromosomes an evolutionary trap?

Squamate reptiles possess two general modes of sex determination: (1) genotypic sex determination (GSD), where the sex of an individual is determined by sex chromosomes, i.e. by sex‐specific differences in genotype; and (2) temperature‐dependent sex determination (TSD), where sex chromosomes are absent and sex is determined by nongenetic factors. After gathering information about sex‐determining mechanisms for more than 400 species, we employed comparative phylogenetic analyses to reconstruct the evolution of sex determination in Squamata. Our results suggest relative uniformity in sex‐determining mechanisms in the majority of the squamate lineages. Well‐documented variability is found only in dragon lizards (Agamidae) and geckos (Gekkota). Polarity of the sex‐determining mechanisms in outgroups identified TSD as the ancestral mode for Squamata. After extensive review of the literature, we concluded that to date there is no known well‐documented transition from GSD to TSD in reptiles, although transitions in the opposite direction are plentiful and well corroborated by cytogenetic evidence. We postulate that the evolution of sex‐determining mechanisms in Squamata was probably restricted to the transitions from ancestral TSD to GSD. In other words, transitions were from the absence of sex chromosomes to the emergence of sex chromosomes, which have never disappeared and constitute an evolutionary trap. This evolutionary trap hypothesis could change the understanding of phylogenetic conservatism of sex‐determining systems in many large clades such as butterflies, snakes, birds, and mammals. © 2009 The Linnean Society of London, Zoological Journal of the Linnean Society, 2009, 156 , 168–183.     

Molecular players involved in temperature-dependent sex determination and sex differentiation in Teleost fish

The molecular mechanisms that underlie sex determination and differentiation are conserved and diversified. In fish species, temperature-dependent sex determination and differentiation seem to be ubiquitous and molecular players involved in these mechanisms may be conserved. Although how the ambient temperature transduces signals to the undifferentiated gonads remains to be elucidated, the genes downstream in the sex differentiation pathway are shared between sex-determining mechanisms. In this paper, we review recent advances on the molecular players that participate in the sex determination and differentiation in fish species, by putting emphasis on temperature-dependent sex determination and differentiation, which include temperature-dependent sex determination and genetic sex determination plus temperature effects. Application of temperature-dependent sex differentiation in farmed fish and the consequences of temperature-induced sex reversal are discussed.     

Sex change in tree species: long-term monitoring of sex expression in Acer rufinerve

We monitored sex expression in Acer rufinerve from 1986 to 1999, in order to study branch-autonomous sex changes in tree species. During this observation period, 70 of 338 stems (20.7 %) changed sexual expression. Fifty of these sex-changed stems exhibited monoecism (having both female and male branches) in the course of the sex change, while the remaining stems changed directly from male to female or vice versa. A sex change resulting in monoecism was called a partial sex change and a total male/female change was referred to as a complete sex change. The mean diameter at breast height of stems that partially changed sex was significantly greater than that of stems that changed sex completely. Thus, it was primarily large stems with many branches that underwent partial sex changes. These findings suggest that sex change is a branch autonomous event in A. rufinerve and underline the importance of taking branching structure into account when studying sex change in trees.     

How to identify sex chromosomes and their turnover

Although sex is a fundamental component of eukaryotic reproduction, the genetic systems that control sex determination are highly variable. In many organisms the presence of sex chromosomes is associated with female or male development. Although certain groups possess stable and conserved sex chromosomes, others exhibit rapid sex chromosome evolution, including transitions between male and female heterogamety, and turnover in the chromosome pair recruited to determine sex. These turnover events have important consequences for multiple facets of evolution, as sex chromosomes are predicted to play a central role in adaptation, sexual dimorphism, and speciation. However, our understanding of the processes driving the formation and turnover of sex chromosome systems is limited, in part because we lack a complete understanding of interspecific variation in the mechanisms by which sex is determined. New bioinformatic methods are making it possible to identify and characterize sex chromosomes in a diverse array of non‐model species, rapidly filling in the numerous gaps in our knowledge of sex chromosome systems across the tree of life. In turn, this growing data set is facilitating and fueling efforts to address many of the unanswered questions in sex chromosome evolution. Here, we synthesize the available bioinformatic approaches to produce a guide for characterizing sex chromosome system and identity simultaneously across clades of organisms. Furthermore, we survey our current understanding of the processes driving sex chromosome turnover, and highlight important avenues for future research.     

Dynamic sex chromosomes in Old World chameleons (Squamata: Chamaeleonidae)

Much of our current state of knowledge concerning sex chromosome evolution is based on a handful of ‘exceptional’ taxa with heteromorphic sex chromosomes. However, classifying the sex chromosome systems of additional species lacking easily identifiable, heteromorphic sex chromosomes is indispensable if we wish to fully understand the genesis, degeneration and turnover of vertebrate sex chromosomes. Squamate reptiles (lizards and snakes) are a potential model clade for studying sex chromosome evolution as they exhibit a suite of sex‐determining modes yet most species lack heteromorphic sex chromosomes. Only three (of 203) chameleon species have identified sex chromosome systems (all with female heterogamety, ZZ/ZW). This study uses a recently developed method to identify sex‐specific genetic markers from restriction site‐associated DNA sequence (RADseq) data, which enables the identification of sex chromosome systems in species lacking heteromorphic sex chromosomes. We used RADseq and subsequent PCR validation to identify an XX/XY sex chromosome system in the veiled chameleon (Chamaeleo calyptratus), revealing a novel transition in sex chromosome systems within the Chamaeleonidae. The sex‐specific genetic markers identified here will be essential in research focused on sex‐specific, comparative, functional and developmental evolutionary questions, further promoting C. calyptratus’ utility as an emerging model organism.     

Same Sex Marriage and the Perceived Assault on Opposite Sex Marriage

Background

Marriage benefits both individuals and societies, and is a fundamental determinant of health. Until recently same sex couples have been excluded from legally recognized marriage in the United States. Recent debate around legalization of same sex marriage has highlighted for anti-same sex marriage advocates and policy makers a concern that allowing same sex couples to marry will lead to a decrease in opposite sex marriages. Our objective is to model state trends in opposite sex marriage rates by implementation of same sex marriages and other same sex unions.

Methods and Findings

Marriage data were obtained for all fifty states plus the District of Columbia from 1989 through 2009. As these marriage rates are non-stationary, a generalized error correction model was used to estimate long run and short run effects of same sex marriages and strong and weak same sex unions on rates of opposite sex marriage. We found that there were no significant long-run or short run effects of same sex marriages or of strong or weak same sex unions on rates of opposite sex marriage.

Conclusion

A deleterious effect on rates of opposite sex marriage has been argued to be a motivating factor for both the withholding and the elimination of existing rights of same sex couples to marry by policy makers–including presiding justices of current litigation over the rights of same sex couples to legally marry. Such claims do not appear credible in the face of the existing evidence, and we conclude that rates of opposite sex marriages are not affected by legalization of same sex civil unions or same sex marriages.     

The sex chromosome system can influence the evolution of sex‐biased dispersal

Sex‐biased dispersal is a much‐discussed feature in literature on dispersal. Diverse hypotheses have been proposed to explain the evolution of sex‐biased dispersal, a difference in dispersal rate or dispersal distance between males and females. An early hypothesis has indicated that it may rely on the difference in sex chromosomes between males and females. However, this proposal was quickly rejected without a real assessment. We propose a new perspective on this hypothesis by investigating the evolution of sex‐biased dispersal when dispersal genes are sex‐linked, that is when they are located on the sex chromosomes. We show that individuals of the heterogametic sex disperse relatively more than do individuals of the homogametic sex when dispersal genes are sex‐linked rather than autosomal. Although such a sex‐biased dispersal towards the heterogametic sex is always observed in monogamous species, the mating system and the location of dispersal genes interact to modulate sex‐biased dispersal in monandry and polyandry. In the context of the multicausality of dispersal, we suggest that sex‐linked dispersal genes can influence the evolution of sex‐biased dispersal.