瓢虫性选择行为及进化机制研究

昆虫性选择行为一直是行为生物学家和进化生物学家所关注的热点。早期对瓢虫性选择行为研究主要集中在非随机性交配模式,随着研究的深入,近些年对瓢虫性选择行为研究取得了许多新成果,包括多次交配的行为机制、性选择的识别机制、精子传送及竞争等。为全面地了解瓢虫性选择行为研究现状,本文总结了瓢虫非随机性交配模式,综述了近十余年对瓢虫性行为及进化的研究成果,同时对瓢虫性选择行为未来的研究方向进行了展望。     

父方投资与性角色逆转现象: 螽斯类昆虫的婚礼食物及对性选择方向的影响

大多数动物在繁殖过程中,雌性在繁殖过程中要比雄性付出更大投资,如相对于精子较大的卵子细胞,较长的育幼时间等,因而在交配过程中,雌性具有选择权,而雄性之间相互竞争以取得与雌性的交配权。然而自然世界中并不总是竞争的雄性（competitive male）-选择的雌性（selective female）这种婚配形式。在螽斯类昆虫中,雄性同样具有较大的父方投资。在繁殖期间,雄性螽斯争相鸣叫,求偶,且在交配后要给予雌性特殊的营养物质-精包,供雌性取食。因此在特定情况下,雌性之间将进行竞争以获取雄性配偶,雄性变得更具有选择性。影响这种性角色逆转的主要因素是可获得资源的紧缺。父方投资理论和性选择理论预测雄性显著地对后代投资时,雌性将表现出典型的雄性特征,她们竞争追求性活跃的雄性,而雄性将表现出典型的雌性特征,对配偶具有选择性。螽斯类昆虫中这种特殊的性角色逆转现象符合性选择理论和父方投资理论的预测。     

非人灵长类性打搅行为研究进展

性打搅行为是指非人灵长类社群内非交配个体对正在发生性行为个体的干扰行为,该行为在非人灵长类中普遍存在,通过综述目前已知的36种非灵长类的性打搅行为的报道,探讨性打搅行为的功能和意义。性打搅行为具有更高度的种间和种内差异,种间的性打搅的方式不同、同时受到社会结构和婚配制度的影响;在种内受到性别、年龄、等级等因素的影响。结合川金丝猴性打搅的研究结果,从性打搅的类型、被打搅的反应、性打搅的功能以及相关假说等方面入手,对非人灵长类性打搅行为进行系统总结,旨在为我国相关领域的研究提供参考,为生殖行为学研究者启发思路,推动本领域的发展。     

昆虫性信息素研究进展

一、什么是昆虫性信息素性信息素(sexpheromone)是由一种昆虫产生和释放出来,引诱或激起同种异性昆虫交配的化学物质。昆虫性信息素按其作用方式可分为两种:一种是挥发性性信息素,有远距离的引诱效果,它广泛存在于鳞翅目昆虫及其它种类的昆虫中;另一种是非挥发性性信息素,须由接受的一性与释放的一性接触才能起作用,称之为性识     

性选择、配偶外父亲身份确认程度、遗传变异性和保护

岛屿动物中的性选择强度不高,其原因可能是由于岛屿种群的遗传变异性水平较低。本文作者检验了鸟类岛屿种群是否具有较低的遗传变异性、性选择强度大的种群是否具有较高的突变输入率（rate of mutational input),在鸟类岛屿种群中是否具有较低的性选择强度（可以根据配偶外父亲身份的频率来估计）。小卫星共有谱带系数（minisatellite band sharing coefficient)可确定无亲源关系个体之间的遗传变异性,对与遗传变异性有关的雄性个体的父亲（paternity)进行了成对比较以检验如下假说：在具有较多遗传变异的种群中,雌性个体更经常地进行配偶外交配。在小卫星谱带系数较低的鸟类种群中,配偶外父亲的频次较高。对岛屿和大陆鸟类进行的第二个比较分析表明：岛屿种群中的配偶外父亲频次较低,遗传变异性也较低,其部分原因在于突变输入（mutational input)减少。上述发现表明：（1）父亲确认程度（parternity)随遗传变异性的数量而增加;（2）在遗传变异性较大的种群中,突变率较高,性选择的程度更激烈;（3）岛屿种群中性选择的强度一般比大陆种群弱。这对于理解遗传变异性的空间变异、理解岛屿种群和其它隔离种群的保护问题有重要启示。     

斜纹夜蛾的性选择行为

【目的】为了解斜纹夜蛾Spodoptera litura Fabricius体重、日龄、交配经历及形态特征对其性选择行为的影响。【方法】本实验通过标记成虫后,采用观察记录的方法对其进行探究。【结果】斜纹夜蛾雌虫的体重对雄虫的性选择影响比较明显,体重较大雄虫优先选择体重较小的雌虫(71.43%),而体重较小雄虫喜欢选择体重较大的雌虫(72.00%)。体重较大和体重较小的雄虫都能获得体重较大雌虫的交配选择,但是体重较大者被选择的机会更大(70.00%),体重较小的雄虫不能获得体重较小雌虫的选择。雄虫仅选择1日龄的雌虫,而雌虫偏向选择3日龄和5日龄雄虫。交配经历影响斜纹夜蛾的性选择,未交配的雄虫优先选择未交配的雌虫(86.67%),但未交配的雌虫则优先选择已交配的雄虫(66.67%)。雄虫的形态特征(体长、翅展、腹长、复眼间距和触角长)对雌虫性选择有较明显的影响,但雌虫的形态特征除翅展的大小外,其体长、腹长、复眼间距和触角长等形态特征在雄虫选择进行交配中的作用不大。【结论】体重、日龄、交配经历及形态特征都能不同程度影响斜纹夜蛾的性选择行为。     

动物的性选择

有性生殖为个体之间设置了一个冲突和竞争的环境,因为雌雄个体都希望最大限度地把自己的基因传递给后代。性选择保证了动物的繁殖成功。性选择可以分为性别内选择和性别间选择。性别内选择促使动物格斗器官或其他有利于在格斗中获胜的一些特征得到发展;性别间选择促使用来吸引异性的一些特征得到发展。雌性动物的配偶选择或与所选择的特征协同进化,或可以从选择中得到直接的利益。     

昆虫寄主选择行为的进化机制

昆虫的寄主选择行为受到遗传、可传承的环境因素或学习行为的调控。尽管大量实验已证实昆虫寄主选择中的遗传变异,但在实际中很难将其与温度、营养、条件作用和可传承的环境因素的作用区别开来。一些报道已证实可传承的环境因素会影响昆虫的寄主选择行为。幼虫期和成虫期对寄主的经历可以改变该虫态的取食和产卵寄主偏嗜行为。虽然巴甫洛夫条件反射和神经组织移植实验初步揭示了幼虫经历对成虫气味选择行为的影响,但寄主选择行为中的前印象条件作用尚需进一步验证。在城市垃圾生态系统中,杂食性的蝇类的取食和产卵选择行为较腐食性的蝇类更易受到学习经历的重塑。     

性的起源和性选择初探

蟑螂腹内的微生物类似于20亿年前就已在地球上生存的微生物。这些微生物活动的特点之一是彼此相食,但没有将同伴完全消化,而是细胞合并,两个细胞融合,融合后又有规律的分离,结果能更好的适应变化的环境。这可能是当今动植物性起源史的关键所在。一、性的起源现在所有的动植物(包括人类)都存在减数分裂的细胞分化方式。对此,现代达尔文主义学派认为:生物个体的特征是由其基因型决定的,细胞融合可以改变这种基因型。外界环境条件也     

寄生蜂寄主选择行为研究进展

寄生蜂是膜翅目昆虫中的重要类群,在自然界种类多,数量大。据文献报道全世界膜翅目昆虫大约有10万种”’,其中许多种类与农林害虫长期保持一定的制约关系,在害虫防治中占有重要地位。由于大量使用化学农药导致害虫的抗药性增加,利用天敌昆虫来防治害虫越来越显示出其重要性和优越性。但是,直到近20年来,寄生蜂的寄生行为才受到重视,并给予了广泛的、深入的研究”－‘’严格地讲,寄生蜂应该称为拟寄生蜂,它与通常所说的寄生昆虫像虱子、臭虫等有明显不同,主要区别在于：1．寄生仅仅发生在未成熟阶段,而成虫阶段营自由生活;2．寄…     

The total opportunity for sexual selection and the integration of pre‐ and post‐mating episodes of sexual selection in a complex world

It is well known that sexual selection can target reproductive traits during successive pre‐ and post‐mating episodes of selection. A key focus of recent studies has been to understand and quantify how these episodes of sexual selection interact to determine overall variance in reproductive success. In this article, we review empirical developments in this field but also highlight the considerable variability in patterns of pre‐ and post‐mating sexual selection, attributable to variation in patterns of resource acquisition and allocation, ecological and social factors, genotype‐by‐environment interaction and possible methodological factors that might obscure such patterns. Our aim is to highlight how (co)variances in pre‐ and post‐mating sexually selected traits can be sensitive to changes in a range of ecological and environmental variables. We argue that failure to capture this variation when quantifying the opportunity for sexual selection may lead to erroneous conclusions about the strength, direction or form of sexual selection operating on pre‐ and post‐mating traits. Overall, we advocate for approaches that combine measures of pre‐ and post‐mating selection across contrasting environmental or ecological gradients to better understand the dynamics of sexual selection in polyandrous species. We also discuss some directions for future research in this area.     

Increased postcopulatory sexual selection reduces the intramale variation in sperm design

Sperm competition is an important force driving the evolution of sperm design and function. Inter- and intraspecific variation in sperm design are strongly influenced by the risk of sperm competition in many taxa. In contrast, the variation among sperm of one male (intramale variation) is less well understood. We investigated intramale variation in sperm design in passerine birds and found that risk of sperm competition is negatively associated with intramale variation. This result is the first clear evidence that variation among sperm within an individual male is influenced by postcopulatory sexual selection. Our finding has important implications for male traits under pre- and postcopulatory sexual selection.     

High opportunity for postcopulatory sexual selection under field conditions

In polygamous systems, male fitness is determined not only by mating success but also by fertilization success. Despite the growing interest over the past several decades in postcopulatory sexual selection, its relative importance compared to precopulatory sexual selection remains a subject of debate. Here, we use extensive behavioral observations of a seminatural population of Hawaiian swordtail crickets, Laupala cerasina, and molecular paternity assignment to measure the opportunities for pre‐ and postcopulatory selection. Because postcopulatory selection has the potential to operate at multiple stages, we also separately attribute its effects to factors specific to mating events versus factors specific to males. We find that variance in postcopulatory success is over four times as great as variance in precopulatory success, with most of it unexplained by male mating order or the number of nuptial gifts given. Surprisingly, we also find that male singing effort is under postcopulatory selection, suggesting that males who sing more frequently also have more competitive ejaculates. Our results are consistent with the hypothesis that high polyandry levels promote greater relative postcopulatory selection. They also highlight the need for detailed behavioral observations under conditions as natural as possible when measuring mating and reproductive success.     

The mismeasurement of sexual selection

Sexual selection can explain major micro‐ and macro‐evolutionary patterns. Much of current theory predicts that the strength of sexual selection (i) is driven by the relative abundance of males and females prepared to mate (i.e. the operational sex ratio, OSR) and (ii) can be generally estimated by calculating intra‐sexual variation in mating success (e.g. the opportunity for sexual selection, I_s). Here, we demonstrate the problematic nature of these predictions. The OSR and I_s only accurately predict sexual selection under a limited set of circumstances, and more specifically, only when mate monopolization is extremely strong. If mate monopolization is not strong, using OSR or I_s as proxies or measures of sexual selection is expected to produce spurious results that lead to the false conclusion that sexual selection is strong when it is actually weak. These findings call into question the validity of empirical conclusions based on these measures of sexual selection.     

Sperm competition,sexual selection and the diverse reproductive biology of Osteoglossiformes

Osteoglossiformes are an order of “bony tongue” fish considered the most primitive living order of teleosts. This review seeks to consolidate known hypotheses and identify gaps in the literature regarding the adaptive significance of diverse reproductive traits and behaviour of osteoglossiforms within the context of sperm competition and the wider lens of sexual selection. Many of the unusual traits observed in osteoglossiforms indicate low levels of sperm competition; most species have unpaired gonads, and mormyroids are the only known vertebrate species with aflagellate sperm. Several osteoglossiform families have reproductive anatomy associated with internal fertilization but perform external fertilization, which may be representative of the evolutionary transition from external to internal fertilization and putative trade-offs between sperm competition and the environment. They also employ every type of parental care seen in vertebrates. Geographically widespread and basally situated within teleosts, osteoglossiforms present an effective study system for understanding how sperm competition and sexual selection have shaped the evolution of teleost reproductive behaviour, sperm and gonad morphology, fertilization strategies, courtship and paternal care, and sexual conflict. The authors suggest that the patterns seen in osteoglossiform reproduction are a microcosm of teleost reproductive diversity, potentially signifying the genetic plasticity that contributed to the adaptive radiation of teleost fishes.     

How multiple mating by females affects sexual selection

Multiple mating by females is widely thought to encourage post-mating sexual selection and enhance female fitness. We show that whether polyandrous mating has these effects depends on two conditions. Condition 1 is the pattern of sperm utilization by females; specifically, whether, among females, male mating number, m (i.e. the number of times a male mates with one or more females) covaries with male offspring number, o. Polyandrous mating enhances sexual selection only when males who are successful at multiple mating also sire most or all of each of their mates'' offspring, i.e. only when Cov_♂(m,o), is positive. Condition 2 is the pattern of female reproductive life-history; specifically, whether female mating number, m, covaries with female offspring number, o. Only semelparity does not erode sexual selection, whereas iteroparity (i.e. when Cov_♀(m,o), is positive) always increases the variance in offspring numbers among females, which always decreases the intensity of sexual selection on males. To document the covariance between mating number and offspring number for each sex, it is necessary to assign progeny to all parents, as well as identify mating and non-mating individuals. To document significant fitness gains by females through iteroparity, it is necessary to determine the relative magnitudes of male as well as female contributions to the total variance in relative fitness. We show how such data can be collected, how often they are collected, and we explain the circumstances in which selection favouring multiple mating by females can be strong or weak.     

Ejaculate expenditures of male crickets in response to varying risk and intensity of sperm competition: not all species play games

Costs incurred in the manufacture of ejaculates may constrainthe number of sperm that males can produce, so males shouldshow some economy in their allocation of sperm across multiplematings. In species in which females mate with multiple malesand are capable of storing sperm for extended periods, spermallocation of males should be tailored to the risk of spermcompetition. Recent game theory predicts that males shouldtransfer the least sperm when there are no other rivals, andthe most sperm when only one other rival is likely to inseminatethe female. However, as the numbers of competitors increasesbeyond two, the models predict a corresponding decrease in ejaculate expenditure. We tested these predictions in three cricket species, Gryllodes sigillatus, Gryllus veletis, and Gryllus texensis, assessing the sperm allocation of males held under three levelsof apparent interrival competition: no rivals, one rival andsix rivals. Sperm allocation of G. veletis varied accordingto theory: males increased their sperm allocation with an increasedrisk of sperm competition (no rivals vs. one), but decreasedtheir allocation with an increased intensity of sperm competition(one rival vs. six). Sperm allocation of male G. texensis showedno significant response to the density of rivals, and spermallocation in G. sigillatus was influenced by an unexpectedinteraction between treatment density and the order in whichmales experienced the three treatments. The observed interspecificvariation in facultative sperm allocation may be due to interspecificdifferences in population density, rearing environment, orfemale mating behavior.     

Sexual conflict and sexual selection: lost in the chase

The emergent field of evolutionary biology that studies disparities between the evolutionary interests of alleles expressed in the two sexes, or sexual conflict, promises to offer novel insights into male-female coevolution and speciation. Our theoretical understanding of basic concepts is, however, still incomplete. In a recent perspective paper, Pizzari and Snook provided a framework for understanding sexually antagonistic coevolution and for distinguishing this process from other models of male-female coevolution and suggested an experimental protocol to test for sexually antagonistic coevolution. Here, I show that the framework is flawed, primarily because it is built upon the mistaken assumption that male and female fitness can evolve independently. Further, while the empirical strategy advocated has indeed offered important insights in the past, it does not allow unambiguous discrimination between competing hypotheses.     

Ejaculate size varies with socio-sexual situation in an insect

Abstract.

• 1 Males operate within a finite energy budget and cannot produce limitless supplies of sperm. On the other hand, when a female mates with a second male while still containing fertile sperm from a rival male, selection should favour the male that inseminates more sperm. Optimal strategy should thus be for males to exercise discretion in the allocation of sperm to individual females. Assuming the outcome of sperm competition to be based on either the raffle or kamikaze principles, the sperm competition hypothesis predicts a positive association between the probability that the sperm will find themselves in competition with sperm from rival males and the number of sperm inseminated.
• 2 The beetle, Tenebrio molitor L., behaves in accordance with this hypothesis. Males accompanied by a rival male before and during mating inseminate more sperm per ejaculate than unaccompanied males. Accompanied males are also faster to initiate mating and more likely to show post-copulatory guarding. Adjustment of number of sperm inseminated was shown by males subjected to both long-term (5 days) and short-term (5 min) exposure to potential intrasexual competitors. Individual males exposed to both levels also demonstrated the ability to adjust their ejaculate according to socio-sexual situation.
• 3 We conclude that male T.molitor adjust the number of sperm they inseminate according to some perception of the risk of sperm competition.

     

Quantifying episodes of sexual selection: Insights from a transparent worm with fluorescent sperm

Sexual selection operates through consecutive episodes of selection that ultimately contribute to the observed variance in reproductive success between individuals. Understanding the relative importance of these episodes is challenging, particularly because the relevant postcopulatory fitness components are often difficult to assess. Here, we investigate different episodes of sexual selection on the male sex function, by assessing how (precopulatory) mating success, and (postcopulatory) sperm‐transfer efficiency and sperm‐fertilizing efficiency contribute to male reproductive success. Specifically, we used a transgenic line of the transparent flatworm, Macrostomum lignano, which expresses green fluorescent protein (GFP) in all cell types, including sperm cells, enabling in vivo sperm tracking and paternity analysis. We found that a large proportion of variance in male reproductive success arose from the postcopulatory episodes. Moreover, we also quantified selection differentials on 10 morphological traits. Testis size and seminal vesicle size showed significant positive selection differentials, which were mainly due to selection on sperm‐transfer efficiency. Overall, our results demonstrate that male reproductive success in M. lignano is not primarily limited by the number of matings achieved, but rather by the ability to convert matings into successful fertilizations, which is facilitated by producing many sperm.