利用RAPD对稻蝗属昆虫亲缘关系的研究

通过20个随机引物的PCR扩增,得到了日本主要稻蝗的随机扩增多态性DNA（RAPD）图谱,根据扩增结果,计算了种间相似系数和遗传距离,建立了UPGMA系统树。结果表明,分布没有重叠、种间容易交配、能产生杂种的中华稻蝗台湾亚种与小翅稻蝗的亲缘关系最近;分布重叠的日本稻蝗与中华稻蝗台湾亚种、日本稻蝗和小翅稻蝗的亲缘关系较近。小稻蝗与其它3种稻蝗的亲缘关系较远。     

小翅稻蝗的精子竞争及交配行为的适应意义

许多昆虫有多次交配行为 ,因多次交配而引起不同雄虫的精子竞争 ,提供雌虫一种有效的性选择方式。小翅稻蝗 (Oxyayezoensis Shiraki)具多次交配行为 ,雌雄交配时间长 ,且交配后常伴有长时间的抱对行为。利用近缘种的种间交配 ,对小翅稻蝗的精子竞争、交配后抱对行为的适应意义进行了探讨。结果表明 ,小翅稻蝗的 P2 值 (最后交配雄虫子代的比例 )达 94 .3%±5 .3% ,说明最后交配雄虫的精子优先用于卵子的受精 ,交配时存在着精子置换。长时间的交配后抱对行为是为了阻止雌虫与不同雄虫个体的再交配 ,保护精子免被置换。     

赤拟谷盗和杂拟谷盗的生殖隔离研究

赤拟谷盗和杂拟谷盗是两个同域发生的近缘储粮害虫。为明确它们的生殖隔离程度和机制,本研究比较分析了赤拟谷盗和杂拟谷盗雄虫对同种和异种雌虫的交配选择;赤拟谷盗与杂拟谷盗交配后,测定了精子在异种雌体内的存活情况;将赤拟谷盗和杂拟谷盗进行正反杂交,研究其F1代、F2代和回交代杂种是否产生及其雌雄比。结果显示,赤拟谷盗和杂拟谷盗雄虫对同种雌虫的爬跨率和交配率高于其对异种雌虫的爬跨率和交配率,表明赤拟谷盗和杂拟谷盗种间性隔离不完全;赤拟谷盗和杂拟谷盗交配后精子在异种雌体内是存活的,杂交所产的F1代卵为受精卵,说明交配后完成了精子传送和受精过程,表明种间机械隔离和配子隔离不完全;赤拟谷盗和杂拟谷盗的杂种F1代自交和回交产生了F2代和回交代,表明种间不存在杂种不育;一些杂交组合产生的F2代和回交代数量少且存在雌雄性比偏离,表明种间存在部分杂种不活和杂种衰败。本研究明确了赤拟谷盗和杂拟谷盗的生殖隔离机制,这对于揭示它们的物种进化关系有着重要意义。     

山稻蝗不同地域种群染色体C带核型研究

对我国分布的山稻蝗OxyaagavisaTsai不同种群进行了染色体C带核型研究 ,并对山稻蝗武夷山种群染色体C带核型进行了深入探讨 ,分析了其带型特殊性及该种群与其它山稻蝗种群染色体C带核型的区别与联系。同时通过对山稻蝗与中华稻蝗Oxyachinensis (Thunberg)、日本稻蝗Oxyajaponica (Thunberg)的形态、分布及染色体C带核型等方面的比较 ,探讨了该 3个种之间的进化关系 ,认为作为稻蝗属中的大型种类 ,上述 3个种之间有着较近的亲缘关系。染色体带型的实验结果表明 ,中华稻蝗为较原始的种类 ,而日本稻蝗和山稻蝗则可能是由原始中华稻蝗进化而来 ,其中日本稻蝗L2染色体的形成是由于原始中华稻蝗该染色体常染色质部分异染色质化的结果 ,山稻蝗L2染色体则可能是由于原始中华稻蝗该染色体近端部的臂间倒位所致。通过对武夷山山稻蝗的研究 ,对日本稻蝗和山稻蝗之间的近缘关系进行了分析和讨论。     

山稻蝗不同地域和种群染色体C带核型研究

对我国分布的山稻蝗Oxya agavisa Tsai不同种群进行了染色体C带核型研究,并对山稻蝗武夷山种群染色体C带核型进行了深入探讨,分析了其带型特殊性及该种群与其它山稻蝗种群染色体C带核型的区别与联系。同时通过对山稻蝗与中华稻蝗Oxya chinensis(Thunberg)日本稻蝗Oxya japonica(Thunberg）的形态,分布及染色体C带核型等方面的比较,探讨了该3个种之间的进化关系,认为作稻蝗属中的大型种类,上述3个种之间有着较近的亲缘关系。染色体带型的实验结果表明,中华稻蝗为较原始的种类,而日本稻蝗和山稻蝗则可能是由原始中华稻蝗进化而来,其中日本稻蝗L2染色体的形成是由于原始中华稻蝗该染色体常染色质部分异染色质化的结果,山稻蝗L2染色体则可能是由于原始中华稻蝗该染色体近端部的臂间倒位所致。通过对武夷山山稻蝗的研究,对日本稻蝗和山稻蝗之间的近缘关系进行了分析和讨论。     

中国稻蝗属细胞分类学研究(英文)

本文对分布于中国境内11省区,27个采集地点的八种稻蝗进行了染色体C带核型比较研究。结果表明:中华稻蝗Oxya chinensis,上海稻蝗O.shanghaiensis,无齿稻蝗O.adentata C带分布型式相似,但染色体分组型式、交叉定位数据以及异染色质含量具有差异;山稻蝗O.agauisa具有本身独特的带纹结构,与本属其它种类迥异;双带稻蝗O.bicingula染色体带型结构相似于山稻蝗及中华稻蝗类群,表明三者在进化历程中有一定联系。小稻蝗O.hyla intricata中一个亲缘种团(Sibling species group),体现在种内的形态差异及染色体带型结构的不同。显示该种近期内分化速率较高。据此,本文讨论了稻蝗属内八个种相互间的亲缘关系和分类地位,本文认为稻蝗属内务物种进化速率是不均衡的,这种状态应归因于各物种的遗传背景和环境因素的影响。     

蝗总科精子超微形态比较及其在系统分类上的意义（直翅目）

通过对８科１９属２３种蝗虫精子超微形态结构的观察和比较,发现其精子有４种类型。这４种类型精子间的主要差异反映在中心粒侧体及线粒体衍生体的超微形态结构方面。经过比较和分析,确认８科中癞蝗科种类（除友谊华癞蝗外）的精子最原始,斑腿蝗科、斑翅蝗科、网翅蝗科、槌角蝗科、剑角蝗科（除中华蚱蜢外）种类的精子最进化。根据精子的演化类型建立了蝗总科精子系统,在这个系统里蝗总科８科昆虫在演化趋势上可分为３大类群     

中华稻蝗不同龄期的形态多样性研究

【目的】中华稻蝗Oxya chinensis的个体发育中经历体型渐变发育过程,随着龄期增加,一些功能器官逐渐发育完善,并执行相应的功能。研究中华稻蝗的个体发育规律,对于充分认识蝗虫体型的形成规律,机体结构与功能的关系,具有重要意义。【方法】本研究运用几何形态测量学方法分析不同虫龄的中华稻蝗身体结构的发育过程,探讨各器官结构的形成规律以及其功能的实现。【结果】研究结果表明:中华稻蝗不同龄的后翅、前胸背板、腹板、颜面、后足股节大小存在显著差异,随着虫龄的增加,各结构呈线性增大。PCA法和薄板样条法结果表明后翅从4龄到6龄,翅型结构呈渐变规律,成虫时肘脉域变小,轭脉域及臀脉域扩大,后翅的形状随其功能的实现显著不同于翅芽时期。前胸背板、颜面和后足股节随虫龄的增加在PC1轴呈渐变规律,随着取食和运动能力的增强,前胸背板变得更加宽阔、颜面的颊侧更加宽大,后足股节更加细长。腹板的形状在低龄阶段差异不大,成虫时在后足股节的着生区大而且向外突出。【结论】中华稻蝗不同虫龄间在后翅、前胸背板、腹板、颜面、后足股节等功能器官上存在显著差异。随着龄期的增加,各功能器官的形态呈渐变规律,然而这些功能器官的形成并非等比例扩大,而是形成特定的形态来实现其功能。     

四种斑腿蝗科昆虫染色体带型的比较

应用染色体C带及银染核仁组成区定位分析方法对斑腿蝗科4种昆虫,即小蹦蝗属2种;峨眉小蹦蝗Pedopodisma emeiensis和秦岭小蹦蝗P.tsinlingensis;无翅蝗属2种;小无翅蝗Zubovskiaparvula和柯氏无翅蝗Z.koeppeni进行了研究,结果表明：4种蝗虫染色体数目（2n♂=21,XO)一致,小蹦蝗属M8染色体上具有端带;无翅蝗属X染色体具有特殊带纹,银染核仁组成区定位在两属各有特点,小蹦蝗属位于第8号染色体端部区域;无翅蝗属位于X染色体端部区域,除上述属内共性之外,各物种C带带纹又存在明显差异,其中峨眉小蹦蝗带型极为特殊。文中还对上述4种蝗虫带型结构特征及其进化意义作了讨论。     

稻蝗属部分种类RAPD及其分子系统学关系

用经筛选的8个随机引物对稻蝗属(Oxya Audient-Serville)中的中华稻蝗(Oxya chinensis)、日本稻蝗(Oxyajaponica)、山稻蝗(0xya agaxisa)、短翅稻蝗(Oxya brachyptera)和小稻蝗(Oxya intricata)等5个种41个个体进行扩增,均扩增出特异性产物,在96条清晰稳定的扩增片段中,多态性片段为95条,种间共有片段1条(引物S362扩增的约850 bp的片段),所获片段的长度大小为200—2500bP,单个引物扩增的条带数在8-16之间,平均为12。根据扩增结果,应用SPSS软件包中的Between-groups linkage法进行聚类分析,得到5种稻蝗的分子系统树。结果显示：中华稻蝗与短翅稻蝗关系密切,日本稻蝗与山稻蝗关系较近,而小稻蝗与它们的亲缘关系较远。聚类图所呈现的种间关系与传统的形态及细胞分类学结果基本一致,5种稻蝗亲缘关系的远近程度得以清楚显示,说明RAPD技术在稻蝗属种间分子系统学研究中具有很好的适用性。     

Postmating-prezygotic isolation is not an important source of selection for reinforcement within and between species in Drosophila pseudoobscura and D. persimilis

Abstract Most work on adaptive speciation to date has focused on the role of low hybrid fitness as the force driving reinforcement (the evolution of premating isolation after secondary contact that reduces the likelihood of matings between populations). However, recent theoretical work has shown that postmating, prezygotic incompatibilities may also be important in driving premating isolation. We quantified premating, postmating-prezygotic, and early postzygotic fitness effects in crosses among three populations: Drosophila persimilis, D. pseudoobscura USA (sympatric to D. persimilis ), and D. pseudoobscura Bogotá (allopatric to D. persimilis ). Interspecific matings were more likely to fail when they involved the sympatric populations than when they involved the allopatric populations, consistent with reinforcement. We also found that failure rate in sympatric mating trials depended on whether D. persimilis females were paired with D. pseudoobscura males or the reverse. This asymmetry most likely indicates differences in discrimination against heterospecific males by females. By measuring egg laying rate, fertilization success and hatching success, we also compared components of postmating-prezygotic and early postzygotic isolation. Postmating-prezygotic fitness costs were small and not distinguishable between hetero- and conspecific crosses. Early postzygotic fitness effects due to hatching success differences were also small in between-population crosses. There was, however, a postzygotic fitness effect that may have resulted from an X-linked allele found in one of the two strains of D. pseudoobscura USA. We conclude that the postmating-prezygotic fitness costs we measured probably did not drive premating isolation in these species. Premating isolation is most likely driven in sympatric populations by previously known hybrid male sterility.     

No character displacement for reproductive isolation between Drosophila bipectinata and Drosophila malerkotliana.

To test whether character displacement for reproductive isolation between Drosophila bipectinata and Drosophila malerkotliana exists, the degree of sexual isolation was measured between their sympatric and allopatric populations. Although the isolation indices vary in different crosses, the average isolation index for sympatric populations is very close to that for allopatric populations. This shows no difference in the degree of sexual isolation between sympatric and allopatric populations of D. bipectinata and D. malerkotliana. Thus there is no evidence for the existence of character displacement for sexual isolation between these two closely related sympatric species.     

REPRODUCTIVE CHARACTER DISPLACEMENT OF MALE STICKLEBACK MATE PREFERENCE: REINFORCEMENT OR DIRECT SELECTION?

Reproductive isolation can evolve between species as a byproduct of adaptation to different niches, through reinforcement, and by direct selection on mating preferences. We investigated the potential role of direct selection in the reproductive isolation between sympatric species of threespine sticklebacks. Each sympatric pair consists of a small-bodied limnetic species and large-bodied benthic species. We compared the mate preferences and courtship behavior of males from one sympatric limnetic population and two allopatric populations. We used limnetic-like allopatric populations to control for the effects of ecological character displacement and adaptation to different niches on mate preferences. The sympatric limnetic males preferred the small limnetic females, whereas the allopatric limnetic-like males preferred the large benthic females, suggesting that adaptation to the limnetic niche does not automatically confer a preference for small limnetic females. This reproductive character displacement of male preference is consistent with the predictions of both reinforcement and direct selection on mate preferences. To test for direct selection, we assessed a prediction of one proposed mechanism: predation by benthic females on eggs guarded by limnetic males. The allopatric males come from populations in which there is no egg predation. Sympatric limnetic males were more aggressive toward benthic females than toward limnetic females, whereas the allopatric limnetic-like males did not treat the two types of females differently. The contrast in male behavior suggests that egg predation has shaped male preferences. Direct selection is potentially more effective than indirect selection via reinforcement, and it is likely that it has been important in building up reproductive isolation between limnetic and benthic sticklebacks.     

SIMULATING RANGE EXPANSION: MALE SPECIES RECOGNITION AND LOSS OF PREMATING ISOLATION IN DAMSELFLIES

Prolonged periods of allopatry might result in loss of the ability to discriminate against other formerly sympatric species, and can lead to heterospecific matings and hybridization upon secondary contact. Loss of premating isolation during prolonged allopatry can operate in the opposite direction of reinforcement, but has until now been little explored. We investigated how premating isolation between two closely related damselfly species, Calopteryx splendens and C. virgo , might be affected by the expected future northward range expansion of C. splendens into the allopatric zone of C. virgo in northern Scandinavia. We simulated the expected secondary contact by presenting C. splendens females to C. virgo males in the northern allopatric populations in Finland. Premating isolation toward C. splendens in northern allopatric populations was compared to sympatric populations in southern Finland and southern Sweden. Male courtship responses of C. virgo toward conspecific females showed limited geographic variation, however, courtship attempts toward heterospecific C. splendens females increased significantly from sympatry to allopatry. Our results suggest that allopatric C. virgo males have partly lost their ability to discriminate against heterospecific females. Reduced premating isolation in allopatry might lead to increased heterospecific matings between taxa that are currently expanding and shifting their ranges in response to climate change.     

Sperm numbers vary between inter- and intra-population matings of the grasshopper Chorthippus parallelus

Comparing the reproductive output of intra- and inter-population matings is the most common way to assess whether post-mating reproductive isolation is caused by genetic incompatibilities. Such genetic incompatibility can however, only assume that the quantity of the post-mating signals involved does not differ between intra- and inter-population matings. This assumption may not be true because sexual selection predicts reduced mating effort towards low-quality mates and in many circumstances, allopatric partners are low-quality mates. Post-mating efforts may, therefore, be reduced in inter- compared to intra-population matings. Here, I test this crucial assumption by studying variation in one post-mating trait, sperm number, in crosses of two parapatric grasshopper populations. In both populations, males transferred fewer sperm to allopatric than sympatric females. If such plasticity with respect to population is common in other post-mating traits, differences between inter- and intra-population crosses may be more frequently caused by differences in sperm number rather than gamete incompatibility. Additionally, I found that sperm numbers declined less rapidly in the female storage organ of allopatric than sympatric females but its rate differed markedly between populations. This is discussed with respect to female adaptations to male traits.     

ETHOLOGICAL DIVERGENCE IN ALLOPATRY AND ASYMMETRICAL ISOLATION IN THE SOUTH PACIFIC AEDES SCUTELLARIS SUBGROUP

Ethological isolation among eight species of mosquitoes in the Aedes scutellaris subgroup of the south Pacific was investigated by offering females a simultaneous choice between males of their own species and males of another species. The degree of ethological isolation between these largely allopatric, island-dwelling mosquitoes was associated with time since the species had become geographically isolated by the fragmentation of the Outer Melanesian Arc 2–10 mya. The degree of ethological isolation between species pairs was observed to be significantly correlated with the degree of genetic isolation based on other published studies of allozyme variation and percentage egg hatch from interspecific hybridizations. However, ethological isolation was asymmetrical for some species pairs within the same island region. Asymmetrical isolation was especially prominent in Polynesia, where females of two older species discriminated against males of newer species, while females of the newer species failed to discriminate.     

REINFORCEMENT OF STICKLEBACK MATE PREFERENCES: SYMPATRY BREEDS CONTEMPT

Detailed studies of reproductive isolation and how it varies among populations can provide valuable insight into the mechanisms of speciation. Here we investigate how the strength of premating isolation varies between sympatric and allopatric populations of threespine sticklebacks to test a prediction of the hypothesis of reinforcement: that interspecific mate discrimination should be stronger in sympatry than in allopatry. In conducting such tests, it is important to control for ecological character displacement between sympatric species because ecological character divergence may strengthen prezygotic isolation as a by-product. We control for ecological character displacement by comparing mate preferences of females from a sympatric population (benthics) with mate preferences of females from two allopatric populations that most closely resemble the sympatric benthic females in ecology and morphology. No-choice mating trials indicate that sympatric benthic females mate less readily with heterospecific (limnetic) than conspecific (benthic) males, whereas two different populations of allopatric females resembling benthics show no such discrimination. These differences demonstrate reproductive character displacement of benthic female mate choice. Previous studies have established that hybridization between sympatric species occurred in the past in the wild and that hybrid offspring have lower fitness than either parental species, thus providing conditions under which natural selection would favor individuals that do not hybridize. Results are therefore consistent with the hypothesis that female mate preferences have evolved as a response to reduced hybrid fitness (reinforcement), although direct effects of sympatry or a biased extinction process could also produce the pattern. Males of the other sympatric species (limnetics) showed a preference for smaller females, in contrast to the inferred ancestral preference for larger females, suggesting reproductive character displacement of limnetic male mate preferences as well.     

Strength of sexual and postmating prezygotic barriers varies between sympatric populations with different histories and species abundances

The impact of different reproductive barriers on species or population isolation may vary in different stages of speciation depending on evolutionary forces acting within species and through species’ interactions. Genetic incompatibilities between interacting species are expected to reinforce prezygotic barriers in sympatric populations and lead to cascade reinforcement between conspecific populations living within and outside the areas of sympatry. We tested these predictions and studied whether and how the strength and target of reinforcement between Drosophila montana and Drosophila flavomontana vary between sympatric populations with different histories and species abundances. All barriers between D. montana females and D. flavomontana males were nearly complete, while in the reciprocal cross strong postzygotic isolation was accompanied by prezygotic barriers whose strength varied according to population composition. Sexual isolation between D. flavomontana females and D. montana males was increased in long‐established sympatric populations, where D. flavomontana is abundant, while postmating prezygotic (PMPZ) barriers were stronger in populations where this species is a new invader and still rare and where female discrimination against heterospecific males was lower. Strengthening of sexual and PMPZ barriers in this cross also induced cascade reinforcement of respective barriers between D. flavomontana populations, which is a classic signature of reinforcement process.     

Does sympatry predict life history and morphological diversification in the Mexican livebearing fish Poeciliopsis baenschi?

Understanding why some species coexist and others do not remains one of the fundamental challenges of ecology. Although there is evidence to suggest that closely‐related species are unlikely to occupy the same habitat because of competitive exclusion, there are many cases where closely‐related species do co‐occur. Research comparing sympatric and allopatric populations of co‐occurring species provides a framework for understanding the role of phenotypic diversification in species coexistence. In the present study, we compare phenotypic divergence between sympatric and allopatric populations of the livebearing fish, Poeciliopsis baenschi. We focus on life‐history traits and body shape, comprising two sets of integrated traits likely to diverge in response to varying selective pressures. Given that males and females can express different phenotypic traits, we also test for patterns of divergence among sexes by comparing size at maturity and sexual dimorphism in body shape between males and females in each population type. We take advantage of a natural experiment in western Mexico where, in some locations, P. baenschi co‐occur with a closely‐related species, Poeciliopsis turneri (sympatric populations) and, in other locations, they occur in isolation (allopatric populations). The results obtained in the present study show that sympatric populations of P. baenschi differed significantly in life‐history traits and in body shape compared to their allopatric counterparts. Additionally, males and females showed different responses for size at maturity in sympatric conditions versus allopatric conditions. However, the amount of sexual dimorphism did not differ between sympatric and allopatric populations of P. baenschi. Hence, we conclude that not all traits show similar levels of phenotypic divergence in response to sympatric conditions. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100 , 608–618.