山姜属植物花柱卷曲性传粉机制的研究

暂性雌雄异株是一种在两性花或雌雄同株植物个体上表现出的雄蕊和雌蕊成熟时间不同而形成的暂时性雄性阶段和雌性阶段不重叠的现象。这种现象减少了自交亲和的雌雄同株和两性花种类发生自交的可能性。作系统研究了花柱郑曲性传粉机制在西双版纳姜科山姜属（Alpinia Roxb.）植物中的普遍性,这一机制使得植物通过完全的暂性异株达到了异交的目的。这类植物的种群中具有两种独特的表现型,其差异央开花行为的不同：柱头下垂型个体在刚开花时其柱头向上反卷。位于已开裂的花药上方,到中午开始向下运动,下午则位于花药下方;柱头上举型个体的柱头在开花初期向花冠内卷曲,位于未开裂的花药和唇瓣之间中午开始向上运动,当柱头上举到花药上方后,花药开裂,花偻开始散发。两种个体的开花行为是同步的,通过两种柱头反向运动授粉方式（不同时间的自花和异花授粉）具有相同的结实率,但套代的花序几科不结实,两种表型在自然种群中的比例为1：1。     

花柱卷曲性异交机制及其进化生态学意义

 有花植物具有纷繁复杂的繁育系统,以避免或促进自交或异交。花柱卷曲性异交机制(Flexistyly)是最近在热带山姜属(Alpinia)植物中发现的一种促进异交的行为机制。具有这一机制的种类其自然种群中的个体根据开花行为的不同分为两种表型：一种上午散发花粉而其柱头向上反卷,远离昆虫拜访的通道;另一种其柱头上午垂向唇瓣,能够接受拜访昆虫的传粉,但自身的花药却不打开。到中午时分,两种表型花通过互为相反的柱头卷曲运动转换性别——前者柱头向下卷曲,后者柱头向上卷曲且花药打开。每朵花的花期为12 h,两种表型在自然种     

马来良姜花柱卷曲运动的结构基础

山姜属(Alpinia L.)植物的花柱具卷曲运动的能力,该属植物的野生种群有两种表型的个体,其花柱运动方向相反。该文通过观察马来良姜(Alpinia mutica Roxb.)花柱的显微和超微结构来研究花柱卷曲运动的结构基础。结果表明两种表型的花柱解剖结构相同。花柱仅形态学上端区域(约占花柱总长度的25%)有卷曲运动能力,其它区域不能运动。运动区近轴侧分布着几层直径较大、形状不规则、相对较短且细胞壁较薄的细胞,远轴侧的细胞直径较小、狭长;非运动区近轴和远轴侧的细胞都呈狭长形。花柱运动区域近轴侧和远轴侧细胞结构和细胞层数的不对称可能是导致花柱卷曲运动的结构原因。     

马来良姜花柱卷曲运动的结构基础

山姜属(Alpinia L.)植物的花柱具卷曲运动的能力, 该属植物的野生种群有两种表型的个体, 其花柱运动方向相反。该文通过观察马来良姜(Alpinia mutica Roxb.)花柱的显微和超微结构来研究花柱卷曲运动的结构基础。结果表明两种表型的花柱解剖结构相同。花柱仅形态学上端区域(约占花柱总长度的25%)有卷曲运动能力, 其它区域不能运动。运动区近轴侧分布着几层直径较大、形状不规则、相对较短且细胞壁较薄的细胞, 远轴侧的细胞直径较小、狭长; 非运动区近轴和远轴侧的细胞都呈狭长形。花柱运动区域近轴侧和远轴侧细胞结构和细胞层数的不对称可能是导致花柱卷曲运动的结构原因。     

温度和湿度对草果花柱卷曲的影响

草果（Amomum tsaoko）为姜科植物,有花柱卷曲机制。研究表明温度和湿度均影响草果上举型花和下垂型花的花柱卷曲,相对恒定的低温和高湿可促使花柱的同步卷曲。当8∶00-19∶30期间的平均温度小于18℃、平均湿度大于90%时,花柱卷曲没有滞后现象,卷曲的同步性较好。当平均温度大于18℃、平均湿度小于90%时,随着温度的升高和湿度的降低,花柱卷曲滞后愈加明显。和上举型花相比,下垂型花的花柱卷曲对湿度变化更为敏感;可能两种花型之间存在一定的分化。居群初花期19.17~19.52℃的平均温度和51.00%~51.44%的平均湿度,导致单朵下垂型花的寿命由1d延长为2d。温度和湿度变化对花柱卷曲的影响导致在居群水平上没有完全形成功能上的雌雄异株,可能影响草果的繁育和降低其适合度。从不同角度对花柱卷曲机制的深入研究,有助于更好的探索其起源和进化。     

连翘花柱二型的繁育系统特征研究

花柱二型是植物雌雄蕊交互异位的一种花多态现象.该研究以花柱二型植物连翘(Forsythia suspensa)为材料,通过检测其交配系统特征,比较两花型的胚珠产量、花粉质量及活力特性,以探讨花柱二型连翘两花型的功能性别分化及其进化意义.结果表明:连翘自交和型内异交坐果率均极低(<12.12％),主要以型间交配为主.长柱...     

异型花柱植物喀什补血草的传粉者功能群与花粉转移效率

异型花柱是受遗传控制的花柱多态现象, 被达尔文认为是植物通过在传粉者体表不同部位滞落花粉以促进型间花粉准确传递的一种适应。该现象虽已受到广泛关注, 但在一些花型变异较大且不稳定的传粉系统中, 不同传粉者对各花型繁殖所产生的影响仍知之甚少。该研究以分布于新疆天山南坡的一个有同长花柱共存的异型花柱植物喀什补血草(Limonium kaschgaricum)种群为研究对象, 对其花型构成及频率、传粉者及花粉转移效率等进行了调查分析。结果表明: 1)种群中除了存在雌/雄蕊长度交互对应的长(L)/短(S)花柱型花外, 还有雌/雄蕊同长的花(H型), 且各花型花的花冠口直径、花冠筒长及花粉量等参数间无差异, 但花粉纹饰和柱头乳突细胞形态具二型性。其中, H型花的花粉和柱头形态与L型花(或S型花)的一致。2)花型内和自花授粉均不亲和; 型间授粉时, 花粉和柱头形态不同的花型间亲和, 反之不亲和。3)种群内存在长/短吻两类传粉昆虫。在以短吻传粉者为主的盛花初、中期, L和H型花柱头上的异型花粉数均显著高于S型花的, 且L和S型花高位性器官间的异型花粉传递效率高于低位性器官间的; 而在以长吻传粉者为主的盛花后期, L和S型花的柱头间异型花粉数无显著差异, 且高/低位性器官间具有相同的异型花粉转移效率; 与传粉者出现时期相对应的、在花期不同阶段开放花的结实率也明显不同。4)长/短吻昆虫具明显不同的传粉功能, 短吻昆虫只能对L和H型花进行有效传粉, 且访花频率和型间花粉转移效率较低, 为低效传粉者; 而长吻昆虫对各花型均能有效传粉, 具高的访花频率和型间花粉转移效率, 为高效传粉者。因为长吻昆虫的阶段性出现所形成的不稳定传粉系统, 使低效的短吻昆虫可能会成为种群中花型变异的驱动力, 并使S型花受到更大的选择压力。H型花克服了柱头缩入的弊端, 可能会成为不稳定传粉系统下的一个替代花型而持续存在。     

果蝇Drosophila biarmipes翅斑二型性的生态学意义(英文)

雌性对雄性表饰的偏好性有利于性别选择。目前尚不清楚这一偏好性是否只限于雄性表饰或这一偏好性实际上是源于影响后代适合度的基因。对于雄性可直接有利于雌性或其后代适合度的交配系统而言,答案是肯定的--雌性偏好于与对气候胁迫具有更强生理抗性的雄性交配。对果蝇Drosophila biarmipes 的室内研究已经证明了求偶过程中翅斑的作用,但是其生态学意义仍然不清楚。我们检验了有翅斑与无翅斑雄性果蝇D. biarmipes 及雌性偏好的雄性所产生的后代对环境胁迫的抗性是否不同。结果表明：在干燥或冷胁迫条件下,有翅斑的雄性果蝇比无翅斑的雄性果蝇的交配成功率明显要高。相反,在高湿条件下,无翅斑雄性果蝇的交配频率更高。我们也发现在较为干旱的条件下,与有翅斑雄性交配的雌性果蝇的生殖力以及所得后代从卵至成虫的存活率更高。我们的结果与优良基因性选择假说一致,说明交配选择能给雌性带来间接好处。这是对热带物种D. biarmipes翅色二型性生态学意义的首次报道。     

普通小麦、Cheyenne与黑麦的可交配性基因及其在染色体上的位置

中国春-Cheyenne二体代换系5A、5B和5D、中国春(Chinese Spring)、Cheyenne、中国春缺体5A—四体5D、中国春缺体5B—四体5D、中国春缺体5D—四体5B与兰州黑麦的杂交结实率分别为72.5%、53.5%、84.5%、88.0%、19.0%、73.5%、67.0%和67.0%,推测Cheyenne和黑麦的可交配性基因型是Kr1 Kr1、Kr2 Kr2和kr3 kr3,它们分别位于染色体5B、5A和5D上。     

艳丽耳草的二型花柱及异型自交不亲和系统

异型花柱是一种受遗传因素控制的花型多态性现象,包括二型花柱和三型花柱两种类型.本文以茜草科艳丽耳草(Hedyotis pulcherrima)为实验材料,通过对其野外居群的花型、花部形态及花粉特征等观察,发现艳丽耳草野外居群同时存在长花柱型花和短花柱型花,长/短花柱型花的数量比例为1∶1.两型花具有精确的交互式雌雄异位特征,并且该特征与花冠长度相关性显著.长/短花柱型花的柱头裂片长度、花粉大小及淀粉含量等具有二型性.花粉体外培养时花粉萌发率及花粉管生长速率无显著性差异.人工授粉后,艳丽耳草长/短花柱型花型间异交花粉管生长形态正常,授粉24 h后花粉管均已进入子房.而长/短花柱型花在自交及型内异交下均表现为不亲和,花粉管生长停止于柱头,花粉管顶端累积胼胝质并膨大.艳丽耳草没有无融合生殖现象,型间人工辅助异交授粉结实率为100％,显著高于自然结实率.本研究结果表明,艳丽耳草是典型的二型花柱植物,并具有异型自交不亲和系统.     

Modification of phenotypic and functional gender in the monoecious Arum italicum (Araceae)

Other than studies on sex-labile Arisaema species, studies of gender patterns in Araceae are scarce. The modification of phenotypic and functional gender was investigated in three populations of the monoecious Arum italicum Miller. The probability of reproduction and the number of inflorescences produced increased with plant size, and flower number (total, male, staminodes, female, pistillodes) increased with both plant and inflorescence sizes. However, plant and inflorescence sizes were poor predictors of floral sex ratio (female to male flower ratio). In contrast, change in floral sex ratio towards increasing femaleness was found among inflorescences sequentially produced by a plant. This change could not be explained by either a decrease in inflorescence size or a change in the mating environment. Differences in functional gender did not appear to be related to plant size or stage in the flowering period. Instead, different patterns of functional gender were found between plants with different number of inflorescences. Multi-inflorescence plants showed a functional gender around 0.5, while plants with one inflorescence showed a more extreme functional gender (either male, female, or functionally sterile). Sex of flowers in this species did not seem to exhibit a phenotypic trade-off.     

Disassortative mating, sexual specialization, and the evolution of gender dimorphism in heterodichogamous Acer opalus

In sexually polymorphic species, the morphs are maintained by frequency-dependent selection through disassortative mating. In heterodichogamous populations in which disassortative mating occurs between the protandrous and protogynous morphs, a decrease in female fitness in one morph is hypothesized to drive sexual specialization in the other morph, resulting in dimorphic populations. We test these ideas in a population of the heterodichogamous species, Acer opalus . We assessed both prospective gender of individuals in terms of their allocations and actual parentage using microsatellites; we found that most matings in A. opalus occur disassortatively. We demonstrate that the protogynous morph is maintained by frequency-dependent selection, but that maintenance of males versus protandrous individuals depends on their relative siring success, which changes yearly. Seeds produced later in the reproductive season were smaller than those produced earlier; this should compromise reproduction through ovules in protandrous individuals, rendering them male biased in gender. Time-dependent gender and paternity analyses indicate that the sexual morphs are specialized in their earlier sexual functions, mediated by the seasonal decrease in seed size. Our results confirm that mating patterns are context-dependent and change seasonally, suggesting that sexual specialization can be driven by seasonal effects on fitness gained through one of the two sexual functions.     

Morph-ratio variation, population size and female reproductive success in distylous Pulmonaria officinalis (Boraginaceae)

Theory predicts that morph ratios in heterostylous populations are governed by negative frequency-dependent selection typically resulting in equal morph ratios at equilibrium. Previous work on the distylous perennial herb Pulmonaria officinalis, however, showed asymmetric mating between floral morphs and a weak self-incompatibility system, with the long-styled morph (L-morph) producing significantly higher seed set following intramorph crosses and even selfing than the short-styled morph (S-morph), two aspects thought to affect female fecundity and morph-ratio variation. Here, we evaluated morph ratios and population size of all known P. officinalis populations in the northern part of Belgium. Morph ratios deviated significantly from 1:1 (range 0.09-1 L-morph frequency, mean = 0.58). Relative fecundity of the S-morph (i.e. mean seed set of the S-morph/mean seed set of the L-morph) was on average 0.73, was positively related to the frequency of the L-morph, and reached 1 (similar levels of female fecundity) at an average L-morph frequency of 0.66 in the population. As some small populations had the S-morph in majority, our results suggest that local morph ratios are influenced both by the relative fecundity of L- and S-morph individuals and by stochastic processes in small populations.     

Impact of mate availability, population size, and spatial aggregation of morphs on sexual reproduction in a distylous, aquatic plant

In distylous, self-incompatible plants, clonal propagation, unbalanced floral morph frequencies, and reduced population size can interfere with the functioning of distyly by compromising legitimate intermorph pollinations, resulting in reduced reproductive output. Here, we examined the mating system and the impact of mate availability, population size, and spatial aggregation of morphs on reproductive output in the distylous, clonal, aquatic plant Hottonia palustris. Controlled pollinations under greenhouse conditions detected no spontaneous selfing without the action of a pollen vector (autonomous autogamy) and demonstrated very low fruit and seed development after self-pollination. Intermorph (legitimate) crossings resulted in high reproductive output in both floral morphs (long- and short-styled individuals), whereas intramorph (illegitimate) crossings decreased fruit and seed development by more than 50%, indicating that the species has partial intramorph-incompatibility. In natural populations, small population size and increasing deviation of floral morph frequencies negatively affected reproductive outcome. Individuals of the majority morph type developed significantly fewer fruit and seeds than individuals of the minority morph type. This rapid decline in fecundity was symmetrical, indicating that regardless of which morph was in the majority, the same patterns of negative frequency-dependent mating occurred. Increasing spatial isolation between compatible morphs significantly reduced fruit and seed set in both morphs similarly. This study provides clear indications of frequency- and context-dependent mating in natural populations of a distylous plant species.     

Sexual selection and the evolutionary dynamics of the major histocompatibility complex

The genes of the major histocompatibility complex (MHC) are a key component of the adaptive immune system and among the most variable loci in the vertebrate genome. Pathogen-mediated natural selection and MHC-based disassortative mating are both thought to structure MHC polymorphism, but their effects have proven difficult to discriminate in natural systems. Using the first model of MHC dynamics incorporating both survival and reproduction, we demonstrate that natural and sexual selection produce distinctive signatures of MHC allelic diversity with critical implications for understanding host–pathogen dynamics. While natural selection produces the Red Queen dynamics characteristic of host–parasite interactions, disassortative mating stabilizes allele frequencies, damping major fluctuations in dominant alleles and protecting functional variants against drift. This subtle difference generates a complex interaction between MHC allelic diversity and population size. In small populations, the stabilizing effects of sexual selection moderate the effects of drift, whereas pathogen-mediated selection accelerates the loss of functionally important genetic diversity. Natural selection enhances MHC allelic variation in larger populations, with the highest levels of diversity generated by the combined action of pathogen-mediated selection and disassortative mating. MHC-based sexual selection may help to explain how functionally important genetic variation can be maintained in populations of conservation concern.     

Parents’ genetic dissimilarity and offspring sex in a polygynous mammal

Offspring quality may benefit from genetic dissimilarity between parents. However, genetic dissimilarity may trade‐off with additive genetic benefits. We hypothesized that when sexual selection produces sex‐specific selective scenarios, the relative benefits of additive genetic vs. dissimilarity may differ for sons and daughters. Here we study a sample of 666 red deer (Cervus elaphus) microsatellite genotypes, including males, females and their foetuses, from 20 wild populations in Spain (the main analyses are based on 241 different foetuses and 190 mother‐foetus pairs). We found that parental lineages were more dissimilar in daughters than in sons. On average, every mother was less related to her mate than to the sample of fathers in the population when producing daughters not sons. Male foetuses conceived early in the rutting season were much more inbred than any other foetuses. These differences maintained through gestation length, ruling out intrauterine mortality as a cause for the results, and indicating that the potential mechanism producing the association between parents’ dissimilarity and offspring sex should operate close to mating or conception time. Our findings highlight the relevance of considering the sex of offspring when studying genetic similarity between parents.     

Perceptual Processes and the Maintenance of Polymorphism Through Frequency-dependent Predation

One of the key challenges of both ecology and evolutionary biology is to understand the mechanisms that maintain diversity. Negative frequency-dependent selection is a powerful mechanism for maintaining variation in the population as well as species diversity in the community. There are a number of studies showing that this type of selection, where individuals of a rare type (i.e. a rare morph or a rare species) experience higher survival than those of more common type(s). However, it is still not clear how frequency-dependent selection operates. Search image formation has been invoked as a possible, proximate explanation. Although the conceptual link between search image and frequency-dependent predation is often assumed in ecological and evolutionary studies, a review of the literature reveals a paucity of evidence demonstrating the occurrence of both in a natural predator-prey system. Advances in the field of psychology strongly support the existence of search image, yet these findings are not fully recognized in the realm of ecology and evolutionary biology, in part, we feel because of confusion and inconsistencies in terminology. Here we try to simplify the language, clarify the advances in the study of frequency-dependent predation and search image, and suggest avenues for future research. We feel that the investigations of both proximate (perceptual mechanisms) and ultimate (pattern of predation) processes are necessary to fully understand the importance of individual behavioural processes for mediating evolutionary and ecological diversity.Co-ordinating editor: O. Leimar     

Evolution in heterogeneous environments: Effects of migration on habitat specialization

Summary Richard Levins introduced fitness sets as a tool for investigating evolution within heterogeneous environments. Evolutionary game theory permits a synthesis and generalization of this approach by considering the evolutionary response of organisms to any scale of habitat heterogeneity. As scales of heterogeneity increase from fine to coarse, the evolutionary stable strategy (ESS) switches from a single generalist species to several species that become increasingly specialized on distinct habitats. Depending upon the organisms' ecology, the switch from one to two species may occur at high migration rates (relatively fine-grained environment), or may only occur at very low migration rates (coarse-grained environment). At the ESS, the evolutionary context of a species is the entire landscape, while its ecological context may be a single habitat.Evolution towards the ESS can be represented with adaptive landscapes. In the absence of frequency-dependence, shifting from a single strategy ESS to a two strategy ESS poses the problem of evolving across valleys in the adaptive surface to occupy new peaks (hence, Sewell Wright's shifting balance theory). Frequency-dependent processes facilitate evolution across valleys. If a system with a two strategy ESS is constrained to possess a single strategy, the population may actually evolve a strategy that minimizes fitness. Because the population now rests at the bottom of a valley, evolution by natural selection can drive populations to occupy both peaks.