马先蒿属植物花冠分化与繁殖适应的研究进展

结合已有的研究报道和作者近年来的工作,对马先蒿属（Pedicularis）植物的花冠多样化成因与繁殖适应特性进行了总结和探讨。通过对该属4种进化花冠型的花器官发生和分化的研究发现,花部各器官在发生和发育初期基本一致,后期上唇形态的分化是导致成熟花形态结构产生较大差异的重要阶段。孢粉学研究认为,花冠类型与花粉萌发孔类型之间具有显著相关性;萌发沟的演化可能与繁殖适应有一定的关系。分子系统学研究表明,多样化的花冠类型在不同的谱系内经过若干次的独立进化而表现出了高度的平行演化（parallelism）。传粉生物学研究证实,该属植物花冠多样化与其主要传粉者熊蜂属（Bombus）昆虫的传粉行为存在较为密切的关系。具有相同（似）花冠类型的马先蒿可能被同种或不同种的熊蜂以相同的方式访问,但在花粉落置位置上存在显著差异,这可能有助于同域分布重叠的物种间在生殖上的机械隔离,而花冠的分化在一定程度上促进了新的物种形成。     

马先蒿属花冠形态的多样性与传粉式样的关系

马先蒿属(Pediculais)是有花植物中花冠形态多样化最为集中的属。该属主要的传粉者是熊蜂属(Bormbus)昆虫;在北美,熊蜂和蜂鸟是马先蒿植物一些种类有效的传粉者;也发现壁蜂(Osmia)为其传粉。不同的传粉机制要求某一特定的取食式样储藏和释放花粉。本文讨论了花冠类型的进化趋势与传粉式样和花粉形态的关系。传粉者的选择压力是决定花冠多样化的重要因素之一;花冠类型与传粉者和传粉行为紧密相关。马先蒿植物和传粉者的相互依赖与其花冠类型、功能和物候互相适应,但花冠类型与花粉形态两者之间似乎没有明显的一一对应关系。通过北美、日本和喜马拉雅不同地理分布马先蒿种类的比较研究表明,具有相同花冠类型的种类有着相同的传粉方式,花冠形态与传粉式样存在紧密的协同进化关系。     

大王马先蒿的传粉综合征状及其生物地理学意义

对云南西北部中甸和昆明黑龙潭的大王马先蒿（ＰｅｄｉｃｕｌａｒｉｓｒｅｘＣｌａｒｋｅＣ．Ｂ）的不同居群进行了传粉生物学观察。大王马先蒿花为黄色,花冠短管、无喙、具二齿、无蜜腺,是一种原始的花冠类型。该种由红腹熊蜂（ＢｏｍｂｕｓｆｒｉｓｅａｎｕｓＳｋｏｒｉｋｏｖ）和明亮熊蜂（ＢｏｍｂｕｓｌｕｃｏｒｕｍＬ．）的工蜂在直立的位置上,通过震动花粉背触式传粉;同时也观察到红腹熊蜂的工蜂在倒悬的位置上,通过震动花粉腹触式传粉。熊蜂的工蜂在大王马先蒿上的这两种传粉综合征状的发现,可能是仅存在于马先蒿原始类型中的一种特殊现象。     

滇西北马先蒿属传粉生物学的初步研究

对云南西北部的中甸和德钦高山地区４种马先蒿属（ＰｅｄｉｃｕｌａｒｉｓＬ．）植物的传粉生物学进行了观察。晚夏开花的马先蒿与传粉熊蜂（ＢｏｍｂｕｓＬａｔｒ．）的出现在物候上有一定的相关性。其中短管、无喙、无蜜腺的肉根马先蒿（Ｐ．ｒｏｙｌｅｉＭａｘｉｍ．）和茨口马先蒿（Ｐ．ｔｓｅｋｏｕｅｎｓｉｓＢｏｎａｔｉ）是由熊蜂工蜂震动花粉、背触式传粉,这与其花冠类型的较原始性有关;长管、具喙、无蜜腺的斑唇马先蒿（Ｐ．ｌｏｎｇｉｆｌｏｒａｖａｒ．ｔｕｂｉｆｏｒｍｉｓ（Ｋｌｏｔｚ．）Ｔｓｏｏｎｇ）和云南长管马先蒿（Ｐ．ｓｉｐｈｏｎａｎｔｈａＤｏｎ．ｖａｒ．ｄｅｌａｖａｙｉ（Ｆｒａｎｃｈ．）Ｔｓｏｏｎｇ）通过熊蜂工蜂震动花粉、腹触式传粉。长管类马先蒿在植株相对矮小的情况下,通过较长的花冠管具喙向外伸出以实现授粉,这可能是与其传粉熊蜂协同进化的结果。     

中国西南地区当归属植物花粉形态及其系统进化分析

用光学显微镜和扫描电镜研究了分布于中国西南地区的当归属(Angelica L.)16种植物的花粉形态,其中有7种植物的花粉形态为首次报道。研究结果表明当归属植物花粉粒较大,分化明显,包含了伞形科花粉的原始、中等进化和进化的类型,其形态以菱形、椭圆形、近长方形、赤道收缩形为主,萌发孔为角孔或边孔,从花粉的这种多类型证明该地区的当归属植物既起源古老同时又在不断分化着。从孢粉学角度初步分析了当归属的属下系统,为该属植物种的划分及系统演化关系的探讨提供依据。     

鼠尾草属东亚分支的传粉模式

简述了世界鼠尾草属传粉模式多样性,从宏观层面对东亚鼠尾草属分布中心———中国的鼠尾草属传粉模式进行归纳与总结。研究补充了以往所缺乏的东亚鼠尾草属核心类群的雄蕊结构和传粉模式,并提出雄蕊结构的可能进化方向。根据花器官形态、内部结构、雄蕊特征、花粉接触传粉昆虫的部位,将中国分布的鼠尾草属植物划分为3种模式类型:TypeⅠ,短药隔杠杆传粉模式(short-lever type),主要发生在弧隔鼠尾草亚属(subg.Salvia Benth.),其雄蕊药隔短,属原始结构类型;TypeⅡ,长药隔杠杆传粉模式(long-lever type),主要发生在荔枝草亚属(subg.Sclarea Benth.),雄蕊药隔明显伸长,是典型的背部杠杆传粉结构;TypeⅢ,退化杠杆传粉模式(degraded-lever type),主要发生在鼠尾草亚属(subg.Allagospadonopsis Briq.),花冠筒变短变窄,雄蕊下臂明显退化,传粉者无需进入冠筒即可取食花蜜,花粉触碰昆虫头部,进而杠杆作用弱化。研究表明,鼠尾草属传粉模式的进化趋向于提高传粉者的专一性,同时保证传粉过程的有效性、精确性和忠实性,推测具有退化雄蕊下臂的TypeⅢ模式可能更为进化。比较美洲和地中海2个进化分支的雄蕊结构和进化趋势,东亚多样性中心可能是一个独立的进化分支。毫无疑问,雄蕊结构与花器官和传粉功能高度相关,是适应传粉者的进化表型,它的进化对东亚分支的物种辐射与多样性形成可能具有关键作用。     

高山物种栗色鼠尾草(Salvia castanea Diels)访花昆虫多样性与传粉行为变化

唇形科鼠尾草属是世界性分布、物种多样性丰富的大类群,具有独特的传粉模式和多样化的生态类型及繁殖策略,以往对鼠尾草属的花结构和雄蕊杠杆的生态功能、雄蕊杠杆机制对传粉者空间变异的进化响应和表型选择等方面已有较深入的研究,但至今对分布于不同区系代表性物种的传粉者组成、访花行为和繁育系统特征仍知之甚少。对分布于喜马拉雅东段至横断山高海拔地区栗色鼠尾草的传粉生态、交配系统和繁殖特性进行了研究,分析了2014年至2016年的年际间、2014年晴天和阴雨天的传粉者组成和传粉行为变化,探讨了这些变化对繁殖成功的影响。研究结果表明：3年共发现栗色鼠尾草有9种访花昆虫,传粉者组成及其行为变化较为明显。2014年有桔尾熊蜂Bombus friseanus、灰熊蜂B.grahami、圣熊蜂B.religiosus和中华蜜蜂Apis cerana 4种有效传昆虫,2015年仅有桔尾熊蜂是有效传粉者,而2016年的有效传粉昆虫改变为灰熊蜂和圣熊蜂。栗色鼠尾草的盗蜜现象较为普遍,主要盗蜜昆虫为灰熊蜂和桔尾熊蜂。桔尾熊蜂访花行为的年际变化较大,受天气条件的影响明显,同时其有效传粉行为可能显著影响了灰熊蜂的盗蜜行为。栗色鼠尾草的繁育系统为专性异交,主要依靠传粉者进行授粉,缺少传粉者时低程度的主动自花授粉可为其提供繁殖保障,且没有花粉限制和近交衰退。研究揭示了在高海拔地区,多变的天气条件可能显著影响着鼠尾草属植物的传粉者种类组成、访花行为和传粉效率,进而影响植物的繁殖成效和种群稳定。有效传粉频率是保证栗色鼠尾草较高自然结实率的主要因素,在一定程度上,盗蜜强度对繁殖成功具有中性的影响。本研究结果为阐明高山鼠尾草物种的繁殖如何受气候环境变化的影响,以及保证繁殖成功的可能策略奠定基础。     

草乌传粉过程中的广告效应与回报物质研究

虫媒传粉植物与其传粉者之间的相互作用被认为是被子植物花多样性的一个重要选择压力。这种相互作用体现在植物对传粉者的吸引以及传粉者行为对花粉的转运两个方面。本项研究通过去除不同的花部器官研究了草乌(Aconitum kusnezoffii)对其传粉者的吸引, 并结合传粉者的访问行为和草乌花的生物学特性探讨了传粉过程与交配系统的适应。红光熊蜂(Bombus ignites)是草乌的有效传粉者。去除花萼片显著降低了红光熊蜂的访问频率, 但去除特化成蜜腺叶的花瓣并没有显著改变红光熊蜂的访问频率, 这表明草乌吸引红光熊蜂的主要结构是由5枚萼片组成的花部外观形态, 而非花瓣。花蜜是草乌提供给红光熊蜂的回报物质, 糖浓度为39.23%, 组氨酸浓度为0.25 μg/μL。草乌花较大、单花花期长、雌雄异熟、花粉寿命长, 是一个自交亲和但需传粉者传粉完成繁殖过程的异交物种。草乌花序是无限花序, 当上部的花处于雄性阶段时, 下部的花正好处于雌性阶段。而红光熊蜂在草乌花序上的访问顺序通常自下而上, 带来异交花粉为下部的花进行异花授精, 同时又带走上部花的花粉, 这就很好地促进了草乌的异交。草乌雄蕊自外向内逐渐成熟, 是一种有效的限制传粉者单次访问浪费大量花粉的花粉装配策略, 能提高植物通过花粉散布获得的雄性适合度。     

苦苣苔科镜像花的多样性及演化

泛热带分布的苦苣苔科(Gesneriaceae)在我国南方具有极高的物种丰富度与特有率,花部特征变化丰富,是研究物种形成与适应演化的代表类群。镜像花(mirror-image flowers)是极为特化的传粉系统,在苦苣苔科中出现了较多的不同类型,可能与苦苣苔科物种多样性形成与维持有关。该研究总结与分析了苦苣苔科镜像花的类型多样性以及系统分布与适应演化等,讨论了镜像花对苦苣苔科物种形成与维持的积极意义。结果表明:镜像花仅分布在亚洲和非洲的苦苣苔亚科(Didymocarpoideae)的7个属,在历史上就至少发生了5次独立起源。长冠苣苔属(Rhabdothamnopsis)、南洋苣苔属(Henckelia)及长蒴苣苔属(Didymocarpus)镜像花的花柱与可育雄蕊分别向左、右两侧偏转,形成互补镜像花;蛛毛苣苔属(Paraboea)、喜鹊苣苔属(Ornithoboea)、非洲堇属(Saintpaulia)镜像花缺乏与花柱对应侧偏的可育雄蕊(非互补镜像花);而海角苣苔属(Streptocarpus)直立堇兰亚属(subg.Streptocarpella Engler)则同时出现了互补、非互补镜像花。不同于其他被子植物(离瓣花、缺乏花冠筒),苦苣苔科中的镜像花大多伴随着明显的花冠筒、内藏的雄蕊、合生的花药,以非互补镜像花为主;传粉者以小型的无垫蜂(Amegilla spp.)和熊蜂(Bombus spp.)为主。这些特殊的花部综合征与特化的传粉机制,提高了传粉精确性,可能促进了传粉隔离与物种适应辐射。今后的一个研究重点应通过分子系统发育方法,进一步揭示苦苣苔亚科互补与非互补镜像花的进化顺序及其在物种分化与长距离扩散过程中的可能作用。     

番荔枝科(Annonaceae)传粉室类型及其演化意义

花部结构与传粉者协同进化是有花植物成功演化的关键原因,在番荔枝科的植物中传粉室是一个非常明显的花部结构。由于该科花瓣的大小、轮数及每轮花瓣数、花瓣间的连合方式等高度多样,导致其传粉室形态也高度多样。番荔枝科107属中68属具详细的花部结构研究,该文根据开花期传粉室的闭合情况将这68属的传粉室分为开放型、半闭合型和闭合型3类,研究其系统演化意义。结果表明:(1) 24属具开放型传粉室,38属具半闭合型传粉室,26属具闭合型传粉室;约17属具2种或3种传粉室类型。(2)不同传粉室类型的植物与传粉者之间具有一定的对应关系,蜂类和蝇类主要为开放型传粉室或传粉室空间较大的半闭合型和闭合型传粉室植物传粉;蓟马主要为半闭合型与闭合型传粉室植物传粉。(3)古热带和新热带是番荔枝科植物的分布中心。分布于古热带的植物种数最多,但传粉室类型和传粉者较单一;分布于新热带的植物种数相对较少,但传粉室类型与传粉者都高度多样性。已有研究表明非洲是番荔枝科植物的起源地,开放型传粉室的植物主要分布于热带非洲,普遍存在于各族早期分化的属中,且均由小甲虫进行传粉,是该科较原始的传粉室类型;半闭合型分布于热带非洲、热带亚洲及热带美洲,闭合型传粉室主要分布于热带亚洲,这两类传粉室植物的传粉者也较多样性,是番荔枝科植物中较进化的传粉室类型。     

Pollination Ecology and Endemism of Pedicularis pulchella Pennell (Scrophulariaceae)

Abstract Pedicularis pulchella Pennell, endemic to sparsely vegetated areas of alpine tundra scree in southwestern Montana and northwestern Wyoming, was found to be roat-hemiparasitic and obligately dependent for its pollination upon bumblebees of three non-tundra species that forage primarily in an inverted position for pollen scraped from anthers concealed in the galea, This sternotribic pollination syndrome is considered related to the short (5–6mm) proboscides of pollinators on flowers with deep (12.4mm), nectariferous corolla tubes and favoring pollen as an insect attractant. Photographic and spectropholomelric analysis of the red-purple floral color included prominent blue corolla and ultraviolet calyx reflections corresponding to dominant colors of bumblebee visual spectra. Nectar analysis by thin-layer chromatography and refractomctry indicated, respectively, the presence of fructose and sucrose, and a sucrose-equivalent concentration of dissolved solids exceeding 50%; both coincide with the general pattern of the genus. Analysis of pollen from corbicular loads of P. pulchella pollinators indicated relatively low pollen-constancy of insects and substantial foraging association with Vaccinium in the montane-subalpine zone. By contrast, pollinators on P. cystopteridifolia and Phyllodoce glanduliflora in a diverse tundra plant community on rich alpine turf revealed broad pollinator spectra (7–8 species), high pollen-foraging constancy on Pedicularis, and high nectar-foraging frequency on Phyllodoce : The pollination ecology and endemism of Pedicularis pulchtella are interpreted in terms of resource sharing, spatial competition of plant species, and selective stress of the physical environment.     

Variation in stigma morphology – How does it contribute¶to pollination adaptation in Pedicularis (Orobanchaceae)?

 Stigma morphology in Pedicularis and its role in pollination have not been evaluated. This paper reports for the first time the relationship between stigma morphology and other aspects of floral design. 17 species of Pedicularis representing all the different types of corolla structure in the genus were studied in the field and in the laboratory. Results indicate that the stigmatic surface morphology of Pedicularis species is related to the type of corolla structure occurring in the species. Pollination studies in eight Pedicularis species demonstrated adaptation between stigmatic surface morphology and other aspects of floral biology. Species with larger, more corrugated stigmatic surfaces always possess a subsidiary construction (“tooth” or “beak”) on the galea. In addition, they have relatively longer flower tubes, higher stigmatic pollen loads, bigger pollen size and a shorter blooming period for individual flowers. Finally, the authors discuss the evolutionary significance of floral design in genus Pedicularis. Received April 8, 2002; accepted June 11, 2002 Published online: December 11, 2002     

Pollination Ecology of Pedicularis megalantha D. Don (Scrophulariaceae) in the Himachal Himalaya

Abstract In the summer of 1990, the pollination ecology of Pedicularis megalantha was studied in the montane-subalpine spruce-fir forest zone (2750-3050 m) on the north slope of Mt. Huttoo at Narkanda, Himachal Pradesh, in the Indian Himalaya. Its yellow, long-tubed, nectarless flower with a curled rostrum overarched by a broad, inverted lower corolla lip was pollinated exclusively by Bombus albopleuralis and B. tunicatus workers hanging inverted from the corolla and vibrating pollen from introrse anthers concealed within the galea and releasing pollen through a small ventral opening in the galea base. The stigma, protruding from the tip of the rostrum, contacted pollen deposited on the ventral side of the insect's thorax. Corbicular pollen loads from P. megalantha pollinators indicated equal numbers of monolectic and oligolectic foragers. P. megalantha appeared to suffer from competition for pollinators by Cynoglossum wallichii at one site but to be favored in a mixed plant community with nectariferous species offering a forage resource complementary to Pedicularis pollen. As in P. punctata , the long, nectarless corolla tube of P. megalantha appears to function in extending the rostrate vibration pollination mechanism beyond the plant's foliage, which would interfere with its function. It is not an adaptation for nectar-foraging lepidopteran pollinators. P. megalantha was also found to be a root hemiparasite.     

Floral ecology of Oreocharis pumila (Gesneriaceae): a novel case of sigmoid corolla

Attraction of pollinators and successful pollen transfer represent the primary targets of selection during flower evolution, leading to repeated evolutionary shifts between pollinators and consequently to the diversification of floral forms. However, most studies in floral evolution focus on the characteristics of flowers with straight corolla tube. Here, we report on an unusual form of sigmoid corolla combined with protandry and herkogamy in a Chinese species of Gesneriaceae, Oreocharis pumila (formerly Opithandra pumila). Contrary to species with sigmoid corollas studied previously, the base of the corolla tube of this species is inclined at an oblique angle downwards before the tube bends forward, and the stigma and anthers are included in the upper part of the corolla tube. The plants were found to be self‐compatible but incapable of autonomous selfing. Successful pollination was found to depend fully on the presence of insect pollinators (Nomia sp.) and pollen grains are the greatest reward for the visitors. Different from the other sigmoid flowers, the sigmoid corolla of O. pumila was not found to favor insect pollinators with long flexible proboscises. A mechanical fit between floral morphology and pollinator was found, in which only small insect visitors with specialized visiting behavior are legitimate pollinators. The protandry combined with herkogamy in the sigmoid corolla tube strongly ensures pollination efficiencies. Oreocharis pumila is the only species with sigmoid corolla in the genus Oreocharis. We hypothesize that such a corolla has arisen through selection due to inadequate pollination in early spring in the mountainous habitat that O. pumila occupies.     

Pollen morphology in relation to floral types and pollination syndromes in Pedicularis (Orobanchaceae)

Floral diversification in the genus Pedicularis (Orobanchaceae) is remarkable among flowering plants. In this genus, floral morphology and pollinator behavior are closely co-adaptive. In the current paper, pollen grains of 23 representative species of Pedicularis mainly from North America, with two species from Japan and two species from China, whose pollination ecology was previously studied, were examined using light microscopy and scanning electron microscopy. Two pollen aperture types and three kinds of exine ornamentation were recognized among these species. In addition, pollen data from previous and the current studies of Pedicularis were integrated and analyzed, together with some pollination characters. There was a significant association between pollen aperture types and corolla types, as well as between pollination syndromes and corolla types. However, there was no association of exine ornamentations with corolla types. The relationships and evolution of this genus were discussed with regards to pollen morphology, corolla types and pollination syndromes.     

The Pollination Syndrome of Pedicularis rex (Scrophulariaceae) and Its Biogeographic Significance

The pollination biology of different populations of Pedicularis rex Clarke C B. was studied in Zhongdian of Northwest Yunnan and in Kunming of central Yunnan, respectively. Seed production depends exclusively upon pollination by bmnblebees ( Bombus Latr. ). The flowers are yellow, with short-tubed, erostrate and nectarless corolla. Two species of the bumblebee workers, Bombus friseanus Skorikov and B. lucorum L. foraged in an upright (nototribic) position for pollen. Meanwhile, Bombus friseanus workers also foraged in an inverted (stemotribic) position on P. rex, vibrating pollen from the anthers within the galea. This pollination syndrome was previously reported in the North American species, e.g.P, labradorica which has the same corolla-type with P. rex. A comparison of the corolla types and pollination syndrome on the species of Pediadaris in East Asia and North America indicates that such a pollination syndrome may be only found in the primitive corolla type of Pedicularis. In spite of the separation in the geological history, P. rex and P.labradorica share the same corolla type and pollination syndrome. Further study is needed to elucidate the biogeography of the Pedicularis.     

The role of pollinators in floral diversification in a clade of generalist flowers

Pollinator‐mediated evolutionary divergence has seldom been explored in generalist clades because it is assumed that pollinators in those clades exert weak and conflicting selection. We investigate whether pollinators shape floral diversification in a pollination generalist plant genus, Erysimum. Species from this genus have flowers that appeal to broad assemblages of pollinators. Nevertheless, we recently reported that it is possible to sort plant species into pollination niches varying in the quantitative composition of pollinators. We test here whether floral characters of Erysimum have evolved as a consequence of shifts among pollination niches. For this, we quantified the evolutionary lability of the floral traits and their phylogenetic association with pollination niches. As with pollination niches, Erysimum floral traits show weak phylogenetic signal. Moreover, floral shape and color are phylogenetically associated with pollination niche. In particular, plants belonging to a pollination niche dominated by long‐tongued large bees have lilac corollas with parallel petals. Further analyses suggest, however, that changes in color preceded changes in pollination niche. Pollinators seem to have driven the evolution of corolla shape, whereas the association between pollination niche and corolla color has probably arisen by lilac‐flowered Erysimum moving toward certain pollination niches for other adaptive reasons.