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1.
The terrestrial orchid Epipactis helleborine is a morphologically variable species with a wide distribution in Europe. It is pollinated by social wasps, and most populations
show the morphological characteristics of outcrossing species. However, local predominantly selfing subspecies and varieties
have been documented from drier habitats. To document geographic variation in floral morphology, ability to produce seeds
through autogamy, and reproductive success in E. helleborine, we sampled 13 populations from three geographic regions along a latitudinal gradient of c. 1000 km from northern to southern Sweden. In the southernmost region, populations in dry and mesic habitats were compared.
Supplemental hand-pollination was conducted to determine whether among-population variation in fruit set could be explained
by differences in the natural level of pollination, and whether any relationship between floral morphology and fruit production
could be explained by interactions with pollinators. Bagging experiments showed no evidence of autogamy in any of the study
populations. Number of flowers, pollinia removal and fruit set varied significantly among populations but did not differ among
regions. Pollinia removal was positively correlated with population size and both pollinia removal and fruit set were lower
in dry than in mesic habitats. At the level of the individual plant, the number of pollinia removed increased more rapidly
with flower number than did number of fruits produced. The hand-pollination experiment indicated that the positive relationship
between number of flowers and fruit production was due to a higher degree of pollen limitation in plants with few flowers
than in plants with many flowers. The experiment also showed that variation in the level of pollen limitation could only partly
explain variation in fruit set among populations.
Received November 6, 2001; accepted April 27, 2002 Published online: December 3, 2002 相似文献
2.
少花鹤顶兰(Phaiu delavayi)是多年生、多次结实的具有克隆能力的地生兰科植物,是中国特有种。目前少花鹤顶兰开花物候、花寿命、繁殖成功等生物学特征尚不清楚,而这些资料是开展少花鹤顶兰进化和保护生物学研究的基础。利用2005-2007年四川黄龙沟少花鹤顶兰的调查数据,对少花鹤顶兰繁殖成功特征进行了研究。结果表明黄龙沟少花鹤顶兰每个花序的平均花朵数为3(1-7)朵。叶和花的形态指标在年季间无显著变异。2005-2007年3年间的开花物候没有明显的差异,花期始于6月中旬,于7月底至8月初结束,持续约6-7周,80%-90%的花在7月初的开花高峰期开放,属花集中开放模式。花寿命与是否授粉密切相关,成功授粉的花寿命比没有授粉的花寿命短。少花鹤顶兰是自交亲和的,但其结实完全依赖于两种熊蜂的传粉,不存在自动自花授粉和无融合生殖现象。柱头可授性和花粉活力可维持15 d左右。繁殖成功率年季间的变化很大,并表现出逐年下降的趋势,花粉移走率为18%-51%,自然结实率为10%-36%。繁殖成功下降的趋势可能与黄龙沟喷洒农药有关。 相似文献
3.
Isozyme analysis was used to assess the origin of the DanishEpipactis renzii, a local endemic of open coastal dunes. It seems to have evolved recently in several local populations of the more or less allogamousE. helleborine subsp.neerlandica. The obligately autogamousE. renzii is restricted to the easternmost part of the Danish range ofE. helleborine subsp.neerlandica, indicating that transition to obligate autogamy has been a selective advantage in that area. This may be explained by water stress, caused by a higher evapotranspiration (cf. the mean temperature of July which increases towards the east) — obligate autogamy shortens the time span from anthesis to fruit set due to a rapid pollination process. We propose thatE. renzii should only be recognized as a variety ofE. helleborine subsp.neerlandica. 相似文献
4.
The role of geitonogamy in the evolution of inflorescence design is not well understood. The plant's dilemma hypothesis proposes that evolution of larger inflorescences is driven by selection for greater pollinator attraction, but constrained by higher rates of geitonogamy experienced by larger inflorescences. Here we investigate the role of geitonogamy on fruit set in natural populations of Asclepias speciosa. We compared fruit set from three pollination treatments: (1) inflorescences bagged before and after receiving 6 hand outcross pollinia (Bag), (2) inflorescences unbagged and receiving 6 hand outcross pollinia (Open), and (3) naturally pollinated inflorescences (Control). The Bag and Open treatments initiated significantly more fruits than the Control. Bag aborted significantly fewer fruits than Open or Control. Fruit set was significantly higher in Bag than Open, and Open had significantly higher fruit set than Control. From these results, we conclude that (1) high rates of geitonogamy significantly increase fruit abortion and reduce fruit set in natural populations of A. speciosa and (2) natural populations are compatible pollen limited. Both findings are consistent with the plant's dilemma hypothesis. 相似文献
5.
Background
Plant species have several mechanisms to avoid selfing such as dichogamy or a self-incompatibility response. Dichogamy in a single flower may reduce autogamy but, to avoid geitonogamy, plants must show flowering synchronization among all their flowers (i.e. synchronous dichogamy). It is hypothesized that one species would not simultaneously show synchronous dichogamy and self-incompatibility because they are redundant mechanisms to reduce selfing; however, this has not been accurately assessed.Methodology/Principal Findings
This expectation was tested over two years in two natural populations of the closely related Mediterranean spurges Euphorbia boetica and E. nicaeensis, which completely avoid autogamy by protogyny at the cyathia level. Both spurges showed a high population synchrony (Z<79), and their inflorescences flower synchronously. In E. nicaeensis, there was no overlap among the cyathia in anthesis of successive inflorescence levels and the overlap between sexual phases of cyathia of the same inflorescence level was uncommon (4–16%). In contrast, E. boetica showed a high overlap among consecutive inflorescence levels (74–93%) and between sexual phases of cyathia of the same inflorescence level (48–80%). The flowering pattern of both spurges was consistent in the two populations and over the two successive years. A hand-pollination experiment demonstrated that E. nicaeensis was strictly self-compatible whereas E. boetica was partially self-incompatible.Conclusions/Significance
We propose that the complex pattern of synchronized protogyny in E. nicaeensis prevents geitonogamous crosses and, consequently, avoids selfing and inbreeding depression. In E. boetica, a high probability of geitonogamous crosses may occur but, alternatively, this plant escapes selfing through a self-incompatibility response. We posit that synchronous dichogamy and physiological self-incompatibility do not co-occur in the same species because each process is sufficiently effective in avoiding self-fertilization. 相似文献6.
G. Pellegrino D. Caimi M. E. Noce A. Musacchio 《Plant Systematics and Evolution》2005,251(2-4):119-129
The rewardless orchid Dactylorhiza sambucina shows a stable flower colour polymorphism, with both yellow- and red-flowered morphs growing sympatrically. Pollination biology and breeding system were investigated to examine the effects of density of plants, colour polymorphism, inflorescence dimension, and flower position within inflorescence on male and female reproductive success in three natural populations of D. sambucina. There were significant differences among sites in the number of pollinia removed and in fruit set per inflorescence. Number of removed pollinia and capsule production in D. sambucina were independent from flower and inflorescence size or flower position. As a whole, the red morphs showed the highest number of capsules produced, while the yellow morphs had the greatest male success. The relative male and female reproductive success were independent from plant density but were significantly correlated with the yellow morph frequency at the population level. Overall, our findings show that the contribution to the total reproductive success deriving from the two colour morphs does not conform with the predictions of negative frequency-dependent selection. 相似文献
7.
Opportunities for selfing through geitonogamy are possible if more than one flower within the same clone, inflorescence, or floral unit is open at the same time. In a total of 200 inflorescences in two natural populations of Iris versicolor, flowers were observed and classified daily on the basis of anther dehiscence and stigma receptivity. Analysis of the flowering phenology demonstrated that (1) protandry limits opportunities for autogamy, (2) flowers mature sequentially within a floral unit (defined as a cluster of flowers borne on a single branch within an inflorescence), preventing the opportunity for geitonogamous fertilization between flowers of the same floral unit, and (3) 77% of all flowers had no opportunity to be pollinated by another flower within the same inflorescence. Both the number and the proportion of flowers with opportunities for geitonogamy increased with the number of flowers open in each population, and opportunities for geitonogamy also increased with the number of floral units within inflorescences. These morphological and phenological controls suggest that when selfing occurs in this species, it is most likely to occur between flowers on different inflorescences within the same clone. Since the organization of whole inflorescences in space is determined primarily by rhizome placement, clonal architecture may play an important role in mating system regulation in this species. 相似文献
8.
S. Gale 《Plant Systematics and Evolution》2007,268(1-4):59-73
The pollination biology of the critically endangered Nervilia nipponica was investigated at two sites on Shikoku Island, Japan, to shed light on the species' ecological strategy and to help prioritise
management decisions for its conservation. Though the solitary flowers failed to attract pollinators, high rates of fruit
set were observed in control plants at both sites. Comparable rates were obtained in bagged plants and following induced autogamous
and xenogamous pollinations, indicating that the species is capable of outbreeding, but self-compatible and not pollinator-limited
for fruit set under natural conditions; rates were significantly lower following emasculation. The number of seeds set per
fruit and their fertility did not differ significantly between open-, self- and cross-pollinated treatments. Epifluorescence
microscopy revealed that, in open-pollinated plants, pollen grains germinate within the anther on the first day of anthesis,
and that fertilisation occurs within the following 96 hours. The position of the stigma, which overlaps the clinandrium, friable
pollinia, and the absence of a rostellum ensure efficient, non-mechanical autopollination. Though this confers reproductive
assurance, inbreeding depression may be limiting fitness at subsequent stages of the recruitment cycle and low genetic diversity
is inferred. 相似文献
9.
Henrik Æ. Pedersen Santi Watthana Alexander Kocyan Kanok-orn Srimuang 《Plant Systematics and Evolution》2013,299(1):177-185
A population of Luisia curtisii (Orchidaceae: Aeridinae) in northern Thailand was studied with regard to pollination biology. Although a high level of self-compatibility was demonstrated experimentally, the very low natural fruit set (1.4–1.9 %) clearly indicated that the species depends on external agents for pollination. Our observations suggest that L. curtisii is pollinated by beetles, as Lema unicolor (Chrysomelidae) and Clinteria ducalis (Scarabaeidae) were the only flower visitors observed to carry pollinaria of this species. The hypothesis of specialised cantharophily is further supported by 2-methylbutyric acid and caproic acid being striking components of the floral scent. Judging from the lack of nectar and the behaviour of visiting beetles, the pollination system seems to rely on food or brood site deception. Retention of the anther on the pollinarium for some time after pollinarium removal probably reduces the frequency of insect-mediated autogamy and geitonogamy in Luisia curtisii—a possibility that was supported by comparative data on (1) the anther retention time and inflorescence visitation time of Lema unicolor and (2) stigma and anther length in the orchid. Existing reports of specialised beetle pollination in orchids are reviewed, and we conclude that there is accumulating evidence that specialised cantharophily is more common in the Orchidaceae than previously assumed. 相似文献
10.
Pterocarpus santalinus blooms massively in the dry season. Flowering is not continuous during the season and mass bloom recurs only on certain days with 2–5 days interval or sometimes there may be little flowering in between two days of massive bloom. A tree may have five such occasions of mass bloom. At the inflorescence level such intermittent flowering occurs also. The flowers open at the mid of night and are bright yellow in colour. They are typically papilionaceous flag blossoms and thus zygomorphic. They are homogamous and are visited by the rockbee Apis dorsata at moonlit nights or otherwise at dawn and up to 0730 h. The flowers permit several effective visits by the rockbee and as long as the pressure of the bee continues the stamens and stigma project from the keel and permit sternotribic pollination. Controlled pollinations show fruit formation after autogamy (25%), geitonogamy (60%) and xenogamy (85%). Staggered anther dehiscence minimises pollen discounting. Flower bud, flower and fruit abortions occur on a large scale. Natural fruiting is very low compared to the mass bloom. Compatibility to geitonogamy and autogamy may function as a reproductive assurance mechanism. The natural habitat of P. santalinus has a hot dry climate, and the nocturnal flowering and foraging of the rockbee at that time during moonlit nights appear to be an adaptation to avoid the adverse effects of daytime high temperatures. 相似文献
11.
Habitat alteration can deteriorate plant-pollinator interactions and thereby increase the risk of population extinction. As
part of a larger study on the effects of changes in land use on fen grassland vegetation, factors influencing the seed set
of a short-lived, endangered wetland plant,Pedicularis palustris, were studied. We conducted field pollination experiments in one large and one small population. To investigate the effect
of pollen source on seed set, individual flowers of caged plants were left unpollinated or were pollinated with pollen from
the same flower, the same population or another population. To study pollen limitation and flower display, whole plants were
subjected to pollinator exclosure, hand pollination or natural pollination. Self-compatibility was high, but differed between
populations (61% and 97% of seed set after cross-pollination within populations). Cross-pollination between populations did
not significantly alter seed number per capsule. Pollinator exclosure resulted in a very low seed set (<15% of natural seed
set), despite high self-compatibility. The most likely explanations for high self-compatibility in combination with low autofertility
are geitonogamy as reproductive assurance, selective neutrality of self-compatibility and phylogenetic constraints. Because
of low autofertility, the seed set inP. palustris depends on pollinators. In the study populations, natural pollination was clearly sufficient for maximum seed production
per plant, but seed set per capsule was significantly pollen-limited in the smaller population. Plants in this population
also had a higher maximum percentage of simultaneously open flowers than those of the large population (31% vs. 13%), while
flower longevity was generally extended without pollination. It is concluded thatP. palustris may influence pollinator behaviour and therefore the risk of pollen limitation by flower display.P. palustris showed a flexible reaction to differing pollination regimes without losses in overall seed set in the study populations. 相似文献
12.
? Despite the wide inflorescence diversity among angiosperms, the effects of inflorescence architecture (three-dimensional flower arrangement) on pollinator behaviour and mating success have not been sufficiently studied in natural plant populations. ? Here, we investigated how inflorescence architecture affected inter- and intra-plant pollinator movements and consequent mating success in a field population of Spiranthes sinensis var. amoena (S. sinensis). In this species, the flowers are helically arranged around the stem, and the degree of twisting varies greatly among individuals. The large variation in inflorescence architecture in S. sinensis results from variation in a single structural parameter, the helical angle (the angular distance between neighbour-flower directions). ? The numbers of visits per inflorescence and successive probes per visit by leaf-cutting bees decreased with helical angle, indicating that individual flowers of tightly twisted inflorescences received less visitations. As expected from pollinator behaviour, pollinia removal and fruit set of individual flowers decreased with helical angle. Meanwhile, geitonogamy decreased in tightly twisted inflorescences. ? Our novel findings demonstrate that natural variation in inflorescence architecture significantly affects pollinator behaviour and reproductive success, suggesting that inflorescence architecture can evolve under pollinator-mediated natural selection in plant populations. We also discuss how diverse inflorescence architectures may have been maintained in S. sinensis populations. 相似文献
13.
《Aquatic Botany》2005,82(2):113-120
Eriocaulon parkeri B. L. Robinson is a monoecious, pioneer species of tidal mudflats that displays characteristics that suggest outcrossing as a preferred breeding system. Analyses of breeding system dynamics, fruit set, and pollen and seed viabilities were undertaken in Connecticut and Wisconsin to test the hypothesis of entomophyly and outcrossing as a preferred breeding strategy. Potential pollinators included syrphid and long-legged flies. Seed viability was estimated at 94 ± 16% (n = 133); pollen viability at 88 ± 13%. Pollen production averaged ∼500 grains per flower. Pollen–ovule ratios within inflorescences averaged 196:1, suggesting facultative autogamy. Seed set in natural populations averaged 74%, not significantly different between early and late season plants or between greenhouse controls and hand pollinations. Emasculated plants produced small amounts of seed under controlled greenhouse conditions. Pollen tube growth through the styles of E. aquaticum, a related species, was much more prevalent than that of E. parkeri. Results suggest that E. parkeri relies heavily on geitonogamy for seed production. Some seed may be produced by agamospermy. 相似文献
14.
Leaf undulation is used as a diagnostic feature in the taxonomy of different taxa of the Epipactis (Orchidaceae) genus. It is considered a specifically important trait, apart from the column (gynostemium) structure, in the identification of E. muelleri. However, leaf undulation is a common developmental phenomenon in various plants, including orchids, thus the main goal of the research presented was to validate the usefulness of this feature in Epipactis taxonomy. In the course of this study, the leaf structure of six Epipactis species was analyzed, i.e., E. albensis, E. atrorubens, E. helleborine, E. muelleri, E. palustris and E. purpurata. The leaf margin outline and the cellular pattern of the leaf surface, as well as the presence of papillae, were examined in detail. The results obtained showed that in all taxa analyzed, representing different groups of the Epipactis genus, leaf undulation was present. The phenomenon was related to leaf blade development and the local differential growth of leaf sectors rather than to the taxonomic position of the species. Therefore, leaf undulation studied in Helleborines does not have a diagnostic value as a non-programmed intrinsic feature and should not be applied to taxa identification. The valid trait in Epipactis classification (including E. muelleri) is the column structure. 相似文献
15.
Allozymic variation in seven enzymes coded by eight loci was studied in seven populations of terrestrial Epipactis orchids, including four populations of E. helleborine, one population of E. palustris and two of E. microphylla, from Latium (Central Italy).Heterozygosity estimates reveal that E. helleborine (EH) is the most variable species (HET=0.233; P=0.59; A=1.8), followed by E. palustris (EP) (HET=0.085; P=0.29; A=1.3) while E. microphylla (EM) is monomorphic for all the loci examined.It is suggested that the two EM populations examined, with a total lack of genetic variability, could originate from the same genetically impoverished ancestral population. Also the low variability amount of EP can be ascribed to genetic drift, probably due to a founder event.Nei's identity coefficients were also calculated. These show a high similarity in EH (=0.987) and EM (=1.000) populations. Average identity value between EP and EM is 0.289, between EP and EH is 0.336 and between EM and EH is 0.784. These data reveal that E. palustris presents a remarkable genetic, besides geographical and ecological, differentiation. 相似文献
16.
Petagnaea gussonei (Apiaceae) is an endangered species endemic to the Nebrodi mountains (north-eastern Sicily). Although an increasing number of studies have been performed on this species, its reproductive biology remains poorly understood. The aim of this study was to investigate in detail the structure of the flower and the fruit of Petagnaea, and the possible implications for its breeding system and seed dispersal mechanism. Results from fieldwork, light microscopy and scanning electron microscopy suggest (1) the presence of protandrous hermaphrodite flowers; (2) geitonogamy, autogamy, and allogamy as breeding system mechanisms of P. gussonei, even if asexual reproduction is preferred by the plant; and (3) epizoochory and hydrochory as possible modalities of fruit dispersal. 相似文献
17.
Abstract: The pollinators, flower longevity, and reproductive success of Gongora quinquenervis were studied in Refúgio Ecológico Charles Darwin, a preserved fragment of Atlantic Forest in Pernambuco. G. quinquenervis is epiphytic, and its flowers have osmophores, glands that produce aromatic volatiles, that are collected by males of Euglossini (Hymenoptera, Apidae). Every flower of an inflorescence opened simultaneously, however, overlaps in floral phases between individuals were low. Pollinaria deposition on the stigma caused immediate wilting of the perianth, while pollinaria removal had no influence on flower longevity. The reproductive system experiments showed that the species is self-compatible. The characteristics of floral morphology and its highly specialized pollination mechanism are efficient in limiting autogamy and geitonogamy and favouring cross-pollination. Three species of Euglossa were found ( E. cordata, E. perpulchra and an undescribed species) visiting the flowers of G. quinquenervis. All these efficiently removed the pollinaria of the flowers, which adhered to the posterior margin of the scutellum. Even though there was a high pollinaria removal rate by pollinators, the reproductive success in the field was extraordinarily low. We suggest that low fruit set, despite high pollinator frequency, is a result of a combination of the particular phonological characteristics of G. quinquenervis, such as short flower longevity and low overlap of flowering phases between individuals, leading to the reduced population of this orchid in the degraded Atlantic Forest. Conservation measures are necessary to guarantee the survival of G. quinquenervis in the northern part of the Atlantic Forest of Brazil. 相似文献
18.
Diego Medan 《Plant Systematics and Evolution》1994,193(1-4):173-186
Various aspects of the reproductive biology of the perennial hermaphroditeFrangula alnus
Mill. were studied in two populations located in the province of Cádiz, southern Spain. Flowering extends from the second week of May to early July. The small, whitegreenish, entomophilous flowers are incompletely protandrous and last 8–10 days, but pollen transfer takes place only on days 1–3. A very weak, pleasant odour along with nectar and pollen attract over 45 insect species, of which 21 are probable pollinators. These are mainlyDiptera but also includeHymenoptera and the unusual (as flower visitors)Mecoptera. Reproduction is exclusively sexual and strictly xenogamous, with pollen transfer depending solely on insect vectors. Although flower morphology and individual flower phenology do not fully prevent self-pollination, and geitonogamy can easily take place, the level of autogamy was negligible. Therefore, some self-incompatibility mechanism is operative in this species. Only 2.8% of open-pollinated flowers set fruit. At the flower level, fruit initiation was apparently limited by availability of cross-pollen, which in turn seemed influenced by the structure of the population. The seed/ovule ratio in ripe fruits was ca. 50%. Predispersal (maternal) reproductive success (percent ovules becoming filled seeds) was 1.42%. For mature individuals this corresponded to ca. 430 to 1560 potential offspring per year. 相似文献
19.
Maternal reproductive success was examined in Styrax obassia (Styracaceae), a bumble-bee pollinated mass-flowering tree in a cool-temperate deciduous forest in northern Japan. The effects of flower number on the success of individual flowers at three levels (inflorescence, individual, and population) were considered. During 1995 and 1996, variations in size, light availability to branches, floral display size, and fruit set were monitored in 37 out of 211 individual S. obassia trees in a 4-ha forest plot. In addition, the locations of the 211 trees in this plot were mapped and the number of inflorescences in each tree was counted. A multiple regression analysis showed that flower number per inflorescence and inflorescence number per individual had negative effects on fruit set, and inflorescence number of aggregated clumps of flowering trees, tree size, and light resource had positive effects on fruit set although significant level were marginal. It is concluded that pollinator attraction may occur not at the individual tree level, but at the level of a clump of flowering trees. It is also suggested that geitonogamy increased with inflorescence number of tree and inflorescence size and that resource limitation was related to the light condition and variation of tree size. 相似文献
20.
Is Floral Longevity Influenced by Reproductive Costs and Pollination Success in Cohniella ascendens (Orchidaceae)? 总被引:1,自引:0,他引:1