Relative importance of diurnal and nocturnal pollinators for reproduction in the early spring flowering shrub Stachyurus praecox (Stachyuraceae)

Generalized pollination systems may be favored in early spring flowering plants, as during this period pollinator activity is unpredictable. Many previous studies have concentrated on the importance of diurnal visitors in pollination, and consequently, information on the contribution of nocturnal visitors to pollination in early spring is limited. This study was conducted to evaluate the relative importance of diurnal and nocturnal pollinators in the early spring flowering dioecious shrub Stachyurus praecox (Stachyuraceae), in two temperate forests in central Japan. Visitors to the female and male flowers were observed during day and night, and their relative contributions to seed set were compared. The pollinator observations revealed that the diurnal and nocturnal insects visited both male and female flowers, and that the main flower visitors were diurnal small bees and flies as well as nocturnal settling moths. The diurnal and nocturnal flower visitors also acted as pollinators, as the pollen grains of S. praecox were attached to the insects collected from the female flowers. Pollination experiments demonstrated that the contributions of diurnal pollinators to the seed set were higher than those of the nocturnal pollinators. The results of this study indicate that S. praecox has a generalized pollination system, comprising both diurnal insects and nocturnal settling moths. Although the roles of diurnal insects are more important in the pollination of S. praecox, nocturnal settling moths may have a complementary role in early spring.     

ON THE DARWINIAN HYPOTHESIS OF THE ADAPTIVE SIGNIFICANCE OF TRISTYLY

Darwin proposed that the function of the stamen-style polymorphism in heterostylous plants is to increase the probability of legitimate (compatible) pollinations among the floral morphs. Conspicuous pollen trimorphism in tristylous Pontederia cordata enables a test of the hypothesis. Comparison of the composition of pollen loads in naturally pollinated stigmas of intact and emasculated flowers were made at a population in Paugh Lake, Ontario, which was visited primarily by bumblebees. The magnitude of legitimate pollination was analyzed by ANOVA. In intact flowers, significant legitimate pollination was detected in the long-styled morph only. Following emasculation legitimate pollination was evident in the long- and short-styled morphs, with the mid-styled morph just short of displaying significant legitimate pollination. Similar results were obtained by chi-square analysis. It has been suggested that heterostyly may reduce mutual interference between maternal and paternal reproductive function. Two aspects of pollen-stigma interference were investigated in P. cordata. The potential importance of stigmatic or stylar clogging by incompatible pollen was examined by controlled field pollinations and measurements of seed set. The results indicate that prior application of large amounts of incompatible pollen has no significant effect on the seed set of open-pollinated inflorescences. Comparison of legitimate pollen capture in intact and emasculated flowers provided no evidence that the presence of stamens within flowers of the floral morphs interferes with the receipt of legitimate pollen. Pollen-stigma interference remains to be demonstrated in heterostylous plants.     

The functional implications of active and passive pollination in dioecious figs

Fig-pollinating wasps lay their eggs in fig flowers. Some species of fig-pollinating wasps are active pollinators, while others passively transfer pollen. In dioecious fig species, the ovules of male figs produce wasps but no seeds. By observations and experiments on four dioecious Ficus species we show that (i) passive pollinators distribute pollen haphazardly within figs, but fertilization of female flowers in male figs is inhibited. Consequently, wasp larvae will develop in nonfertilized ovules: they cannot benefit from pollination; (ii) active pollinators efficiently fertilize flowers in which they oviposit. Lack of pollination increases larval mortality. Hence, fig pollinators are not obligate seed eaters but ovule gallers. Active pollination has probably evolved as a way to improve progeny nourishment.
Comparison of pollination and oviposition process in male and female figs, suggests that stigma shape and function have coevolved with pollination behaviour, in relation to constraints linked with dioecy.     

独叶草的不育雄蕊、花被片和可育雄蕊对传粉昆虫和传粉的影响

为确定独叶草（Kingdonia uniflora）不育雄蕊、花被片和可育雄蕊对传粉昆虫和传粉的影响,分别进行去除不育雄蕊（A组）,去除花被片（B组）,去除可育雄蕊（C组）和对照组（D组）处理。结果表明：昆虫访花频率分别为A组0．4次／h、B组0次／h、C组0．9次／h、D组2．2次／h;被授粉花朵百分比分别为A组29．09％、B组40．38％、C组70.91％、D组91．67％;被授粉心皮百分比分别为A组17．77％、B组20．94％、C组为40．58％、D组为75．27％。与对照组相比,处理后被授粉花朵百分比、被授粉心皮百分比下降幅度均为A组〉B组〉C组。结合昆虫访花频率与不育雄蕊蜜汁的分泌量呈正比,可确定不育雄蕊产生的蜜汁是吸引昆虫访花的最主要因素。花被片为昆虫取食提供停歇的平台,可育雄蕊与花被片产生的色差及可育雄蕊提供的花粉,是吸引昆虫的辅助因素。     

Pollination success in a population of dioecious rain forest trees

Pollination success in female trees was determined for a population of Neolitsea dealbata (R. Br.) Merr., a locally abundant dioecious tree pollinated by small, unspecialized insects in northern Queensland rain forest, Australia. The population consisted of a clustered group of trees with a mean male-to-female distance of 4.5 m and more isolated individuals, including females more than 90 m away from the nearest pollen source. A map of all reproductive trees was produced to determine accurate male-to-female distances. The size of the pollen source available to females was defined as a function of the distance to the nearest ten male trees and their sizes (male neighbourhood index). The rate of pollen movement to females was measured by counting pollen tubes (and the number of tubes per style) in female trees 6 days after the commencement of population flowering. The pollination rate decreased steeply to less than half when the nearest male was only 6.5 m away. Although pollen reached a female 330 m away from the nearest pollen source, only 10% of receptive flowers had been pollinated. The short flowering period (2–3 weeks) combined with the the slow rate of pollen movement means that a large proportion of flowers in isolated trees are unpollinated, confirming an earlier finding that isolated females set fewer fruits than gregarious females. The reliability of pollen transfer to females was determined by quantifying insects and their pollen loads trapped at female trees with a range of male neighbourhood indices. Quantities of insects and pollen were significantly correlated with the size of the male neighbourhood index, indicating a strong density-dependent response by vectors to flowering. Pollen was also collected from insect visitors to non-flowering trees. Females with large male neighbourhood indices received more pollen than non-flowering trees with equivalent male neighbourhood indices. However, when the male neighbourhood indices were small for both female and non-flowering trees, the changces of pollinators encountering female and non-flowering trees were similar, suggesting random movements of pollinators in sparse-flowering sub-populations. The dioecious breeding system, brief, synchronous flowering period, clustered population structure and random, opportunistic foraging behaviour of vectors interacted in a way that reduced reproduction in relatively isolated trees. These results demonstrate a mechanism for differential breeding success between trees in natural populations and emphasize the possible impact of logging regimes on pollen flow between trees. Large interconspecific distances in species-rich environments may have been a factor in the selection for synchronous flowering between trees in outcrossing tree species with generalist insect pollinators.     

Floral biology and pollination mechanisms of four Mexico-endemic Fuchsia species with contrasting reproductive systems

Aims The evolution of the outstanding variation of reproductive systems in angiosperms has been considered an important driver of lineage diversification. Closely related hermaphroditic and dioecious species with biotic pollination provide the opportunity to study and compare traits related to pollinator attraction and their consequences on reproductive components. A higher predictability of pollination syndromes is expected in dioecious species, which are dependent on pollinators, than in self-compatible hermaphroditic taxa. Dioecious species may suffer pollen limitation depending on the quality of floral rewards and the kind and abundance of pollinators, whereas no pollen limitation is expected in hermaphroditic species with autonomous self-pollination. Additionally, in the absence of pollen limitation, more or better seeds are expected in dioecious species, according to the sexual specialization hypothesis.Methods In natural populations of the hermaphroditic Fuchsia fulgens and Fuchsia arborescens and dioecious Fuchsia parviflora and Fuchsia obconica, all endemic to Mexico, we first described flower phenology, flower production and longevity and nectar volume and concentration. Then, we evaluated the correspondence between floral visitors and pollination syndromes. In hermaphrodite plants, we determined the level of herkogamy and the potential for autonomous self-pollination. Finally, we evaluated the effect of pollen limitation on fruit set and seed number and assessed seed germination for all species.Important findings In contrast to our prediction, dioecious species did not show a higher correspondence between pollination syndromes and floral visitors than did hermaphrodites; however, male flowers exhibited a higher correspondence than female flowers. No pollen limitation was detected in dioecious species, for which visitation rate did not differ between male and female flowers. The hermaphroditic F. fulgens showed pollen limitation for seed number, despite the presence of autonomous selfing. Fruit set from autonomous pollination was higher in F. arborescens, which showed a lower level of herkogamy compared with F. fulgens. Finally, dioecious species produced fewer but heavier seeds compared with hermaphrodite species. Although Fuchsia is classified as an outcrossing genus, both hermaphroditic species showed autonomous self-pollination. The heavier but lower number of seeds per fruit in dioecious species may be related to the more efficient resource allocation expected from sexual specialization. This could play an important role in the evolution of dioecy; however, a comparative phylogenetic approach is required to confirm this hypothesis.     

Natural levels of pollination intensity and effects of pollen loads on offspring quality in females of Thalictrum pubescens (Ranunculaceae)

Females of Thalictrum pubescens produce stamens containing sterile pollen. Earlier studies have shown the presence of stamens does not increase seed set through increased visitation by insects. Insects may, however, increase pollen deposition on stigmas and increase pollen competition. This paper examines: 1) pollen deposition levels in natural populations and 2) whether larger pollen loads lead to higher quality offspring. The majority of stigmas in two populations received less than 15 grains, but a small proportion had large loads. The latter may represent the occasional insect visit. These visits may provide the opportunity for pollen tube competition. In the greenhouse, flowers receiving heavy-pollen loads had higher seed set than flowers receiving light-pollen loads. Seeds from the two treatments were the same mass, had similar germination times, and seedlings had the same mass. In conclusion, it does not appear that pollen tube competition can account for the maintenance of stamens in females of T. pubescens.     

Female reproductive success in gynodioecious Thymus vulgaris: pollen versus nutrient limitation and pollinator foraging behaviour

Gynodioecy is a dimorphic breeding system in which female individuals coexist with hermaphroditic individuals in the same population. Females only contribute to the next generation via ovules, and many studies have shown that they are usually less attractive than hermaphrodites to pollinators. Several mechanisms have been proposed to explain how females manage to persist in populations despite these disadvantages. The ‘resource reallocation hypothesis’ (RRH) states that females channel resources not invested in pollen production and floral advertisement towards the production of more and/or larger seeds. We investigated pollination patterns and tested the RRH in a population of Thymus vulgaris. We measured flower display, flower size, nectar production, visitation rates, pollinator constancy and flower lifespan in the two morphs. In addition, we measured experimentally the effects of pollen and resource addition on female reproductive success (fruit set, seed set, seed weight) of the two morphs. Despite lower investment in floral advertisement, female individuals were no less attractive to pollinators than hermaphrodites on a per flower basis. Other measures of pollinator behaviour (number of flowers visited per plant, morph preference and morph constancy) also showed that pollinators did not discriminate against female flowers. In addition, stigma receptivity was longer in female flowers. Accordingly, and contrary to most studies on gynodioecious species, reproductive success of females was not pollen limited. Instead, seed production was pollen limited in hermaphrodites, suggesting low levels of cross‐pollination in hermaphrodites. Seed production was resource limited in hermaphrodites, but not in females, thus providing support for the RRH. © 2014 The Linnean Society of London, Botanical Journal of the Linnean Society, 2014, 175 , 395–408.     

光果甘草二体雄蕊的发育及其适应意义

甘草属(Glycyrrhiza)植物具“9 + 1”二体雄蕊, 其中9枚合生雄蕊的上部花丝分离, 分离的花丝在发育过程中存在由早期长、短交错的二组排列方式转变为后期以雄蕊管最长的1枚雄蕊为中心向两边渐次缩短的倒“V”形排列。为了解这种雄蕊发育动态、分化现象及发育成熟后的适应意义, 该文以光果甘草(G. glabra)为实验材料, 比较了雄蕊发育过程中的形态变化、成熟花粉的理化性质及在传粉中的作用。结果显示: 雄蕊发育早期长、短两组雄蕊在花药大小与形状上存在分化, 但后期伴随着花丝的快速生长与花粉的成熟、散出, 花药大小与形状趋于一致; 花粉组织化学成分及授粉成功率无差异, 但成熟花粉的数量和花粉活力存在差异; 去雄处理虽然使访花者在一天内的两个访花高峰期的访花频次降低, 但结实率高于自然对照, 说明以异交为主的花去除雄蕊后, 降低了雌、雄蕊间的功能干扰, 提高了传粉昆虫的授粉率; 发育早期长、短交错排列的二组雄蕊到成熟期时发生的倒“V”形排列的转变, 使不同数量与活性的花粉分布在花内不同空间, 最大化接触访花者, 实现了资源节约, 提高了雄蕊的雄性适合度, 即在有限的空间内用最节约的雄性资源投入、使传粉空间与传粉几率最大化的方式, 来提高雄性功能。     

Staminal hairs enhance fecundity in the pollen‐rewarding self‐incompatible lily Bulbine abyssinica

Flowering plants typically use floral rewards to attract animal pollinators. Unlike nectar, pollen rewards are usually visible and may thus function as a signal that influences landing decisions by pollen‐seeking insects. Here we artificially manipulate the presence of both pollen and staminal hairs (a putative false signal of pollen reward availability) in the hermaphroditic lily Bulbine abyssinica (Xanthorrhoeaceae) to investigate their effects on bee visitation and fecundity, and also test for trade‐offs between pollen production and seed production. Honeybees, the primary floral visitors, are probably not able to distinguish between colours of petals, staminal hairs and pollen of B. abyssinica, according to analysis of reflectance spectra in a bee vision model. Flowers with both pollen and hairs removed had the lowest levels of bee visitation, seed set and seed abortions. Flowers containing hairs had an ～50% increase in visitation rate and seed set compared with emasculated flowers, while intact controls had the highest seed abortion rate. Ovule discounting in intact flowers is probably due to ovarian self‐incompatibility (or strong early inbreeding depression) as ovules penetrated by tubes from self‐pollen uniformly failed to develop into seeds. These results show that staminal hairs can enhance plant fecundity by increasing attraction of pollen‐seeking insects to flowers without increasing the risk of ovule discounting through pollinator‐mediated self‐pollination. © 2015 The Linnean Society of London, Botanical Journal of the Linnean Society, 2015, 177 , 481–490.     

Insect and wind pollination of an alpine biennial Aconitum gymnandrum (Ranunculaceae)

Wind pollination can provide reproductive insurance for animal‐pollinated dioecious plants in the absence of available pollinators, but combinations of insect and wind pollination (ambophily) have rarely been studied in hermaphrodite herbs. We examined the stable occurrence of insect pollination and wind pollination over 4 years in a population of a biennial Aconitum species (A. gymnandrum) with actinomorphic and degenerate sepals. The total frequency of visits of two bumblebee species showed no distinct fluctuations in the studied population among the 4 years. However, seed production of netted flowers after emasculation indicated wind pollination had occurred. The seed number of bagged flowers with one visit by bumblebees was significantly less than that of netted flowers after one visit, or in control flowers. Both seed number and fruit set of netted flowers were significantly lower than in control flowers. These results suggest that wind pollination provides supplementary pollen to unvisited and/or once‐visited flowers, but accounts for only a small amount of seed production compared to bumblebee pollination in natural conditions. Such a combination of insect and wind pollination might play an important role in maintaining sexual reproduction of this biennial herb, allowing it to persist in arid habitats on the Qinghai‐Tibetan Plateau, especially during Quaternary glacial periods when pollinator populations oscillated extensively.     

Entomophily of the cloudberry (Rubus chamaemorus)

Cloudberry (Rubus chamaemorus L.), a dioecious perennial plant of boreal circumpolar distribution, is greatly prized for its berries. We crossed two treatments, pollinator exclusion and supplementary hand-pollination, to determine i) the relative importance of insects as pollinators, ii) if pollinator activity was a limiting factor for the sexual reproduction of the plant, and iii) the relative contribution of diurnal vs. nocturnal visitors to pollination. The activity of natural pollinators resulted in 97.5 and 88.5% fruit set, along with 76.7 and 62.5% seed set in 1998 and 1999, respectively. When insects were excluded, fruit-set dropped significantly to 18.4 (1998) and 12.8% (1999) and seed-set to 5.4 (1998) and 5.0% (1999) showing the importance of mid- and large-sized insects as pollinators. Natural levels of insect activity were sufficient to ensure complete pollination in both years as supplementary hand-pollination did not significantly increase either parameter in plots where pollinators had free access. Nocturnal insects may serve as pollinators (fruit-set = 41%), although they were less effective than diurnal pollinators (fruit-set = 93%).     

Male interference with pollination efficiency in a hermaphroditic orchid

Hermaphroditism can lead to both intra‐ and intersexual conflict between male and female gender functions. However, the effect that such gender conflicts have on pollination efficiency has seldom been investigated. By artificially reducing the number of available male gametes on an individual, we quantified whether male interference with pollination efficiency occurs in the self‐compatible, moth‐pollinated orchid Satyrium longicauda. We partially emasculated S. longicauda inflorescences and compared pollination success and fecundity in these plants to intact controls. Pollen in both groups of plants was colour‐labelled so that its dispersal by pollinators could be tracked directly in the field. Intact flowers on partially emasculated inflorescences exported more pollen and received more cross‐pollen and less self‐pollen than those on intact inflorescences. Proportion of fruit set per plant was similar between the two treatments; however, fruits on partially emasculated plants had proportionally more viable seeds than those on intact controls. These results provide empirical evidence that male interference with pollination efficiency can occur in a hermaphroditic plant and that such interference can compromise fecundity. The most likely mechanism for such male interference is competition for placement on the proboscis of hawkmoth pollinators. Consequently, male competition for siring success may influence the evolution of sexual systems in hermaphroditic pollinator‐dependent plants.     

Pollen transfer in fragmented plant populations: insight from the pollen loads of pollinators and stigmas in a mass‐flowering species

Pollinator and/or mate scarcity affects pollen transfer, with important ecological and evolutionary consequences for plant reproduction. However, the way in which the pollen loads transported by pollinators and deposited on stigmas are affected by pollination context has been little studied. We investigated the impacts of plant mate and visiting insect availabilities on pollen transport and receipt in a mass‐flowering and facultative autogamous shrub (Rhododendron ferrugineum). First, we recorded insect visits to R. ferrugineum in plant patches of diverse densities and sizes. Second, we analyzed the pollen loads transported by R. ferrugineum pollinators and deposited on stigmas of emasculated and intact flowers, in the same patches. Overall, pollinators (bumblebees) transported much larger pollen loads than the ones found on stigmas, and the pollen deposited on stigmas included a high proportion of conspecific pollen. However, comparing pollen loads of emasculated and intact flowers indicated that pollinators contributed only half the conspecific pollen present on the stigma. At low plant density, we found the highest visitation rate and the lowest proportion of conspecific pollen transported and deposited by pollinators. By contrast, at higher plant density and lower visitation rate, pollinators deposited larger proportion of conspecific pollen, although still far from sufficient to ensure that all the ovules were fertilized. Finally, self‐pollen completely buffered the detrimental effects on pollination of patch fragmentation and pollinator failure. Our results indicate that pollen loads from pollinators and emasculated flowers should be quantified for an accurate understanding of the relative impacts of pollinator and mate limitation on pollen transfer in facultative autogamous species.     

Floral Variation in Tepals,Sterile and Fertile Stamens of Kingdonia uniflora (Ranunculaceae) with Reference to Pollinators and Pollination

To understand the influence of different floral organs of Kingdonia uniflora to the pollinators and pollination, we divided the flowers into four groups, A, with the sterile stamens removed, B, with the tepals removed, C, with the fertile　stamens removed and D, without the remove of any organ. The results showed that the insects visiting frequency were 0.4 time h in group A, 0 time h in group B, 0. 9 time h in group C and 2. 2 time h in group D. The percentage of pollinated flowers was 29.09% in group A, 40. 38% in group B, 70.91% in group C and 91. 67% in group D. The percentage of pollinated carpels was 17.77% in group A, 20.94% in group B, 40.58% in group C and 75.27% in group D respectively. The relationships between the insect visiting frequency and the nectarial secretion of the sterile stamens were observed in the field. To compare with group D, the decrease of the rate of pollinated flower and the carpel was group A > group B>group C. To combine the observation of the relationships between the nectarial secretion of the sterile stamens and the insect visiting frequency, we considered that the sterile stamens with nectar as the reward of the visiting insects play the most important rule for the pollinators and pollination. However, the tepals that could afford the platform of staining and moving of the insects on the flowers are also important for the pollinators. The fertile stamens that could form the chromatic to attract some of the pollinators and supply the pollen grains as the food of some pollinators play less important rule .     

Differentiation during fig ontogeny suggests opposing selection by mutualists

Dioecy allows separation of female and male functions and therefore facilitates separate co‐evolutionary pathways with pollinators and seed dispersers. In monoecious figs, pollinators' offspring develop inside the syconium by consuming some of the seeds. Flower‐stage syconia must attract pollinators, then ripen and attract seed dispersers. In dioecious figs, male (“gall”) figs produce pollen but not viable seeds, as the pollinators' larvae eat all seeds, while female (“seed”) figs produce mostly viable seeds, as pollinators cannot oviposit in the ovules. Hence, gall and seed figs are under selection to attract pollinators, but only seed figs must attract seed dispersers. We test the hypothesis that seed and gall syconia at the flower stage will be similar, while at the fruiting stage they will differ. Likewise, monoecious syconia will be more similar to seed than gall figs because they must attract both pollinators and seed dispersers. We quantified syconium characteristics for 24 dioecious and 11 monoecious fig species and recorded frugivore visits. We show that seed and gall syconia are similar at the flower stage but differ at the fruit stage; monoecious syconia are more similar to seed syconia than they are to gall syconia; seed and gall syconia differentiate through their ontogeny from flower to fruit stages; and frugivores visit more monoecious and seed syconia than gall syconia. We suggest that similarity at the flower stage likely enhances pollination in both seed and gall figs and that differentiation after pollination likely enhances attractiveness to seed dispersers of syconia containing viable seeds. These ontogenetic differences between monoecious and dioecious species provide evidence of divergent responses to selection by pollinators and seed dispersers.     

The pollination ecology of buzz-pollinated Rhexia virginica (Melastomataceae)

We examined the function of floral traits associated with buzz pollination through studies of Rhexia virginica (Melastomataceae) in the Muskoka region of Ontario, Canada. Controlled pollinations demonstrated that the species is self-compatible, but dependent on insects for pollen transfer. Bumble bees made 82 and 90% of observed insect visits to R. virginica in 1996 and 1997, respectively, and effectively buzzed flowers. Buzz pollination did not appear to be highly "specialized" since various species of bumble bee were capable of pollination, and pollen transfer efficiency appeared to be relatively low. Experimental manipulations provided little support for the hypothesis that the yellow color of melastome anthers mimics abundant pollen, thereby deceiving pollinators to visit regardless of whether most pollen has been removed. Fruit set averaged 52.6% among populations, owing largely to infrequent pollinator visits and pollen limitation. Flowers of R. virginica were infertile after a single day of anthesis, but petals were subsequently maintained for 1-2 d and stamens underwent a color change from bright yellow to red. Second-day flowers may function to increase floral display size and hence fertility, without a concomitant increase in pollen discounting. Studies of bumble bee foraging behavior and correlates of seed set provided indirect support for this hypothesis.     

AN EXPERIMENTAL STUDY OF THE FLORAL ECOLOGY OF DODECATHEON MEADIA

An established colony of Dodecatheon meadia on glacial drift in southeastern Wisconsin was observed for its insect pollination interrelationships. Twelve randomly distributed plants from which insects were excluded failed to produce seed, while plants exposed to insect visits set abundant seed. Female solitary bees of 2 species, viz., Augochloropsis metallica fulgida (Smith) and Lasioglossum forbesii (Robertson), and queens and workers of 7 species of Bombus were observed collecting pollen from the pendant anther cone by rapid wing vibration, while hanging inverted from the cone tip. This behavior—cinematographically recorded—was found fundamentally identical to that of females of the same species of solitary bees and of queens and workers of 5 species of Bombus on Solanum dulcamara, and of females of Lasioglossum forbesii (Robertson) and workers of 2 species of Bombus on Lycopersicum esculentum Mill. No other insects were found to pollinate these morphologically similar flowers in this manner, and crepuscular pollinators were not observed. Experimental modifications of form, function, and position of Dodecatheon flowers were offered to the pollinators, and behavioral changes of the insects were noted. Constituents of insect pollen loads were examined, and relationships of the pollinators to the flora of the region were noted. The detailed ecological study of insect pollen vector behavior as an aid in discovering biosystematic relationships of plant populations is suggested.     

Pollination in a cryptically dioecious plant Decaspermum parviflorum (Lam.) A. J. Scott (Myrtaceae) by pollen-collecting bees in Sulawesi, Indonesia

Decaspermum parviflorum is a common shrub or treelet in clearings in eastern Sulawesi, Indonesia. It is widely distributed in SE Asia. It produces numerous white flowers and small blue-black fruits. Individual shrubs were of two types in 1:1 ratio, one bearing staminate flowers, the other bearing flowers with both stamens and carpels. The 'hermaphrodite' flowers were shown to have sterile pollen so the species is functionally dioecious. The flowers and floral sprays of the two sexes differed in several measurements: the male flowers had more anthers and were larger and more numerous, making the corporate visual image of male sprays more than twice as large as that for sprays of female flowers. Flowers, individuals of which last only one day, opened only every second day, when all bushes flower synchronously. When the anthers burst in the morning, pollen and sterile pollen was collected vigorously by a variety of bees, mostly Apis dorsata and Nomia spp. Most of the pollen was collected within 1 h of anthesis. Anthesis in males takes place about 20 min earlier than in females; insect visitation follows this pattern. The minute quantity of nectar was collected by only few insects and mostly after the pollen had gone, if at all. Fruits were eaten by birds. The species displays many features typical of dioecious tropical plants with the unusual feature of pollen being the main food reward for pollinators. It was pollinated effectively in Sulawesi.     

多叶斑叶兰繁育系统与传粉生物学研究

为探讨多叶斑叶兰(Goodyera folisa)的繁育系统与传粉生物学特征,对其开花物候、花粉活力与柱头可授性、人工授粉、花的挥发性成分以及昆虫传粉行为进行了研究。结果表明,多叶斑叶兰的唇瓣黄色,萼片白色或白色带红褐色;单花花期为(9.4±0.8)d;花粉在开花后第1天具备活力,柱头在开花后第2天具备可授性,花粉活力和柱头可授性都在开花后第5天达到峰值。去雄套袋和不去雄套袋都不能结实,人工自花授粉、同株异花授粉和异株异花授粉的结实率分别为93.3%、95.0%和96.7%,自然结实率为43.3%。花朵的主要挥发性成分为1-辛烯-3-醇、3-辛醇和N,N-二甲基甲酰胺。多叶斑叶兰传粉者为中华蜜蜂(Apis cerana)。多叶斑叶兰具有自交亲和能力,但在自然界不具有主动自交现象,必须依赖中华蜜蜂传粉,花色及花香气味为吸引传粉者的主要因素。