MOSQUITO POLLINATION OF HABENARIA OBTUSATA (ORCHIDACEAE)

The floral morphology and pollination of Habenaria obtusata (Orchidaceae) are described. Habenaria obtusata occurs in Alaska, Canada, Norway, Siberia, etc., in great numbers and is pollinated by mosquitoes of the genus Aedes. The pollination process is described as observed in glass cages.     

BEETLE POLLINATION OF DIEFFENBACHIA LONGISPATHA (ARACEAE)

Dieffenbachia is an monoecious understory herb of tropical rain forests that exhibits a complex and specialized relationship with its beetle pollinators. The erect protogynous inflorescence has the spadix divided, with the female flowers in the basal half and male flowers in the upper half. Dieffenbachia longispatha Engler & Krause is pollinated by scarab beetles in the genera Cyclocephala and Erioscelis. The enveloping spathe of the inflorescence opens in the evening, but no flowers are sexually functional until the stigmas become receptive about 24 hr later. Beetles fly to the inflorescence in darkness, suggesting that floral odors play a role as an attractant. Beetles remain in the inflorescence for 24 hr, eating protein-rich staminodia that surround the stigmas. On the evening of the third day the anthers dehisce and beetles become covered with pollen as they crawl up the spadix in the process of leaving. Beetles fly an average of 80 m between inflorescences, usually to the nearest female inflorescence, although distances of 400–1,000 m have been observed. Minimal estimate of genetic neighborhood sizes are large for D. longispatha (750 to 8,900 plants) and neighborhood areas encompass 41,000 to 67,000 m². Experiments demonstrate that the species is self-compatible and that fruit production is pollinator limited.     

POLLINATION BIOLOGY OF LISTERA CORDATA (ORCHIDACEAE)

Pollination biology of northern California populations of Listera cordata (L.) R. Br. is presented. The flowers are allogamous, self-compatible, and protandrous. At anthesis, access to the stigma is blocked by the flap-like rostellum. When an insect contacts the touch-sensitive trigger hairs of the rostellum, the pollinia are suddenly released and become cemented to the insect's body. One to two days after the pollinia are removed, the rostellum rises and exposes the receptive stigma. Visitors are attracted to the flowers by their foul odor and minute quantities of nectar presented on the surface of the labellum. Pollination efficiency is high with 61–78% of flowers from several localities setting fruit. The most important and abundant pollinators of L. cordata at our study sites are fungus gnats (Sciaridae and Mycetophylidae). Other less frequently encountered pollinators are members of these families: Braconidae, Ichneumonidae, and Tipulidae. At present, there is no compelling evidence that the floral characteristics of L. cordata have evolved as a result of an evolutionary interaction with any specific group of insects. Nor is there any indication that the flowers are sapromyophilous, despite their putrid odor.     

THE POLLINATION ECOLOGY OF ZENOBIA (ERICACEAE)

Zenobia is a shrub endemic to the coastal plain of the Carolinas and southeastern Virginia. The sole species, Zenobia pulverulenta, appears to be weakly self-compatible and partially self-pollinating. Fruit set was reduced, but not eliminated by excluding insect floral visitors. Insect visitors were collected and their pollen loads examined for Zenobia and foreign pollen. Analysis of these pollen loads and observations of insect-foraging behavior indicate that workers of three species of bumblebee (Bombus bimaculatus, B. griseocollis and B. impatiens) are. the principal pollinators of Zenobia. However, pollinator density and composition appear to be strongly influenced by the habitats in which Zenobia grows. Pollen and nectar serve as the primary rewards for pollinators.     

POLLINATION ECOLOGY OF PYRRHOPAPPUS CAROLINIANUS (COMPOSITAE)

Pyrrhopappus carolinianus and Hemihalictus lustrans constitute a mutualistic association: the early morning flowering of Pyrrhopappus provides the matinal bee with a nearly exclusive pollen source, although other plants must be visited for nectar. Female Hemihalictus, the primary pollen vector, tear open the anthers and remove the pollen before it is available to other bees. The foraging behavior of the bee insures cross-pollination. The flight pattern of the bees generally restricts the pollen dispersal range. If cross-pollination fails, then autogamy results from twisting of the styles that brings the stigmas in contact with the pollen presented on the styles of other florets. Schinia mitis is an important predator of the capitulae of P. carolinianus.     

BEETLE POLLINATION OF CYCLANTHUS BIPARTITUS (CYCLANTHACEAE)

The morphology, inflorescence phenology, and insect visitors of Cyclanthus were observed during two reproductive seasons at Finca La Selva in the Atlantic lowlands of Costa Rica. The inflorescence of Cyclanthus is an elongate spadix that is subtended and enclosed by four large, cymbiform bracts. Staminate and pistillate flowers are arranged in separate cycles along the length of the spadix and show marked dichogamy. Pollinators of Cyclanthus are beetles of the genus Cyclocephala (Scarabaeidae). The beetles arrive at the inflorescence while it is in the pistillate phase, during the first evening of the 2-day flowering period. They remain in the inflorescence for 24 hrs, until the end of staminate anthesis. The bracts of the inflorescence produce specialized tissue that the beetles consume along with pollen. Chemical analysis of the food tissue indicates that it is almost 50% lipid by dry weight. The scarabs use the inflorescence as an aggregation site for mating. Experiments with bagged inflorescences showed that no seeds are produced in the absence of pollinators, which suggests that Cyclanthus is obligately allogamous.     

THE POLLINATION ECOLOGY OF SOLANUM ROSTRATUM (SOLANACEAE)

The pollination mechanisms and pollen vectors of Solarium rostratum have been examined by greenhouse experiments and field studies. Although the capacity for autogamy exists in this weedy annual, it rarely occurs because of two factors: (1) the morphology of the flower and (2) the foraging behavior of the various species of Bombus, the primary pollen vector in the regions studied. The percentages of geitonogamy and xenogamy are dependent on the flight pattern of the bees and the number of open flowers on a plant.     

THE POLLINATION DYNAMICS OF SYMPATRIC SPECIES OF PEDICULARIS (SCROPHULARIACEAE)

Sympatric populations of Pedicularis oederi, P. cystopteridifolia, and P. groenlandica on the Beartooth Plateau (Montana) were obligately dependent on Bombus pollinators. Their corolla colors were mutually distinct to insect vision, but their nectars had identical sugar components. Analysis of corbicular pollen loads of pollinating insects indicated a high degree of polylecty. Queen/worker ratios of pollinators on plant species corresponded to the parallel phenological sequences of plant blooming and insect caste development. The total number of individual pollinators of each Bombus species on all plants was directly related to the number of plant species it pollinated, but a comparable relationship between the number of pollinators on a plant species to the number of Bombus species pollinating it was not found. Morphological and behavioral correspondence of floral mechanisms and pollinators form an integral part of the general pattern of coadaptive evolution of the floral ecology of Pedicularis in North America known from previous studies. Reproductive isolation between Pedicularis species in this study is attributed to internal barriers. Wide overlaps of blooming seasons, proboscis lengths of bumblebee species and castes, and pollinator species on Pedicularis species suggest resource sharing, rather than resource partitioning or competition for resources among plant and insect species and individuals.     

THE POLLINATION ECOLOGY OF DELPHINIUM TRICORNE (RANUNCUL ACEAE)

The pollination ecology of Delphinium tricorne, a spring-ephemeral herb of eastern deciduous forests, was studied at eight sites in the Ohio River basin from West Virginia to southern Illinois. The plant was found to be obligately dependent for its pollination on queen bumblebees (Bombus Latr. spp.) and hummingbirds, to which the flowers are closely adapted in form, color, function, and blooming phenology. Other bees, including Anthophora ursina, Osmia bucephala, Ptilothrix bombiformis, and Xylocopa virginica; Lepidoptera, including Amphion nessus, Danaus plexippus, Epargyreus clams, Erynnis juvenalis, Hemaris thysbe, Papilio glaucus, P. philenor, P. troilus, Poanes zabulon, Vanessa atalanta, and V. cardui; and the beefly Bombylius major foraged for nectar and/or pollen on the flowers without pollinating them. Techniques employed in the study included insect exclosures to test fertility of plants in the absence of pollinators, analysis of floral colors by reflectance spectrophotometry and ultraviolet photography, analysis of pollinator behavior by cinematography and close-range stereophotography, collection and identification of visitors to flowers, and identification of pollen types carried by foragers on the flowers.     

POLLINATION ECOLOGY OF VACCINIUM STAMINEUM (ERICACEAE: VACCINIOIDEAE)

Successful fruit set by deerberry, Vaccinium stamineum (Ericaceae: Vaccinioideae) requires floral visitation by insects, and in particular by bees that collect its pollen by sonication of anthers (“buzz-pollination”). A diversity of bees visit deerberry flowers, but most species are either 1) infrequent, 2) polylectic (broad host range for pollen), or 3) principally nectar-seeking, and so are unimportant as pollen vectors. Both sexes of the solitary, oligolectic bee Melitta americana⁵ (Melittidae) are abundant at flowering deerberry bushes in central New York State. Female M. americana sonicate the deerberry anthers while imbibing nectar, and carry virtually pure scopal loads of deerberry pollen, unlike the other common visitor, Xylocopa virginica (Anthophoridae). Comparative analyses of bee 1) abundances, 2) buzz-pollination behaviors, 3) pollen fidelities, and 4) pollination efficiencies, all indicate that Melitta americana is the primary pollinator of Vaccinium stamineum.     

THE MODE OF POLLINATION IN HABENARIA OBTUSATA (ORCHIDACEAE)

The role of mosquitoes and moths as pollinators of Habenaria obtusata was studied in northern Wisconsin during the summer of 1969. In each population studied, meter-square quadrants were marked and the number of plants, flowers per inflorescence, rate and time of pollinia removed, and capsule set recorded. Carbon dioxide and modified New Jersey Light Traps were set during the flowering period to capture pollinia-bearing insects. The study showed that female mosquitoes of the genus Aedes (particularly A. communis) and two species of Geometrid moths of the genus Xanthorhoe are important pollinators of H. obtusata. Pollination occurred during the last few days of flowering with an average of 18.0% of the pollinia removed and with 14.2% capsule set.     

刺五加传粉生物学研究

本文报道刺五加Eleutherococcus seticosus(Rupr．et Maxim．)Maxim的花朵酬物、访花者类别、访花 者在花序上的访花行为、访花频率及传粉效果。主要结果如下:(1)每朵雄花可提供的报偿是58 000～ 81 000粒花粉,5.5～8.0 µl／d×2～4d花蜜。每朵雌花仅可提供4.0～8.0µl／d× 2～3 d花蜜,不能提 供花粉。每朵两性花可提供19 000～54 000粒花粉和7.0～10.0 µl／d× 2～6 d花蜜。(2)花粉提供者 (雄花和两性花)提供报偿的日期是开花后1～3天,花粉接受者(雌花和两性花在柱头外翻变白时)是 开花后5～7或7～9天,这进一步证实了剌五加雄蕊先熟。另外,花粉提供者提供花蜜的时间在一天中 是8:30至15:30,其高峰是9:00～15:00;花粉接受者提供花蜜的时间在一天中是10:30至16:30,其高 峰是11:00～16:00。这种时间差异可能是刺五加影响传粉者流向(从花粉提供者到花粉接受者)的关键 因素。(3)在刺五加花朵上记录到的访花昆虫有50余种,分别隶属于膜翅目、鳞翅目、鞘翅目、双翅目和 半翅目。在不同天气、不同生境、不同性别的植株记录到的访花频率及高峰时间不同:花粉提供者的 访花高峰早于花粉接受者的;雄株上的访花频率高于雌株的;两性株接受花粉时的访花频率高于提供花 粉时的;而天气越晴朗,刺五加地块(patch)越大,则访花频率越高;每日接受光照越早,访花高峰越早。 (4)从传粉效果看,刺五加种子的形成完全依赖于传粉昆虫的活动。其中,蜂类,如熊蜂、花蜂、切叶蜂、胡蜂和蜜蜂等是最有效的传粉者,其它昆虫如粉蝶、食蚜蝇、寄蝇和鳃角金龟等对传粉也有帮助。     

POLLINATION BIOLOGY OF PHYSALIS VISCOSA VAR. CINERASCENS (SOLANACEAE)

Physalis viscosa var. cinerascens is a self-incompatible, herbaceous perennial which occurs in disturbed or open habitats in the south-central United States and eastern Mexico. The plants are low-growing and the pendant blossoms are often obscured by the foliage. In Oklahoma the species blooms from April through October. The flowers are yellow with dark purple or brown maculations in the center and a mat of white hairs in the throat. Nectar is produced in small quantities at the base of the ovary and pollen is present in copious amounts. The pollinators are solitary bees which visit the flowers for nectar and pollen. Perdita halictoides is the primary pollinator and is oligolectic on Physalis.     

THE POLLINATION BIOLOGY OF TUCKAHOE,PELTANDRA VIRGINICA (ARACEAE)

This study describes the specialized brood-site-based pollination system of Peltandra virginica Kunth (Araceae) with the chloropid fly Elachiptera formosa Loew and provides experimental evidence that gender-related changes in floral odor composition synchronize pollinator behavior with the blooming sequence. P. virginica is protogynous and does not self-pollinate because of a strong temporal separation in sexual function, and it is dependent upon insects for pollination because the spathe completely surrounds the spadix during the pistillate stage. Field observations conducted in central New Jersey and southeastern Pennsylvania showed that E. formosa is closely associated with P. virginica inflorescences. Within the floral chamber, E. formosa adults feed on pollen, mate, and find oviposition sites while the larvae complete their development. Although drosophilid and syrphid flies were collected and reared from inflorescences of both sexual stages, only E. formosa emerged from pistillate-stage inflorescences and adult E. formosa rapidly transferred fluorescent dye particles between inflorescences of both sexual stages in laboratory enclosures. These findings indicate that this fly species is the primary pollinator at our study locations. Field censuses demonstrated that although E. formosa visited P. virginica inflorescences of both sexual stages with equal frequency, the female flies preferentially oviposited within pistillate-stage inflorescences. Analysis of floral volatiles with gas chromatography-mass spectrometry showed that only the spathes emit the floral fragrance and that the composition of the floral volatiles changed during the transition from pistillate to staminate stage. A particularly noticeable change occurred in the emission ratio of the two primary floral odor components, 4,5,7-trimethyl-6,8-dioxabicyclo[3.2.1.]octane and an unidentified chemical analog with molecular weight of 142. The relationship between floral volatile composition and fly oviposition behavior was evaluated using sham inflorescences placed in the P. virginica study population. The sham inflorescences were constructed by covering spadices dissected from mature inflorescence buds with spathes excised from different-age inflorescences. After a 2-hr-long exposure period, sham inflorescences fitted with pistillate-stage spathes contained more E. formosa eggs than the sham inflorescences with staminate-stage spathes. However, the highest number of ovipositions occurred in sham inflorescences fitted with spathes excised from mature inflorescence buds. The fragrance emitted by these spathes was composed almost entirely of the two principal odor components. The decline in ovipositions observed in both real and sham inflorescences corresponded to an increase in the emission ratio of 4,5,7-trimethyl-6,8-dioxabicyclo[3.2.1.]octane to the molecular weight 142 analog. This suggests that gravid flies searching for oviposition sites used the ratio of the two primary floral volatile components as an inflorescence gender or age recognition cue.     

AERODYNAMICS OF WIND POLLINATION IN SIMMONDSIA CHINENSIS (LINK) SCHNEIDER

Wind tunnel analyses of Simmondsia chinensis (Link) Schneider or “jojoba” were conducted to quantify the behavior of airborne pollen grains around individual branches and leaves and near individual carpellate flowers. Field data (wind velocity) were used to ensure a correspondence between wind tunnel and natural conditions. Based upon the visualization of individual pollen grain trajectories, it is concluded that pollen deposition on stigmatic surfaces is influenced by large-scale aerodynamic patterns, generated by foliage leaves, and small-scale airflow patterns, formed around and by floral parts and stigmas. Leaves are seen to deflect airborne pollen grains into trajectories that can intersect ambient airflow at 90° angles, showering decumbent carpellate flowers with pollen. Similarly, flowers can deflect pollen upward and downwind, toward other flowers. The extent of floral bract and sepal recurvature is shown to influence the extent of pollen deposition by determining the characteristic airflow pattern around stigmas. Available evidence concerning the relatively recent evolutionary transition to anemophily in Simmondsia is interpreted within the context of morphological adaptations and exaptations favoring wind pollination.     

STUDIES ON THE POLLINATION ECOLOGY OF TIPULARIA DISCOLOR (ORCHIDACEAE)

Tipularia discolor, a woodland orchid, flowers in mid-summer when reproductive activity is minimal within the herb synusia. Tipularia is insect-pollinated, and artificial crosses showed that seeds are produced after self-pollination, intra-inflorescence pollination, and outcrossing. The single nocturnal pollinator, Pseudaletia unipuncta (Noctuidae), located Tipularia populations within a day or two of anthesis. Pollinators were shown to be capable of utilizing portions of the inflorescences that contained the most nectar. After total nectar resources declined, pollinators were no longer active on the inflorescences, even though flowers and nectar were still available. The mode of pollinator activity seems to be closely related to floral morphology, although the moths are able, early in the flowering phenophase, to successfully obtain nectar without effecting any change in the reproductive status of flowers.     

BREEDING SYSTEM AND POLLINATION ECOLOGY OF TRIENTALIS BOREALIS (PRIMULACEAE)

Selfing in Trientalis borealis is reduced by spatial separation of stigma and anthers during anther dehiscence and by internal self-incompatibility. Artificial self-pollination resulted in low levels of fruit set (2.0%). Crosses made within patches of plants yielded variable (0–72.7%), but generally low fruit set (x̄ = 21.4%). This may be caused by patches often consisting of a single genet. In contrast crosses made among patches resulted in uniformly high levels of fruit set (x̄ = 84.3%). Pollinator activity was higher at open sites than at heavily shaded sites and was correlated with fruit set. Pollinator activity, however, showed no correlation with seed set. We conclude that the primary pollinators, Halictid and Andrenid bees, play an important role in the breeding system of the plant by promoting outcrossing but that availability or efficiency of pollinators may limit seed set.     

POLLINATION OF DALECHAMPIA MAGNOLIIFOLIA (EUPHORBIACEAE) BY MALE EUGLOSSINE BEES

Flowers of Dalechampia magnoliifolia in eastern Peru were pollinated primarily by male Eulaema meriana and E. cingulata, which collected fragrance from the secretory gland borne in the staminate cymule. The fragrance contains carvone oxide, benzyl acetate, limonene, α-pinene, myrcine, β-pinene/camphene, and carvone. Trigona cf. pallens was the most abundant visitor, but was primarily a pollen thief. The rate of contact with the stigmas by Trigona, and hence the bee's efficacy as a pollinator, was highly variable and was determined by variation in the separation of anthers and stigmas. Dalechampia magnoliifolia co-occurred with a congeneric species, D. cissifolia, but did not share pollinators with it.