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Pollen Vectors (pollen + vector)
Selected AbstractsRespiration and thermogenesis by cones of the Australian cycad Macrozamia machiniiFUNCTIONAL ECOLOGY, Issue 6 2004R. S. SEYMOUR Summary 1While cycads are often considered to be wind-pollinated, it is now clear that insects are pollen vectors in many species. This study addresses the role of thermogenesis in pollination biology of the dioecious cycad Macrozamia machinii P.I. Forster & D.L. Jones. 2The patterns of thermogenesis in intact male and female cones were assessed with thermometry and respirometry throughout the pollination period in the field. 3Thermogenic episodes in male cones occurred from about 17.00,00.00 h on successive evenings, in association with dehiscence of sporangia and presence of their pollinating weevils (Tranes sp.). 4Temperatures of the 167 g male cones rose ,6 °C above ambient, and mean rate of oxygen consumption peaked at 7·7 µmol s,1 (3·6 W). Regulation of male cone temperature was not evident, and thermogenesis of female cones was insignificant. 5Male cones probably heat to augment scent production and enhance weevil activity, including mating and egg-laying, but female cones may benefit from reduced visitation and freedom from damage by weevil larvae. Male cones may be sacrificial in providing the reward to the pollinators while the female cones are safeguarded. [source] Environmentally induced variation in floral traits affects the mating system in Datura wrightiiFUNCTIONAL ECOLOGY, Issue 1 2002E. Elle Summary 1If pollination is unpredictable, selection may favour the production of selfed seeds in the absence of pollen vectors, even in plant species with obvious adaptations for outcrossing. Pollination may be less predictable for plants growing in certain environments if environmental factors affect the floral phenotype. Through effects on flower morphology and the floral display, the environment may affect the outcrossing rate. 2We manipulated two environmental factors, water availability and exposure to insect herbivores, in a common-garden experiment using a perennial herb, Datura wrightii. We measured herkogamy (the separation of anthers and stigmas within flowers), total flower length, and flower number, and used a single-gene trichome dimorphism as a marker to determine per-plant outcrossing rates. 3The large amount of variation in herkogamy was affected by trichome type, irrigation and herbivory. In addition, watered plants had longer corollas, and plants attacked by herbivores had fewer open flowers. Thus environmental factors affect floral phenotype. 4However, irrigation and herbivory did not directly affect outcrossing rate. There were indirect effects of these treatments on outcrossing because plants with increased herkogamy and fewer open flowers had higher outcrossing rates. 5, A greenhouse experiment showed that autonomous selfing is more likely when herkogamy is reduced, and can occur both as the flower opens and when the corolla is shed. 6, These experiments are among the first to show that within-population variation in the mating system can be due to environmentally induced variation in floral traits. [source] The influence of pollinator abundance on the dynamics and efficiency of pollination in agricultural Brassica napus: implications for landscape-scale gene dispersalJOURNAL OF APPLIED ECOLOGY, Issue 6 2006KATRINA E. HAYTER Summary 1It is important to understand the pollination processes that generate landscape-scale gene dispersal in plants, particularly in crop plants with genetically modified (GM) varieties. In one such crop, Brassica napus, the situation is complicated by uncertainty over the relative importance of two pollen vectors, wind and insects. 2We investigated pollination in two fields of B. napus that bloomed at different times of year (April vs. July) and attracted different abundances of foraging social bees. Rates of pollen transfer were quantified by counting the pollen grains deposited on stigmas and remaining in the anthers at intervals after flower opening. 3Flowers open in April were adequately pollinated only after 5 days and only 10% received even a single bee visit. Flowers open in July received three bee visits per hour and were fully pollinated within 3 h. 4Based on published measurements of airborne pollen dispersal, we estimate that wind-pollination from a hypothetical field 1 km distant could have fertilized up to 0·3% of the field's seed when bees were scarce in April but only up to 0·007% when bees were abundant in July. 5The efficiency of pollination (the proportion of pollen released from anthers that landed on receptive stigmas) was seven times greater in July (1·5%) than in April (0·2%). The relatively high efficiency of insect pollination may help to explain the evolutionary maintenance of entomophily. 6Synthesis and applications. Our results begin to resolve a long-standing inconsistency among previous studies by suggesting that the susceptibility of fields of B. napus to long-distance cross-pollination by wind depends on the level of bee activity. Models for predicting GM gene flow at the landscape-scale in this crop should take this into account. [source] Ornithophilous canopy species in the Atlantic rain forest of southeastern BrazilJOURNAL OF FIELD ORNITHOLOGY, Issue 2 2008Márcia A. Rocca ABSTRACT In tropical ecosystems, birds play a relevant role in plant reproduction. Although hummingbirds are regarded as the most important vertebrate pollinators in the Neotropics, the possible role of perching birds as pollinators has been neglected. From 2003 to 2005, we observed 68 species of plants visited by birds in an Atlantic rainforest in southeastern Brazil, including three canopy species: Spirotheca rivieri (Malvaceae, Bombacoidea), Schwartzia brasiliensis (Marcgraviaceae), and Psittacanthus dichrous (Loranthaceae). Flowers of these three species were visited by 15 different species of perching birds and by hummingbirds. The flowers of these three plants are colorful, ranging from deep red or purple to orange. Spirotheca rivieri blooms during the austral winter and Schwartzia brasiliensis during the summer. The flowers of these two species produce copious amounts of dilute nectar in easily accessible structures and both species appear to depend primarily on perching birds as pollinators, with hummingbirds being secondary or minor pollen vectors. The tubular, narrow flowers of P. dichrous are produced during the austral summer and are visited primarily by hummingbirds. Perching birds also visit the flowers, but destroy them. Our results suggest that previous estimates of the number of perching birds that feed on nectar may be too low and that flowers pollinated by perching birds may be more common in the canopy of Neotropical forests than previously thought. SINOPSIS En los ecosistemas tropicales, las aves desempeñan un papel importante en la reproducción de las plantas. Aunque se consideran a los colibríes como el grupo más importante de polinizadores en el neotrópico, este posible rol ha sido relegado en las aves de percha. De 2003,2005, observamos 68 especies de plantas visitadas por aves en el Bosque Pluvial del Atlántico en el sudeste de Brasil. Las flores en el dosel de Spirotheca rivieri (Malvaceae, Bombacoidea), Schwartzia brasiliensis (Marcgraviaceae) y Psittacanthus dichrous (Loranthaceae) fueron visitadas por 15 especies de aves, siendo colibríes y especies de aves de percha. Las flores de estas plantas son de gran colorido, desde rojo subido o púrpura hasta anaranjado. Spirotheca rivieri florece durante el invierno austral y Schwartzia brasiliensis durante el verano. Las flores de estas especies producen grandes cantidades de néctar y tienen estructuras de gran accesibilidad para las aves. Ambas especies parecen depender principalmente de aves de percha como polinizadores, siendo los colibríes polinizadores secundarios o vectores menores de polen. Las flores angostas y tubulares de P. dichrous se producen durante el verano austral y son visitadas, principalmente, por colibríes. Hay aves de perchas que también visitan a estas flores, pero al hacerlo las destruyen. Nuestros resultados sugieren que los estimados previos del número de aves de percha que se alimentan de néctar son muy bajos y que la polinización por aves de percha, parece ser más común en el dosel forestal de los bosques neotropicales que lo previamente pensado. [source] Pollination of the Lady's slipper orchid (Cypripedium calceolus) in Scandinavia , taxonomic and conservational aspectsNORDIC JOURNAL OF BOTANY, Issue 4 2009Alexandre Antonelli The Lady's slipper orchid Cypripedium calceolus L. is considered one of the most beautiful orchids of Europe. Consequently, the species has suffered from over-collecting and is now critically endangered in many countries. Although pollination success is suspected to influence the long-term survival of Cypripedium calceolus, relatively little is known about the identity of its pollinators in mainland Sweden , a region that comprises the largest European populations. In order to identify which species pollinate eight representative populations in mainland Sweden, we observed and sampled visitors to flowers using a standardized protocol. Specimens were identified and any pollen smear found on their body was examined for the presence of Cypripedium pollen. Nine species were recognized as effective pollen vectors (Andrena cineraria, A. carantonica, A. haemorrohoa, A. helvola, A. nigroaenea, A. praecox, Colletes cunicularius, Lasioglossum fratellum and L. fulvicorne), four of them for the first time in Scandinavia. This is the first time that a species of Colletes is reported to carry pollen of Cypripedium in this region. All but one specimens were females. Our results suggest a taxonomically heterogeneous pollinator fauna for Cypripedium calceolus and are discussed in light of the management of this species. [source] | ||||||||||