Interspecific variation in pollen-ovule ratio is negatively correlated with pollen transfer efficiency in a natural community

Knowledge of efficiency of pollinators is valuable in the derivation of (i) the degree of mutualism specialization of a flower visitor in the natural plant communities, (ii) the optimum number of pollinators needed for the maximum pollination in a plant population, and (iii) the pollinator risk assessment in the sustainable agriculture. Earlier researchers used many direct and indirect methods for measuring the pollination efficiency (PE) of flower visitors. However, a great ambiguity exists in the usage of this terminology that necessitated its fresh scrutiny. I tested the available three standard methods afresh to find the efficiency of pollinators. These included comparing the (i) number of pollen grains removed and deposited by the visitors; (ii) seed set resulting from a single and the multiple visits of the visitors; and (iii) “pollen transfer efficiency (PTE)” derived from the foraging behavior and abundances of the visitors. Observations were recorded on the visitors of four plant species in an agroecosystem of Northwest India. These plants represented a wide variety of the floral types across the angiosperms. The first two methods, namely, the “number of pollen grains removed and deposited” and the “seed set resulting from a single and the multiple visits,” were appropriate in finding differences between the efficiency ranks of the pollinators of those flowers where the number of deposited pollen grains was less than the number of ovules in the ovary. However, these two methods completely failed in situations where exactly reverse condition of pollen grains and ovules existed. Thus, these two methods of measuring the PE of visitors had limited approach and lacked a universal application over the entire angiosperm taxa. On the other hand, use of “pollen transfer efficiency”, derived from the foraging behavior and abundance of the visitors, seemed to have an edge over the other two methods as this was helpful in finding differences between the efficiency ranks of the pollinators of plants in all the three situations tested in this study. However, validation of all the three methods through the plant reproductive potential seemed to be an integral confirmatory step for drawing inferences about the efficiency of pollinators.

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Fly Pollination of Kettle Trap Flowers of Riocreuxia torulosa (Ceropegieae-Anisotominae): A Generalized System of Floral Deception

Plants ◽

10.3390/plants10081564 ◽

2021 ◽

Vol 10 (8) ◽

pp. 1564

Author(s):

Annemarie Heiduk ◽

Ulrich Meve ◽

Frank Menzel ◽

Jean-Paul Haenni ◽

Michael von Tschirnhaus ◽

...

Keyword(s):

Chemical Ecology ◽

Floral Scent ◽

Pollen Transfer ◽

Male And Female ◽

Intensive Research ◽

Generalized System ◽

Plant Group ◽

Pollen Transfer Efficiency ◽

Linalool Oxide ◽

Fly Pollination

Elaborated kettle trap flowers to temporarily detain pollinators evolved independently in several angiosperm lineages. Intensive research on species of Aristolochia and Ceropegia recently illuminated how these specialized trap flowers attract particular pollinators through chemical deception. Morphologically similar trap flowers evolved in Riocreuxia; however, no data about floral rewards, pollinators, and chemical ecology were available for this plant group. Here we provide data on pollination ecology and floral chemistry of R. torulosa. Specifically, we determined flower visitors and pollinators, assessed pollen transfer efficiency, and analysed floral scent chemistry. R. torulosa flowers are myiophilous and predominantly pollinated by Nematocera. Pollinating Diptera included, in order of decreasing abundance, male and female Sciaridae, Ceratopogonidae, Scatopsidae, Chloropidae, and Phoridae. Approximately 16% of pollen removed from flowers was successfully exported to conspecific stigmas. The flowers emitted mainly ubiquitous terpenoids, most abundantly linalool, furanoid (Z)-linalool oxide, and (E)-β-ocimene—compounds typical of rewarding flowers and fruits. R. torulosa can be considered to use generalized food (and possibly also brood-site) deception to lure small nematocerous Diptera into their flowers. These results suggest that R. torulosa has a less specific pollination system than previously reported for other kettle trap flowers but is nevertheless specialized at the level of Diptera suborder Nematocera.

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Flowering phenology and trap pollination of the rare endemic plant Ceropegia thaithongiae in montane forest of northern Thailand

Botany ◽

10.1139/cjb-2018-0045 ◽

2018 ◽

Vol 96 (9) ◽

pp. 601-620 ◽

Cited By ~ 1

Author(s):

Phakpoom Auttama ◽

Doyle McKey ◽

Aroonrat Kidyoo

Keyword(s):

Floral Scent ◽

Flowering Phenology ◽

High Viscosity ◽

Pollen Transfer ◽

Endemic Plant ◽

Pollen Transfer Efficiency ◽

Insect Visitation ◽

Flower Visiting ◽

Rare Endemic ◽

Effective Pollinators

Although Ceropegia species are well known for their complex pitfall flowers that temporarily imprison their pollinators, various aspects of their pollination ecology are still unknown. This study investigated flowering phenology, functional floral traits, and insect visitation in a natural population of a rare endemic lithophyte, Ceropegia thaithongiae Kidyoo. Flowering of C. thaithongiae was not synchronous but staggered. Anthesis lasted mostly 1–2 days, but its duration was shorter in flowers with a pollinium inserted into the stigmatic chamber. Several different insects visited flowers, but only chloropid and milichiid flies were effective pollinators. At anthesis, the epithelial osmophores on the corolla lobes emitted a floral scent that was simple in composition. Nectar of high viscosity was exuded from the nectaries hidden behind the guide rails. When transported by an insect, the pollinarium was attached to bristles on the mouthparts. Size and shape of the thin pellucid margin of the pollinium enable it to fit into the stigmatic chamber in a lock-and-key arrangement. The pollen transfer efficiency was 6.8%. The plant’s staggered flowering and pollination-induced ending of anthesis are advantageous in decreasing competition for pollinators when flower-visiting insects are scarce.

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Pollinator effectiveness and importance between female and male mining bee ( Andrena )

Biology Letters ◽

10.1098/rsbl.2019.0479 ◽

2019 ◽

Vol 15 (10) ◽

pp. 20190479 ◽

Cited By ~ 2

Author(s):

Ju Tang ◽

Qiu-Mei Quan ◽

Jing-Zhu Chen ◽

Ting Wu ◽

Shuang-Quan Huang

Keyword(s):

Foraging Behaviour ◽

Pollen Grains ◽

Pollen Foraging ◽

Pollen Transfer ◽

Natural Ecosystems ◽

Pollinator Effectiveness ◽

Visit Frequency ◽

Pollen Transfer Efficiency ◽

Food Provision ◽

Effective Pollinators

Bees are often considered to be effective pollinators in both agricultural and natural ecosystems but could be ineffective pollinators in that they collect large quantities of pollen for food provision but deliver little to stigmas. Male bees do not collect pollen to feed larvae, and their pollination role has been underappreciated. Here we compare pollination effectiveness, visit frequency and pollen foraging behaviour between female and male individuals of a mining bee, Andrena emeishanica , visiting a nectariferous spring flower ( Epimedium pubescens ). Female bees were observed to forage for both pollen and nectar, but male bees foraged only for nectar. Female bees had large hairy hind tibiae with conspicuous scopae, and nearly 90% of the pollen grains they collected went onto the hind legs. Male bees removed less pollen from anthers than female bees but deposited more pollen on stigmas per visit. The higher pollen transfer efficiency of male bees was due to 48.4% of pollen grains remaining ungroomed on the thorax and abdomen, available for stigma contact, but their visitation rate to flowers was much lower. Our results indicate that male solitary bees could transfer more pollen on the stigma per visit but were less important (transferred less pollen in total, because they made fewer visits per unit time) than females.

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