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

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.

Specialization for Tachinid Fly Pollination in the Phenologically Divergent Varieties of the Orchid Neotinea ustulata

Despite increased focus on elucidating the various reproductive strategies employed by orchids, we still have only a rather limited understanding of deceptive pollination systems that are not bee- or wasp-mediated. In Europe, the orchid Neotinea ustulata has been known to consist of two phenologically divergent varieties, neither of which provide rewards to its pollinators. However, detailed studies of their reproductive biology have been lacking. Our study aimed to characterize and understand the floral traits (i.e., morphology, color, and scent chemistry) and reproductive biology of N. ustulata. We found that the two varieties differ in all their floral traits; furthermore, while Neotinea ustulata var. ustulata appears to be pollinated by both bees (e.g., Anthophora, Bombus) and flies (e.g., Dilophus, Tachina), var. aestivalis is pollinated almost entirely by flies (i.e., Nowickia, Tachina). Tachinids were also found to be much more effective than bees in removing pollinaria, and we show experimentally that they use the characteristic dark inflorescence top as a cue for approaching inflorescences. Our results thus suggest that while both N. ustulata varieties rely on tachinids for pollination, they differ in their degree of specialization. Further studies are, however, needed to fully understand the reproductive strategy of N. ustulata varieties.

Preliminary observations on the flower visitors of Nasa colanii (Loasaceae), a poorly known species endemic to northern Peru

Nasa is the most diverse genus among the family Loasaceae, and it is mainly distributed in Peru. Most species of this genus are microendemics, with distributions restricted to a very specific location; such is the case of Nasa colanii. This species—previously only known from the type collected in 1978 from the Amazonas region of Peru—lacks information about its biology and ecology. To improve our understanding of the reproductive biology and pollination ecology of N. colanii, we observed the flower development and insect floral visits in a cloud forest in the Amazonas region. The flowers of N. colanii are nectariferous and protandrous. The typical stamen movement to the flower center of the subfamily Loasoideae appears to be autonomous. Only well-developed (elongated) pistils showed positive stigmatic receptivity to 3% hydrogen peroxide. Syrphid flies (Baccha sp.) and small beetles (Baridinae sp. and Alticini sp.) were the only observed flower visitors. The syrphid flies visited the flower and foraged for pollen, whereas the small beetles were found already in the flowers and seemingly used it as a shelter. Results suggest that N. colanii might be adapted to fly pollination.

From Bees to Flies: Global Shift in Pollinator Communities Along Elevation Gradients

Bees decrease in abundance and richness along elevation gradients, while flies replace bees as the dominant flower visitors in higher elevation systems. We reviewed the existing literature to determine if this global phenomenon of pollinator communities switching from bees to flies occurs at the same place along a temperature gradient. Here we examined five studies that have documented this bee-to-fly transition in the North America, South America, Europe & Australia. We determined where the bee-to-fly transition occurred along a temperature/elevation gradient for each study that ranged from 1.1 to 8.3°C. We found that pollinator communities shifted from bee dominated to fly dominated communities between 4.9 and 5.7°C on all elevation gradients worldwide. This shift in pollinators could substantially impact ecological systems reliant on fly pollination as temperatures continue to warm.