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

Abstract

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.

Chemical Insect Attractants Produced by Flowers of Impatiens spp. (Balsaminaceae) and List of Floral Visitors

“…This may be due to the small size of the flowers produced, which are too small for most bumblebee species to land on. On the other hand, we believe that it is also due to the fact that this species produces linalool-related monoterpenes (linalool oxide and 8-hydroxylinalool), which, together with linalool, are known to attract Diptera [72][73][74].…”

Specialized pollination by cecidomyiid flies and associated floral traits in Vincetoxicum sangyojarniae (Apocynaceae, Asclepiadoideae)

“…in moth-pollinated Hoya carnosa (Kaiser 1991) and fly-pollinated Riocreuxia torulosa and Ceropegia spp. (Heiduk et al 2021).…”

“…Caryophyllaceae, Rubiaceae, Solanaceae, and Zingiberaceae (Knudsen & Tollsten 1993). It may also be involved in food-deceptive strategies, attracting moth pollinators to the nectarless flowers of Plumeria alba (Apocynaceae, Apocynoideae) (Knudsen & Tollsten 1993), or Nematocera flies (mainly Sciaridae) to the nectarless flowers of Riocreuxia torulosa (Asclepiadoideae) (Heiduk et al 2021). The homoterpene (E )-DMNT is a widespread herbivore-induced VOC released from damaged leaves (Tholl et al 2011) and commonly known as a floral scent component (Kaiser 1991;Knudsen et al 2006).…”

Checklist of the dipterofauna (Insecta) from Roraima, Brazil, with special reference to the Brazilian Ecological Station of Maracá

“…Adults are small and can be found in many different habitats. Adults of some genera sometimes are found feeding on flowers and may act as pollinators (Heiduk et al, 2021). Occasionally, populations can be observed in large numbers aggregated over the substrate (Amorim, 2009b;Haenni & Amorim, 2017).…”