Butterfly pollination in Pteroglossa (Orchidaceae, Orchidoideae): a comparative study on the reproductive biology of two species of a Neotropical genus of Spiranthinae

Abstract

Spiranthinae orchids are known for being self-compatible and offering nectar as a reward. Although data on their pollinators are scarce, members of this tribe are mostly pollinated by bees, hummingbirds and moths. Some of them even reproduce through facultative self-pollination. Nothing is known about the pollinators and reproduction system in Pteroglossa. Based on records on flowering phenology, floral morphology, reward production, pollinators and breeding system, this paper aims to study the reproductive biology of two Pteroglossa spp. Both species offer nectar as a resource and are pollinated exclusively by diurnal Lepidoptera at the studied areas. Nectar is produced by two glandular nectaries, and is stored in a spur. Pollinaria possess a ventrally adhesive viscidium that is deposited on the basal portion of butterfly proboscides. Both species are self-compatible but pollinator-dependent. The reproductive success is low when compared to other Spiranthinae. Although no evident mechanical barrier to avoid self-pollination or geitonogamy was identified, the erratic behavior of the butterflies, with their infrequent visits to only one flower per inflorescence, contributes to an increased fruit set produced through cross-pollination. The presence of ventrally adhesive viscidia in Spiranthinae is responsible for greater pollinator diversity when compared to bee-pollinated Goodyerinae with dorsally adhesive viscidia, adapted to attach to bee mouthparts.

Pollinator‐independent orchid attracts biotic pollinators due the production of lipoidal substances

“…Garay (Pansarin & Ferreira ). As in other members of Cranichidae, C. candida possesses large stigmatic surfaces, which are considered an important factor to increase the chance of deposition of multiple pollen loads and, presumably, cross‐pollination (Singer & Sazima ; Pansarin & Ferreira ). In some Cranichidae, the stigma of flowers on the first day is not very adhesive and, in this phase, pollen pads do not adhere.…”

“…In some Cranichidae, the stigma of flowers on the first day is not very adhesive and, in this phase, pollen pads do not adhere. Consequently, pollen deposition is facilitated only in flowers after the second day (Pansarin & Ferreira ). A similar case of protandry has been recorded in Mesadenella (Singer 2002), Spiranthes (Catling & Catling ) and Sauroglossum (Singer 2002).…”

“…Pollinaria deposition on the pollinator's body in members of Cranichidae commonly occurs on mouthparts of pollinators (see Pansarin & Ferreira ). Pollination by moths has been reported for nectar‐offering Prescottia , where pollinaria are deposited on the ventral surface of the pollinator proboscis.…”

“…However, this flower resource has never been recorded within Cranichideae, whose species commonly offer floral nectar as a resource. Generally, the nectar is produced by nectar glands on both margins of the labellum base, and stored in the nectary chamber, which is usually formed by the union of sepals and the labellum (Pansarin & Ferreira ). Consequently, members of Cranichideae are pollinated by nectar‐seeking vectors, such as hymenopterans, hummingbirds and lepidopterans ( e.g .…”

“…Consequently, members of Cranichideae are pollinated by nectar‐seeking vectors, such as hymenopterans, hummingbirds and lepidopterans ( e.g . Singer & Sazima ; Pansarin & Ferreira ).…”