Reproductive biology in Gomphichis valida Rchb. f. (Orchidaceae: Orchidoideae, Cranichidinae): Generalist pollination in a high-Andean terrestrial orchid with long-lived flowers

Abstract

Floral features, the pollination process, the breeding system, and fruiting success are documented in the Andean terrestrial orchid Gomphichis valida. Studies were performed at the Department of Ancash, Peru, at ca. 4250 m a.s.l., from June to November 2022. The breeding system was studied through controlled pollinations in plants excluded from pollinators (bagged). Natural pollination was studied in the field and through photos and videos. The flowers are nectariferous and non-protandrous and present the longest lifespan reported so far for a neotropical terrestrial orchid (53–80 days). This species is pollinator dependent (unable to set fruit and seed without the agency of pollinators) and self-compatible. The observed pollinators belong to three functional groups that appeared successively (in order of appearance): hummingbirds (Chalcostigma stanleyi), bumblebees (Bombus coccineus and Bombus rubicundus), and solitary Halictidae bees (Augochlorella sp.). All recorded pollinators probe the flowers for nectar. The pollinaria adhere to the bee mouthparts and onto the lateral side of the hummingbird bill. Bumblebees were the most frequent and efficient functional group (up to 62.07% of the observed pollination events), followed by Halictidae (31.03%) and hummingbirds (6.90%). Natural fruiting success is high (66.66%–94.49%). Such high natural fruiting success is unexpected at high altitudes, but it is likely explained by a combination of factors, including the long floral lifespan, nectar secretion, and self-compatibility. This is the first report of hummingbirds as pollinators of Cranichidinae orchids, and G. valida is, to the best of our knowledge, a neotropical orchidoid orchid with the most generalist pollination biology recorded so far.