Ornithophily in the subtribe Maxillariinae (Orchidaceae) proven with a case study of Ornithidium fulgens in Guatemala

Abstract

Ornithophily has been long speculated to occur in the subtribe Maxillariinae (Orchidaceae), relying either solely on micromorphological analyses or scarce field observations of undefined species. In Guatemala we were able to observe regular visits of the azure-crowned hummingbirds feeding on flowers of Ornithidium fulgens. These observations have led us to investigation of floral attractants by means of scanning and transmission microscopy, histochemical and chemical analyses (GC–MS). Conducted investigation revealed that the epidermis of basal protuberance of column-foot has features proving the secretory activity and that secreted nectar is sucrose-dominant. Slight secretion on the middle part of the lip is puzzling. The presence of other potential pollinators has not been reported. Based on the results of this study, we confirmed that the flowers of O. fulgens meet all criteria of ornithophily and thus that the hypothesis about bird pollination in the subtribe Maxillariinae is proven. The presented results confirm that the previously described floral features predicting the bird pollination in this group are justified. This strengthens the theory about floral adaptations to different pollinators and gives valid reasons to consider species with flowers with a certain set of traits as ornithophilous, even in the absence of the pollination observation.

Floral attractants in the black orchid Brasiliorchis schunkeana (Orchidaceae, Maxillariinae): clues for presumed sapromyophily and potential antimicrobial activity

“…Crucial observations have been made during the field research in Guatemala, where azure-crowned hummingbirds ( Amazilia cyanocephala ) have been spotted while pollinating flowers of Ornithidium fulgens Rchb. f. This finding was later supported by the results of micromorphological, histochemical, and chemical studies [ 9 ].…”

“…ex R.Br. [ 8 ], O. fulgens [ 9 ], and Maxillaria anceps Ames & C. Schweinf [ 6 ]. Davies et al [ 6 ] estimate that within the core of the subtribe only 8% of species produce nectar.…”

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

“…Of note, G. valida does not present floral traits suggestive of hummingbird pollination. Typical hummingbird-pollinated flowers are tubular, red-or orange-colored, and scentless and present high volumes of diluted nectar (Abrol, 2012;Dudash et al, 2011;Faegri & van der Pijl, 1979;Lipi nska et al, 2022), as reported in S. lanceolata, an orchid pollinated by three hummingbird species (Singer & Sazima, 2000). Nevertheless, recent evidence shows hummingbirds pollinating and feeding on "atypical" flowers that provide significant support for their residency and long-distant migration (Maruyama et al, 2013;Waser et al, 2018).…”

The orchids of Megaméxico and their interactions with pollinators

“…Orchids are one of the most amazing and intriguing examples of pollinator interactions (Tremblay, 1992) and are among the most specialized plants with respect to their pollination (Schiestl and Schlüter, 2009;Phillips et al, 2009Phillips et al, , 2011Castro and Singer, 2019;Lipińska et al, 2022). It is estimated that about 60% of orchids interact with a single species of pollinator (Tremblay, 1992).…”

“…Ornithophilous orchids usually have a callus that partially closes the floral tube at the level of the anther and the stigma (van Der Pijl and Dodson, 1966). The pollen sacs of most orchids are yellow, but this yellow would produce a high visual contrast with the color of the bill and hummingbirds would be stimulated to clean their bills, implying crossbreeding failure in orchids (Lipińska et al, 2022). That is why, to avoid detection, a large part of the orchids pollinated by hummingbirds evolved to have a dark pollinarium (Dressler, 1971).…”