Comparative reproductive biology and pollinator specificity among sympatricGomesa(Orchidaceae: Oncidiinae)

Abstract

The incredible pollination mechanisms displayed by orchid flowers has inspired biologists over the centuries. Based on the intriguing flower structures, the relationship among orchid species and their pollinators has been frequently regarded as very specialised. Given that visits on flowers pollinated by oil-collecting bees are regularly rare, and in Oncidiinae the flowers frequently attractexclusively species that act as effective pollinators, the comparative reproductive biology and pollinator specificity of two sympatric Gomesa (G. varicosa and G. montana; Oncidiinae) were analysedbased on records of floral morphology, production of floral rewards, pollinators and pollination mechanisms. Furthermore, experimental pollinations were carried out in order to examine the breeding systems. The results have show that in the studied population, both Gomesa are visited by several bee species, but these orchids present a specific pollination system.Pollinaria are deposited on the head of Centridini (G. varicosa and G. montana) and Epicharitini (G. varicosa) bees when landed on the central callus of the labellumto collect lipoidal substances produced by glandular elaiophores on lateral lobes of the labellum. Both species are dependent on a biotic pollen vector to set fruits. Gomesamontana is completely self-incompatible, while G. varicosa is partially self-compatible. Our results indicate that although the occurrence of self-sterile species seems to be common in Oncidiinae, in partially self-incompatible species, as is the case of G. varicosa, self-compatibility has been considered as an important factor favouring reproductive assurance in populations with low visitation frequencies, despite occurrence of inbreeding depression.

Elucidating cryptic sympatric speciation in terrestrial orchids

“…Stelis Sw., Polystachya Hook., Cleistes Rich.). Furthermore, parallelisms in flower characteristics involving distinct genera within Orchidaceae and between orchids and other plant families frequently occur (Vale et al, 2011;Pansarin et al, 2017).…”

A literature review of the pollination strategies and breeding systems in Oncidiinae orchids

“…Tremblay et al (2005) provided a list of self-incompatible species of orchids and the references to each study, in which are included species of the Oncidiinae genera Cyrtochilum, Gomesa, Grandiphyllum, Oncidium, Tolumnia and Trichocentrum. Self-incompatibility was demonstrated for most of the Oncidiinae species studied so far (East 1940;Ackerman & Montero-Oliver 1985;Warford 1992;Ackerman 1995;Ackerman et al 1997;Cingel 2001;Torretta et al 2011;Singer & Koehler 2003;Carvalho & Machado 2006;Damon & Cruz-López 2006;Pemberton 2008;Vale et al 2011;Ospina-Calderón et al 2015;Pansarin et al 2016;2018)…”

“…In several Oncidiinae species the elaiophores are most present in the callus and parts of the lateral lobes (Stpiczyńska et al 2007;. In a few cases, the elaiophores occur solely on the lateral lobes (Singer & Cocucci 1999b;Stpiczyńska et al 2007;Pansarin et al 2016).…”

“…In a recent study, Pansarin et al (2016) described the pollination mechanisms and pollinators of Gomesa varicosa and G. cf. blanchetii -misidentified as G. montana.…”

“…However, only Centris and Epicharis bees were able to pollinate them. The authors indicate that the elaiophores are present only in the lateral lobes of the lip, but the callus deceives the bees due to resemblance to stamens of some Malpighiaceae species, where Centridini bees collect pollen (Sigrist & Sazima 2004;Pansarin et al 2016).…”