Mating systems in the Pleurothallidinae (Orchidaceae): evolutionary and systematic implications

Abstract

aBstract. We developed a project addressing the determination of the reproductive system through experimental pollinations of species in the major genera representing all major lineages of Pleurothallidinae in order to determine occurrence of self-incompatibility in the subtribe, in which group it has possibly appeared for the first time, and how many times it has evolved. Additionally we surveyed the floral biology of species of Octomeria, a genus with morphological characters typical of bee-pollinated flowers that was previously regarded as mellitophilous. At the moment, all but one of the species studied in selected large genera of the major lineages (Acianthera, Anathallis, Masdevallia, Octomeria, Specklinia, and Stelis) are self-incompatible. The species studied may possess complete, strong or partial self-incompatibility. We found two different sites where self-incompatibility reactions occur, the stigma and the stylar channel, and both sites were not found in the same genus except for Anathallis. In Anathallis, the two groups that differ morphologically (formerly Pleurothallis subgen. Specklinia sect. Muscosae and sect. Acuminatae) exhibit different sites of reaction. Flowers of Octomeria species produce nectar and are pollinated by both male and female Sciaridae flies, and the populations have high genetic variability similar to that found in Acianthera species. Our results indicate that self-incompatibility is a generalized widespread feature of the myophilous clade of the Pleurothallidinae and possibly evolved early in the subtribe, enabling the maintenance of high levels of genetic variability in the populations of each species in spite of pollinator behavior. Moreover, although sapromyophily (pollination by female flies by deceit) is much more common in the group, myophily s.s. (pollination by anthophilous flies seeking nectar) apparently evolved first from the plesiomorphic mellitophilous condition. In addition to the morphological synapomorphy uniting the members of the former circumscription of the subtribe (an articulation between the ovary and pedicel), our results also point to the occurrence of two biological synapomorphies in the group -self-incompatibility and myophily. Based on these differences, we suggest the splitting of Pleurothallidinae as presently recognized into two subtribes: one composed of the large, self-incompatible, myophilous clade and the other of the small, self-compatible, ornithophilous clade.rEsuMEn. Desarrollamos un proyecto dirigido a determinar, a través de polinización experimental, la autoincompatibilidad de los géneros representativos de los linajes más importantes de Pleurothallidinae, buscando el grupo donde posiblemente apareció por primera vez y cuántas veces ha ocurrido desde entonces. Adicionalmente estudiamos la biología floral de algunas especies de Octomeria, un género con características típicas de plantas con flores polinizadas por abejas, que previamente han sido conocidas como melitófilas. Hasta el momento, todas excepto una, de las especies estudiadas...

Plastid phylogenomics resolves ambiguous relationships within the orchid family and provides a solid timeframe for biogeography and macroevolution

“…25,000 species and ~800 genera 1,2 are one of two of the most diverse and widely distributed flowering plant families on Earth and have captivated the attention of scientists for centuries 3 . The family has a striking morphological and ecological diversity and evolved complicated interactions with fungi, animal and other plants 4,5 and a diverse array of sexual systems [6][7][8] . Numerous efforts have been made to understand the natural history, evolution and phylogenetic relationships within the family 2,7,[9][10][11][12][13] .…”

The sweet path of Hansel and Gretel: pollination system of Masdevallia hortensis Luer & R. Escobar (Orchidaceae: Pleurothallidinae) in a cloud montane forest of the Cordillera Occidental, in Colombia

“…Shrestha et al 2020, and information from nearly 2900 orchid species arround the world showed that pollinator attraction is mainly based on rewards i.e. 54%: Ackerman et al 2023) the idea of rewardlessness as the most common pollination strategy in orchids is widespread (Ackerman 1986;Borba et al 2011;Johnson and Schiestl 2016;Schiestl 2005). However, it is necessary to increase our knowledge of orchids' pollination systems to understand which strategies may be involved in attracting and keeping visitors.…”

“…With around 5,100 species, the Neotropical subtribe Pleurothallidinae accounts for about 20% of all described orchids (Karremans 2016), and Colombia harbors an exceptional diversity in this group of plants (Karremans et al 2023) with many species under threat (70% of the Colombian threatened plants are pleurothallids: Ministerio de Ambiente y Desarrollo Sostenible 2020); this makes it urgent to gather basic information about their natural history including reproductive strategies to take in account in conservation actions. Recent assessments of the oral biology and mating systems of pleurothallids have unveiled key synapomorphies that correlate with their oral and/or reproductive traits (Borba et al 2011; Cardoso-Gustavson et al 2017; Karremans et al 2015). Their pollination is mainly attributed to ies (Diptera) and thus often characterized within the frame of 'myiophily' (Borba et al 2011), a generalistic term that does not adequately encompass the functional ecology diversity of the numerous dipteran taxa as well as the high diversity of plant strategies to attract such a diversity of ies (e.g.…”

“…Recent assessments of the oral biology and mating systems of pleurothallids have unveiled key synapomorphies that correlate with their oral and/or reproductive traits (Borba et al 2011; Cardoso-Gustavson et al 2017; Karremans et al 2015). Their pollination is mainly attributed to ies (Diptera) and thus often characterized within the frame of 'myiophily' (Borba et al 2011), a generalistic term that does not adequately encompass the functional ecology diversity of the numerous dipteran taxa as well as the high diversity of plant strategies to attract such a diversity of ies (e.g. Oelschlägel et al 2015; Raguso 2020), including different groups of ies pollinating pleurothallids (i.e.…”