Dual deceit in pseudopollen-producingMaxillaria s.s.(Orchidaceae: Maxillariinae)

Abstract

Most species of Maxillaria s.l. are rewardless and employ deceit pollination strategies. Some, however, reward pollinators with nectar, resins or pseudopollen (farina). Pseudopollen is yellow–white in colour and is usually composed of food‐laden cells formed by detachment or fragmentation of moniliform labellar hairs. As the pollen of epidendroid orchids is bound in pollinia, it is not accessible to pollen‐foraging insects. It has thus been proposed that potential insect pollinators, deceived by the resemblance of pseudopollen to the nutritious, powdery pollen of other angiosperms, gather it and feed it to their larvae. Mimicry here, however, may not be as simple as supposed. This study compares the pseudopollen of selected species of Maxillaria s.s., namely Maxillaria grandis, M. grayi, M. huebschii and M. roseola (all members of the M. grandiflora complex), M. lepidota (M. arachnites complex) and M. buchtienii (M. splendens complex), using light microscopy (LM), fluorescence microscopy, histochemistry, scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and comments on its evolutionary significance. Some members of the M. grandiflora complex produce pseudopollen‐forming hairs, the cells of which contain potential food rewards in the form of an intravacuolar protein body and abundant starch grains. Others produce pseudopollen that is devoid of protein bodies, but contains abundant starch, and others produce pseudopollen that lacks protein bodies and contains negligible amounts of starch. Maxillaria lepidota and M. buchtienii fall into the second and third categories, respectively. Lipid droplets, when present, usually occur in minute quantities. These observations suggest that a dual deceit strategy operates in some species, as pseudopollen not only mimics powdery pollen, but in many instances lacks a food reward. Cryptic evolutionary changes to pseudopollen content may confer biological advantage by reducing expenditure of material and energy in food reward production, while trichome micromorphology simultaneously encourages pollinator visits. The presence or absence of particular foods may, in turn, result in pollinator selection. Conversely, in the absence of food rewards, insect behaviour is unlikely to be reinforced, possibly to the detriment of the orchid. © 2013 The Linnean Society of London, Botanical Journal of the Linnean Society, 2013, 173, 744–763.

Pollen and stamen mimicry: the alpine flora as a case study

“…Consequently, only nectarless orchids that offer pollen in the form of uneatable and uncollectable pollinaria are pollen-and stamen-mimicking species-with few exceptions (Sanguinetti et al 2012). It is noteworthy that some orchids offer pollen surrogates (Beck von Mannagetta andLerchenau 1912, 1914;Davies et al 2013).…”

Orchid conservation: how can we meet the challenges in the twenty-first century?

“…Micheneau et al 2006 ; van der Niet et al 2015 ), crickets (Micheneau et al 2010 ), fungus gnats (Phillips et al 2014 ) and biting midges (Bogarín et al 2018 ) as specialized pollinators. Many orchid species attract pollinators by deceipt, with the forms of deception including food deception, brood-site imitation, shelter imitation, rendezvous attraction and sexual deception (Jersáková et al 2006 ), and recent discoveries of dual deceipt (pseudopollen lacking food value; Davies et al 2013 ), carrion mimicry (van der Niet et al 2011 ) and production of fruitfly aggregation pheromones (Karremans et al 2015 ) demonstrate that we are far from understanding the full complexities of orchid pollination.…”

Labellar secretion and secretory trichomes of Rhetinantha cerifera (Barb. Rodr.) M.A.Blanco (Orchidaceae, Maxillariinae): micromorphology and composition

“…Orchids have a widely diverse and complex combination of rewards, visual and olfactory appealing and tactile stimuli, all involved in the attraction of animal visitors (Knudsen et al 2006;Fay 2010;Vereecken et al 2011;Davies et al 2013). Reports of investigations about the floral glands diversity of Orchidaceae have emphasized the presence of osmophores, nectaries, and elaiophores on the labellum (Davies et al 2005(Davies et al , 2014Davies 2006, 2008;Stpiczynska et al 2007Stpiczynska et al , 2015Pansarin et al 2009;Pacek et al 2012;Francisco and Ascensão 2013;Nunes et al 2013;Borba et al 2014;Pansarin and Pansarin 2014;Kowalkowska et al 2015).…”