Pollinators and visitors of the generalized food-deceptive orchid Dactylorhiza majalis in North-Eastern Poland

Abstract

Pollinator foraging behavior plays a key role in breeding and therefore affects the evolution of the orchid reproductive strategy. Food-deceptive orchids usually implement a generalized plant pollination strategy and a relatively diverse group of pollinators visit them. Dactylorhiza majalis is a food-deceptive, early-flowering orchid that relies on insect-mediated pollination. This study's objectives were to identify D. majalis' pollinators and flower visitors and their foraging behaviors on D. majalis inflorescences. We also assessed the bending movement time to determine the relationship between bending time and the duration of pollinators' visits. To assess pollination efficiency, we measured the spur length of D. majalis flowers, which is expected to affect the mechanical fit to pollinators/Bpotential^pollinators. The arthropod fauna were investigated to examine the availability of Bpotential^pollinators in populations. We identified Apis mellifera as this orchid's main pollinator and confirmed that few of the flower visitors belonged to Diptera (12 individuals, 9 taxa), Hymenoptera (3 individuals, 3 taxa), or Coleoptera (2 individuals, 2 taxa) in our dataset, which was collected over a 2-year period and includes 360 h of video. The arthropods were collected by a sweep net in D. majalis populations and there were fewer Hymenoptera (2.9-23.2%) and Coleoptera (4.4-23.8%) visitors but more Diptera (23.3-58.6%) visitors. We found that A. mellifera foraged in different ways on D. majalis inflorescences, thereby resulting in cross-pollination and/or geitonogamy; however, the bending time data supported the hypothesis about promoting cross-pollination while decreasing self-pollination, but these data do not exclude the possibility of geitonogamy.

What are the drivers of female success in food‐deceptive orchids?

“…Indeed, the lack of specialization in pollinators is thought to be the major constraint on mimicry (Schiestl & Johnson, 2013). In the case of three studied Dactylorhiza, we observed different groups of pollinators (Ostrowiecka et al, 2019;A. Wróblewska, personal observation).…”

“…Pollination occurs in different taxonomic groups of insects (Hymenoptera, Diptera, and/or Coleoptera, Ostrowiecka et al., 2019; Wróblewska et al., 2019), which can promote cross‐pollination and/or geitonogamy (Hedrén & Nordström, 2009; Ostrowiecka et al., 2019). Moreover, the mechanism of spontaneous caudicle reconfiguration in three Dactylorhiza taxa exists, but results in less than 1% autogamous pollination in the studied populations (Tałałaj et al., 2019; Wróblewska et al., 2024).…”

Pollinaria Reconfiguration Mechanism of Widespread Euro-Mediterranean Orchids: The Effects of Increasing Air Temperature

“…The delayed pollinaria bending mechanism limited the events of geitonogamy, and the average rate of self-pollination tended to be higher in the rewarding orchids than in the deceptive orchids [ 32 ]. In any case, the data from the literature show that the bending mechanism limits but does not completely exclude the possibility of geitonogamy in deceptive orchids [ 33 , 34 , 35 ].…”

Analyses of sexual reproductive traits in Dactylorhiza majalis: a case study from East Germany

“…For comparison, recent investigations previously demonstrated that deceptive orchid species in Central Europe, depending on naive pollinators because not offering nectar, can increase their reproductive success by higher seed numbers in the face of a pollinator limitation (Sonkoly et al 2015). For an exact taxonomic identification of D. majalis pollinators and the floral chemical compounds attracting such insects, see Ostrowiecka et al (2019) and , respectively, and the literature cited therein.…”

“…III) The reduced embryo viabilitya trait likely attributable to possible inbreedingis also known to be an intrinsic genetic burden of allotetraploids hybrids under the condition of heterogeneic chromosomal recombination as pointed out at the start of the discussion. IV) Selfing, an extreme form of inbreeding, is unlikely due to the specific blossom morphology of D. majalis (Schoenichen 1940, experimentally shown by Vojtko et al 2015) and pollinaria bending (discussed in Ostrowiecka et al 2019). V) An elevated level of gene flow, counteracting possible inbreeding, will be expected with regard to the fact that the embryo is embedded into a surrounding scaffold of collapsed cork-like cells.…”