Spontaneous caudicle reconfiguration in Dactylorhiza fuchsii: A new self-pollination mechanism for Orchideae

Abstract

Deceptive plants represent a strategy that promotes outcrossing and protects against facilitated selfing. However, deception does not eliminate the possibility of autonomous self-pollination when pollinators are scarce or absent. Spontaneous autogamy is widespread in Orchidaceae, but the scale, mechanism, time of appearance and effectiveness remain underestimated. Using field and laboratory observations and experiments, for the first time, we documented the possibility of autonomous self-pollination in the deceptive orchid Dactylorhiza fuchsii, which might occur through the previously unspecified mechanism in the tribe Orchideae of caudicle reconfiguration. Self-pollination occurred through the pollinarium twisting to the side and downwards, which was different than caudicle bending forward on the body of pollinators. Caudicle reconfiguration was continuously distributed during anthesis and was common in the studied populations. This mechanism was independent on the flower position in the inflorescence, but was sensitive to pollinator activity. (The frequency of caudicle reconfiguration increased when more pollinaria in the inflorescence were untouched.) This process was effective (self-pollination leading to autogamous fruits and seeds) only when a full caudicle rotation occurred and the pollinium touched the stigma. However, most caudicle reconfigurations were completed before the stigma was reached, resulting in less than 1% of autogamous pollination in the studied populations.

Occurrence and Prevention of Delayed Autonomous Selfing in Salvia umbratica (Lamiaceae)

“…In the Orchidaceae and subfamily Asclepiadaceae, for example, deposition of a single pollinium containing millions of pollen grains is more than sufficient to fertilize all ovules of a flower (Johnson and Edwards, 2000). However, even in these plant groups some species have mechanisms enabling selfing to occur should cross-pollination fail (Yamashiro and Maki, 2005;Tałałaj et al, 2019). Species such as S. umbratica, which produce one or a few ovules per flower, are unlikely to experience pollen-limitation following a single visit by a pollinator.…”

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

“…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). Dactylorhiza majalis blooms first, from the beginning of May to the beginning of June.…”

Pollination strategy of Gennaria diphylla (Orchidaceae) on the Canary Islands and on Madeira

“…Little research has been done on the pollination strategy of Gennaria diphylla. It is said to be predominantly autogamous (Claessens & Kleynen, 2011;Tałałaj & Skierczynski, 2015;Marrero et al, 2019;Tałałaj et al, 2019). Fernandes et al (2003) reported Noctuidae, Syrphidae and Tipulidae as (potential) pollinators.…”