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 the 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 of 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.
Spontaneous caudicle reconfiguration in Dactylorhiza fuchsii : A new self‑pollination mechanism for Orchideae
Year: 2019
