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

Izabela Tałałaj,Olgierd Aleksandrowicz,Beata Ostrowiecka,Ada Wróblewska,Emilia Brzosko,Jarosław Kotowicz

doi:10.1007/s00606-019-01570-w

Izabela Tałałaj, Olgierd Aleksandrowicz + Show 4 more

Open Access

https://doi.org/10.1007/s00606-019-01570-w

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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.

Highlights

One of the major selective forces acting on the evolution of plant breeding systems and directly related with the adaptation of floral traits is avoidance of inbreeding (Barrett 2003; Charlesworth 2006; Brys and Jacquemyn 2016)
We found that caudicle reconfiguration within flowers of D. fuchsii began at the beginning of anthesis and was completed at the end
Dactylorhiza fuchsii is a deceptive orchid species with a generalist pollination syndrome that suffers from an unpredictable pollinator environment

Summary

Introduction

One of the major selective forces acting on the evolution of plant breeding systems and directly related with the adaptation of floral traits is avoidance of inbreeding (Barrett 2003; Charlesworth 2006; Brys and Jacquemyn 2016). The time and the mechanism of self-pollination remain the subject of debate in many plant taxa and offer opportunities to increase our knowledge of the evolution of mating systems and floral traits (Zhang and Li 2008; Freitas and Sazima 2009; Brys et al 2013; Bateman et al 2015; Suetsugu 2015; Love et al 2016; Yang et al 2018). The functional studies emphasizing the operation of facultative self-pollination mechanisms acting in autogamy demonstrate that this pollination mode usually occurs at the end of anthesis, after pollinators have failed

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