Sexually deceptive orchids with distinct flower morphologies elicit different behaviours from a shared pollinator

Area of Science:

• Plant-insect interactions
• Pollination biology
• Orchidaceae reproductive strategies

Background:

• Sexual deception is a specialized pollination strategy in angiosperms.
• Co-occurring plant species often share pollinators, potentially using different insect species.
• Investigating pollinator sharing between morphologically distinct orchids is crucial for understanding reproductive isolation.

Purpose of the Study:

• To determine if Caladenia cardiochila and C. lowanensis share the same thynnine wasp pollinator.
• To analyze the influence of floral traits on pollinator behavior.
• To assess the risk of hybridization between these two orchid species.

Main Methods:

• DNA barcoding was used to identify shared pollinators.
• Pollinator behavior was quantified, and floral dissections identified attractant release sites.
• GC-MS, hand crosses, and population monitoring assessed chemical attractants, seed viability, and pollination success.

Main Results:

• Both C. cardiochila and C. lowanensis utilize sexual deception of Phymatothynnus aff. nitidus wasps.
• Attractant location differs: labellum in C. cardiochila, sepal tips in C. lowanensis, with varying pollinator interaction.
• Despite differences, both species showed comparable pollination success and pollen transfer efficiency; hybrid seed viability is high.

Conclusions:

• Orchid sexual deception exhibits flexibility in attractant location and floral morphology while using the same pollinator.
• Overlapping distributions and viable hybrid seed create a significant hybridization risk.
• Conservation management for C. lowanensis must consider pollinator sharing and hybridization potential.