Sexual attraction with pollination during feeding behaviour: implications for transitions between specialized...

Area of Science:

• Plant-pollinator interactions
• Evolutionary biology
• Orchidaceae reproductive strategies

Background:

• Sexual deception pollination in orchids is poorly understood due to highly modified flowers.
• Intermediate forms between sexual deception and ancestral strategies are difficult to study.

Purpose of the Study:

• To investigate a novel sexual deception pollination strategy in the orchid genus Caladenia.
• To understand the evolutionary pathways of deceptive pollination.

Main Methods:

• Observed pollinator behavior (male wasps) on Caladenia robinsonii.
• Determined the source of sexual attractants and their influence on pollinator behavior.
• Used GC-MS to analyze labellum surface chemistry.
• Extended observations to four additional Caladenia species.

Main Results:

• Pollinators were sexually attracted by semiochemicals from sepal tips in C. robinsonii.
• 57% of wasps attempted copulation with sepal tips; 27% fed from the labellum (pollen transfer).
• Similar pollination strategy observed in a distinct Caladenia clade.

Conclusions:

• A new orchid sexual deception strategy involves long-distance attraction and feeding-based pollination.
• This strategy is present in multiple Caladenia species, suggesting it's widespread.
• Findings provide insights into transitional pollination strategies from food-rewarding ancestors.