The missing stink: sulphur compounds can mediate a shift between fly and wasp pollination systems

Area of Science:

• Evolutionary Biology
• Plant Science
• Chemical Ecology

Background:

• Angiosperm radiation is often linked to pollinator shifts, driving floral diversification and reproductive isolation.
• Floral scent is a key trait in pollination, but its role in pollinator transitions is understudied.
• Sulphur compounds may mediate pollinator shifts in the genus Eucomis.

Purpose of the Study:

• Investigate the role of floral scent, specifically sulphur compounds, in pollinator transitions between carrion flies and pompilid wasps in Eucomis.
• Determine if floral scent chemistry, rather than color or nectar, drives pollinator discrimination.
• Understand how scent evolution contributes to reproductive isolation and diversification.

Main Methods:

• Gas chromatography-mass spectrometry (GC-MS) analysis of floral scent headspace extracts from four Eucomis species.
• Comparison of floral color perception in flies and wasps.
• Field experiments involving manipulation of floral scent bouquets.

Main Results:

• Closely related Eucomis species pollinated by flies or wasps exhibit similar floral morphology and nectar but distinct scent profiles.
• Floral color plays a minimal role in pollinator discrimination between these species.
• Experimental scent manipulation demonstrated that sulphur compounds (dimethyl disulphide, dimethyl trisulphide) influence pollinator shifts.

Conclusions:

• Floral scent, particularly the presence or absence of specific sulphur compounds, is a primary driver of pollinator shifts in Eucomis.
• Evolutionary changes in scent production can lead to reproductive isolation and diversification, independent of floral morphology or color.
• This study provides evidence for scent-driven speciation in flowering plants.