Abstract
Flowering plants often use chemical signals to attract their pollinators, and compounds that elicit attraction are known for several groups of pollinators. For other pollinators such as gall midges, however, compounds responsible for their attraction to flowers are largely unknown. Here, we describe the pollination biology of Anthurium acutangulum, a Neotropical aroid species found to be attractive to gall midges. We collected and analyzed its floral scent by dynamic headspace collections and gas chromatography coupled to mass spectrometry, and identified compounds responsible for pollinator attraction. The inflorescences were almost exclusively visited by gall midges (females; Cecidomyiidae: Cecidomyiinae) and released a strong scent reminiscent of freshly cut cucumber, mainly (5S,7S)-trans-conophthorin, (E2,Z6)-2,6-nonadienal, and cis-conophthorin. Behavioral assays with the two most abundant compounds identified (E2,Z6)-2,6-nonadienal as being highly attractive to the female gall midge pollinators, whereas (5S,7S)-trans-conophthorin was not attractive. Overall, we introduce a new specialized gall midge pollination system and identify the chemical mediating communication between the pollinators and their host plants.
Highlights
Many vertebrate and non-vertebrate pollinators are attracted to their host plants by, among other cues, floral scents (Raguso 2008)
Our study showed that inflorescences of Anthurium acutangulum release a strong cucumber-like scent at night and are highly attractive to female gall midge pollinators at this period of the day
The spiroacetal (5S,7S)-trans-conophthorin and (E2,Z6)-2,6-nonadienal were overall the most abundant compounds of the floral scent blend, of which (E2,Z6)-2,6-nonadienal resembled the scent of freshly cut cucumbers
Summary
Many vertebrate and non-vertebrate pollinators are attracted to their host plants by, among other cues, floral scents (Raguso 2008). These volatile organic compounds are highly diverse, with more than 2000 components described so far (El-Sayed 2021; Knudsen et al 2006). Plants mainly pollinated or co-pollinated by gall midges occur in various lineages, such as Schisandraceae (e.g., Illicium spp.), Malvaceae (e.g., Theobroma cacao), and Araceae (Young 1985, 1986, Luo et al 2010; Schwerdtfeger et al 2002). In Araceae, several species of Anthurium are pollinated by these insects (Schwerdtfeger et al 2002). Floral scents have not been studied for any gall midge pollinated Anthurium species so far, and it is currently unclear how these interacting organisms communicate
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