The role of fetid olfactory signals in the shift to saprophilous fly pollination in Jaborosa (Solanaceae)

Abstract

Floral scents can act as important contributing factors to plant reproductive isolation mediated by pollinators. Plants may utilize fetid floral odors that specifically lure saprophilous flies seeking high protein content substrates, such as dung or carrion, to reach sexual maturity or as food sources for their larvae. In this work, we used baits with fetid volatile organic compounds (VOCs) that are produced during the decay of animal protein substrates (oligosulfides and a fermented bone-meal blend) to evaluate the role that olfactory signals may have played in the shift to saprophilous fly pollination in species of the nightshade genus Jaborosa Juss. Traps with the fetid baits attracted the same assemblage of saprophilous fly species that were recorded pollinating the flowers in different populations of the Andean-distributed species J. laciniata, whereas no flies were attracted to the control traps using mineral oil. Furthermore, the addition of oligosulfides to flowers of J. integrifolia, a lowland distributed species pollinated by nocturnal hawkmoths, resulted in the nearly immediate attraction of saprophilous flies (mainly Calliphoridae) to the flowers. These results provide evidence that the emission of fetid floral VOCs is sufficient to attract flies to flowers irrespective of other flower features and geographic region. This suggests that the evolutionary shift to saprophilous fly pollination in the genus Jaborosa could have been initiated with novel floral visitors attracted by the emission of fetid VOCs and then followed by major changes in other flower traits such as corolla color and morphology to optimize pollen export and placement.