Floral Scent Profiles and Visits of Cordyla murina (Mycetophilidae) to Asarum curvistigma (Aristolochiaceae)

Abstract

Species in sect. Heterotropa of the genus Asarum (Aristolochiaceae) exhibit remarkable diversity in their floral traits, which is thought to have arisen from adaptive radiation across the Japanese archipelago. This diversification is likely to have been driven by pollinator interactions, but so far the pollination systems have been investigated for only a handful of Heterotropa species. Cordyla murina (Mycetophilidae) was previously identified as the pollinator of Asarum tamaense, in the Asperum clade, from which it has been suggested that Heterotropa species may exhibit some form of mushroom mimicry. This study investigated the pollination biology of Asarum curvistigma, also in the Asperum clade, using time-lapse photography and field collection of insects followed by identification with DNA barcoding. Cordyla murina was identified as the principal pollinator, and the eggs found inside the flowers provide evidence for oviposition-site mimicry. We also analysed the floral scent profile of A. curvistigma and found that the dominant volatiles are dimethyl sulphide and 2,3-butanediol. These are similar but not identical to the major floral volatiles of sister species A. tamaense, also pollinated by C. murina, suggesting that the mechanism for attracting pollinators by floral mimicry may be more complex than previously thought.