Floral Scents of Deceptive Arum maculatum L. (Araceae) Shape a Taxonomically Diverse Visitor Community of Lesser Dung Flies (Sphaeroceridae) That Af

ABSTRACT

Most angiosperms are pollinated by animals, with insects being the most abundant and diverse pollinators. However, our knowledge about the diversity of Diptera as floral visitors and pollinators, and about their attraction to flowers, is still limited. Fly‐deceptive plant species, such as Arum maculatum , are ideal model systems to explore these interactions, as their floral scents often mimic (parts of) the ecological niches associated with the dipteran life cycle (e.g., mating, breeding). In this study, we investigated the species and sex identity of lesser dung flies (Sphaeroceridae), the second most abundant dipteran floral visitor family of A. maculatum after Psychodidae, across 10 populations of this plant species north and south of the Alps. Using previously published data on floral scent and fruit set, we also tested in a single southern A. maculatum population, where psychodids were limited and sphaerocerids abundant visitors, whether the abundance of the two predominant fly species, Spelobia clunipes and S. cambrica (and their sexes), correlates with inter‐individual differences in floral scent compounds and fruit set. Of the 20 sphaerocerid species identified across all populations, nine are newly reported as floral visitors of A. maculatum , and two represent new country‐specific records. The sex ratio of the flies was balanced within each region, and in the focal southern population the abundance of S. clunipes and S. cambrica correlated with the absolute amount of certain floral scent compounds, with some differences between the sexes of these species. The abundance of both sexes of only S. clunipes correlated with fruit set, suggesting that this species is a potential pollinator of A. maculatum . Overall, our data show that A. maculatum is visited by a high diversity of sphaerocerids both north and south of the Alps. This diversity is higher than for psychodid flies, the most abundant visitors of this plant species. Our data suggest that A. maculatum exhibits a mixed deceptive strategy.