Floral scents of a deceptive plant are hyperdiverse and under population-specific phenotypic selection

Abstract

Floral scent is a key mediator in plant-pollinator interactions; however, little is known to what extent intraspecific scent variation is shaped by phenotypic selection, with no information yet in deceptive plants. We recorded 291 scent compounds in deceptive moth fly-pollinated Arum maculatum from various populations north vs. south of the Alps, the highest number so far reported in a single plant species. Scent and fruit set differed between regions, and some, but not all differences in scent could be explained by differential phenotypic selection in northern vs. southern populations. Our study is the first to provide evidence that phenotypic selection is involved in shaping geographic patterns of floral scent in deceptive plants. The hyperdiverse scent of A. maculatum might result from the plant's imitation of various brood substrates of its pollinators.

Spatial and temporal heterogeneity in pollinator communities maintains within‐species floral odour variation

“…indole, p-cresol and 2-heptanone) were not correlated with species-specific pollinator attraction. A recent study by Gfrerer et al (2021) also found that variation in the aforementioned foetid-smelling VOCs were not among those which significantly influenced fruit sets in A. maculatum. Given that blends of indole, p-cresol and 2-heptanone are known to be attractive to Psychoda species (Kite et al 1998), these compounds appear to be generally attractive to all species.…”

“…Arum maculatum inflorescences (Fig. 1) are pollinated deceptively, by emitting complex VOC blends which are known to vary within and among populations in England (Kite 1995, Kite et al 1998, Diaz and Kite 2002, France (Chartier et al 2011(Chartier et al , 2013 and across the Alps (Gfrerer et al 2021). The floral odour of A. maculatum is similar to dung or decomposing organic matter (Lack and Diaz 1991), mimicking the natural brood sites of their main pollinators, the moth flies Psychoda phalaenoides and Psycha grisescens (Diptera: Psychodidae).…”