Within-species floral odor variation is maintained by spatial and temporal heterogeneity in pollinator communities

Abstract

Floral odor is a complex trait that mediates many biotic interactions, including pollination. While high intraspecific floral odor variation appears to be common, the ecological and evolutionary drivers of this variation are often unclear. Here, we investigated the influence of spatially and temporally heterogeneous pollinator communities on floral odor variation in Arum maculatum (Araceae). Through Europe-wide field surveys, we identified high floral odor diversity and shifts in the dominant pollinator species within several A. maculatum populations compared to pollinator data from the same sites ten years ago. Using common-garden experiments, we further confirmed that inflorescences from native and foreign pollinator backgrounds were equally efficient at attracting local pollinators. The substantial within-population floral odor variation we observed may therefore be advantageous when facing temporally heterogeneous pollinator communities. We propose spatio-temporal heterogeneity in pollinators as one potential mechanism maintaining diverse floral odor bouquets in angiosperms.

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

“…Interestingly, we found a similar number of compounds in some individuals (up to 152 VOCs; median of 102; Fig. 2) as overall detected previously [53][54][55][56][57][58]84 . With the exception of two studies 56,58 , each sharing one of our sampled populations (JOS and MON, respectively), all previous studies sampled scents in other populations across Europe [53][54][55]57 .…”

“…et al,unpubl. , but also coincides with a weak genetic (AFLP) subdivision of A. maculatum across this geographic barrier 59 . Previous studies in A. maculatum also found population effects in scent composition 55,57,58 ; however, our study is the first to demonstrate such population differentiation in scent across the Alps. Intraspecific variation in floral scent among populations and regions has also been reported for other plant species 14,15,34,37,67 .…”

“…The number of volatiles detected across the 233 individuals (11 populations) of A. maculatum (291 VOCs) is five to ten times higher than previously reported for this species (18-61, and 143 VOCs in total [53][54][55][56][57][58]84 ). This discrepancy cannot be explained by differences in sample size, as a similar number of individuals were surveyed in those previous studies (n = 222 in total, representing 23 populations).…”

“…The main pollinators are two moth flies (Psychoda phalaenoides L. and P. grisescens TONN., Psychodidae) that are attracted by the strong, dunglike inflorescence scent of A. maculatum while looking for oviposition sites and/or mating partners [50][51][52] . Previous analyses have shown that the scent profile of A. maculatum consists of up to 60 compounds, also differing among populations [53][54][55][56][57][58] . At least in part, this scent variation appears to reflect variation in the pollinator assemblages of A. maculatum across its distribution range 55,58 .…”

“…Previous analyses have shown that the scent profile of A. maculatum consists of up to 60 compounds, also differing among populations [53][54][55][56][57][58] . At least in part, this scent variation appears to reflect variation in the pollinator assemblages of A. maculatum across its distribution range 55,58 . In Central and much of Western Europe, high abundances of a single Psychoda species and sex (females of P. phalaenoides) were found 52 .…”