Honest floral signalling traits vary across and within populations in an insect-pollinated plant

1. In flowering plants that produce concealed rewards, pollinator foraging preferences may select for floral advertisement traits that are correlated with rewards. To date, studies have not focused on the potential for honest signals to vary across populations, which could occur due to differences in pollinator communities or plant mating system. 2. We tested for variation in honest signals across and within populations and mating systems in Arabis alpina, a broadly distributed arctic-alpine perennial herb that is visited by a variable community of insects. In a greenhouse common garden, we tested for correlations between corolla area, floral scent and nectar volume in 29 populations. In 12 field populations, we examined variation in pollen limitation and corolla area. 3. Across and within populations and mating systems, larger flowers generally produced more nectar. Total scent emission was not correlated with nectar production, but two compounds-phenylacetaldehyde and benzyl alcohol-may be honest signals in some populations. Corolla area was correlated with pollen limitation only across populations. 4. Our results suggest that honest signals may be similar across populations but may not result from contemporary direct selection on floral advertisements.

Automated summary

This study examined variation in honest signals across different populations and mating systems in Arabis alpina. The results suggest that larger flowers generally produce more nectar and corolla area may be correlated with pollen limitation across populations. However, total scent emission is not correlated with nectar production and two specific compounds may act as honest signals in some populations.