Extensive pollinator sharing does not promote character displacement in two orchid congeners

Pollinator sharing between close relatives can be costly, which can promote pollination niche partitioning and floral divergence. This should be reflected by a higher species divergence in sympatry than in allopatry.

We tested this hypothesis in two orchid congeners with overlapping distributions and flowering times. We characterized floral traits and pollination niches and quantified pollen limitation in 15 pure and mixed populations, and we measured phenotypic selection on floral traits and performed controlled crosses in one mixed site.

Most floral traits differed between species, yet pollinator sharing was extensive. Only the timing of scent emission diverged more in mixed than in pure sites, and this was not mirrored by the timing of pollinator visitation. We did not detect divergent selection on floral traits. Seed production was pollen limited in most populations, but not more severely in mixed than in pure sites. Interspecific crosses produced the same or a higher proporti...