THERE IS MORE TO POLLINATOR-MEDIATED SELECTION THAN POLLEN LIMITATION.

Spatial variation in pollinator-mediated selection (Δ βpoll) is a major driver of floral diversification, but we lack a quantitative understanding of its link to pollen limitation (PL) and net selection on floral traits. For 2-5 years, we quantified Δ βpoll on floral traits in two populations each of two orchid species differing in PL. In both species, spatiotemporal variation in Δ βpoll explained much of the variation in net selection. Selection was consistently stronger and the proportion that was pollinator-mediated was higher in the severely pollen-limited deceptive species than in the rewarding species. Within species, variation in PL could not explain variation in Δ βpoll for any trait, indicating that factors influencing the functional relationship between trait variation and pollination success govern a major part of the observed variation in Δ βpoll. Separating the effects of variation in mean interaction intensity and in the functional significance of traits will be necessary to understand spatiotemporal variation in selection exerted by the biotic environment. [ABSTRACT FROM AUTHOR]