WILSON, P.*; CASTELLANOS, M.C.; THOMSON, J.D.; California State Univ. Northridge: Pollen Presentation by Bee- and Bird-Adapted Flowers

Penstemon flowers are pleiomorphically bee-pollinated, but there has been repeated convergence toward hummingbird pollination. Hummingbirds do not groom as much as bees and have flatter pollen carryover curves. This led us to hypothesize that bird-pollinated species ought to have less restrictive pollen presentation than bee-pollinated species. We compared how widely anthers opened, and indeed bird-pollinated species often had anthers that presented pollen more on platters than their closest bee-pollinated relatives, which often had anthers that were canoe-shaped or dehisced by more narrow slits. This was easily seen when the anthers were in their terminally dehiscent state, but for a subset of species we confirmed that the terminally dehiscent state reflects the time course of pollen removability with small pieces of velvet. These results are not complicated by differences in pollen production. Close relatives of differing pollination syndrome do not differ significantly in how much pollen they make. Although we found a clear difference in pollen presentation when comparing close relatives in a paired design, phylogenetic autocorrelation is also evident in that the various phylogenetic groups within penstemon differ in anther morphology in a way that would obscure the bird/bee difference if phylogeny were not taken into account.