Pollen presentation theory (PPT) allows for a re?examination of some classic themes in pollination biology. Here, we outline its implications in the context of bee? and bird?adapted species of Penstemon and Keckiella (Scrophulariaceae). PPT models the . . .

Floral phenotypes may be as much the result of selection for avoidance of some animal visitors as selection for improving the interaction with better pollinators. When specializing on hummingbird‐pollination, Penstemon flowers may have evolved to impr . . .

Certain floral characteristics are associated with specific pollinators. Hummingbird-pollinated flowers are usually red, lack a landing platform, lack nectar guides, and contain a high amount of dilute sucrose-rich nectar. Here we test hypotheses conc . . .

The Juan Fernandez Firecrown Sephanoides fernandensis is an endangered endemic hummingbird that inhabits the Juan Fernandez Islands, 667 km off the coast of Chile. Its population has decreased from several thousand in the early part of this century to . . .

We compared pollen removal and deposition by hummingbirds and bumblebees visiting bird-syndrome Penstemon barbatus and bee-syndrome P. strictus flowers. One model for evolutionary shifts from bee pollination to bird pollination has assumed that, mostl . . .