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 . . .

In certain angiosperm genera, closely related species have diverged from one another to converge on different pollination syndromes, whereas species with intermediate phenotypes are rare or absent. Convergent conformity to syndromes implies the existe . . .

In the clade of Penstemon and segregate genera, pollination syndromes are well defined among the 284 species. Most display combinations of floral characters associated with pollination by Hymenoptera, the ancestral mode of pollination for this clade. . . .

Flowers are often visited by many species of animals. These sometimes differ in size, behavior, and other characteristics that translate into differences in their effectiveness as pollinators. The differences may be manifest in their effect on reprodu . . .

Male-male competition in plants is thought to exert selection on flower morphology and on the temporal presentation of pollen. Theory suggests that a plant’s pollen dosing strategy should evolve to match the abundance and pollen transfer efficiency of . . .

Male-male competition in plants is thought to exert selection on flower morphology and on the temporal presentation of pollen. Theory suggests that a plant's pollen dosing strategy should evolve to match the abundance and pollen transfer efficiency of . . .

Floral evolution has often been associated with differences in pollination syndromes. Recently, this conceptual structure has been criticized on the grounds that flowers attract a broader spectrum of visitors than one might expect of their syndromes, . . .

For over a decade, Bateman's principle has been used to argue that the showy petals and sweet nectar of flowers are evolutionarily more male than female-that they are adaptations principally for promoting the export of pollen rather than the setting o . . .

In the clade of Penstemon and segregate genera, pollination syndromes are well defined among the 284 species. Most display combinations of floral characters associated with pollination by Hymenoptera, the ancestral mode of pollination for this clade. . . .