Learn More
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 based on their syndromes and that flowers often diverge without excluding one type of pollinator in favor of another. Despite(More)
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 optimal schedule of pollen presentation, based on the frequency of visits by pollinators, and the capacities(More)
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. Forty-one species present characters associated with hummingbird pollination, although some of these(More)
Interaction of pathogens with cells of the immune system results in activation of inflammatory gene expression. This response, although vital for immune defence, is frequently deleterious to the host due to the exaggerated production of inflammatory proteins. The scope of inflammatory responses reflects the activation state of signalling proteins upstream(More)
Plants that experience variation in pollinator visitation rates or fluctuations in weather conditions may be expected to have evolved homeostatic mechanisms that regulate their nectar offerings, thereby providing a more constant reward to the pollinators. A limited degree of such nectar homeostasis is reported here for Penstemon. First, nectar removal(More)
Speciation involves the formation of reproductive isolating mechanisms such as a difference in pollinators, incompatibility between pollen tubes and stylar tissue, hybrid seed abortion, or poor growth of hybrid seedlings. We studied reproductive isolating mechanisms in naturally sympatric populations of Penstemon spectabilis Thurber and Penstemon(More)
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, mostly due to grooming, pollen on bee bodies quickly becomes unavailable for transfer to stigmas, whereas pollen(More)
A multivariate search for pollination syndromes among penstemons. – Oikos 104: 345– 361. The seeming ubiquity of spatio-temporal variation in pollination regime suggests that flowers ought to be adapted to a wide range of pollinators, yet many comparative biologists perceive that in groups with complex flowers there is considerable specialization onto(More)
BACKGROUND Efforts to increase access to life-saving treatment, including antiretroviral therapy (ART), for people living with HIV/AIDS in resource-limited settings has been the growing focus of international efforts. One of the greatest challenges to scaling up will be the limited supply of adequately trained human resources for health, including doctors,(More)