Pollinator Competition as a Driver of Floral Divergence: An Experimental Test.

Optimal foraging models of floral divergence predict that competition between two different types of pollinators will result in partitioning, increased assortative mating, and divergence of two floral phenotypes. We tested these predictions in a tropical plant-pollinator system using sexes of purple-throated carib hummingbirds (Anthracothorax jugularis) as the pollinators, red and yellow inflorescence morphs of Heliconia caribaea as the plants, and fluorescent dyes as pollen analogs in an enclosed outdoor garden. When foraging alone, males exhibited a significant preference for the yellow morph of H. caribaea, whereas females exhibited no preference. In competition, males maintained their preference for the yellow morph and through aggression caused females to over-visit the red morph, resulting in resource partitioning. Competition significantly increased within-morph dye transfer (assortative mating) relative to non-competitive environments. Competition and partitioning of color morphs by sexes of purple-throated caribs also resulted in selection for floral divergence as measured by dye deposition on stigmas. Red and yellow morphs did not differ significantly in dye deposition in the competition trials, but differences in dye deposition and preferences for morphs when sexes of purple-throated caribs foraged alone implied fixation of one or the other color morph in the absence of competition. Competition also resulted in selection for divergence in corolla length, with the red morph experiencing directional selection for longer corollas and the yellow morph experiencing stabilizing selection on corolla length. Our results thus support predictions of foraging models of floral divergence and indicate that pollinator competition is a viable mechanism for divergence in floral traits of plants.

Surrogate and patient discrepancy regarding consent for critical care research.

OBJECTIVE: Critically ill patients frequently display impaired decision-making capacity due to their underlying illness and the use of sedating medications. Healthcare providers often rely on surrogates to make decisions for medical care and participation in clinical research. However, the accuracy of surrogate decisions for a variety of critical care research studies is poorly understood. DESIGN: Cross-sectional observational study. SETTING: Academic medical center. PATIENTS: Medical intensive care unit patients and their designated surrogates. INTERVENTION: Patients were asked whether they would consent to participate in hypothetical research studies of increasing complexity, and surrogates independently indicated whether they would consent to enroll the patient in the same scenarios. RESULTS: Overall, 69 medical intensive care unit patients were enrolled into the study. The majority of surrogates were either the spouse (58%) or parent (22%) of the patient. The percentage of patients that would agree to participate in a research study and the percentage of surrogates that would agree to have the patient enrolled into a research study both declined as the risk of the study increased (p < .001 for both analyses). In addition, the overall discrepancy, the false-negative rates, and the false-positive rates between patient and surrogates were greater as the risk of the study increased (p < .001, p < .001, and p = .049, respectively). κ values for all seven scenarios demonstrated less-than-moderate agreement (range 0.03-0.41). CONCLUSIONS: There are significant discrepancies in the willingness to participate in various types of clinical research proposals between critically ill patients and their surrogate decision makers. The results of this study raise concerns about the use of surrogate consent for inclusion of critically ill patients into research protocols.