Different kinds of plant-animal interactions are ordinarily studied in isolation, yet considering the combined fitness effects of mutualistic and antagonistic interactions is essential to understanding plant character evolution. Functional, structural, or phylogenetic associations between attractive and defensive traits may be nonadaptive or result from correlational selection on sets of herbivoryand pollination-linked traits. Nonadditivity of fitness effects of mutualists and antagonists, a requisite for correlational selection, was experimentally tested in the field. We created experimental populations of the insect-pollinated perennial herb, Helleborus foetidus, at 16 different locations distributed among three regions in the Iberian Peninsula. Plants experienced one of four possible selective regimes generated by independently weakening the effects of pollinators and herbivores (flower and fruit predators) according to a two-way fully factorial design. Effects were assessed in terms of number of next-generation offspring recruited per mother plant under natural field conditions. Differences among I nvestigations on the different sorts of plant-animal interactions (e.g., herbivory, pollination, and seed dispersal) have traditionally progressed along separate lanes, the vast majority of studies focusing on just one kind of interaction and ignoring the possible significance of the others. This compartmentalization leads to an artificial oversimplification that may hinder our understanding of the ecology and evolution of plant-animal interactions. It is the composite result of the distinct interactions with all their animal counterparts that plants ''perceive'' in ecological and evolutionary time, and the combined action of different sets of counterparts (e.g., herbivores, pollinators, seed predators, and seed dispersers) exerts intricate ecological and evolutionary influences on plants extending beyond simple additivity of effects (1-5). The combined action of herbivores and pollinators may influence the ecology of plant reproduction and the evolution of pollination-related traits. Through direct or indirect effects on floral displays, flower characteristics, pollen quantity and quality, and plant attractiveness to pollinators, herbivores may ultimately modulate the nature, strength, and fitness consequences of the interaction between plants and their pollinators (6-15). Furthermore, herbivores and pollinators may exert conflicting selective pressures on particular plant traits, and certain characteristics of flowers and inflorescences may reflect compromise adaptations to mutualists and antagonists (5,12,(16)(17)(18)(19)(20).Another possible consequence of the concurrent interaction of plants with herbivores and pollinators that has begun to be recognized recently and the evolutionary origin of which is still poorly understood is the close functional, structural, or phylogenetic association sometimes existing between herbivory-and pollination-related traits. In Hypericum flowers, the same UV pigments play a de...

Through their effects on physicochemical features of floral nectar, nectar‐dwelling yeasts can alter pollinator behavior, but the effect of such changes on pollination success and plant reproduction is unknown. We present results of experiments testing the effects of nectar yeasts on foraging patterns of captive and free‐ranging bumble bees, and also on pollination success and fecundity of the early‐blooming, bumble bee‐pollinated Helleborus foetidus (Ranunculaceae). Under controlled experimental conditions, inexperienced Bombus terrestris workers responded positively to the presence of yeasts in artificial sugar solutions mimicking floral nectar by visiting proportionally more yeast‐containing artificial flowers. Free‐ranging bumble bees also preferred yeast‐containing nectar in the field. Experiments conducted in two different years consistently showed that natural and artificial nectars containing yeasts were more thoroughly removed than nectars without yeasts. Experimental yeast inoculation of the nectar of H. foetidus flowers was significantly associated with reductions in number of pollen tubes in the style, fruit set, seed set, and mass of individual seeds produced. These results provide the first direct evidence to date that nectar yeasts can modify pollinator foraging patterns, pollination success, and the quantity and quality of seeds produced by insect‐pollinated plants.

By analysing patterns of phenotypic integration and multivariate covariance structure of five metric floral traits in nine Iberian populations of bumblebee‐pollinated Helleborus foetidus (Ranunculaceae), this paper attempts to test the general hypothesis that pollinators enhance floral integration and selectively modify phenotypic correlations between functionally linked floral traits. The five floral traits examined exhibited significant phenotypic integration at all populations, and both the magnitude and the pattern of integration differed widely among populations. Variation in extent and pattern of integration was neither distance‐dependent nor significantly related to between‐population variation in taxonomical composition and morphological diversity of the pollinator assemblage. Patterns of floral integration were closer to expectations derived from consideration of developmental affinities between floral whorls than to expectations based on a pollinator‐mediated adaptive hypothesis. Taken together, results of this study suggest that between‐population differences in magnitude and pattern of floral integration in H. foetidus are probably best explained as a consequence of random genetic sampling in the characteristically small and ephemeral populations of this species, rather than reflecting the selective action of current pollinators.

Autonomous self-pollination may be considered as a mechanism enhancing plant reproductive success when plant access to pollen sources may limit seed production. We have studied the relationship between geographical patterns of variation in pollinator service to Helleborus foetidus and self-pollination ability in three widely spaced regions in the Iberian Peninsula. As could be expected from its early flowering period, pollinator visitation rates to both plants and flowers of H. foetidus were very low at all sites. Pollinator composition remained consistent among regions, but there was significant variation among regions in pollinator service. Despite the low visitation rates, fruit set did not appear to be pollen limited in any of the study areas, which may be explained by the long duration of flowers (up to 20 d). When pollinators were excluded experimentally, fruit set decreased significantly, but substantial levels of self-pollination occurred at all regions. Autonomous self-pollination levels were lowest in the two regions with lowest pollinator service and highest in the region with highest pollinator service. This disagreement between our results and the expectations derived from the reproductive assurance hypothesis may reflect a nonequilibrium situation of the northern H. foetidus populations in relation to their current pollinating environment.