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Background: Heterostyly is a genetic polymorphism characterized by a system of sporophyte auto-incompatibility in which the plant populations show two (distyly) or three (tristyly) floral morphs. This reproductive system is known as a promoter of cross-pollination, assuming similar reproductive success between morphs. Hyphothesis: For this assumption to take place, the pollinators must respond in a similar manner to attraction floral traits in both morphs, maintaining a symmetric flow of pollen. We hypothesize that floral damage by antagonists should correspond to similarities or differences in atractiveness among floral morphs. Studied species: We tested this hypothesis in the distylous shrub Bouvardia ternifolia (Rubiaceae). Methods: we evaluated the magnitude of the nectar theft, foliar herbivory, and seed predation by assessing individual plants of both floral morphs throughout their flowering period (June-July 2015) under natural conditions. At the end of the flowering season, we quantified fruit and seed production. Results: The intensity of the herbivore and nectar thieves in this distylous population is similar between morphs, as well as the size of their floral displays. The number of seeds and fruits produced was also similar between morphs. Conclusions: Our study showed that selection pressures imposed by antagonists were similar to both floral morphs in the studied population of Bouvardia ternifolia.

Nectar robbing occurs when floral visitors remove floral nectar through floral damage and usually without providing pollination in return. Even though nectar robbing may have negative, neutral or even positive effects on plant fitness, few studies have investigated temporal and spatial variation in robbing rate and their consequences, particularly in the tropics. In this study, robbing levels were estimated during 3 years in four populations of Salvia gesneriflora, a hummingbird-pollinated shrub endemic to central Mexico that is mainly robbed by birds, carpenter bees and bumblebees. The effect of robbing on nectar availability, flower longevity and on visitation rate by floral visitors was also evaluated. Our results indicate great variation in robbing levels across years and populations and a positive relationship between robbing level and flower abundance per population. Moreover, our results show that nectar availability is about eight times higher in unrobbed flowers than in robbed flowers, and that nectar robbers prefer younger flowers, although lifespan of robbed and unrobbed flowers did not differ statistically. Primary and secondary nectar robbers showed a higher visitation rate compared to legitimate visitors, and neither legitimate nor illegitimate floral visitors seem to discriminate between robbed and unrobbed flowers. These results suggest that robbers may respond to food availability and that no floral visitors apparently could differentiate between robbed and unrobbed flowers. Finally, results show that nectar robbers prefer the youngest flowers, which suggests that strong competition for access to nectar between pollinators and robbers might occur, mainly at the first stages of the flowers. [ABSTRACT FROM AUTHOR]

Spatiotemporal variation in the interactions among plants and animals is widespread; yet our conceptual and empirical understanding of this variation is limited to a few types of visitors, mainly herbivores, pollinators, seed predators, and seed dispersers. Despite the ubiquity of nectar robbing and the strength of its effects on plant fitness, we know relatively little about the magnitude and intensity of spatial and temporal variation in interactions among plants and nectar robbers. The purpose of the present study was to quantify spatial and temporal variation in the interactions between a nectar-robbing bumblebee and its host plants. In the Rocky Mountains of Colorado, USA, over 7 years, and multiple locations, we measured levels of nectar robbing by the bumblebee Bombus occidentalis and its interactions with four different host plants, Delphinium nuttallianum (Ranunculaceae), Ipomopsis aggregata (Polemoniaceae), Corydalis caseana (Fumariaceae), and Linaria vulgaris (Scrophulariaceae). Significant variation was found in the robbing rates experienced by different species. Within species, there was variation in robbing rates on an annual basis, on a seasonal basis, among different sites, and within sites. This variation may have important consequences with respect to the population dynamics of host plants as well as selection on floral and flowering traits. Electronic supplementary material is available if you access this article at http://dx.doi.org/10.1007/s00442-002-1060-z. On that page (frame on the left side), a link takes you directly to the supplementary materials. [ABSTRACT FROM AUTHOR]