[show abstract][hide abstract] ABSTRACT: Most studies assessing the importance of developmental instability of floral characters for pollinator visits and plant fitness
have focused on the fluctuating asymmetry (FA) of the corolla phenotype. The importance of stability process for nectar guide
characters that signal floral reward has not been considered in the literature. In principle, flowers with symmetrical guides
should be more successful at attracting pollinators, therefore increasing their reproductive success in comparison to asymmetrical
flowers. In this paper we test this hypothesis in a population of 171 individuals of the Andean monkey flower, Mimulus luteus in northern Chile. This species shows a conspicuous red spot in the landing yellow petal, which permits assessment of the
functional relationship between nectar guide FA and female fitness. Our results did not reveal a significant linear nor nonlinear
relationship between nectar guide FA and fitness. This result was consistent after controlling the level of FA by guide and
corolla size. Because the corolla of M. luteus did not show evidence of UV wavelength reflectance, our negative result could not be attributable to a confounding effect
of UV guides. Even though we can not rule out that nectar guide FA correlates better with male than female fitness, the low
fraction of the variance in female fitness accounted for nectar guide FA, suggests that other components of the floral phenotype
as well as environmental factors may be more important to predict pollinator preference and reproductive success in this species.
[show abstract][hide abstract] ABSTRACT: Flower herbivory and pollination have been described as interactive processes that influence each other in their effects on plant reproductive success. Few studies, however, have so far examined their joint effects in natural populations. In this paper we evaluate the influence of flower damage and pollination by the hummingbird Oreotrochilus leucopleurus on the fecundity of the Andean monkey flower Mimulus luteus. We performed a 2x2 factorial experiment, with artificial clipping of lower petals and selective exclusion of the hummingbird as main factors. In spite of the relatively low proportion (27.5%) of the variance in seed production accounted for by the full factorial model, artificial damage and hummingbird exclusion, as well as their interaction, were highly significant, indicating nonadditive effects of factors on plant fecundity. In the presence of hummingbirds, undamaged flowers had a seed production that was 1.7-fold higher than for damaged flowers, suggesting that the effect of flower damage on female reproductive success occurs probably as a consequence of hummingbird discrimination against damaged corollas. This result indicates that the impact of flower herbivory on plant fecundity was contingent on the presence or absence of hummingbirds, suggesting that pollinators may indirectly select for undamaged and probably resistant flower phenotypes. A second interaction effect revealed that undamaged flowers produced 78.5% more seeds in the absence of rather than in the presence of O. leucopleurus, raising the question of the ecological mechanism involved. We suggest that the strong territorial behavior exhibited by the bee Centris nigerrima may confine the foraging activities of the remaining bee species to safe sites within exclosures. Overall, our results provide evidence that hummingbird pollination and flower herbivory have interdependent effects on M. luteus fecundity, which indicates that it will be difficult to predict their ecological and evolutionary consequences unless interactions are analyzed in an integrated form.