When hummingbirds are the thieves: visitation effect on the reproduction of Neotropical snowbell Styrax ferrugineus Nees & Mart (Styracaceae)

Abstract

The spectrum of floral visitors associated with a particular plant is frequently larger than predicted by the traditional concept of floral syndromes and the role that unpredicted visitors play in plant reproduction deserves attention. Hummingbirds are frequently recorded visiting flowers with distinct floral syndromes, especially in some hummingbird flower poor ecosystem such as the Cerrado. In this study we investigated the effect of frequent hummingbird visits on the reproduction of melittophilous Styrax ferrugineus. The flowers were visited by many different insect groups and visits by hummingbirds were frequent, especially early in the morning when nectar availability was higher. Nectar parameters varied considerably during the flower life span, and was probably affected by the temperature variation during the day. Hummingbird exclusion experiments showed no effect in the fruit-set of the plant. The inability of hummingbirds to deplete all of the nectar produced in this mass-flowering plant, and the existence of another resource (pollen) for the primary pollinator (large bees), are possible reasons why there was no perceptible hindrance of plant reproduction by the hummingbirds. Although no effect in the fruit-set was observed, the use of non-ornithophilous flowers must be important for hummingbirds, which are specialized nectar consumers.

Self-sterility in the hexaploid Handroanthus serratifolius (Bignoniaceae), the national flower of Brazil

“…The small amount of accumulated nectar in species with a great amount of flowers can force floral visitors to shorten their visits and to visit a greater number of flowers in order to collect the number of calories needed. Studies involving hummingbirds suggest that plants presenting flowers with little or no nectar may save energy and promote pollinator movement, in mimicry of flowers with uniform secretion rates, but with variable nectar availability due to foraging activity (Feinsinger 1978;Maruyama et al 2012). In addition, one experimental study showed that when the number of "empty" (nectarless) flowers increases in an inflorescence, the number of visits by bees decreases (Ishii et al 2008).…”

“…Given the positive correlation between the percentage of empty flowers and the number of flowers per inflorescence (Takar et al 2003), larger displays promote proportionally fewer effective visits by bees (Ishii et al 2008). Therefore, the benefits of large displays in selfincompatible plants may be increased by the presence of empty flowers, encouraging cross-pollinations, although geitonogamy is also favored until pollinators leave one tree to visit another (Maruyama et al 2012).…”

Distribuição vertical dos sistemas de polinização bióticos em áreas de cerrado sentido restrito no Triângulo Mineiro, MG, Brasil

“…Tampouco foram agrupadas as plantas polinizadas por abelhas pequenas entre aquelas polinizadas por insetos pequenos ou muito pequenos (e.g., Oliveira & Gibbs 2000), uma vez que abelhas grandes, como espécies de Xylocopa podem visitar e polinizar efetivamente plantas com flores pequenas (Silva et al 2010) e abelhas pequenas também visitam flores grandes e/ou com corola tubular longa, agindo inclusive como polinizadores efetivos . Como no caso de polinização por beija-flores (Maruyama et al 2012), as abelhas usaram uma espectro grande de recursos florais. Mesmo quando não são importantes para a polinização das plantas visitadas, os recursos oferecidos por estas plantas podem ser vitais para a persistência das populações de abelhas na ausência de outras fontes de alimentos.…”

Floral antagonists counteract pollinator‐mediated selection on attractiveness traits in the hummingbird‐pollinated Collaea cipoensis (Fabaceae)

“…In this regard, the direct contribution of hummingbirds to plant reproduction may be low, even when they are the most frequent visitors (Maruyama et al . , Watts et al . ).…”