Las fluctuaciones diarias en la efectividad explican la mayor eficiencia de las abejas nativas sobre las exóticas en la polinización en Lepechinia floribunda (Lamiaceae)

BARANZELLI, M.C; BENITEZ-VIEYRA, S; GLINOS, E; TRENCHI, A; CÓRDOBA, S; CAMINA, J; ASHWORTH, L; SÉRSIC, A. N; COCUCCI, A. A; FORNONI, J

Congreso; VII Congreso Mexicano de Ecologia; 2019

Background Despite Stebbins? principle of the most efficient pollinator was proposed decades ago, most important pollinators are still mainly identified using the frequency of visits to flowers. This shortcoming faces us with a gap between the characterization of the flower visitors of a plant species and reliable estimation of the plant fitness consequences of the mutualistic interaction. The performance of a mutualistic visitor depends on its abundance, behaviour, its effectiveness (pollen removal and deposition per unit time), and efficiency (seed set per unit time) conditioned by the temporal matching between pollinators activity and temporal patterns of maturation of flowers sexual functions. Although recent attempts to provide a conceptual and methodological framework to characterize pollinators? performance, few have combined all key elements of visitors and plants to provide an accurate estimation of pollinators? performance under natural conditions. Methods we complement information on flower biology and mating system of the subshrub Lepechinia floribunda (Lamiaceae) to provide a daily quantitative estimation of performance (effectiveness and efficiency) of the more abundant pollinators: native bumblebees (Bombus spp.) and leafcutter bees (Megachile sp.), and the exotic honeybee (Apis mellifera).  Key Results Unlike honeybees or leafcutter bees, native bumblebees matched the daily pattern of nectar production and stigma receptivity, and showed higher effectiveness and efficiency. Despite the overabundance of honeybees, visits occurred mainly when stigmas were not receptive, thus reducing the honeybees' overall performance. Conclusions Bumblebees appear as the most important pollinators and potential historical mediators of reproductive trait evolution in L. floribunda. Because the production of seeds by bumblebees involved fewer pollen grains for plants and less investment in floral display than honeybees, contemporary and expected changes in pollinators abundance may affect future L. floribunda floral evolution. If bumblebees were to be further displaced by anthropogenic disturbance or by competition with honeybees, their lower efficiency will select for larger floral display increasing reproductive costs. This scenario may also impose selection to reduce dichogamy to match honeybee foraging activity.