Daily fluctuations in pollination effectiveness explain higher efficiency of native over exotic bees in Lepechinia floribunda (Lamiaceae)

SANTIAGO BENITEZ-VIEYRA; SILVINA CORDOBA; ALICIA NOEMI SÉRSIC; MATIAS CRISTIAN BARANZELLI; ALEJANDRA TRENCHI; LORENA ASHWORTH; JUAN FORNONI; EVANGELINA GLINOS; JULIA LAURA CAMINA; ANDREA ARISTIDES COCUCCI

ANNALS OF BOTANY

OXFORD UNIV PRESS

Lugar: Oxford; Año: 2020 vol. 125 p. 509 - 5020

0305-7364

? Background Despite Stebbins? principle of the most efficient pollinator being proposed decades ago, the mostimportant pollinators are still mainly identified using the frequency of visits to flowers. This shortcoming resultsin a gap between the characterization of the flower visitors of a plant species and a reliable estimation of the plantfitness consequences of the mutualistic interaction. The performance of a mutualistic visitor depends on its abundance, behaviour, effectiveness (pollen removal and deposition per unit time) and efficiency (seed set per unit time)conditioned by the temporal matching between pollinator activity and temporal patterns of maturation of the sexualfunctions of flowers. Although there have been recent attempts to provide a conceptual and methodological framework to characterize pollinators? performance, few have combined all key elements of visitors and plants to providean accurate estimation of pollinators? performance under natural conditions.? Methods We complement information on the flower biology and mating system of the sub-shrub Lepechiniafloribunda (Lamiaceae) to provide a daily quantitative estimation of performance (effectiveness and efficiency) ofthe more abundant pollinators, i.e. native bumble-bees (Bombus spp.) and leafcutter bees (Megachile sp.), and theexotic honey-bee (Apis mellifera).? Key Results Unlike honey-bees or leafcutter bees, native bumble-bees matched the daily pattern of nectarproduction and stigma receptivity, and showed higher effectiveness and efficiency. Despite the overabundanceof honey-bees, visits occurred mainly when stigmas were not receptive, thus reducing the honey-bees? overallperformance.? Conclusions Bumble-bees appear to be the most important pollinators and potential historical mediators of reproductive trait evolution in L. floribunda. Because the production of seeds by bumble-bees involved fewer pollengrains for plants and less investment in floral display than honey-bees, contemporary and expected changes in pollinator abundance may affect future L. floribunda floral evolution. If bumble-bees were to be further displaced byanthropogenic disturbance or by competition with honey-bees, their lower efficiency will select for a larger floraldisplay increasing reproductive costs. This scenario may also impose selection to reduce dichogamy to matchhoney-bee foraging activity