Honeybees disrupt the structure and functionality of plant-pollinator networks

Abstract

The honeybee is the primary managed species worldwide for both crop pollination and honey production. Owing to beekeeping activity, its high relative abundance potentially affects the structure and functioning of pollination networks in natural ecosystems. Given that evidences about beekeeping impacts are restricted to observational studies of specific species and theoretical simulations, we still lack experimental data to test for their larger-scale impacts on biodiversity. Here we used a three-year field experiment in a natural ecosystem to compare the effects of pre- and post-establishment stages of beehives on the pollination network structure and plant reproductive success. Our results show that beekeeping reduces the diversity of wild pollinators and interaction links in the pollination networks. It disrupts their hierarchical structural organization causing the loss of interactions by generalist species, and also impairs pollination services by wild pollinators through reducing the reproductive success of those plant species highly visited by honeybees. High-density beekeeping in natural areas appears to have lasting, more serious negative impacts on biodiversity than was previously assumed.

Gradual replacement of wild bees by honeybees in flowers of the Mediterranean Basin over the last 50 years

“…Correlative and experimental evidence alike has recently shown that, at local or regional scales, honeybees can have strong negative impacts on wild bee populations in both natural and anthropogenic scenarios (Shavit et al 2009, Lindström et al 2016, Torné-Noguera et al 2016, Magrach et al 2017, Ropars et al 2019, Valido et al 2019), and that the absence of honeybees in well-preserved natural areas is associated with increasing wild bee populations (Herrera 2019). Much of the direct or circumstantial evidence on the harmful effects of honeybees on wild bees originated in the Mediterranean Basin, which motivated the hypothesis formulated in this paper of a possible replacement of wild bees by honeybees in the Mediterranean running parallel to the increasing abundance of honeybees.…”

“…S1, Potts et al 2010, vanEngelsdorp and Meixner 2010, Moritz and Erler 2016). Honeybees have been repeatedly shown to have negative impacts on wild bee populations in both natural and anthropogenic scenarios (Goulson and Sparrow 2009, Shavit et al 2009, Lindström et al 2016, Torné-Noguera et al 2016, Magrach et al 2017, Ropars et al 2019, Valido et al 2019). I thus formulated the hypothesis that, if the abundance of managed honeybees has been actually increasing in the Mediterranean Basin over the last decades, then a profound biome-wide alteration in the proportional composition of bee pollinator assemblages could be currently underway there, involving a gradual replacement of wild bees by honeybees in flowers.…”

Spatial variability in a plant–pollinator community across a continuous habitat: high heterogeneity in the face of apparent uniformity

“…In our study area, beekeeping is a common practice (Torné-Noguera et al 2016). Due to their ability to recruit nestmate foragers, honey bees Apis mellifera are able to exploit the most abundant floral resources very efficiently, showing local flower specialization (Lázaro and Totland 2010), and potentially outcompeting other pollinator species (Torné-Noguera et al 2016, Henry and Rodet 2018, Valido et al 2019. Competitive pressure may lead to niche differentiation between honey bees and wild pollinators, whereby honey bees monopolize the most highly-rewarding floral resources forcing wild pollinators to forage on less-preferred plant species (Walther-Hellwig et al 2006, Geslin et al 2017.…”

The economic cost of losing native pollinator species for orchard production

“…Whelan, Ayre, & Beynon, ), activating late‐acting pre‐zygotic or post‐zygotic barriers that reject self pollen (Seavey & Bawa, ), even when pollen deposition is high. Several studies performed in both natural and agricultural ecosystems have also shown a low production of seeds in contexts where honeybee density is very high and dominates the assemblage of pollinators (Rollin & Garibaldi, ; Valido, Rodríguez‐Rodríguez, & Jordano, ).…”

“…Several studies performed in both natural and agricultural ecosystems have also shown a low production of seeds in contexts where honeybee density is very high and dominates the assemblage of pollinators (Rollin & Garibaldi, 2019;Valido, Rodríguez-Rodríguez, & Jordano, 2019).…”