Impact of invasive bees on plant-pollinator interactions and reproductive success of plant species in mixed Nothofagus antarctica forests

J.I. AGÜERO; N. PERÉZ-MÉNDEZ; JUAN PABLO TORRETTA; L.A. GARIBALDI

NEOTROPICAL ENTOMOLOGY

ENTOMOLOGICAL SOC BRASIL

Lugar: BRASIL; Año: 2020

1519-566X

Invasive social bees can alter plant-pollinatorinteractions with detrimental effects on both partners. However, most studieshave focused on one invasive bee species, while the interactions among two or more speciesremain poorly understood. Also, many study sites had a history of invasive bees, being hard tofind sites with historical low abundances. In Patagonia, Bombus ruderatus (F.)invasion begun in 1993 and B. terrestris (L.) in 2006. Though honey bees(Apis mellifera, L.) introduction started in 1859, their density isstill low in some parts. By experimentally increasing honey bee densities, weevaluated the effect of honey bees and bumblebees floral visitation onnative pollinators? floral visitation, pollen deposition, and reproductive success of three plantspecies in mixed Nothofagus antarctica forests of northern Patagonia: Oxalis valdiviensis,Mutisia spinosa, and Cirsium vulgare. Our results show that exotic bees became the main floralvisitors. No negative association was found between invasive bees and native pollinators? visitation rates,but there was evidence of potentialcompetition between honey bees and bumblebees. Floral neighborhood diversity played an important role in pollinators? behavior.Conspecific pollen deposition was high for all species, while deposition of heterospecific pollenwas very high in M. spinosa and C. vulgare. Not asexpected, honey bees visitation rate had a negative effect on heterospecific pollen deposition in C. vulgare. For O.valdiviensis, exotic visitation rates increased conspecific pollen deposition, which was positivelyrelated to reproductive success. Although exotic bees became main floral visitors, theircontribution to reproductive success was only clear for one species.