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While feeding, foragers can alter their environment. Such alteration constitutes ecological niche construction (ENC) if it enables future benefits for the constructor and conspecific individuals. The environmental modification may also affect non‐constructing, bystander species, especially if they share resources with constructor species. If so, ENC could confer the constructor species a competitive advantage by both enhancing its foraging returns and reducing those of bystander species.Expectations – (E1) ENC frequency should vary positively with the recent and current density of the constructor species, and (E2) constructors should use modifications disproportionately. In contrast, bystanders should (E3) experience intensified competition for the affected resource, and (E4) exhibit diverse, possibly mitigating, responses to ENC, depending on opportunity and relative benefits.We investigated these expectations in Argentina for competition for Fuchsia magellanica nectar between an invasive bumble bee Bombus terrestris (terr: putative constructor), which often bites holes at the bases of floral tubes to rob nectar, and native B. dahlbomii (dahl: bystander), which normally accesses Fuchsia nectar through the flower mouth (front visits). Robbing holes constitute ENC, as they persist until the 7‐day flowers wilt. The dynamics of the incidence of robbed flowers, abundance of both bees and the number and types of their flower visits (front or robbing) were characterised by alternate‐day surveys of plants during 2.5 months.After initially accessing Fuchsia nectar via front visits, terr switched to robbing and its abundance on Fuchsia increased 20‐fold within 10 days (E2). Correspondingly, the incidence of robbed flowers varied positively with recent and past terr abundance (E1). In contrast, dahl abundance remained low and varied negatively with the incidence of robbed flowers (E3). When terr ceased visiting Fuchsia, dahl abundance increased sixfold within 10 days (E3), possibly because many dahl previously had avoided competition with terr by feeding on other plant species (E4). While terr was present, dahl on Fuchsia used front visits (tolerance) or used existing robbing holes (adoption: E4). The diverse dahl responses suggest partial compensation for competition with terr.ENC alters competitive asymmetry, favouring constructor species. However, bystander responses can partially offset this advantage, perhaps facilitating coexistence. [ABSTRACT FROM AUTHOR]

Invasive species are one of the main biodiversity loss drivers. Some species can establish and thrive in novel habitats, impacting local communities, as is the case of managed pollinators. In this regard, an invasive species' expansion process over time is critical for its control and management. A good example is the European bumblebee Bombus terrestris, which has rapidly invaded the southern part of South America after being repeatedly introduced in Chile for crop pollination since 1997. We assessed the temporal dynamics of B. terrestris invasion in Argentina and Chile by compiling 562 occurrence points from 2000 to 2019. We used two estimators (minimum convex polygon and 95% fixed kernel) to estimate the increase of the invaded area over time. We found that the area invaded by B. terrestris in the southern part of South America presents a linear increase over time, which was consistent for both estimators. In this scenario, species traits, environmental characteristics, and introduction dynamics facilitate a rapid invasion process that will continue to expand, reaching other South American countries in the near future. As this bumblebee is a super-generalist, it probably will expand across South America, as climate niche modelling predicts, if no actions were taken. [ABSTRACT FROM AUTHOR]

• Biological invasions are a major driver of biodiversity loss. • Citizen science can provide valuable information to understand invasion processes. • We used citizen science information on two exotic and one native bumblebee species. • Exotic bumblebees mainly visited exotic plants preferring certain colours. • Ornamental exotic plant species may act as steppingstones facilitating invasion. Invasive species are one of the most important drivers of biodiversity loss worldwide. As exotic species invade new ecosystems, they establish ecological interactions with the existing species, which may facilitate their spread. Flower colour is an important trait that influences pollination and pollinator preferences. To determine the role of these variables on the bumblebee preferences, we compared the floral associations of two exotic bumblebee species: Bombus terrestris and B. ruderatus (introduced two decades ago for crop pollination) and the native B. dahlbomii with native and exotic plants in Chile. We analysed 3,019 citizen science records in order to understand bumblebee associations with native and exotic plant species regarding flower colour. We found that the exotic bumblebees were mainly recorded visiting flowers of exotic plants (86% for B. terrestris and 93% for B. ruderatus), while the native B. dahlbomii visited exotic and native plant species in a similar proportion. Also, the exotic bumblebees visited purple and pink flowers more often, while the native bumblebee species frequently visited white, pink, and purple flowers. Although the three species share trichromatic vision, they seem to have different flower colour preferences. The association of B. terrestris and B. ruderatus with exotic non-crop species (i.e., exotic ornamental plants) may be acting as steppingstones from croplands to other habitats, facilitating the bee invasion process. Despite its inherent limitations, citizen science data provide large amounts of valuable information that is difficult to be obtained otherwise, which can be used to improve our understanding of invasion processes, as is the case of exotic Bombus species in southern South America. [ABSTRACT FROM AUTHOR]