Behavioural responses by a bumble bee to competition with a niche-constructing congener

ROSENBERGER, N. M.; AIZEN, M.A.; DICKSON, R.G.; HARDER, L.D.

JOURNAL OF ANIMAL ECOLOGY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2022 vol. 91

0021-8790

While feeding, foragers can alter their environment. Such alteration constitutesecological niche construction (ENC) if it enables future benefits for the constructorand conspecific individuals. The environmental modification may alsoaffect non-constructing,bystander species, especially if they share resourceswith constructor species. If so, ENC could confer the constructor species a competitiveadvantage by both enhancing its foraging returns and reducing those ofbystander species.2. Expectations ?(E1) ENC frequency should vary positively with the recent andcurrent density of the constructor species, and (E2) constructors should usemodifications disproportionately. In contrast, bystanders should (E3) experienceintensified competition for the affected resource, and (E4) exhibit diverse,possibly mitigating, responses to ENC, depending on opportunity and relativebenefits.3. We investigated these expectations in Argentina for competition for Fuchsia magellanicanectar between an invasive bumble bee Bombus terrestris (terr: putativeconstructor), which often bites holes at the bases of floral tubes to rob nectar,and native B. dahlbomii (dahl: bystander), which normally accesses Fuchsia nectarthrough the flower mouth (front visits). Robbing holes constitute ENC, as theypersist until the 7-dayflowers wilt. The dynamics of the incidence of robbedflowers, abundance of both bees and the number and types of their flower visits(front or robbing) were characterised by alternate-daysurveys of plants during2.5 months.4. After initially accessing Fuchsia nectar via front visits, terr switched to robbing andits abundance on Fuchsia increased 20-foldwithin 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 withthe incidence of robbed flowers (E3). When terr ceased visiting Fuchsia, dahlabundance increased sixfold within 10 days (E3), possibly because many dahlpreviously had avoided competition with terr by feeding on other plant species(E4). While terr was present, dahl on Fuchsia used front visits (tolerance) or usedexisting robbing holes (adoption: E4). The diverse dahl responses suggest partialcompensation for competition with terr.5. ENC alters competitive asymmetry, favouring constructor species. However,bystander responses can partially offset this advantage, perhaps facilitatingcoexistence.