Impostors in South America: a new Batesian floral mimicry system involving orchids and Bignoniaceae models

BACKGROUND AND AIMS: Although Batesian floral mimicry is likely common, confirmed cases remain scarce. For instance, none have yet been documented in South America. We tested whether the Neotropical orchid Galeandra montana mimics Jacaranda rufa (Bignoniaceae), thereby deceiving its bee pollinators. METHODS: We investigated the mating system of G. montana to assess its dependence on pollinators. We observed pollinators and compared them to those visiting J. rufa. The rewardlessness of G. montana was investigated through anatomical and histochemical tests. We quantified trait overlap based on multivariate trait-space analyses, including inflorescence height, number of flowers, flower area, flower perimeter, and flower contrasts (chromatic and achromatic). We also compared the flowering phenology and geographical overlaps between the two species using circular statistics and ecological niche modelling, respectively. KEY RESULTS: Galeandra montana is pollinator-dependent and visited by nectar-seeking females of Xylocopa suspecta and Bombus morio, which also visit J. rufa. Although G. montana has osmophores at the labellum producing attractant volatiles, it is rewardless. Species are similar in several traits, including funnel-shaped flowers, zygomorphy, horizontal orientation, nectar guides, flower perimeter, spectral reflectances, and colour perception by bees. 81.83% of the floral trait variation of the mimic was contained within the model. Although producing fewer flowers, G. montana has larger flowers with a greater frontal area, displayed higher in the inflorescences. Species exhibit phenological similarity, with no differences in flowering distributions, and the phenology of G. montana was nested within that of J. rufa. They also show a high geographical overlap, corresponding to ∼9% of South America. CONCLUSIONS: We provide the first evidence of Batesian floral mimicry in South American orchids, showing that Bignoniaceae species can function as models. Given the richness, widespread distribution, and general similarity between Galeandra and Bignoniaceae, we propose the existence of a Batesian mimicry complex in the Neotropics.