Reproductive system, floral biology and pollinators of Abutilon grandifolium in urban green spaces of Ciudad Autónoma de Buenos Aires.

Abstract

Urban green spaces have gained importance in view of growing urbanization; however, limited research exists on the interactions of native plants with the local fauna, particularly comparing protected natural areas vs. recreated ones. To help fill this gap, the floral biology and pollination of Abutilon grandifolium (Malvaceae) were studied in an Ecological Reserve and in a square where the local environment had been recreated with native plants, both located in Ciudad Autónoma de Buenos Aires, Argentina. A. grandifolium was self-compatible. The flowers presented typical traits associated with biotic pollination (ornamented pollen, conspicuous perianth and rewards), particularly melittophily (diurnal anthesis, nectar, yellow-orange coloration and pleasant odour). At both sites, the most frequent visitors were Apis mellifera and halictid bees, collecting nectar and/or pollen. While visits from the former were predominantly illegitimate, halictids mostly performed legitimate visits. Occasional visitors included the bees Xylocopa sp. and Bombus pauloensis, syrphid flies and, more rarely, beetles. Large quantities of A. grandifolium pollen were found on all bee species, in positions compatible with an effective transfer to the stigmas, indicating that they likely pollinate when accessing flowers legitimately. In contrast, flies and beetles would be mainly pollen and nectar thieves. In general, the identity, frequency and activity of the floral visitors were similar at both sites, with species richness even higher in the square; suggesting that restored native plantings can support functional pollination processes in urban green spaces.