LAUSR

Deceptive pollination has been reported in the genus Aristolochia, but the floral biology and pollination strategy of Aristolochia bianorii, an endemic species to the Balearic Islands, have not been studied yet. Here, we aimed to investigate the floral anthesis, the mating system, the pollinators and the volatile organic compounds (VOCs) emitted by its flowers. Flower buds were marked and monitored daily to define floral stages and their duration. Experimental bagging and hand pollination treatments were performed to test for autonomous self-pollination, induced self-pollination, and cross-pollination. Flowers were collected to analyse the presence of entrapped pollinators. VOCs emitted by flowers were evaluated by means of a solid phase microextraction followed by immediate gas chromatography-mass spectrometry. Anthesis lasted between 63 and 96 hours, and the species exhibited autonomous self-pollination with a moderate inbreeding depression. Pollinators were mainly females of Oscinomorpha longirostris (Diptera; Chloropidae), and the number of pollinators inside flowers was affected by the floral stage and the time of flowering. The most common VOCs were alkanes, oximes, esters, alkenes, cyclic unsaturated hydrocarbons, isocyanates, amides and carboxylic acids. Aristolochia bianorii can set seeds by autonomous self-pollination, in contrast to other Aristolochia species in which both protogyny and herkogamy prevent from autonomous self-pollination. However, the species may encourage cross-pollination by attracting female chloropid flies though the emission of floral scents that may mimic an oviposition site and possibly, freshly killed true bugs (i.e., Heteroptera). In conclusion, A. bianorii promotes cross-pollination but delayed autonomous self-pollination assures the reproductive success in putative absence of pollinators.