Pollination biology and floral longevity of Aristolochia chilensis in an arid ecosystem

Background: In Aristolochia species the pollination process involves temporary imprisonment of pollinators. Floral longevity is an essential trait for pollination biology, influencing the total number of pollinator visits. Floral longevity should balance costs of flower maintenance and time to fulfil reproduction. For Aristolochia species there is an extra factor: survival of trapped insects. Environmental conditions may affect floral longevity because pollinator visits are likely to be less frequent in stressful habitats. Aims: Our aim was to study the pollination biology of A. chilensis in an arid ecosystem and to determine the relationship between floral longevity in Aristolochia and aridity. Methods: We measured floral longevity, pollinator quantity and identity and tested the viability of self-fertilisation in A. chilensis. We also compiled information on floral longevity and habitat characteristics of Aristolochia species using published literature. Results Dipterans were the only effective pollinators of A. chilensis, which required pollinators to set fruit. A. chilensis had the greatest floral longevity recorded for the genus and the study population was located in the most arid and least productive environment reported for any Aristolochia species. When data from nine Aristolochia species were analysed, floral longevity increased with habitat aridity and decreased with habitat productivity. Conclusions: Floral longevity varies consistently with habitat aridity and productivity in Aristolochia. Further research should determine the relative importance of biotic and abiotic factors in the evolution of floral longevity in Aristolochia.