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Bignons set bait for bats
The phenomenon of bat pollination (chiropterophily), occurring mainly in the tropics, has been known for many years. One example of a bat-pollinated plant is Adenocalymna dichilum (Bignoniaceae), a liana of north-eastern Brazil in which the pollination mechanism has only recently been confirmed, as reported by Machado and Vogel (Recife, Brazil and Vienna, Austria, pp. 609-613). These authors have studied in detail the features of the flowers that are associated with chiropterophily. This involved field and laboratory investigation of floral biology and night-time photography of pollinators visiting the flowers. Although this species is classified as a liana, the particular individuals studied by the authors were ‘free-standing’ and approx. 1.5 m tall, a life-form that is adopted in the absence of trees capable of supporting a climbing vine. There is a single inflorescence; at any one time only one or two flowers (which are functional for only one night) are open, but the flowering season goes on for several weeks, giving rise to a ‘steady state’. As is now regarded as typical of bat-pollinated flowers, the corolla is sturdy and the nectary disk is large. In an individual flower, anthesis starts at the end of the day and by the time the bats start feeding, there is copious pollen. Nectar secretion also starts late in the day and the flowers give off a weak but distinct fruity or musky odour. The bats feed on nectar by hovering very close to the flower, inserting their snouts into the flower and using their tongues to reach the nectaries, the whole process lasting less than 1 s. Pollen becomes dusted onto the bats’ necks and shoulders and is transferred to the stigma of the next flower visited. Because each plant only produces one or two flowers at a time, it is very likely that the next flower visited is on another plant, thus favouring out-breeding.
j.a.bryant{at}exeter.ac.uk
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