The siren call of the vine - how plants lure bats in for supper
Plants have developed quite a sophisticated bag of tricks to get birds, bees and butterflies to help with the hard work of reproduction for them. But a new study in Science shows that one distinctive species of tropical vine has gone a step further - turning to sound-sculpting to pull in pollinating bats. That considerably extends the sensory repertoire of plants, who can now add aural beacons to the better known sensual magnets of alluring sights, and scented delights.
The vine in question, Marcgravia evenia, is to be found in the Cuban rainforest, clambering up tall tree trunks. But M. evenia is quite widely dispersed, so in order to ensure that pollination is a success, it has to attract pollinators from far and wide. That's where the need to stand-out to nectar-sucking bats has pushed the vine to evolve its unique dish-shaped leaves.
The 'echo-beacon' leaf is found next to the vine's drooping bunch of flowers; it is concave-shaped very much like a satellite dish. It seems that these odd-structures are shaped in such a way that a burst of ultrasound, from bats flying by, produces a powerful aural flag - essentially telling the bats that 'supper is here!' The research in this paper has now shown that these leaves make it twice as likely that the bats will stop by to sup nectar - which makes the effort of producing the echo-beacon well worthwhile.
In order to test the effectiveness of the leaf's siren echo, the team, from German and UK-based universities, set up some experiments with Pallas's Long-tongued Bat (Glossophaga soricina). This is a common nectar-feeding bat native to Central America. A nectar-laden feeder was placed at random in amongst some artificial foliage. Sometimes it was on its own, sometime it had leaves similar to the background foliage - and sometimes it had the vine's echo-beacon leaf attached.
Image: Nectar-feeding bats. Glossophaga soricina Source Credit: AUPEC
The researchers found that the time to find the feeder was cut in half, when the dish-shaped leaf was present. In contrast, the bats took almost the same time to discover the feeder when normal leaves were attached, or when the feeder was unadorned. This appears to show that the echo-beacon leaf really does grab the bat's attention.
Co-author Dr Marc Holderied, from the University of Bristol, said 'This echo beacon has benefits for both the plant and the bats. On one hand, it increases the foraging efficiency of nectar-feeding bats, which is of particular importance as they have to pay hundreds of visits to flowers each night to fulfill their energy needs. On the other hand, the M. evenia vine occurs in such low abundance that it requires highly mobile pollinators.'
Top Image Credit: Stock picture of bats © Tolits