The term ‘pollination’ almost always makes us to think about honey bees probing and collecting pollen from a brightly coloured flower. Today, I will be talking about a hidden world of pollinators, much of which is still unfolded – ‘the nocturnal system of pollination’.
Pollination at night is performed by moths, bats and some other nocturnal animals like nocturnal bees, beetles and some primates etc. The plants typically have nocturnal anthesis, however, some generalist flowers attract both diurnal and nocturnal visitors and may have day anthesis. The bat pollination syndrome is called chiroptophily, the flowers being born on a stout branch, having musky odour, pale or white colours. They produce copious amount of nectar. The phalaenophilous or moth pollinated flowers are tubular, pale in colour and having strong fragrance.
A very interesting story is that of the baobab (Adonsonia grandieri) from Madagascar. The huge, generalist flowers open at night. Some sphingid moths come early being attracted to the sugary nectar oozing out of the petals. While drinking the nectar, they collect the pollen unknowingly on the body scales. When they go to another flower, some of the pollen is transferred to the stigma. But, this is not the end of the story. Some mouse lemurs emerge from their prolonged sleep and come to the baobab flowers and have a feast of the energy rich nectar. But its just a starter for them. In the main course, they devour the fleshy moths. But upon their fight with the moth, they also become brushed with pollen, which is deposited in the next visited flower. However, the chief pollinators of baobab are the bats.
In 1862, Charles Darwin published a article about an orchid (Angraecum sesquipedale), with a spur length of 35 cm, the nectar chambered below it. He predicted that there must be a moth having a proboscis length equal to the spur length, to reach the nectar source, collect the pollinia and pollinating the orchid. He was criticized in the scientific community variously. In 1902, researchers found a sphingid moth (Xanthopan morgani) having a proboscis length similar to the Darwin’s prediction, where the orchid is found in general.
Apart from insects, Nocturnal carpenter bees (e.g. Xylocopa tenuliscapa) or other nocturnal bees like Megalopa spp. are pollinators of many plants, usually the forest trees.
Bats are mysterious and usually either are hated or scared by people in general. But they pollinate some economically important fruit plants like banana, mango, guava, peaches, agave (from which tequila is derived) etc. Usually many long-nosed fruit bats (megachiropterans) are good pollinators. Apart from pollination, they (microchiropterans) eat many insect pests also. Bats consume the nectar and also the pollen, in turn they help in pollination of the plant.
Cullenia exarillata, a canopy tree, studied in southern India shows a dual strategy of getting pollinating by bats as well as some non flying mammals. The day visitors are the lion-tailed macaque, Nilgiri langurs, giant squirrel etc, while brown plam civet, flying squirrel and some bats are the nocturnal visitors.
In my study, I will be exploring the nocturnal pollination system of some cucurbit crops like spine gourd and pointed gourd.
Some Relevant Articles:
Ganesh T and Davidar P. 1997. Flowering phenology and flower predation of Cullenia exarillata (Bombacacae) by arboreal vertebrates in western ghats, India. Journal of Tropical Ecology. 13 (3): 459-468.
Hector T. and Wilson D. 1987. Long-nosed bats and Agaves: the tequila connection. The Bat Magazine. 5 (4).
Hopkinms M. et al. 2000. Nocturnal pollination of Parkia velutina by Megalopa bees in Amazonia and its possible significance in the evolution of chiropterophily. Journal of Tropical Ecology. 16: 733-746.
Wasserthal, L.T. 1997. The pollinators of the Malagasy star orchids Angraecum sesquipedale, A. sororium and A. compactum and the evolution of extremely long spurs by pollinator shift. Botanica Acta. 110, 343-359