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Animal Pollination in the Tropics: Hummingbirds to Hawkmoths

Inside a tropical rainforest, there's not a lot of wind, apart from high up in the canopy, and plant species tend to be very rare and quite far away from each other. Therefore wind pollination is not an effective means of plant reproduction. The preferred method is animal pollination, and many fascinating processes have evolved both in the pollinizer (the plant) and pollinator (the animal).

It's a coevolutionary process - both plants and pollinators become specialized to attract each other. Tropical plants have evolved flowers that entice their preferred pollinator - be it hummingbird, insect, or bat - so that the pollinator will hopefully carry the plant's genes, via the pollen, to another plant of the same species. Sometimes it entices by rewards like nectar - making it a mutualistic relationship - sometimes by trickery,* but it will match its characteristics to the characteristics of a specific pollinator and discourage all other pollinators. At the same time, the pollinators have evolved traits - like a long beak or a long tongue - to better pollinate certain flowers.

photo by Danny Perez
For instance, hummingbird-flowers are usually bright red or orange (hummingbirds have excellent eyesight), non-odorous (they don't have a good sense of smell), and tubular. They produce nectar that is high in sugar but low in nutrients, supplying the highly-active hummingbird with a source of energy. (It's not the hummingbird's primary food source though - that would be insects.) The tubular flowers and the hummingbird's long, thin beak are a perfect match and because the flowers don't have a landing platform, the hummingbird must hover to feed. These characteristics discourage other would-be pollinators.

hummingbird hawkmoth - photo by Sue Snowdon

On the flip side of this we have the hawkmoth - the nighttime version of the hummingbird - who is also capable of hovering. Flowers pollinated by hawkmoths are also tubular - to accommodate the hawkmoth's long tongue - and do not provide a firm place to land. These jasmine-scented flowers bloom at night and are white, making them easier for the hawkmoth to see and smell in the dark. (Not sure what kind of flower the hawkmoth is pollinating above.)

Then we have the bees and the butterflies...

photo by Danny Perez

Bee-flowers are typically yellow, blue, or ultraviolet (colors they can see) and sweet-scented (which they can smell).

Bosque del Cabo, Costa Rica

Butterfly-flowers are usually brightly colored and odorless - butterflies have good vision but a weak sense of smell.

So we have the birds, bees, butterflies, and moths, but it's the bats - very important rainforest pollinators - that will get their own post... "Chiropterophily: Bat Pollination"

* There's a species of orchid that tricks male tachinid flies into believing it is a tachinid female so that when the male fly copulates with the "female," he is actually just pollinating the orchid.

Note: Though the text is about pollination in the tropics, the only photo actually taken in the tropics was my butterfly pic - but the others are oh so beautiful.


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