Birds Work a Double Shift For Osmoxylon

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Plants go to great lengths to achieve pollination. Some can be tricky, luring in pollinators with a promise of food where there is none. Others, however, really sweeten the deal with ample food reserves. At least one genus of plants has taken this to the extreme, using the same techniques for pollination as it does for seed dispersal. Ladies and gentlemen, I present to you the genus Osmoxylon.

Comprised of roughly 60 species spread around parts of southeast Asia and the western Pacific, the genus Osmoxylon hail from a variety of habitats. Some live in the deep shade of the forest understory whereas others prefer more open conditions. They range in size from medium sized shrubs to small trees and, upon flowering, their place within the family Araliaceae becomes more apparent.

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Look closely at the flowers, however, and you might notice a strange pattern. It would appear that as soon as flowers develop, the plant has already produced berries. How could this be? Are there cleistogamous flowers we aren't aware of? Not quite. The truth, in fact, is quite peculiar. Of the various characteristics of the genus, one that repeatedly stands out is the production of pseudo-fruits. As the fertile flowers begin to produce pollen, these fake fruits begin to ripen. There aren't any seed inside. In truth, I don't think they can technically be called fruits at all. So, why are they there?

Although actual observations will be required to say for sure, the running hypothesis is that these pseudo-fruits have evolved in response to the presence of birds. They are quite fleshy and would make a decent meal. It is thought that as birds land on the umbel to eat these pseudo-fruits, they invariably pick up pollen in the process. Each plant the birds then visit dusts off its own pollen while picking up pollen from previous visits. Thus, pollination is achieved.

The relationship with birds doesn't end here. Like other members of this family, pollination results in the formation of actual fruits full of seeds. Birds are known for their seed dispersal abilities and the Osmoxylon capitalize on that as well. As such, the reproductive input of their avian neighbors is thought to be two-fold. Not only are birds potentially great pollinators, they are also great seed dispersers, taking fruits far and wide and depositing them in nutrient-rich packets wherever they poop.

Photo Credits: [1] [2]

Further Reading: [1]