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 16 happy adult coconut DHJanzen101229.jpg high resolution
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| An adult reproductive wild naturally established coconut palm tree, well behind the upper storm tide line where its coconut was deposited and buried 20-40 years before. There is almost no natural vegetation left on tropical islands, and very little left on the coasts of tropical mainlands. However, a combination of inference and some few observations indicate that on the mainland, adult coconuts palms are naturally found only just in the microgeographic position indicated in image DHJanzen1012229.jpg above. In contrast, historical records suggest that on uninhabited islands they naturally occured throughout much of the island. Why should there be this dichotomy of habitat occupation? Since a coconut that falls directly below a parent should at least in some cases be able to create a seedling (well above the reach of even storm tides), the coconut population should gradually march inland on the mainland, just as it apparently did on islands (though in all fairness it is easy to imagine a truly severe storm depositing coconuts many hundreds of meters inland on an exposed oceanic island). But it does not make this march. The only currently viable hypothesis for the failure of coconuts to spread inland on the mainland is seed predation by climbing rodents. Tropical forest is full of climbing squirrels and other rodents, many species of which are capable of chewing into young coconuts while still in the crown of the tree. However, these animals appear reluctant to forage intensively and widely on the very exposed trunks and crowns of coconut trees growing at the edge of the beach. On the other hand, were the coconut palm crown to be embedded in the general forest canopy, there would be no shortage of rodent visitors, and such a palm would never successfully produce seeds. Islands? Natural oceanic islands have no mammals except for the occasional bat. Some credence is lent to this idea by what happens to coconut plantations. | ||
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