To the biologists who study the ecology of The Amazon, it is no secret that the region is home to a tremendous variety and volume of plants and trees in incredible proportions. According to some estimates, The Amazon has over 2 million square miles of tropical rainforest which is home to an estimated 390 billion individual trees comprised of at least 16,000 known species. In every 2.47 acres of Amazonia, there are 1500 plant species, 750 tree species, and 900 tons of living plants, and roughly a third of the world’s oxygen is produced there. When combined with the astounding variety of insects, mammals, and other life forms this makes The Amazon Rainforest the most bio-diverse region on the planet. What has puzzled researchers and scientists about this is exactly what causes all of this diversity. Although there have been many theories on the subject, a new idea is emerging to explain why this particular region of the world is home to so many more types of trees in such a dense area than anywhere else. Surprisingly this new theory centers on insects as a major contributor to this diversity.
Throughout the Amazon, there is a silent battle being waged between a hoard of insects and their major food source- plants and trees. Insects are known to consume the leaves, stems, and seeds of all varieties of plants. To avoid destruction, plants have evolved an array of defenses, some of which can get elaborate. Plants with leaves that appear simply a little fuzzy to the human eye are more like little barbed hooks to the insects that feed on them, tearing at the underbellies of caterpillars. Some plants have even developed little pots of nectar that draw in a select group of ants to prey on other insects on the plant.
One of the most common defenses that plants and trees in the rainforest use against insects is to produce their own natural pesticide residues through their leaves. Since the weather is warm in the tropics year round most insect species can reproduce faster than in temperate climates, so they have more generations in a faster time. Since the bugs regenerate faster, they can actually develop resistance to some of the pesticides of the plants. This leads to a sort of arms race between the plants and insects.
Scientists now believe that as the plants evolve new pesticide defenses, they may also be attracting different pollinating insects that the plants need to reproduce. The ants are constantly shifting the focus of their feeding on different plants as the plant’s pesticide and their resistance to it changes rapidly. As this happens, the insects that are pollinating the plants also change. Some pollinators may only select one specific group of trees due to slight differences in that tree’s chemicals. Those same pollinators may avoid another group of trees that are nearby even if the two groups of trees are of same species. This isolates the gene pools of plants that are of the same species in a way that is unique, and this isolation may allow plants and trees of The Amazon to evolve into new species faster than elsewhere. At least that is the theory. Whatever the case, it is interesting to discover the different ways that jungle life interacts, and the important role that tiny insects play in it all.
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