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Co-Evolution

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The Madagascar star orchid produces nectar at the bottom part of its slim, foot-long throat. After observing a specimen, Charles Darwin predicted the existence of a moth with a proboscis long enough to reach that nectar. Sure enough, decades later the giant hawk moth of Madagascar was discovered and named Xanthopan morganii praedicta in honor of Darwin's prescience. As the moth sucks up the nutrient-rich nectar from the orchid, packets of pollen stick to its body. When the moth visits other star orchids to feed again, the pollen rubs off and pollinates those orchids. The moth gets exclusive access to food and the orchids get a reliable pollinator.

Very nifty, but how does such an interaction develop? The "Partners in Evolution: Butterflies & Plants" exhibit coming to the National Museum of Natural History in February will explore how animals and plants evolve in response to one another, a process that biologists call co-evolution. But there were not always flowers and butterflies. Early plants lacked what we know as flowers, and there were no butterflies, only moths. Then about 100 million years ago, plants with bowl-shaped flowers emerged with a novel food source for moths: nectar. About 50 million years ago, day-flying moths—butterflies!—evolved; they were well suited for taking advantage of nectar.

Hummingbirds, flies, bats, bees and other creatures are also pollinators, often to our benefit. Bats pollinate more than 300 kinds of plants used by humans; pollination by bees, flies, beetles and other insects is responsible for providing about one-third of the human diet. Today 350,000 species of flowering plants and more than 150,000 kinds of moths and butterflies inhabit our planet. The new exhibit will illuminate some of the fascinating dynamics of their co-evolution. For example, in one species of fly, various flowers leave pollen on different parts of the fly's body—ensuring that different pollens don't mix. The exhibit will also include a walk-through butterfly pavilion, featuring live tropical butterflies and plants from around the world.

Next year will bring other spectacular exhibitions at the Smithsonian. The American History Museum will reopen with its new Star-Spangled Banner exhibit next summer. In September, a huge new Ocean Hall at Natural History will open; high-definition videos on large screens and a live coral reef will give visitors the feeling that they are deep beneath the waves in a giant submarine, looking out through its big picture windows. We welcome you to 2008, a year of new and fascinating exhibits.

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