'em back alive
If you're interested in studying -- and possibly reversing -- plant extinction, Hawaii's the obvious destination. The remotest archipelago on the planet is home to 51 percent of U.S. endangered plants -- a total of 281 species. About 100 plants have already gone extinct on the islands, and as you can read, the remainder face enormous threats.
The Why Files visited Limahuli Garden, operated by the National Tropical Botanical Garden, on the north coast of Kauai. We already described the garden's effort to control alien species that are overwhelming natives plants.
Sites cleared for reintroduction are chosen because their altitude, rainfall and exposure to sun resemble the endangered plant's native habitat. The clearing of weedy species often "looks like modern forestry," says David Bender, a botanist working for the garden. "We remove everything, hit the reset button, then replant the area with native species."
Here's a letter from Hawaii on preserving endangered plants.
While the milkweed is common in Kansas and Missouri, the plants usually mowed for hay, preventing mature seeds from developing. In the east, in Illinois and nearby states, milkweed habitat has been chopped and sliced by all the forces of development,. That's been enough to place the plant on the federal list of threatened species.
Marlin Bowles, a plant conservation biologist at Morton Arboretum, says the fragmented habitat prevents the plant from setting seeds because the milkweed is "self-incompatible." Don't feel bad for the plant -- it doesn't hate itself -- but when genetically identical plants are crossed, no seeds result.
The phenomenon protects against inbreeding, but at a cost: The milkweed is a perennial, able to survive without seeds, but Bowles says it will eventually, through chance alone, get whacked by disease, development, fire, storm or predation -- unless it can set seeds and move to new terrain. The process of fertilization also maintains genetic diversity in succeeding generations, allowing the plant to evolve and adapt to changing circumstances.
Starting in the early 1990s, Bowles and associates began propagating seeds from the Kansas and Missouri plants. They also fertilized these plants in Kansas with pollen from the surviving relatives from the Illinois region, to sustain the remaining genes in the eastern part of its range.
The group set out their first plants in 1994, but the plants grew slowly in the wild, and seeds did not appear until this year. The seeds are expected to mature in September, at which point the restorationists must decide whether to bring them to the greenhouse for propagation, or permit them to take their chances in the wild.
Tell me more on the genetics of species reintroductions.
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