Return of the species



1. Wolves. Endangered?
2. Wolves on the rebound
3. History of extermination
4. Midwestern wolves

5. Causes of extinction
6. Trumpeter swan sings
Wisdom of reintroductions
8. Helping the plants
9. Moving the plants

10. Genetics movement
11.House flies!





























































photo of a monarch caterpillar eating
A monarch caterpillar hangs upside down while munching on a milkweed leaf.
© S.V. Medaris

  Bringing 'em back alive

A remote valley with a green-shrouded mountain looking like a giant tooth, in the background.
This remote valley on Kauai, Hawaii, hosts a small-scale effort to reintroduce some of Hawaii's rarest plants.
Courtesy National Tropical Botanical Garden

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."

From ground zero
Bender says restoration is "very site-specific," meaning that the details vary from one valley to the next. Plant reintroduction is a chancy business. There are no guarantees of success, but these guidelines can help:

Gather local varieties. "Plants are micro-adapted to conditions," says Bender, so a plant from the next valley is preferable to one from across the island or another state.

Select plants that need little care. Hauling water deep into the Limahuli Valley is helicopter work. That's expensive.

Select plants adapted to the sunlight and windiness in clearings. Once these pioneer plants are established, they will create conditions allowing shade-adapted species to be introduced.

Avoid fire. Fire, used to great effect in restoring many contintental ecosystems, is an exotic force in Hawaii. Two months after a major fire, Bender says, "there would not be a square inch that didn't have a seed," mainly from invasive alien plants.

Learn about ecological relationships. "To recover plants in the wild, you have to deal with pollinators," says Adam Asquith, an entomologist with the U.S. Fish and Wildlife Service. He says Hawaii has the world's greatest collection of plants where individuals have either male or female flowers, but not both. These plants often require insects, birds or bats to exchange pollen. The relationships go both ways, he indicates. Plants depend on insects, and vice versa: "Most native plants have 100 unique insects living on them, but the insects go" when the plant starts to disappear.

Here's a letter from Hawaii on preserving endangered plants.

Milking that weed

Yellow flowers in a down-pointing spray. Long, thin green leaves on the stem point upward.
Mead's milkweed (Asclepias meadii) can't breed with identical twins. Botanists are lending a hand in the struggle for survival.
John Schwegman, U.S. Fish & Wildlife Service

Compared to animal reintroductions, returning plants to their native range is cheap, but the research still costs money, and can take many years. The Morton Arboretum in Illinois is trying to restore Mead's milkweed to prairie remnants in that state. The plant is related to common milkweed, but it's just 12 to 18 inches tall; like its better known relative, it feeds larva of the monarch butterfly.

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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