Waking Up in Eden (15 page)

Starting in the 1960s, biologists' interests shifted away from the pure revelatory amazement at the diverse speciation on islands to a concern for determining the why and how of evolution. What factors drive a species to diverge, mutate, and adapt? What are the underlying mechanisms that allow for this divergence?
When Warren Wagner arrived in Hawaii he embodied this new approach. Another small, intense man, Wagner had straight, dark, lank hair and a big walrus mustache that lent him a slight chipmunk appearance. Bright, aggressive, with a newly minted Ph.D. and full of the know-it-all obnoxiousness of youth, he eagerly flaunted his newfangled thinking. Wagner was more balanced, and sometimes lumped and sometimes split. He examined all available specimens, identified general characteristics, but allowed for some variation.

Honolulu's Bishop Museum hired Wagner in 1982 to produce a new, comprehensive Hawaiian flora. It was to be the most complete list of flowering species ever compiled. The first and, up until Wagner, the only flora of the Hawaiian Islands was published in 1888 by William Hillebrand, a German doctor who spent twenty years in Hawaii studying the vegetation. Wagner was charged with creating the definitive record of Hawaiian plants for the twentieth century and well beyond. It would consume him and nearly sixty collaborators for a decade.

Warren concluded early on that St. John was just an old coot, and so deliberately left him out of the flora project. Wagner and St. John had a daily opportunity to sort out their disagreements but did not. During Wagner's tenure at the Bishop Museum, he, St. John, and the rest of the botany staff lunched together every day, seated at a picnic table outside the herbarium. They got along cordially but didn't talk about Wagner's book.

As Wagner neared completion of his project he had identified 2,270 plant species growing in Hawaii, including 988 native Hawaiian species. St. John apparently grew more and more furious. He seethed quietly, like a spider in waiting. And then he struck. Just after Wagner sent the final galleys of his book
to the printer with his last revisions, St. John let loose a flurry of publications in tiny, obscure botanical journals. He claimed to identify a total of 800 more Hawaiian native species, nearly doubling the number reported by Wagner.

St. John succeeded in casting doubts on the accuracy of Wagner's new flora before it was even reviewed. The old man died a few months later, just a few months shy of one hundred years. He left a tangled, spiteful legacy of disputed classifications that has taken Wagner and other Hawaii botanists more than a decade to sort out. How silly. This was just the sort of petty malice that wasted time. Why couldn't they have joined forces and sorted out the classifications together? Perhaps it was the island effect of confined spaces; it seemed to drive people to stake out a small patch of turf and defend it to the end.

W
HEN
W
ARREN
W
AGNER
was still a graduate student at Washington University in St. Louis, he received some valuable advice from G. Ledyard Stebbins, the landmark geneticist and evolutionary biologist who was among the first to apply modern evolutionary theory to plants. By all means, study the Hawaiian endemics, Stebbins said, but if you really want to study evolution, study the new weeds. They're the future of the archipelago.

After completing the Hawaii flora, Wagner became a leading voice in the new field of plant evolutionary genetics on oceanic islands. He's still studying the weeds, now as chairman of the botany department at the Smithsonian Institution in Washington, D.C. Every few years or so he flies to Nuku Hiva, then sails to the small outer Marquesas Islands, made famous by Paul Gauguin and Herman Melville. For three to six weeks, he treks up mountains and through rain forests to collect plant samples for DNA extractions. Wagner's work shows an ancestral genetic link between the Marquesas Islands and the waif plants that settled in Hawaii, 2,800 miles to the northeast.

Some scientists call Hawaii the Rosetta stone of evolution: the perfect place to decode the formation of new species, that
elusive process that Charles Darwin called “the mystery of mysteries.”

Geography dictated evolutionary fate. As most of the Hawaiian Islands lie within the earth's tropical zone between the latitudes of the Tropic of Cancer and Tropic of Capricorn, sun rays hit them directly, at times perpendicularly, creating a hot zone. The higher temperatures warm the ocean and increase evaporation, which allows trade winds to vacuum up enormous amounts of water, then disgorge it in seasonal monsoons that made the islands habitable.

Because the Hawaiian Islands are
the
most isolated in their distance from continents, very few plants or animals could travel the vast distances over open water to reach the archipelago. Once on the islands, the colonists met an onslaught of varied climates and ecologies, all packed into a tiny area smaller than Rhode Island. It was adapt or fail to survive. This superheated, supercharged evolutionary crucible caused the few colonists to evolve new traits in a shorter time compared to elsewhere. It produced Hawaiian plant and animal species so diverse, so multiformed and adaptive as to represent one of the natural wonders of the world.

The central questions for evolutionary scientists are, When did adaptation occur, and why? Many of the Hawaiian species exhibit affinities with continental species, yet how were they transported such great distances? Where did each of the immigrant lines come from? Did they evolve here, or exist unchanged from their original form, perhaps from now-disappeared land masses?

These puzzles have consumed scientists for centuries and drove Darwin to formulate his theory of natural selection. Now,
however, new techniques using computer programs and DNA analysis are beginning to provide real answers.

What Darwin suspected and could only postulate based on careful observations, Wagner now proves.

As I dug deeper into scientific papers and tomes, I found that the story has been revealed in odd places — in the giant chromosomes and many-shaped penises of the Hawaiian fruit fly, in a remote Arctic violet, and in a common California weed.

W
HEN
H
AWAII AND
A
LASKA
were admitted to the union in 1959, my fourth grade class at Oak Knoll Elementary School in Hopkins, Minnesota, celebrated by constructing relief maps of the mountainous terrains of the forty-ninth and fiftieth states. Sculpting the continental Alaskan landmass out of a crumbly mixture of salt, flour, cream-of-tartar, and water was easy compared to trying to make the Hawaiian archipelago. We created a Pacific Ocean by painting a box lid blue, then formed islands from little blobs of homemade Play-Doh. We learned that a long, undersea fissure in the earth's crust created escape hatches for molten lava lurking at the center of the earth. Each leak erupted into its own volcano that grew and grew until it parted the sea waters above. When cooled, the lava spire became an island. The explanation could almost have come from the Book of Genesis: Let the dry land appear, and it was so.

The story has changed dramatically.

That very year, Princeton Geology professor Harry Hess informally presented his hypothesis that the seafloor was in constant motion, slowly spreading apart. Three years later, in his 1962 paper “History of Ocean Basins,” one of the most important contributions in the development of plate tectonics, Hess
outlined the basics: molten rock (magma) oozes up from the earth's interior along mid-oceanic ridges, forming new seafloor that spreads away from the active ridge crest and, eventually, sinks into deep oceanic trenches. The earth's hard crust floats over a slippery core, propelling continents to move in massive plates — similar to the way a cracked shell slides over a hard-boiled egg. Subsequent testing of the ocean floor showed Hess was right in his estimate that ocean sediment had accumulated only for three hundred million years or so, a very short time compared to what it would have been if the sea bottom had rested undisturbed since the oceans first formed.

Hess's work soon led to an explanation for the Hawaiian Islands. Canadian geophysicist J. Tuzo Wilson postulated in 1963 that the islands formed successively over a fixed hot spot, then slowly moved, conveyer-belt style, to the north and west. The eight current high Hawaiian islands occupy the southeast end of a much longer submerged archipelago that extends 3,616 miles north and west, culminating in Meiji Seamount (an underwater mountain) up near the Bering Strait. Those ancient underwater islands resulted from initial volcanic activity about seventy-five to eighty million years ago. Thus, over a compacted span, islands formed some of the highest mountains in the world, then eroded or broke off in great slumps into the ocean until they dwindled to mere atolls or slips of sand barely a few yards high. And then many of them disappeared under the ocean's surface.

The southernmost volcano, Kilauea on the Big Island, has flowed more or less continuously since missionaries first sighted its red-hot spouts and belches in 1823. Farther south, the underwater seamount of Loihi is currently forming, although scientists
project it won't poke above water for another million years or so.

Tectonic movement is slow: three and a half inches per year.

The end result of these scientific advances is that we know that many of the Hawaiian Islands were quickly created and then disappeared, all in neat and tidy order, which now can be almost precisely dated.

Back at Oak Knoll Elementary, we also learned that Hawaii was called the melting pot. The islands attracted peoples from around the Pacific Rim and North and South America, and they lived together peaceably.

As I investigated island biology further, I found that the melting pot metaphor also serves well to explain the truly exceptional fauna and flora of Hawaii.

A
LTHOUGH
D
ARWIN BECAME
the world's most famous naturalist, it didn't always look like he, or his theories, would amount to much. Captain Robert FitzRoy hired the twenty-two-year-old genteel Darwin as company for a two-year surveying voyage to Tierra del Fuego and the East Indies. Loneliness and isolation had been known to drive sea captains insane, and Captain FitzRoy wanted diversion. The voyage of the HMS
Beagle
stretched into a fifty-seven-month journey through the Pacific islands and around the South American continent. It turned Darwin into an acute observer. Although dazzled by the Galapagos Islands fauna, it was the birds that inspired his eureka moment.

He noticed that the Galapagos finches all resembled the common finch on mainland Ecuador but varied slightly from island to island. Seed-eating finches cracked open nuts with gross,
heavy beaks. Others developed straight, narrow, chisel-like bills to pry insects from trees. Still other species' beaks grew thin and curved, all the better to sip nectar from flowers. Perhaps, Darwin theorized, they had somehow descended from the same parental lineage. “The most curious fact is the perfect gradation in the size of the beaks,” he wrote in his journal. “There are no less than six species with insensibly graduated beaks. . . . Seeing this gradation and diversity of structure in one small, intimately related group of birds, one might really fancy that from an original paucity of birds in this archipelago, one species had been taken and modified for different ends.”

Fascinated by the way that plants and animals moved around the globe, Darwin sensed that long-distance dispersal might be key to how and why species evolved, or what he called “radiated,” into different forms. He reasoned that Galapagos animals must have traveled the six hundred miles from South America over water, as no evidence of a land bridge existed. After his return to England, he mounted experiments for several years, to test whether plants and animals were capable of long-distance travel. He put seeds into saltwater tanks in the basement of his house in Downe, happily reporting later, “I found that out of 87 kinds, 64 germinated after an immersion of 28 days and a few survived an immersion of 137 days.” He hung a pair of chopped-off duck's feet in an aquarium and with satisfaction observed that freshwater snails clung to them, evidence that the mollusks could have traveled as stowaways. He shot partridge after a heavy rainfall, then counted the seeds in the mud stuck to the birds' feet.

He finally published his five-hundred-page tome,
On the Origin of Species,
in 1859, twenty-three years after the return of
the
Beagle
. Buttressing his theories was an impressive array of evidence, including a growing fossil record, new estimates of the geological age of the earth's strata, and his own experiments. He postulated that species evolved slowly by a process he called “natural selection.” Traits that contributed to successful survival tended to be reproduced through the next generations in greater proportion. Eventually a trait mutated, or evolved, into a different species or even split into several directions of mutation, in response to new surroundings.

Darwin noted even then that endemism was a byproduct of evolution — the creation of species that exist in only one place and nowhere else.

What would have happened if Darwin had visited Hawaii and seen its honeycreepers, regarded as perhaps the most spectacular example of adaptive radiation in the world, even greater than that of the Galapagos finches? All thirty-three known Hawaiian honeycreeper species and another fourteen known from fossil records share similar bodies. But the honeycreeper bills vary in astounding directions, from a short chisel to a long, curved scimitar. Tongues also grew, some like Pinocchio's nose, in astonishing lengths and directions. Would the differences be so startling that Darwin would have missed their commonality?

He based his studies on morphology — the examination of form and structure. He put forth the idea of drawing evolutionary trees — grouping species that exhibit the same characteristics and branching into ever-more refined, distinct features. In the old days, botanists such as Harold St. John manually sketched family trees to diagram familial relationships; these sketches were called “cladograms.” The new evolutionists like Warren Wagner use such structural study only as a starting
point. Sophisticated computer programs now spew out faster and more complex cladograms.