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World's Smallest Gecko/ Lizard.... Discovered....on Hispaniola....

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  • N Manwaring
    Tiny Lizard Illustrates Big Lessons on Habitat By Guy Gugliotta Washington Post Staff Writer Monday, December 3, 2001; Page A09 The world s smallest reptile
    Message 1 of 1 , Dec 3, 2001
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      Tiny Lizard Illustrates Big Lessons on Habitat


      By Guy Gugliotta
      Washington Post Staff Writer
      Monday, December 3, 2001; Page A09


      The world's smallest reptile can sit on a dime and lives on a tiny,
      scrub-covered Caribbean island that larger predatory species -- including
      humans -- either couldn't find or didn't want.

      This little gecko lizard, Sphaerodactylus ariasae, suggests that good
      things come in small packages. The Caribbean islands, together about the
      size of Oregon, are also home to the Lesser Antillean threadsnake and the
      bee hummingbird -- the world's smallest snake and bird, and the Cuban
      coqui, the smallest frog in North America.

      Islands have been renowned for unique ecosystems since Charles Darwin
      visited the Galapagos, but they also provide lessons in the intricate
      relationship between habitat and the ability of animals, both large and
      small, to survive amid humankind's intrusions.

      "Islands get colonized by species that float over on logs or get carried in
      a bird's feathers," said biologist Blair Hedges of Pennsylvania State
      University. "Some groups never make it, but the groups that do, have more
      room to spread out. They don't have competition."

      Hedges and University of Puerto Rico biologist Richard Thomas found the
      tiny gecko in "leaf litter" surrounding a limestone sinkhole on Isla Beata,
      a 16.3-square-mile islet off the Dominican Republic. Their findings, which
      are being announced today, are reported in the December issue of the
      Caribbean Journal of Science.

      The gecko is dark brown, measures six-tenths of an inch and is easily
      recognizable as a lizard. "You have to get down on your hands and knees and
      root through the forest floor to look for a sudden movement," Hedges said.
      "They're very dark and very fast."

      Hedges said he and Thomas found eight lizards on Isla Beata and in nearby
      Jaragua National Park, on the Dominican mainland, but traces soon vanished
      as the searchers moved inland.

      "It's a national park, but there are people living there," Hedges said.
      "They have to eat, so they cut trees to plant cassava and beans, and to
      make charcoal. One family can wipe out acres and acres."

      Because of dangers like these, ecologists regard the Caribbean as one of 25
      threatened biodiversity "hot spots," areas making up only 1.4 percent of
      the Earth's surface but where 44 percent of all plant species and 35
      percent of all vertebrate land species can be found.

      Besides the Caribbean, hot spots include the islands of Sri Lanka,
      Polynesia-Micronesia, Madagascar, New Zealand, Indonesia and the
      Philippines. They also include mainland sites such as Panama's Darien Gap,
      the Mediterranean coast (including all of Italy and Greece) and the Burmese
      peninsula.

      Threats can be deliberate -- from poachers or slash-and-burn farmers -- but
      can also come from almost incidental human encroachments on fragile
      habitat. "The areas that survive are the areas farthest away from roads,"
      Hedges said.

      Yet species endure in the Caribbean, even though only about 10 percent of
      the region's virgin forest remains. Isla Beata has a long history as a
      pre-Columbian indigenous settlement, a colonial-era pirate hideout, a salt
      mine that closed in 1960 and a campsite for today's local fishermen.

      Scientists are quick to point out that the isolation of island living does
      not ensure species prosperity. "It may be true that as we create an island
      world, we may create new species," said Columbia University biologist
      Stuart L. Pimm, an expert in species extinction and survival. "But we may
      have to wait a few million years for them to evolve."

      Also, "islandizing" mainland habitat by accidentally framing chunks of
      wilderness with highways or hedgerows is not likely to preserve
      biodiversity. "Water is not a threat to a real island," Pimm said. "But as
      we create forest fragments, the areas around them become weedy, invasive
      and bring in bad species."

      Tiny animals like Hedges's gecko may be able to survive in shrinking
      habitat, but large animals suffer. "On average, big species become extinct
      a lot faster than small species," Pimm said.

      This phenomenon -- that bigger species need bigger land masses to survive
      -- is the theme of a new study describing the largest land vertebrates at
      25 oceanic locations and five continents over the last 65,000 years.

      The study, published last week in the Proceedings of the National Academy
      of Sciences, found that animal species grew bigger on larger land masses,
      that plant-eaters were approximately 10 times as big as carnivores in the
      same area, and that cold-blooded animals, with lower metabolism, were much
      bigger than warm-blooded creatures, who needed more to eat.

      The study examined habitats ranging from the 29-acre Galapagos islet of
      Plaza Sur, where the six-pound Galapagos land iguana is king, to the 21
      million-square-mile Eurasian land mass, home of the now-extinct,
      12,000-pound woolly mammoth.

      "Roughly it takes between a thousand [individuals] or a few thousand of
      anything to survive," said Jared Diamond, a UCLA Medical School
      physiologist and the study's co-author.

      Since land requirements are greater for big animals, those are "the most
      threatened, because they evolved to occupy the full size of their habitat."
      Humans, increasingly, are filling their space.

      Diamond said he and his co-authors chose 65,000 years as the study's cutoff
      point because that is when modern humans reached Australia. The largest
      species on this biggest of islands were marsupials, mammals who nurse
      offspring in an external pouch, and the biggest was the 2,500-pound
      diprotodon. By 40,000 years ago, however, it had been hunted to extinction.
      The biggest marsupial in Australia today is the 190-pound red kangaroo.

      A similar fate befell the giants of the Americas after humans crossed the
      land bridge from Asia between 13,000 and 20,000 years ago. The Columbian
      mammoth, at 13,000 pounds, the sabretooth tiger, at 860 pounds, and the
      950-pound American lion are all extinct.

      By contrast, today's African lion and elephant, considerably smaller than
      their departed American cousins, are still the biggest animals that
      continent ever produced over the last 65,000 years. They survive, Diamond
      suggested, because they watched modern humans evolve over several million
      years.

      "Animals had a chance to get more suspicious as humans got more
      sophisticated," Diamond said. "Unfortunately for the mammoths, mastodons
      and sloths in America, the first humans they encountered were professional
      hunters."
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