World's Smallest Reptile Discovered in Caribbean

By Cat Lazaroff

WASHINGTON, DC, December 3, 2001 (ENS) - The world's smallest lizard has been discovered on a tiny Caribbean island off the coast of the Dominican Republic. The newly discovered species is also the smallest of the Earth's 23,000 species of reptiles, birds and mammals, according to a paper to be published in the December issue of the "Caribbean Journal of Science."

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An adult female Jaragua lizard from Beata Island, on a U.S. dime (Photo S. Blair Hedges)
The 16 millimeter (0.6 inch) lizard Jaragua Sphaero, or dwarf gecko, is believed to exist only on Beata Island and nearby areas in the Dominican Republic's Jaragua National Park.

The lizard was discovered by Pennsylvania State University evolutionary biologist Blair Hedges and University of Puerto Rico biologist Richard Thomas.

"Our discovery illustrates that we still don't know everything about the Earth's species, even in areas that are very close to the United States," said Hedges. "The island home of this tiny lizard is closer to Miami than Miami is to Puerto Rico, and we did not even know the species existed, although the area has been studied by biologists for several hundred years."

So small it can curl up on a U.S. dime, a typical adult of the species, whose scientific name is Sphaerodactylus ariasae, is only about three quarters of an inch from the tip of the snout to the base of the tail. It shares the title of world's smallest lizard with another lizard species named Sphaerodactylus parthenopion, discovered in 1965 in the British Virgin Islands.

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The Jagarua Sphaero is the world's smallest vertebrate (Photo S. Blair Hedges)
Hedges and Thomas discovered small groups of the new species living in a sink hole and a cave in a partially destroyed forest on Beata Island. They went to the remote island with the specific goal of discovering previously unknown species that might be living there.

"It is hard to say whether this lizard is as small as a lizard can get, but you would think it probably is approaching that limit because it is the smallest of all 23,000 known species of reptiles, birds, and mammals," Hedges noted. "The smaller an animal gets, the larger its surface area gets as a percentage of the volume or mass of its body. At some point, it gets to be physiologically impossible to get any smaller."

For the lizard, which lives in a dry environment surrounded by comparatively moist leaf litter, the limiting factor is the danger of drying out.

"If we don't provide a moist environment when we collect them, they rapidly shrivel right up and die by evaporation from the proportionally large area of their surface," Hedges said.

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View looking south at low, flat Beata Island from the southernmost point in the Dominican Republic (Photo S. Blair Hedges)
But the habitat that the lizards need to survive is disappearing rapidly, he said.

"In the Caribbean, forests that used to cover all of the land now typically cover less than five percent - and they are being cut down at an increasing rate, mainly for subsistence farming and fuel," warned Hedges. "People are cutting down trees even within the national parks and, if they take the forest away, these lizards and other species will disappear."

The Jaragua Sphaero (Sphaerodactylus ariasae) is named in honor of Yvonne Arias, who heads the Dominican conservation organization Grupo Jaragua. Arias, a herpetologist, is a leading voice for preserving Caribbean biodiversity.

Grupo Jaragua was formed to advocate protection of Jaragua National Park, and Arias was instrumental in getting the people who already lived on that land to preserve it. Today, residents of the park are playing a major role in running it on their own.

The tiny lizard is just one of several miniature species found in the Caribbean. The world's smallest bird, the Bee Hummingbird, is found only in Cuba. The Northern Hemisphere's smallest frog, a one centimeter long frog known as Monte Iberia Eleuth, ties as the world's smallest frog.

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Beata Island is located off the coast of Hispaniola - one of the most biologically diverse region's on Earth (Photo courtesy Penn State Eberly College of Science)
Species of extreme size, both smallest and largest, often evolve on islands, where they face fewer competitors than they would on the continents. If a species of spider is missing from an island, for example, the lizards there might evolve into a very small species to fill the missing spider's ecological niche.

Although much is still unknown about the diversity of life in the Caribbean, Michael Smith, senior research fellow for the Center for Applied Biodiversity Science at the environmental group Conservation International, says scientists have enough information to appreciate its critical importance.

"The Caribbean is one of the richest places on Earth in terms of unique species, but they are extremely threatened," Smith said. "If the Caribbean continues to lose species at the current rate, then one of the world's most distinctive natural systems will be devastated in our lifetimes."

Many biologists believe the Caribbean ranks as one of the world's top biodiversity hotspots, defined as the 25 places in the world that represent a combined 1.4 percent of the Earth's landmass, but which contain a staggering 60 percent of all terrestrial species diversity.

Rapid population growth is a major threat to the Caribbean's species.

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An adult Jaragua lizard from Beata Island gets comfortable on a Dominican Republic one peso coin, which is about the size of a U.S. quarter (Photo S. Blair Hedges)
"If you add all of the islands together, you would have a landmass about the size of Oregon," said Smith. "But if you add their populations, you would have as many people as the states of Oregon, Washington and California combined. Imagine the effects of concentrating so many people in these small islands, and it becomes clear why so many species are threatened."

Agricultural practices and barriers to regional cooperation between the Caribbean islands also play a role in the loss of biodiversity in the region, as does lack of access to centralized biological data within the Caribbean.

Hedges and Thomas have discovered and described more than 50 new species of amphibians and reptiles throughout the Caribbean, mostly for genetic and evolutionary studies. Finding them, collecting them, and naming them is a necessary first step for other types of research, and is critical for protecting biodiversity, Hedges said.

"It is difficult to protect a species when you don't know it exists," said Hedges.

The research was sponsored by the Biotic Surveys and Inventories program of the U.S. National Science Foundation.