Focus on Research
Penn State Intercom......January 17, 2002

World's smallest lizard
lounges on a dime

By Barbara Kennedy
Eberly College of Science
RESEARCH_Lizard

The world's smallest lizard has been discovered on a tiny Caribbean islandoff the coast of the Dominican Republic. The newly discovered species not only ranks as the smallest lizard, but it also is the smallest of all 23,000 species of reptiles, birds and mammals, according to Blair Hedges, an evolutionary biologist at the University, and Richard Thomas, a biologist at the University of Puerto Rico.

So small it can curl up on a dime or stretch out on a quarter, a typical adult of the species, whose scientific name is "Sphaerodactylus ariasae," is only about 16 millimeters long, or about three quarters of an inch, from the tip of the snout to the base of the tail. It shares the title of "smallest" with another lizard species named Sphaerodactylus parthenopion, discovered in 1965 in the British Virgin Islands.

Hedges and Thomas discovered small groups of the new species living in a sink hole and a cave in a forest on the remote island of Beata, which is part of the Jaragua National Park in the Dominican Republic.

"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," Hedges said. "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."

Hedges says the habitat that this species needs to survive is disappearing rapidly. "People are cutting down trees

even within the national parks and, if they

take the forest away, these lizards and other species will disappear."

Economic and law-enforcement difficulties are contributing to deforestation of the Caribbean forests, which are even more fragile and more threatened than those in the Amazon of South America because they are so small.

"In the Caribbean, forests that used to cover all of the land now typically cover less than 5 percent, and they are being cut down at an increasing rate, mainly for subsistence farming and fuel," Hedges said. "Although there are laws against cutting down trees in the national parks, the enforcement of the laws is not enough to protect the forests, for a variety of reasons."

Hedges and Thomas went to the remote Isla Beata specifically with the goal of discovering previously unknown species that might be living there.

The "smallest" and "largest" species of animals tend to be found on islands, the researchers said, because species can evolve there over time to fill ecological niches in the habitat left vacant by other organisms that never reached the remote locations. 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.

"Habitat destruction is the major threat to biodiversity throughout the world," said Hedges, who has studied Caribbean species for many years, and has long recognized it as a "hot spot" of threats to biodiversity. "The Caribbean is now widely recognized by conservationists and biologists as an ecological hot spot because it clearly is an area that has an unusually high percentage of endangered species that occur nowhere else in the world," Hedges said. "Most land species on Earth have evolved to live in forested regions, and now humans are destroying the forests, which is a big problem, especially on islands, where species have restricted ranges."

Hedges and Thomas named the new lizard in honor of Yvonne Arias, a champion of conservation efforts in the Dominican Republic. Arias is president of the organization known as Groupa Jaragua, a non-governmental organization set up specifically for preserving the biodiversity of the Jaragua National Park.

Hedges and Thomas have discovered and described more than 50 new species of amphibians and reptiles throughout the Caribbean. Hedges says this exploration and discovery is critical for protecting biodiversity.

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


Barbara Kennedy can be reached at science@psu.edu.

Fossil teeth show

recent origin of

growth pattern

 

The long period of development leading up to a modern human's adulthood arose relatively late in our evolutionary history, according to an analysis of growth patterns in fossil teeth, written by Christopher Dean of University College, London, and colleagues including Alan Walker, distinguished professor of anthropology and biology at the University.
"One of the things that sets modern humans apart from the living great apes is our long period of growth and development," Dean explained. "While humans take a good 18 to 20 years to grow up, other primate species like chimpanzees and gorillas take just 11 or 12 years."
"Dental development is a good measure of overall growth and development," said Walker, who was one of the first to use scanning electron microscope studies of fossil teeth. "Teeth grow in an incremental manner like trees or shells, preserving a record of their growth with daily marks along the prisms that make up the enamel."

By making thin sections of modern and fossil teeth, the researchers were able to count the daily incremental markings within the enamel of humans, apes, and fossil "hominin" species in the human lineage in order to calculate and compare their rates of enamel formation.

"Of the 13 fossil tooth fragments we studied -- both those attributed to the earliest australopith hominins that lived roughly between 4 and 1 million years ago, and those of the earliest members of our own Homo genus that lived about 1.5 million years ago -- none showed the slower pattern of modern human enamel growth," said Walker. "We found that the first dental evidence for a modern human-like growth period appears much more recently, in a Neanderthal fossil that lived about 120,000 years ago."

Researchers had expected that Homo erectus -- the first fossil human ancestor to show a suite of modern human-like characteristics -- would show evidence of a modern human-like growth period. However, because the brain in Homo erectus was still not as large as a modern human's and because a long growth period is linked with the time needed to grow and learn to use a large brain, these findings are compatible with predictions that could be made on the basis of brain size alone.

"It seems our prolonged period of growth and development may be a more recent evolutionary acquisition that arose in step with our comparatively recent development of a larger, modern, human-sized brain," Walker said.

Criminal justice system
penalizes Hispanics, study says

The Pennsylvania criminal justice system deals with Hispanic defendants more harshly than either whites and blacks, both for drug-related and non-drug related offenses, a researcher said.

Darrell Steffensmeier, professor of sociology and crime, law and justice, and Stephen Demuth, assistant professor of sociology at Bowling Green State University, studied Pennsylvania Commission on Sentencing figures for 14 counties which contain 89 percent of the state's Hispanic population and 93 percent of the black population.

In drug-related cases, Hispanics were 26 percent more likely to be incarcerated than white offenders, and blacks were 7 percent more likely. Hispanics received sentences on average about eight months longer than those given to whites. As opposed to this, blacks were handed sentences only an average of three weeks longer than whites. The tougher sentences imposed on blacks and especially Hispanics seem to result from the keen attention given by the media and law enforcement agencies to black and Hispanic drug-distribution networks, he said.

The American mainstream has a long history of prejudice against Hispanics, who have been often stereotyped as irresponsible and more prone to serious crime and recidivism, he noted. This in turn may color the attitudes of various court officials -- police, prosecutors, probation officers and judges -- in their processing of Hispanic defendants, causing them to view Hispanics as poorer risks for rehabilitation and a greater potential danger to the community.

The courts' treatment of Hispanics has important implications since they now constitute almost 12 percent of the population, and by 2005 they will replace blacks as the United States' largest "minority" group, Steffensmeier said.

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