The world's smallest lizard has been discovered
on a tiny Caribbean island off 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 a paper published
in the December issue of the Caribbean
Journal of Science. Blair Hedges,
an evolutionary biologist at Penn State,
and Richard Thomas, a biologist at the
University of Puerto Rico, are co-authors.
The National Science Foundation (NSF)
funded their research.
"Many extraordinary species still await
discovery and, unfortunately, the time
left to discover them is rapidly disappearing
because of habitat destruction and other
forms of environmental degradation," says
Larry Page, program director in NSF's
division of environmental biology. "This
discovery of what appears to be the world's
smallest reptile is particularly interesting
because of the physiological constraints
associated with decreasing body size.
Discoveries of unusual organisms have
a great deal to tell us about biological
evolution and our environment."
So small it can curl up on a dime or stretch
out on a quarter, a typical adult of the
species 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 found small groups of the new species
living in a sink hole and a cave in a
partially destroyed forest on the remote
island of Beata, which is part of the
Dominican Republic's Jaragua National
Park.
"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 says. "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."
Hedges and Thomas went to Isla Beata specifically
to discover previously unknown species
that might be living there. The "smallest"
and "largest" species of animals tend
to be found on islands, the researchers
say, 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.
"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 says. "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 desiccation.
"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 explains.
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All photos copyright
S. Blair Hedges
Jaragua lizard (adult female), from Beata
Island.
A larger
version is here.
Photo credit: Copyright S. Blair Hedges
Jaragua lizard (adult female), from Beata
Island, on U.S. dime.
A larger
version is here.
Photo credit: Copyright
S. Blair Hedges
Jaragua lizard (adult female), from Beata
Island, on Dominican Republic one peso
coin (approximately size of U.S. quarter).
A larger
version is here.
Photo credit: Copyright
S. Blair Hedges
View of campsite on Beata Island.
A larger
version is here.
Photo credit: Copyright
S. Blair Hedges
View looking south at low, flat Beata
Island (in distance) from the southernmost
point in the Dominican Republic.
A larger
version is here.
Photo credit: Copyright
S. Blair Hedges
Map of Hispaniola and Beata Island.
A larger
version is here.
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