ITHACA, N.Y. -- Salamanders with unusual, asymmetrical spots have been found in a pond in the middle of an Ithaca golf course. Cornell University biologists, who have compared the amphibians with symmetrically spotted specimens gathered from the same pond six decades earlier, believe they are seeing indications that changes in a salamander's spots can signal environmental trouble.
"Salamanders and frogs are considered an early-warning system for environmental stress," says Kelly Zamudio, Cornell assistant professor of ecology and evolutionary biology. "With the dramatic change in these spots, this is an early-warning system for an early warning system."
Zamudio and Amber N. Wright, a Columbia University biology graduate student, who conducted the research while she was a Cornell undergraduate, have published their findings, "Color Pattern Asymmetry as a Correlate of Habitat Disturbance in Spotted Salamanders," in the March 2002 issue of The Journal of Herpetology. The biologists embarked on this research to determine if evidence of environmental health or stress could be seen in the degree of the salamander populations' spot symmetry. Comparing today's salamanders with those gathered in the same breeding area 60 years ago, they found that over the decades the salamander spots have changed from a regular pattern to a more-asymmetrical one.
Zamudio and Wright collected salamander samples from two breeding areas that are about six miles apart and within the same watershed area in Ithaca: Bull Pasture Pond, on Cornell's Robert Trent Jones golf course, and Ringwood Pond, part of a nature reserve protected and managed by Cornell. Zamudio and Wright also examined salamanders in the Cornell Museum of Vertebrates, where the specimens are kept in ethanol-filled jars, gathered from the 1910s to the 1960s by Cornell herpetologist Albert Hazen Wright and his wife, Anna. The Wrights collected the amphibians in the central New York region, including Ithaca's Bull Pasture Pond and Ringwood Pond, and other parts of the eastern United States.
Last year, Amber Wright and Zamudio took digital images of the museum's salamanders from the 1930s to the 1940s and of individual salamanders living in the two populations today. Using imaging software developed by the National Institutes of Health, the biologists found that the Bull Pasture Pond salamanders' spots had changed over time, but the Ringwood Pond salamanders' spots had not. The results confirmed the researchers' predictions that the presence of the golf course has changed the appearance of the Bull Pasture Pond's salamanders. "Adults currently breeding on the golf course are significantly more asymmetrical than individuals collected from that population before the golf course was constructed," said Wright in the journal article.
While Wright and Zamudio have studied the salamander's spots, they will not speculate on the cause of the changes. Frank Rossi, Cornell assistant professor of horticulture, who specializes in turf management, says that persistent and toxic materials, such as calcium arsenate and mercurous chloride, would have been used on the Robert Trent Jones golf course during the 1950s, 1960s and 1970s. Rossi said that golf course turf managers, in general, did not seek environmentally friendly ways to improve turf until the late 1980s.
Zamudio admits to scientific controversy over using museum samples and measuring them against contemporary specimens, because the older samples can fade or shrink. "But our animals were taken from the same two places, so we are only pooling samples over time. Our historical salamander samples fairly represent the degree of symmetry in their populations before the construction of the golf course," she said.
Notes Wright: "If amphibians are being touted as sentinels of ecosystem health and if asymmetry has been implicated as an early-warning system for monitoring population health, then using museum collections and comparing them to modern samples could lead to a powerful strategy for amphibian and ecosystem conservation."
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