Apr. 17, 2000 University Park, Pa. --- Using a standard statistical method to examine the relationships among geographical range size, body size, habitat breadth and local abundance in North American sunfish and suckers, a Penn State biologist has identified 13 extinction prone species -— and says that there could more.
Dr. Mark Pyron, assistant professor of biology, Penn State Erie, The Behrend College, says the statistical analysis that he used primarily helps biologists to identify characteristics associated with a species being extinction prone. In sunfish and suckers, he found that the combination of larger body size and smaller geographical range size appears to be a good predictor of extinction-prone species.
"A single environmental catastrophe could result in extinctions of several of these species, due to their isolated distributions," he adds.
Although several other research groups have predicted that species with higher local abundance will also have larger geographical ranges, Pyron did not find that to be true for sunfish and suckers. However, he did find the expected positive relationship between body size and habitat breadth but only in sunfishes, not suckers.
"Sucker species that are extinction prone are not the largest bodied species, but may require larger home ranges and larger geographical ranges than smaller bodied species to avoid extinction, " he notes.
In addition, Pyron notes that because the extinction prone species tend to have very specialized habitats, if they were introduced in other areas in an effort to save them, they would likely not make it.
In a recent interview, the Penn State researcher said that the species he identified as extinction prone were probably already known to be rare because they have a small geographic range size. The extinction prone species of sunfishes are found almost exclusively in the Eastern United States. Only one of the extinction prone sunfishes is found in the west. The extinction prone suckers, on the other hand, are primarily found in the Western United States. The robust species, in contrast, are found all over North America.
When he graphed the species characteristics as part of his study, the Penn State researcher noted that one extinct sucker did not appear on the graph in the same location with the other extinction prone species. The existence of the "outlier" indicates to him that there could be an additional group of sunfish and suckers that are also extinction prone.
Pyron’s findings were detailed in the Journal of Biogeography last year. Data for the study were drawn from Page and Burr’s Field Guide to Fresh Water Fishes of North America. Pyron took the range size maps from the guide, digitized them and calculated the areas. The guide also contains the information on body sizes and habitat that Pyron used.
The 13 species of sunfish and suckers identified as extinction prone in Pyron’s study:
Roanoke Bass — found in Virginia and North Carolina.
Ozark Rock Bass — found only in Arkansas and Southern Missouri.
Sacramento Perch — found only in California. There are attempts to introduce it in Nevada.
Red Eyed Bass — found in northern Alabama and Northern Georgia.
Suwannee Bass — found only in the Suwnanee River and Ochlockonee Rivers in Florida.
Guadeloupe Bass — found in the Guadeloupe and San Antonia Rivers near Austin, Texas.
Modoc Sucker — found in three streams that drain into the Pit River in Northern California.
Owens Sucker — found in the Owens River in Central California.
Yaqui Sucker — found in the Yaqui and Rio Rivers in Arizona and Mexico.
Lost River Sucker — found in the Klamath and Agency Lakes in Oregon and some northern California Lakes and reservoirs.
West Mexican Redhorse Sucker — found on the Pacific Coast of Mexico.
Cu-ui Sucker — found in Pyramid Lake Nevada.
June Sucker — found in Lake Utah, Utah.
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