Rattlesnakes sound warning on biodiversity

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John Carberry

Like the canary in a coal mine, the timber rattlesnake may be telling us something about the environment we share. Roads -- even small, low-traffic roads -- can fragment wildlife populations genetically, reports a new Cornell study.

Such fragmentation can make populations less genetically diverse, which can make them more susceptible to illness or environmental changes that threaten their survival.

Cornell researchers -- using cutting-edge tools, including fine-scale molecular genetics and microsatellite markers -- tracked rattlesnakes in four regions of upstate New York to understand how wildlife habitats are affected by even modest human encroachment.

"We used this species as a model to investigate general processes underlying population-level responses to habitat fragmentation," said the authors, led by former Cornell postdoctoral researcher Rulon Clark, Ph.D. '04, now an assistant professor at San Diego State University, in the paper "Roads, Interrupted Dispersal and Genetic Diversity in Timber Rattlesnakes," available online and to be published in the August issue of Conservation Biology.

The researchers discovered that fragmentation of natural habitats by roads has had a significant effect over the past 80 years on genetic structure of timber rattlesnakes in New York. "Our study adds to a growing body of literature indicating that even anthropogenic habitat modifications that does not destroy a large amount of habitat can create significant barriers to gene flow," the researchers write in their paper.

The new findings reinforce earlier work on other terrestrial animals -- from grizzly bears to frogs -- and provides a fresh warning about habitat fragmentation that all plans for future human development must consider.

The researchers used fine-scale molecular genetics as well as behavioral and ecological data to look at timber rattlesnakes from 19 different hibernacula -- shared wintering quarters -- in four regions in New York: the Adirondacks, Sterling Forest, Bear Mountain and Chemung County. In each case they used microsatellite markers to track how populations dispersed from their winter dens, their subsequent reproductive patterns and how roads in these areas altered that gene flow. The roads themselves -- all paved roadways built in the late 1920s to early 1930s for motorized traffic -- were examined for use and relationship to natural barriers. Tissue samples from more than 500 individual snakes were examined.

"Over all four regions and 19 hibernacula, none of the genetic clusters ... spanned either major or minor roads; hibernacula belonging to the same genetic deme (a local population of organisms of one species) were always on the same side of the road," the paper states. "This fine-scaled analysis, repeated over four geographic regions, underscores the significance of roads as barrier to dispersal and natural population processes for timber rattlesnakes and perhaps other species."

The research team also included Kelly Zamudio, Cornell ecology and evolutionary biology professor; William Brown of Skidmore College, Saratoga Springs, N.Y.; and Randy Stechert, an environmental consultant for the New York State Department of Environmental Conservation.

The research was funded by the National Science Foundation and the New York State Biodiversity Research Institute.


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