Thomas Daniels, Ph.D., director of the center, said the research being conducted in labs there is more important than ever, as every major problem we face today has a biological basis at some point.

“When we talk about global warming, it means forests are changing, vector-borne diseases are coming into places they’ve never been before, world hunger is becoming an issue as our population size is likely to outstrip carrying capacity, and landscapes are going to change with rising sea levels.” he said.

“So if we don’t have people at ground level making good decisions, going to meetings to talk about the value of conservation, and understanding the fact that climate change is a function of human activity, then it’s going to lead to further and further hardship down the road. That’s the value of having an educated populace. Certainly Fordham sees that, and we see it here at Calder.”

Until now. In the last two years, facilities crews have cleared out overgrown shrubbery and dead trees, many of which were felled by the winds of Hurricane Sandy. The eastern shore path is now open to visitors—part of a half-mile, easy-to-follow loop around the lake and through the surrounding forest.

Tom Daniels, PhD, director of the center and associate research scientist in vector ecology, said the re-opening of the path is part of larger, long-term effort to better manage the forests and wetlands of the 113-acre property. He hopes it also makes it more attractive to members of the wider Fordham community and other science communities, looking for locations to do research.

“If you’ve got a piece of property that has a certain value to researchers, one of the goals is to maintain its value. So we have to manage the property at a level that we haven’t done before,” he said.

Some of that management involves clearing out invasive flora, like Japanese barberry, stilt grass, tree of heaven, and garlic mustard. The center has also formed a committee of faculty members, and drafted a master plan for the property with the help of a consultant whose previous clients include the New York Botanical Garden.

It also involves making the larger Fordham community aware of the research opportunities there on disease vectors like ticks and mosquitoes, aquatic systems, herpetology (amphibians and reptiles), bird, and mammal studies, as well as plant evolution and urban ecology research.

Although staffing limits and the station’s mission of providing an academic environment conducive to faculty and student research on ecological issues mean that the center will have to occasionally decline visitors, Daniels said he wants to accommodate as many members of the Fordham community as possible. He noted that Ram Vans depart from the Rose Hill campus three times a day, five days a week.

“Biologists aren’t the only ones that might find Calder exciting. We’ve got things like geological outcroppings that are interesting if you’re a geologist. We have scenic views that are really great if you’re a photographer. We have animals that are fun to look at if you’re interested in wildlife illustration, and we have a variety of plants— both native and ornamental—that are great to take pictures of and to illustrate,” he said.

“We want to make Calder a better-known resource to the Fordham community and to scientists as a whole, because there’s a lot to take advantage of.”

The hypothesis, known as the “dilution effect”, says that disease pathogens are less frequent in areas with a greater number of host species.

“Some hosts are really bad at maintaining and transmitting the Lyme disease pathogen, and some are very good, what we call competent reservoirs,” said Christine Zolnik, PhD, a recent doctoral graduate and co-author of the study recently published in PLoS ONE. “The thinking is that the more species you have, then the more you’re able to dilute what we call the ‘competent reservoir.’”

Computer Simulation vs. Hard Numbers

Blacklegged ticks are known to transmit Lyme disease to a variety of animals. They have more than 100 potential host species, and in the past 10 to 15 years the Lyme/tick/host relationship has become an oft-cited example of the dilution effect.

Many of the studies on dilution effect are built on computer simulations with limited empirical data—i.e.—hard numbers from the real world, said Zolnik. But for her study, she chose to compare actual areas.

“Because there’s such large number of potential tick hosts at a site, it’s very difficult to assess biodiversity at each collection location,” she said. “Therefore, I used habitat fragmentation as a proxy for biodiversity.”

The area of less biodiversity was one with “landscape fragmentation,” meaning lots of buildings and streets interrupting nature. The area of more biodiversity consisted of woodlands that provide uninterrupted food and shelter for a variety of creatures.

The thinking was that pathogen prevalence within a blacklegged tick population would vary greatly between a fragmented landscape and a less-fragmented landscape.

Fragmented Bronx Landscapes vs. the Woods of Westchester

Zolnik collected tick samples at 14 sites across the Bronx, Westchester, and Putnam counties in New York, and in Litchfield County, Connecticut.

The Bronx sites were far more fragmented than the other sites, but, to Zolnik’s surprise, fragmentation didn’t affect the number of infected ticks found.

“I did find variation between the sites, but I didn’t find any evidence to the dilution effect,” she said. “So we still really don’t have a handle on what’s influencing the infection rate.”

“This study provides evidence that is not in support of a hypothesis that is taken as dogma in the Lyme disease field,” she said. “Just because something is accepted doesn’t always make it correct. But this opens the door for other studies.”

Zolnik said that there’s plenty more to be studied, such as the composition of the host community beyond the well-known dominant species and reservoirs. She said that this is just the type of work that’s ongoing at Fordham’s Vector Ecology Lab where she began her dissertation work with advisors Thomas J. Daniels, PhD, the director of the Calder Center and Sergios-Orestis Kolokotronis, PhD, of the Biological Sciences department. Daniels, Kolokotronis and Richard Falco, PhD, of the New York State Department of Health co-authored the study.

Zolnik said that she didn’t set out to prove or disprove the hypothesis in her dissertation.

“I wanted to find evidence that either supported the hypothesis or not,” she said. “There was a gap in the literature that needed to be filled.”