Evan Campbell Grant

Evan Grant

Evan Campbell Grant

Advised by Dr. Margaret Palmer, Professor of Entomology, and Jim Nichols, Wildlife Biologist and Chief Scientist of the USGS Patuxent Wildlife Research Center
PhD Candidate, Marine-Estuarine-Environmental Sciences (MEES) Program
From: born in New York, grew up in New Jersey
Education/work:

  • Bachelor of Science in Natural Resources, Cornell University
  • Has worked at the Patuxent Wildlife Research Center as part of the Northeast Amphibian Research and Monitoring Initiative since 2003.

Interesting fact: Evan's wife Pamela Toschik, now an International Policy Specialist at NOAA, received her M.S. from the MEES Program. They have a big garden and enjoy planting fruit trees in their yard.

Evan Grant grew up in New Jersey, but his parents were very interested in the outdoors and environmental changes. Visits to Rocky Mountain National Park particularly influenced him, and he recalls that during his second visit to the park a ranger pointed out that just a few years before one could see Denver from the lookout point where they were standing, but it had become obscured by haze most days of the year. "I remembered being able to see Denver on my first trip," Evan says, "and that was probably [my] earliest memory of wondering how human populations might be affecting the environment."

Evan hopes to use the results of his research on plethodontid salamanders to highlight the importance of headwater streams and improve land management decisions.

Human-related impacts to amphibian communities especially troubled Evan, given that global scientific data suggests that many amphibian species are heading toward extinction. Evan had a fondness of amphibians growing up as he enjoyed playing with frogs on my grandmother's dairy farm in upstate New York. He chose to attend the University of Maryland based on its proximity to Washignton D.C., coupled with the fact that it was the only graduate school in the area that catered to his interests.

Understanding the Importance of Spatial Networks to Stream Salamanders

Evan is currently studying several species of plethodontids, a diverse family of salamanders along streams in the National Capital Region Network of Parks and in Shenandoah National Park, Virginia. He hopes that his research will help to shed some light on how the spatial elements that influence ecological patterns and processes impact the populations within them. “People have not really studied stream salamanders, so we know relatively little about this aspect of their ecology," he says. One theory is that the movement of stream salamanders may be influenced by the spatial layout of the stream habitat, which might enhance the stability of stream-dwelling salamander populations.

His research addresses how four species of plethodontid salamanders move through a particular type of spatial network called "dendritic ecological networks (DENs)" that include common streams, plants, and caves. DENs have a unique branch-like structure (or hierarchical stucture), where smaller branches are connected to larger branches that together create a network of connected habitats.

Many stream-dwelling salamanders have the potential to move through the network along two possible pathways (1) upstream and downstream within the stream channel, or (2) overland between stream branches. By conducting this research Evan hopes to uncover which movement path is favored by each of the four species of salamanders, and how this choice could potentially impact the stability of the local population.

The Importance of Headwater Connectivity

Evan's study was broken into three elements: (1) development of simulation models, (2) collecting field observations of stream salamander distribution, and (3) an intensive mark-recapture study. Once the simulations were complete, he found that a small increase in overland movement (as little as 1%) led to a drastic increase in the persistence of the population living in a DEN. This implies that the presence of overland movement could greatly reduce the time required to reestablish plethodontid populations after a local extinction event.

By analyzing patterns of stream occupancy, connectivity was highlighted as an important factor in the presence of plethodontid populations. There was a consistent positive response, across three species of stream salamanders, to headwater streams that were connected to other streams versus streams which were not connected to another headwater stream. This response decreased along more isolated streams. He also found that a higher number of salamanders were observed when there was connectivity between two or more first-order streams, as opposed to streams that were connected to larger waterbodies that could support fish and like predators. The magnitude of the response to connectedness, however, varied between species which may be due to the variance in species-specific life history patterns. Evan is still in the process of analyzing his mark-recapture data of 5500 uniquely tagged individual, to determine by which pathway each species of plethodontid is moving. Monitoring is a difficult process because salamanders move very quickly and at any given time Evan estimates that about half of the population is underground. He on occasion has been able to detect juveniles (~20 mm long) making movements across land, while others are found to move up- or down-stream within the stream channel. He anticipates that they wait for the rain associated with afternoon summer storms to make their overland movements.

Making More Informed Land Management Decisions

Evan hopes that his study will highlight the importance of first-order streams and provide science-based evidence to support management decisions associated with landscape change. Due to graduate in May of 2009, Evan hopes to continue working at the USGS Patuxent Wildlife Research Center on amphibian populations and dendritic ecological networks. He would like to research the status of populations in parks and wildlife refuge lands to investigate how management can affect populations.