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Harvard Forest Symposium Abstract 2013

• Title: Effects of changing hostplants, climate, and landscape on Baltimore checkerspot butterflies
• Primary Author: Elizabeth Crone (Tufts University)
• Additional Authors: Greg Breed (Harvard Forest); Leone Brown (Harvard Forest); Paul Severns (Washington State University); Sharon Stichter (Massachusetts Butterfly Club)
• Abstract:

  Human activities change environments in many ways, and ecologists are increasingly asked to evaluate the impacts of these changes on plant and animal populations. We are using the Baltimore checkerspot (Euphydryas phaeton) as a model system with which to evaluate the roles of multiple possible drivers in determining population dynamics:
  
  
  
  First, this species, which was historically specialized on a single native plant species (turtlehead, Chelone glabra) expanded its diet to include feeding and ovipositing on a widespread nonnative plant species (English plantain, Plantago lanceolata). However, P. lanceolata is a lower-quality food source than C. glabra. It is not clear whether adding a large amount of low-quality resources to the landscape should increase abundance, as opposed to creating an ecological trap or sink.
  
  
  
  Second, this species may be increasing due to climate warming. We evaluated trends in abundance of butterflies statewide, using data from the Massachusetts Butterfly Club. These data show that southern species tend to be increasing in abundance, whereas northern species tend to be declining. The Baltimore checkerspot’s population increase in Massachusetts, is typical for southern species, and it is also a species of conservation concern near its southern range limit in Maryland. However, it is not clear that the species is limited by thermal tolerance here, since it also occurs much farther north. Most ecologists would assume populations are limited by hostplants and/or habitat.
  
  
  
  Third, suitable habitat for this species may be increasing at landscape scales. Baltimore checkerspots inhabitat wet meadows, with some flowing water. These meadows may be becoming more abundant on the landscape, particularly in response to changes in beaver trapping laws, and subsequent increase in beaver activity, during the mid-1990’s. Although it is clear that beavers are more abundant, it is not clear if this change has really led to more available open meadows at scales that are meaningful to butterflies.
  
  
  
  We are conducting demographic and movement studies to investigate how responses to these changes play out quantitatively. In other words, are changes in any of the above factors sufficient to cause butterfly populations to increase (or decline)? Understanding mechanisms for this focal species should provide insight and methodological tools for understanding how animals respond in general to large-scale environmental changes.

• Research Category: Biodiversity Studies
  Conservation and Management
  Ecological Informatics and Modelling
  Physiological Ecology, Population Dynamics, and Species Interactions