Harvard Forest Research

Moths, ants, and carnivorous plants: the spatial dynamics of tritrophic interactions

Principal Investigator: Aaron Ellison
Harvard Forest: Apr 01 2007 - Dec 01 2011:

Abstract:
Most theoretical models of species coexistence assume that habitat patches are spatially fixed in size and constant in quality. How communities are organized in systems with dynamic habitat patches – those that are neither spatially fixed in size nor temporally constant in quality – is a crucial yet unresolved ecological question. The proposed research uses realistic field manipulations to understand the creation of dynamic habitat patches and how associated communities interact with them. The research takes advantage of a model ecological system: the carnivorous pitcher plant Sarracenia purpurea, its associated aquatic food web, its prey, and its
herbivores. In this system, the tubular leaves of the plant fill with rainwater and function as dynamic habitat patches for a self-contained aquatic food web. Changes in patch location, quantity, and quality may be mediated by reciprocal interactions and feedback loops among patches (the plant and its growing leaves), its primary prey (ants), and its herbivores (moth larvae that feed on the plants’ leaves). A set of field experiments are proposed in which patch size, density, and spatial pattern, and levels of herbivory are manipulated. These experiments address the following questions:
1. Do the feedback loops between the moth, the plant, and the ant result in local aggregations of plants and spatial association between ant nests and plants?
2. Does spatial clustering of moth larva attacks leads to “traveling waves” of suitable and unsuitable patches?
3. How does the structure of the aquatic food web in a pitcher respond to changes in patch structure (leaf size and number of plants)?

Update 2009
Moth colonization of experimental plots observed in summer 2008. Summer 2009 will involve only continued monitoring of plots.
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