Ecological Factors Influencing Community Composition of Leaf-tying Caterpillars
Open AccessThe composition of ecological communities is determined by a variety of factors that span multiple scales, from interactions between individuals to landscape characteristics. Leaf-–tying caterpillars that build shelters between leaves are ecosystem engineers--—species that influence local community composition via modifications of the abiotic environment. Other arthropods secondarily inhabit leaf ties, which leads to an increase in arthropod abundance and diversity on the plant. I examined the composition of the arthropod community within leaf ties at multiple scales as well as the mechanisms driving compositional differences. The arthropod community occupying leaf ties was examined throughout a summer season on two host plants, American beech and white oak. Weekly censuses were combined into three time periods: early, middle and late summer. Density of arthropods was significantly higher on white oak than beech and increased on both tree species as the season progressed. Diversity measures for the arthropod community within ties varied little, but the composition of the community differed between host tree species and time periods. Though the arthropod communities on American beech and white oak differed, they showed similar patterns of compositional turnover, with distinct communities in early and late summer and a transitional community mid- –summer. The impact of leaf ties on the arthropod community is well documented, but interactions within the ties have largely been ignored. Using artificial leaf ties composed of one leaf and a piece of transparency paper, I compared the behavior of four species of common oak leaf- –tying caterpillars when competing over an existing shelter. The caterpillars were observed to push and hit each other with their head until one retreated from the shelter. The caterpillar that built the shelter was more likely to maintain possession of its shelter than lose or share possession, especially when it was larger than the intruding caterpillar. The four species examined differed significantly in their behavior toward other caterpillars with Psilocorsis cryptolechiella and P. reflexella being more aggressive than P. quercicella and Pseudotelphusa quercinigracella. Leaf- –tying caterpillars frequently engage in direct, physical competition for shelters that serve as a territory as well as a food source. The behavioral differences found between species led to speculation that the caterpillar species that initially builds a shelter may influence which arthropods colonize that shelter. In the field, I created experimental ties occupied by one of three species of caterpillar and allowed the ties to be naturally colonized for one or two weeks. The community changed from one to two weeks, with more arthropods and more species per tie after two weeks. While there were no differences between communities within ties initially built by different species, different communities assembled in ties that initially contained a caterpillar compared to initially empty control ties. There were also compositional differences in the communities within leaf ties where the initial occupant remained in the tie throughout the study compared to ties that had been abandoned. This indicates that the arthropod community inhabiting leaf ties responds dynamically to the presence of a leaf- –tying caterpillar, but not to its species identity.
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Rubin_gwu_0075A_11843.pdf | 2018-01-16 | Open Access |
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CaterpillarFights2.mov | 2018-01-16 | Open Access |
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