Distribution and Spread of an Invasive Shrub (Pyrus calleryana, Decne.) across Environmental Gradients in Southern Indiana
Invasive species represent one of the greatest challenges to ecological management today. With new species introductions occurring every year, understanding the impacts, mechanisms of spread, and characteristics of invaded habitats is vital in developing appropriate control methods. One newly escaped invasive species, Pyrus calleryana, is rapidly expanding its invasive range and potentially altering forest structure and composition in southern Indiana. This research investigated characteristics of invaded environments and patterns of spread in P. calleryana. I found an association between P. calleryana and areas with high levels of light and high stocking of shade intolerant species. Data further revealed an association between P. calleryana and dryer aspects. These results indicate P. calleryana is associated with more xeric environments with high light availability and will likely be found in early successional environments. The genetic structure of the study population indicated it was likely composed of two populations. This population structure indicated the importance of density to the spread of P. calleryana as one population corresponded most closely with areas composed of high densities of P. calleryana and the second population was more associated with the expanding edge of the invasion. These results indicate that bird driven dispersal, introduction of new individuals via horticulture, and population density are the factors with the greatest influence on P. calleryana overcoming its self-incompatibility. Overall, P. calleryana has the potential to rapidly expand into disturbed environments and successfully invade, particularly when population densities are high.^
Michael R. Saunders, Purdue University, Michael A. Jenkins, Purdue University.
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