Gorchov, David , Castellano, Steve , Frank, Peter A. , Khanal, Sujan .
Using age structure to infer dispersal processes in the invasion of an exotic shrub, Lonicera maackii (Rupr.) Herder (Caprifoliaceae), Amur honeysuckle, in forest fragments.
A fundamental question in invasion biology is the importance of expanding fronts (diffusion) vs. long-distance dispersal events. As part of a broader study to understand the patterns and processes of the invasion of Lonicera maackii, we are using age structure to infer whether populations were founded by diffusion or long-distance dispersal. This upright shrub, native to northeast Asia, does not reproduce clonally, but is self-compatible. Because individuals do not reproduce before age 4, the age structure of a population founded by one or a few long-distance colonists would be expected to have 1-few old individuals followed by a gap of several years. Alternatively, we expect a continuous age distribution if populations were founded by diffusion from nearby sources, where propagule pressure could deliver seeds each year. We quantified the age structure of L. maackii in 17 woodlots in an agricultural matrix in a 20 km2 recently invaded region in Darke County, Ohio. Woodlots ranged in size from 1-10 hectares and generally 50 - 1000 m from potential propagule sources. For small populations (N< 30) we sampled all individuals; for larger populations we sampled the largest 30 shrubs. Individuals are readily located in spring and fall because of this species' extended leaf phenology. For each individual we collected the basal portion of the largest 2-4 stems, made clean cuts with a miter saw, scanned cross sections, processed the images with 'Image J,' and counted annual rings. Individuals ranged in age from 2 to 21, with populations (oldest individual) ranging from 4 to 21. Most populations analyzed to date show continuous age distributions, consistent with diffusion rather than long-distance dispersal. We interpret these finding in light of evidence from microsatellite markers for diffusion vs. long-distance dispersal, and discuss implications for management and control.
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1 - Miami University, Botany
2 - Miami University, Botany, 316 Pearson Hall, 700 East High Street, Oxford, OH, 45056, USA
Presentation Type: Oral Paper:Papers for Sections
Location: Portland Room/Chase Park Plaza
Date: Monday, July 11th, 2011
Time: 9:30 AM