Greer, Gary , Aldrich, Preston .
Plasticity in Phytotoxin Production by Ailanthus altissima Across a U.S. Megatransect.
Ailanthus altissma (tree-of-heaven) is an invasive from China introduced to the eastern U.S. at least once beginning in the late 1700ís and repeatedly (presumably) on the west coast during the 1800ís. Ailanthus now occurs in all but two of the contiguous states. Its success as an invader has been attributed to a number of traits including rapid growth and maturation, prolific production of wind dispersed seed, and exudation of at least one phytotoxin, ailanthone. Production of allelototoxins is expected to have allocational and selection-dependent costs that are the basis of fitness relevant tradeoffs. Habitats with low rates of herbivory or competition should favor genotypes that do not produce allelochemicals or do so only when competition is perceived or herbivory incurred. We investigated large-scale patterns of Ailanthus phytotoxin production and plasticity of production in response to simulated injury across an East-West U.S. transect in search of patterns that might reflect these adaptive tradeoffs. Ailanthus seed were collected from five maternal trees in each of nine locations, including: CA, UT, CO, IL, OH, and 4 locations in WV. Seedlings from each maternal tree were grown in an OH greenhouse and half from each location were injured one week prior to harvest. Aqueous extracts were used in bioassays on commercial lettuce (Lactuca sativa buttercrunch) and annual rye (Secale cereale). Phytotoxin production was observed in all Ailanthus populations and substantial variation was observed in (1) levels of phytotoxin production and (2) the magnitude and direction of plasticity in phytotoxin production in response to injury across regional and local scales; however, effects varied considerably across traits (i.e., germination versus radicle growth) and assay species. These patterns reflect genetic differences among Ailanthus populations due to genetic drift or selection; however, evidence of selection on phytotoxicity was not evident at the scale of our study.
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1 - Grand Valley State University, Biology Department, 1 Campus Drive, Allendale, Michigan, 49401, USA
2 - Benedictine University, Department of Biological Sciences, 5700 College Road, Lisle, Illinois, 60532-0900, USA
Presentation Type: Poster:Posters for Sections
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM