Date of Award
Master of Science
TRAVIS NEAL, for the Master of Science Degree in Plant Biology, presented on May 2018 at Southern Illinois University at Carbondale. TITLE: COMPARISON OF POPULATIONS OF ACHYRANTHES JAPONICA IN THE OHIO RIVER VALLEY MAJOR PROFESSOR: Dr. David J. Gibson Achyranthes japonica (Miq.) Nakai or Japanese chaff flower is a perennial herb that has a native range throughout southeast Asia but is considered an exotic invasive species in the United States. This species is spreading rapidly through hardwood floodplain forest communities of the Ohio River Valley. Its spread into new locations may provide selection pressure from the environment and result in variation in growth traits. Populations possessing heritable traits favored by the environment are likely to pass these traits on to their offspring, resulting in more highly adapted populations to local conditions. In this study, I investigated variation in traits of six populations of A. japonica across its invaded range. Additionally a comparison of populations from the native range (Japan) and these six invaded sites were incorporated to evaluate shifts in morphological traits upon invasion into novel environments; such as forests heavily invaded by invasive species, agricultural margins, and human-shaped landscapes. Performance of A. japonica was quantified in common garden experiments, both in field and greenhouse settings. Plant functional traits were measured to monitor growth and adaptation in order to identify differences in populations. In the field study, plant height varied among populations across sites located along the Ohio River (F10, 182=15.97, p<0.0001). In the greenhouse common garden experiment, above-ground biomass (F10, 86= 5.51, p<0.0001) and below-ground biomass (F10, 86= 5.05, p<0.0001) were highly variable across populations and soil sources. In the field common garden experiment, there was a population by soil source interaction for above-ground biomass (F10, 71= 1.98, p=0.048), below-ground biomass (F10, 71= 2.45, p<0.0001) and root:shoot ratios (F10, 71= 1.98, p=0.0483). Plants grown in soil collected in Warfield, Kentucky close to the site where A. japonica was first recorded in 1981 produced the most vigorous individuals and the largest plants overall. Each location has different environmental pressures shaping the performance of A. japonica. Samples from Japan and Warfield had a higher degree of variability than populations further along the chronosequence in the invaded range. Functional traits varied in performance related to environmental characteristics and source population. The study determined that performance of A. japonica varies across its invaded range including in response to local soils.
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