Genetic structure of rheophytic and nonrheophytic populations of Farfugium japonicum on Yaeyama Islands, Japa

摘要

Farfugium japonicum (L.f.) Kitam., a facultative rheophyte occupying both dryland and riparian habitats within the species range, exhibits various shapes of leaves ranging from stenophyllous to round. The present study assesses variability in leaf morphology (five leaf characters) and genetics (305 AFLP markers) for populations from dryland and riparian habitats on Yaeyama Islands, Japan. Results from the two datasets produced somewhat different patterns indicating that selection for habitat type is effective on leaf shape attributes, while lack of differentiation was observed for neutral markers caused by extensive gene flow. Leaf-shape attributes were clustered into three groups: shade (round), sun (round), and narrow (stenophyllous) leaves. Narrow leaves were only found in riparian populations, indicating that flood intensity acts as a selective agent for this attribute. Although high within-population variation was demonstrated by AMOVA, the populations were distinct enough to be classified in separate groups irrespective of habitat type. However, Neis genetic diversity index (H) was low; suggesting lack of barriers to gene flow among individuals and selection for narrow leaves may act on the survivorship of young seedling.