Impact of soil water chemistry on the apparent sex ratio of the flowering ramets of the dioecious plant Myrica gale var. tomentosa
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We determined whether the apparent (M/Fl) sex ratio (male ramets/flowering ramets) and apparent reproductive ramet ratio (Fl/Li ratio; flowering ramets/living ramets) in 15 Myrica gale var. tomentosa populations varied with dissolved total nitrogen, dissolved total phosphorus, potassium, magnesium, calcium, or pH in the soil water. Our aim was to define the environmental factors affecting the M/Fl sex ratio and Fl/Li ratio of the populations. We also examined the habitat conditions of these populations by analyzing soil water chemistry and water dynamics. In 2007, 3 of the 15 populations had no females. The remaining 12 had significantly male-biased (M/Fl sex ratio = 0.59–0.97). Although we could not explain the absence of females by the current potassium levels alone, as potassium increased, so did the M/Fl sex ratio. As nitrogen increased and potassium decreased, Fl/Li ratio decreased. Our soil water chemistry analyses suggested that the potassium supply by soil surface erosion from flooding and the inflow of anthropogenic nitrogen were the important factors influencing the M/Fl sex ratio and Fl/Li ratio. Nitrogen management would be important in one of the endangered populations where inflow of nitrogen was the highest among 15 habitats.
KeywordsMale-biased Apparent reproductive ramet ratio Nitrogen Isotope Potassium Wetlands
The authors thank those responsible for all the study sites for permitting our field work; T. Ohmori, M. Maruyama, R. Maruyama, and Y. Konno for their advice on field work; M. Yamasaki for his advice on statistical analysis; and H. Satake for his advice on isotope analysis. This research was supported partly by a Ministry of Education, Science, Sports, and Culture Grant-in-Aid for Scientific Research (B; No. 18380099), and Young Scientists (No. 19780119).
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