Observations on the Phenology and Reproductive Success of the Critically Endangered Nervilia nipponica (Orchidaceae) in Kochi Prefecture, Japan

概要

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Nervilia nipponica is critically endangered and poorly known throughout its range in Japan. In order to illuminate details of the species' life history, observations on the phenology and reproductive success of two large populations in Kochi Prefecture were made from 2003-2004. Patterns of emergence were comparable and individuals in both populations exhibited a highly synchronous phenology. The average individual flowering period lasted 12.3 and 11.0 days respectively at the two sites, and dehiscence of fruit capsules occurred 25.6 and 25.3 days after flowering. Only 34.2% and 28.4% of plants at the two sites successfully flowered, but rates of seed set were 38.2% and 52.4% despite the virtual absence of a nectar reward and the lack of pollen vectors, probably indicative of self-pollination. The failure of individuals marked in 2003 to re-emerge, as well as the appearance of unmarked individuals in 2004, suggests that the species has a capacity for dormancy and/or rapid propagation via the tuber. Evidence for the latter is provided by the excavation of 89 tubers from 58 individuals, representing an average rate of increase of 1.5 per individual per year. Recommendations are made for ongoing studies towards the development of a conservation strategy for the species.
日本植物分類学会の論文
2006-04-28