Seed Ecology of Lobelia boninensis Koidz. (Campanulaceae), an Endemic Species in the Bonin Islands (Japan)

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We examined seed germination of Lobelia boninensis Koidz. (Campanulaceae) in incubators and its seed production in a greenhouse. This monocarpic perennial is an endemic and endangered species in the Miscanthus boninensis vegetation on coastal cliffs in the Bonin Islands. Seeds germinated over a range of from 10° to 30℃ ; at these temperatures germination began only after eight days of incubation. A cool, moist stratification treatment did not promote germination. Based on these temperature responses, it is expected that in their native habitat Lobelia seeds germinate between October and November, when precipitation is frequent. Lobelia seeds, which remain capable of germinating for a few years after storage in the lab, are positively photoblastic, and this may allow the seeds to detect gaps or safe sites in vegetation. These results suggest that Lobelia seeds may form a seed bank beneath a closed canopy, due to enforced dormancy. Lobelia seeds germinated under saline conditions up to 300 mM NaCl. In the greenhouse, some individuals began to reproduce 2.5 years after germination. Plants are self-compatible, and they produced an average of >4.5 × 10^5 small seeds (ca. 0.12 mg). Lobelia has a strategy of seed germination suited to colonize the M. boninensis vegetation, where the maritime impact is reduced. This endangered species can easily be propagated ex situ.
種生物学会の論文