Differential sex allocation strategies between females and facultative hermaphrodites of Chamaelirium hisauchianum (Melanthiaceae)

Species of Chamaelirium are known to be highly diversified in sexual characters, but there has been no detailed empirical approach to elucidate the mechanism and process of sexual diversification in the genus. This paper reports the results of population-based analyses on various sexual aspects of C. hisauchianum endemic to Japan. Of the 20 populations surveyed, eight (40%) were composed of facultative hermaphrodites highly labile in sexual expression, exhibiting a wide range of gradational variation from hermaphroditism through andromonoecy to male. The remaining 12 populations (60 %) consisted of females and facultative hermaphrodites. In them, 11.8–30.9% (mean 22.2%) of the individuals were female. With no reciprocal sex changes, females and facultative hermaphrodites were regarded as, plausibly genetically determined, discrete sex morphs. In contrast, sexual expression in both sex morphs appeared resource dependent. Besides the difference in floral sexual traits, the average ratio o..., Survey of sex morphs in populations
A total of 20 populations of Chamaelirium hisauchianum, 18 are of subsp. kurohimense, and one each of subsp. hisauchianum and subsp. minoense, were surveyed in yearly flowering seasons mainly in the 1980s (Table 1). When populations were comparatively small, scapes (flowering stems) of all flowering plants were harvested and their sexual characters were examined in detail at a laboratory of Teikyo University at Hachioji, Tokyo, Japan. When populations were large, two to eight patches with an area from 1 m × 1 m to 7 m × 11 m were selected, and scapes of all flowering plants occurring therein were harvested and analyzed. The sex morph of a spike or plant was directly determined by calculating ratios of the component flower sex morphs (including abortive asexual flowers if present), or indirectly assessed by categorizing estimated ratios of component flower morphs into one of the morphs defined below (e.g. F1, AM2, M3). Though rare, when a plant has tw...,