DOI: 10.5061/dryad.0gb5mkm5v
title: Differential sex allocation strategies between females and facultative hermaphrodites of Chamaelirium hisauchianum (Melanthiaceae)

description: 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 of ovuliferous flowers in females was higher than that in
 facultative hermaphrodites. The production of ovuliferous flowers by
 females was less susceptible to both field and cultivated conditions and
 tended to be significantly relatively higher under unfavorable growing
 conditions. Females were thus less plastic (or more persistent) in
 producing ovuliferous flowers (or female organs) than facultative
 hermaphrodites irrespective of internal and external conditions. In all
 populations, andromonoecious plants dominated (50.8–100%), which appeared
 to reflect the high plasticity in sex allocation of facultative
 hermaphrodites. The different modes of sex allocation were regarded as
 secondary sex characters and presumably stem from a difference in easiness
 or attainability of sexual reproduction between the two sex
 morphs. 
description: Survey
 of sex morphs in populations A total of 20
 populations of <em>Chamaelirium hisauchianum</em>, 18 are of
 subsp. <em>kurohimense</em>, and one each of subsp.
 <em>hisauchianum</em> and subsp.
 <em>minoense</em>, 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 two or more
 flowering scapes, the ratios of flower morphs were averaged and the mean
 was taken to represent the plant.  Observation
 of floral characters and measurements of floral parts
 Observations of floral characters and
 measurements of floral parts were made under a stereomicroscope. Lengths
 of well-developed tepals (upper tepals of flowers) and filaments were
 measured for at least three representative flowers selected from each
 spike. The measurements were averaged and the mean value for each spike
 was used. Where applicable, Student’s t-tests were used to statistically
 test the significance of differences between two groups of
 samples.  Survey of changes in sex form or expression
 under cultivation Plants
 sampled from natural habitats were transplanted into the experimental
 botanical nursery of Teikyo University. Each plant was planted
 individually with an accession number in a pot. Using them, changes in
 spike length, total flower number (including abortive asexual flowers) per
 spike, and the combination and/or ratio of flower sex morphs per spike
 were successively monitored and recorded in each flowering season for up
 to seven consecutive years (i.e. up to eight flowering seasons, including
 the initial one when plants were first transplanted from natural
 habitats). Data obtained during cultivation were pooled and integrally
 compared with data obtained from natural habitats just prior to
 cultivation. List of
 abbreviations for sexual characters 
 A: Abortive and
 asexual. A(-H): Innately hermaphroditic plant (spike)
 bearing only abortive flowers. A(-F): Innately female plant (spike) bearing
 only abortive flowers. 
 AM:
 Andromonoecious. AM1: Andromonoecious plant (spike) with a ratio
 of hermaphroditic flowers &gt; ca. 2/3 of all flowers borne (abortive flowers
 ignored). AM2: Andromonoecious plant (spike) with a ratio
 of hermaphroditic flowers ca. 1/3–2/3 of all flowers borne (abortive
 flowers ignored). AM3: Andromonoecious plant (spike) with a ratio
 of hermaphroditic flowers &lt; ca. 1/3 of all flowers borne (abortive flowers
 ignored). 
 F: Female. 
 F1: Female plant (spike)
 with a ratio of female flowers &gt; ca. 2/3 of all flowers borne (including
 abortive flowers). F2: Female plant (spike) with a ratio of female
 flowers ca. 1/3–2/3 of all flowers borne (including abortive
 flowers). F3: Female plant (spike) with a ratio of female
 flowers &lt; ca. 1/3 of all flowers borne (including
 abortive flowers). 
 H:
 Hermaphrodite. Fac. H: Facultative hermaphrodites,
 conditionally exhibiting hermaphroditism, andromonoecy, male or
 abortive/asexual state. 
 M: Male
 M1: Male plant
 (spike) with a ratio of male flowers &gt; ca. 2/3 of all flowers borne (including
 abortive flowers). M2: Male plant (spike) with a ratio of male
 flowers ca. 1/3–2/3 of all flowers borne (including abortive
 flowers). M3: Male plant (spike) with a ratio of male
 flowers &lt; ca. 1/3 of all flowers borne (including
 abortive flowers).