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Population Biology of Chamelirium luteum, A Dioecious Lily. II. Mechanisms Governing Sex Ratios

Thomas R. Meagher
Evolution
Vol. 35, No. 3 (May, 1981), pp. 557-567
DOI: 10.2307/2408202
Stable URL: http://www.jstor.org/stable/2408202
Page Count: 11
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Population Biology of Chamelirium luteum, A Dioecious Lily. II. Mechanisms Governing Sex Ratios
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Abstract

The dioecious forest floor herb, Chamaelirium luteum, has been shown to have a strongly male-biased sex ratio both among plants in flower in a particular year and among adult plants within populations. A variety of factors have been considered as possible influences on sex ratios in C. luteum. Observed seedling sex ratios for C. luteum were one to one so that genetic effects on the primary sex ratio can be discounted as an influence on adult sex ratios. Ecological effects, such as relative availability of suitable male or female microsites, may have some influence on adult sex ratios, as indicated by the segregation of the sexes in natural populations. The mechanism by which such segregation would occur is through life history differences between males and females. Even in the absence of microsite heterogeneity, life history differences between the sexes in age at first reproduction and in mortality rates appear to have a strong influence on adult sex ratios. Such ecological influences are probably the predominant factors leading to the excess of males in adult populations of C. luteum. This bias in favor of males in the adult sex ratio along with differences between the sexes in flowering schedules leads to the more dramatically male-biased flowering sex ratio observed in any particular year.

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