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Environmental sex determination in response to light and biased sex ratios in Equisetum gametophytes
Author(s) -
Guillon JeanMichel,
Fievet Daniel
Publication year - 2003
Publication title -
journal of ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.452
H-Index - 181
eISSN - 1365-2745
pISSN - 0022-0477
DOI - 10.1046/j.1365-2745.2003.00744.x
Subject(s) - gametophyte , biology , population , botany , ecology , zoology , demography , pollen , sociology
Summary1 Sexual differentiation of Equisetum (horsetails) gametophytes is influenced by environmental conditions, and wild populations tend to be female biased. We show that photon irradiance has a very significant and reproducible effect on sex determination in three species of Equisetum grown in vitro . 2 Under our experimental conditions, high light levels (PAR = 24–48 µmol m −2 s −1 ) induce most gametophytes to differentiate as female, whereas only males are observed at PAR < 6 µmol m −2 s −1 . Addition of sugar to the culture medium, however, promotes male development, suggesting that the effect of increasing photon irradiance is not related to the accumulation of photosynthates. 3 According to evolutionary theory, environmental sex determination can cause population sex ratios to deviate from unity, and is favoured when the environment consists of patches that differentially affect fitness as a male or a female. However, in two out of three species, we found that the fitness of males increases faster than the fitness of females with increasing light levels, contrary to the predictions of the Charnov and Bull model. 4 We conclude that environmental sex determination in response to light cannot alone account for the female bias in natural populations of Equisetum gametophytes.