Biased primary sex ratio in the bushcricket Poecilimon
veluchianus,an insect with sex chromosomes |
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Authors: | K Reinhold |
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Institution: | (1) Institute of Zoology II, University of Erlangen, Staudtstr. 5, D-91058 Erlangen, Germany, DE |
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Abstract: | Offspring sex ratio at hatching was examined in the bushcricket Poecilimon veluchianus. Offspring sex ratios varied significantly between females (Fig. 1). Low mortality prior to sex determination established
that this heterogeneity was already present in the primary offspring sex ratio. Sperm age and female age had no influence
on offspring sex ratio (Fig. 2). Male age at copulation, however, correlated significantly with offspring sex ratio (Fig. 3).
There were two types of males: one type produced predominantly daughters when young and an increasing proportion of sons with
age. The other type produced, independent of age, 1:1 offspring sex ratios (Fig. 4). The two types of males seem to occur
in approximately equal numbers. Sex ratio variation (1) may adaptively compensate for local sex ratio biases caused by sex-specific
motility, or (2) it may be adaptive if there is a sex-differential effect of laying date on offspring fitness.
Received: 14 March 1996/Accepted after revision: 24 June 1996 |
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Keywords: | Sex ratio Evolution Heterogeneity Orthoptera Motility |
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