Abstract
Seven natural populations of the grasshopper Aiolopus strepens were analysed to investigate the effects of a pericentric inversion in the smallest chromosome (S11) on chiasma formation and nucleolus organizer regions (NORs) activity. This polymorphism was stable in one population after comparing the frequencies of standard and inverted S11 chromosomes in two samples taken 5 years apart. Furthermore, mean cell chiasma frequency in this population tended to decrease over these 5 years. Males homozygous for the S11 inversion showed a higher frequency of inactivity of one of the NORs located on the L3 chromosome than that found in standard homozygous and heterozygous males. The results suggest that this stable polymorphism is maintained by heterosis, and that inversion homozygotes are less fit than standard homozygotes, which explains the low frequency of inverted chromosomes in all populations analysed. However, the possibility of recurrence of the inversion cannot be ruled out.
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Acknowledgements
This work was partially supported by grants from the Direccion General de Investigation Cientifica y Técnica (no. PB87-0886) and Plan Andaluz de Investigation, Grupo no. 3094 (Spain).
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Viseras, E., Camacho, J. Effects and maintenance of a pericentric inversion polymorphism in the grasshopper Aiolopus strepens. Heredity 66, 325–331 (1991). https://doi.org/10.1038/hdy.1991.41
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DOI: https://doi.org/10.1038/hdy.1991.41