, Volume 96, Issue 5, pp 376–381 | Cite as

A correlation between B chromosome frequency and sex ratio in Exochomus quadripustulatus

  • S. A. Henderson


A survey of natural populations of the British ladybird Exochomus quadripustulatus revealed the presence of a single large, acrocentric, supernumerary (B) chromosome in all sites visited. Studies were confined to male meiosis, where more than one B was never found to accompany the six bivalents and neo-XY sex pair. The percentage of males possessing B chromosomes varied from 6.4% to 28.6% in 14 different populations. The sex ratios present in these populations also varied. In some equal numbers of males and females were present, in others there were significant excesses of females. A linear regression was found between the percentage of B chromosomes and the percentages of males and females in those populations. It is suggested that the B chromosomes are not in themselves responsible for the sex ratio differences found for similar differences in sex ratio have been found in related neo-XY species lacking B chromosomes. It is more likely that those factors affecting sex ratio are also responsible for affecting the frequencies of B chromosomes in different populations.


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Copyright information

© Springer-Verlag 1988

Authors and Affiliations

  • S. A. Henderson
    • 1
  1. 1.Department of GeneticsUniversity of CambridgeCambridgeUK

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