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The evolution of unusual chromosomal systems in coccoids: extraordinary sex ratios revisited

  1. David Haig†

Article first published online: 11 DEC 2002

DOI: 10.1046/j.1420-9101.1993.6010069.x

Issue

Journal of Evolutionary Biology

Journal of Evolutionary Biology

Volume 6, Issue 1, pages 69–77, January 1993

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How to Cite

Haig, D. (1993), The evolution of unusual chromosomal systems in coccoids: extraordinary sex ratios revisited. Journal of Evolutionary Biology, 6: 69–77. doi: 10.1046/j.1420-9101.1993.6010069.x

Author Information

  1. Department of Plant Sciences, University of Oxford, South Parks Road, Oxford OX1 3RA, U.K.

  1. †

    Present address: Department of Organismic and Evolutionary Biology, Harvard University, Cambridge MA 02138, USA

Publication History

  1. Issue published online: 11 DEC 2002
  2. Article first published online: 11 DEC 2002
  3. Received 20 January 1992; accepted 19 February 1992.

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Keywords:

  • Sex ratio;
  • intragenomic conflict;
  • meiotic drive;
  • haplodiploidy;
  • coccoids

Abstract

Coccoids (scale insects) exhibit a wide variety of chromosomal systems. In many species, paternal chromosomes are eliminated from the male germline such that all of a male's sperm transmit an identical set of maternal chromosomes. In such species, an offspring's sex is determined by whether or not paternal chromosomes are inactivated in the egg's cytoplasm after fertilization. This paper presents a model of the evolution of paternal genome loss in coccoids from an ancestral system of XX-XO sex determination. The model is based on Hamilton's (1967) theory that different genetic elements within the genome have different unbeatable sex ratios. In this model (1) meiotic drive by the X chromosome in XO males causes female-biased sex ratios; (2) the maternal set of autosomes in males evolves effective sex linkage to exploit X-drive; and (3) genes expressed in mothers are selected to convert some of their XX daughters into sons. A similar model may explain the evolution of haplodiploidy.

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