Telling Sex from Growth: Dissolving Maynard Smith's Paradox

• Published in: Bulletin of marine science Vol. 45; no. 2; pp. 433 - 446
• Main Authors: Pearse, John S., Pearse, Vicki B., Newberry, Todd A.
• Format: Journal Article
• Language: English
• Published: Lawrence, KA University of Miami - Rosenstiel School of Marine and Atmos 1989; Allen
• Subjects: Biological and medical sciences; Biological evolution; Fundamental and applied biological sciences. Psychology; Genetics of eukaryotes. Biological and molecular evolution; Parthenogenesis; Mating system; Asexual reproduction; Growth; Theory; Biological evolution; Mutation; Sexual reproduction
• ISSN: 0007-4977; 1553-6955

For nearly two decades, theoretical concern about the evolution of sex has centered on Maynard Smith's paradox: Assume egg-production by parthenogenesis equals that by sex, and assume that in a sexual species a female parthenogen appears by mutation. Initially, the proportion of parthenogens will double in each generation-the "twofold cost of sex." And yet, paradoxically, most species are overwhelmingly sexual. We suggest that there is no such cost, and that the "paradox" results from an inappropriate comparison between two processes: sex (anisogamous) and growth (clonal through ameiotic parthenogenesis). Unwarranted focus on selection at the level of individual bodies (ramets), rather than on individual genomes (genets) and genetic lineages, also has led to considerable confusion. Understanding the "uses" of sex that account for its origin and persistence still stands as a major challenge to evolutionary biology. But equating sexual reproduction with such disparate processes as clonal growth (by a meiotic parthenogenesis, in Maynard Smith's paradox) is unlikely to illuminate the problem of why sex itself is such an integral part of the biology of most organisms.