Gene flow between sexual and asexual strains of parasitic wasps: a possible case of sympatric speciation caused by a parthenogenesis-inducing bacterium

Authors

  • TETSUYA ADACHI-HAGIMORI,

    1. Graduate School of Biosphere Sciences, Hiroshima University, Fukuyama, Hiroshima, Japan
    2. Japan Society for the Promotion of Science, Chiyoda-ku, Tokyo, Japan
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  • KAZUKI MIURA,

    1. Graduate School of Biosphere Sciences, Hiroshima University, Fukuyama, Hiroshima, Japan
    2. National Agricultural Research Center for Western Region, Fukuyama, Hiroshima, Japan
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  • YOSHIHISA ABE

    1. Graduate School of Social and Cultural Studies, Kyushu University, Motooka, Fukuoka, Japan
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Tetsuya Adachi-Hagimori, Research Institute of Environment, Agriculture and Fisheries, Osaka Prefectural Government, 442 Shakudo, Habikino 583-0862, Japan.
Tel.: +81 72 958 6551; fax: +81 72 956 9691;
e-mail: tetsuya3science@gmail.com

Abstract

Sympatric speciation is strictly defined as the emergence of two species from a population in which mating has been random with respect to the place of birth of the mating partners. Mathematical models have shown that sympatric speciation is possible, but very few examples have been documented in nature. In this article, we demonstrate that arrhenotokous and thelytokous strains of a parasitic wasp, Neochrysocharis formosa, speciated sympatrically through infection by a symbiotic bacterium Rickettsia for the following reasons: First, Rickettsia infection was detected in all of the thelytokous strains collected throughout Japan. Second, the arrhenotokous and thelytokous strains have been collected sympatrically. Third, crossing experiments between the two strains did not result in fertilized offspring. In addition, the two strains were genetically isolated at the nuclear and mitochondrial genes. Fourth, the two strains showed a sister relationship in nuclear 28S rRNA gene. Finally, thelytokous females treated with antibiotics produced Rickettsia-free male offspring of the same reproductive form as arrhenotokous females indicating that the thelytokous strain could have speciated sympatrically from an individual of the arrhenotokous strain.

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