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Intra-population genetic variation in diapause incidence of adult-diapausing Tetranychus pueraricola (Acari: Tetranychidae)

Authors

  • KATSURA ITO

    Corresponding author
    1. Laboratory of Insect Ecology, Faculty of Agriculture, Kochi University, Nankoku, Japan
    • Correspondence: Katsura Ito, Faculty of Agriculture, Kochi University, Monobeotsu 200, Nankoku, Kochi 783-8502, Japan. E-mail: ktr@kochi-u.ac.jp

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Abstract

  1. Diapause is an important seasonal adaptation for arthropods in temperate regions. Recent global warming has had a profound effect on the timing of diapause induction, but the potential for evolutionary changes in diapause attributes remains largely unknown because of a scarcity of information about genetic architecture in these traits.
  2. Genetic variation in diapause incidence within a population and the genetic correlation with different environmental conditions are both important for predicting evolutionary responses to climatic changes.
  3. The main aim of this study was to determine these parameters at temperatures representative of the winter season (stationary 18–20 °C) by using 12 isofemale lines established from females of a single population of the adult-diapausing spider mite Tetranychus pueraricola (Acari: Tetranychidae).
  4. To compare the response between field and laboratory, their ancestral phenotypes were randomly chosen from diapausing (eight) or non-diapausing (four) females. Diapause incidence was investigated at 18, 19, and 20 °C under LD 10:14 h conditions with two to five replicates for each strain. At 18 °C, more than 90% of the females entered diapause, and the genetic variation among strains (intraclass correlation coefficient; ICC) was relatively small (44%), whereas highly variable diapause incidences were observed for the warmer conditions (both 87% ICC). The correlation between temperatures was as high as 0.79 between 19 and 20 °C, whereas the correlation estimates between 18 and either 19 or 20 °C were still positive, but not significant. In addition, the analyses demonstrated the existence of variation in the entire response curves (significant genotype × environment interaction).
  5. These results demonstrate that significant genetic variation in response curves is maintained in this population, and accordingly this population has a capacity to respond to climatic changes. Crossing reaction curves across temperatures may prevent the fixation of a single optimal response curve, and maintain genetic variation at each temperature.
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