- 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.
- 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.
- 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).
- 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).
- 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.