Meeting Abstract
Many organisms time their development to ensure that a specific life stage coincides with a specific resource. Development rate of ectotherms varies with temperature, and therefore environmental temperature can affect life history timing. Many temperate insects overwinter in diapause, a dormant state of developmental arrest that can promote appropriate life history timing, mitigating the effects of temperature on development. However, this may not be the case for all insects, especially for non-photoperiodic insects, whose diapause is not regulated by daylength. The apple maggot fly Rhagoletis pomonella spends most of the year as a pupa in diapause, eclosing as an adult in late summer to lay its eggs in the fruits of its host plants. However, R. pomonella has a surprisingly flexible and dynamic diapause program, and can terminate diapause without any chilling or photoperiodic cues. R. pomonella is therefore an interesting model to study how non-photoperiodic insects regulate the timing of diapause termination, and the role of temperature in this regulation. To test the thermal sensitivity of the diapause program, we collected diapause R. pomonella pupae from hawthorn fruits in Denver, CO, and exposed them to differing lengths of winter conditions (4 °C) at different times during their pupal development. We then measured time to eclosion after transfer to summer conditions (21 °C). The impact of low temperatures on eclosion varied with both the timing and length of winter, suggesting that the thermal sensitivity of diapause development changes with age. This study challenges our understanding of how insects “keep track of” physiological time in diapause.
