Geographical variation in the larval diapause of Chymomyza costata (Diptera; Drosophilidae)

Abstract

Induction of the larval diapause in Chymomyza costata is controlled by two mechanisms, temperature‐dependent induction and a photoperiodic response. Geographical, clinal variation was observed in both mechanisms, Critical photoperiods increased northwards 1 h 9 min per 5 degrees of latitude. The cline relaxes north of 65°N, however. The critical temperature measured under long‐day conditions varied little in areas south of 63°N, but increased from 13°C at that latitude to 17°C at 65°N and to 24°C at 68°N. Selection experiments revealed extensive intrapopulation variation in both diapause characteristics. The mean temperature in the middle of the breeding Season for C. costata is above the long‐day critical temperature in areas south of 63°N, the same or slightly lower than the critical temperature in areas between 63°N and 66°N and well below the critical temperature in areas north of 67°N. The relative importance of temperature and photoperiod in diapause induction changes from south to north, the photoperiod being the main determinant in the south and temperature assuming the main role in the north. The forms and positions of the two clines can be explained when data on the estimated number of generations per year are combined with data on weather and illumination conditions at each locality.

Diapause and bet‐hedging strategies in insects: a meta‐analysis of reaction norm shapes

“…the inflection point of diapause reaction norms increases with latitude (Danilevskii 1965). The latitudinal gradient was estimated as 60-90 min in day length change per 5°N, and this ruleof-thumb remains persistent in the literature (Riihimaa et al 1996, Tyukmaeva et al 2011, Hou et al 2016). Yet, even though the early empirical observations were based on few case studies with data of relatively low resolution, the findings have never been systematically validated.…”

Diapause is not selected as a bet-hedging strategy in insects: a meta-analysis of reaction norm shapes

“…the inflection point of diapause reaction norms increases with latitude [34]. The latitudinal gradient was estimated as 60 – 90 minutes in day length change per 5°N, and this rule-of-thumb remains persistent in the literature [56–58]. Yet, even though the early empirical observations were based on few case studies with data of relatively low resolution, the findings have never been systematically validated.…”

The Drosophilidae (Diptera) of Lithuania

“…costata (Zetterstedt, 1838) This is one of the most common wild drosophilids in Northern Europe (Hackman et al 1970). Its larvae go into diapause (Riihimaa et al 1996 Subgenus Drosophila Fallén, 1823 funebris species group These flies come to fermenting bait and are easily cultured.…”