Seasonal life cycles and adaptations of four species of Drosophila at high altitudes in central Japan

Seasonal life cycles and adaptations of Drosophila alpina, D. kuntzei, D. maculinotata and D. unipectinata were studied by laboratory experiments and field survey at high altitudes in Nagano, central Japan. These four species were abundant in subalpine coniferous forests (alt. 2000 m), but absent or rare at lower elevations. Laboratory experiments suggested that summer heat at lowlands is adverse to these subalpine species. D. alpina entered pupal diapause at short and long daylengths, while other three species entered reproductive diapause at a short daylength but did not at a long daylength. In the subalpine forest (2000 m), D. alpina passes only one generation in a year; i.e., adult flies reproduce in August and their offspring enter pupal diapause in autumn. D. kuntzei passes one or two generations in a year and enters diapause in autumn. D. maculinotata and D. unipectinata pass two and three generations in a year, respectively, and they enter reproductive diapause in autumn. It is also suggested that these species move to low altitudes in late summer or autumn and return to high altitudes in early summer.