Adaptation of Drosophila simulans in Japan.

Abstract

Drosophila simulans has been found for more than 10 years in Japan, mainly in suburban areas whereas its sibling species D, melanogaster tends to be found in houses. Seasonal activities of the two species were clearly different; In a typical hot summer the frequency of D. simulans decreased temporarily in August making two peaks in July and September. But in a cool summer the two peaks disappeared making a single peak in September or October. On the other hand, D. melanogaster showed higher activity in August in the hot summer but it occasionally shifted the active peak during the season avoiding competition with D. simulans. A nine year survey of D. simulans around the area of Mt. Fuji revealed that the species gradually invaded from the Pacific coast to the inland. Population size in autumn was strongly affected by the temperature of the preceeding winter. Cold winters such as in 1977 and x1981 decreased the size drastically at every collection site.

Seasonal fluctuation in susceptibility to insecticides within natural populations of Drosophila melanogaster. Empirical observations of fitness costs of insecticide resistance.

“…The population size of Drosophila in Japan is affected by many factors, including temperatures of the preceding winter (Watanabe et al, 1984) and other meteorological factors as well as temperatures (Mikasa, 1991). Concerning the Katsunuma population, it is well known that the seasonal distribution pattern of D. melanogaster is unimodal with a single peak in fall.…”

Further genetic studies on the Katsunuma population of Drosophila melanogaster.

“…simulans, a most closely related species to D. melanogaster, was first found in Katsunuma in 1977 (Watada et al, 1986). It was a minor species until the 1990s, especially in the vineyards where we collected D. melanogaster.…”

“…Several females were susceptible to P transposition like an M strain from the cross A*, whereas males from one line inducing transposition was detected in 1996 (12.1% Numbers in parentheses were obtained by using the balancer stock with the original (laboratory) genetic background (see Discussion). 1975, 1976, and 1977-1985 are from Watanabe and Kawanishi (1976), Watanabe and Kawanishi (1978), and Watada et al (1986), respectively.…”

“…Invasion of D. simulans (a sibling species of D. melanogaster) into the mainland of Japan, including Katsunuma, has been reported Kawanishi, 1976, 1978;Watanabe et al, 1984;Watada et al, 1986). If a newly introduced species comes to occupy the same ecological niche, it may cause changes in genetic structure in another species that is already existing.…”

Cold temperature resistance in Drosophila lutescens and D. takahashii.

“…Fig. 1: Kikkawa and Peng 1938;Okada 1956;Wakahama 1964;Bock and Wheeler 1972;Watanabe et al 1978), although both species overlap in the border region of these two areas and can be caught together .…”