Adaptations to environmental stress in altitudinal populations of two Drosophila species

Abstract

Opposite clinal variation for desiccation and starvation tolerance are observed in four altitudinal populations (219-2202 m), each of two sympatric and cold adapted species: Drosophila takahashii and Drosophila nepalensis from northern India. The high-altitude populations are more tolerant to desiccation than those from lower altitudes, whereas the reverse trend occurs for starvation tolerance. The magnitude of tolerances are significantly high in D. nepalensis, which is better adapted to cold conditions. During winter months (November to February), there are significant decreases in T max , T min and relative humidity along the altitudinal transect. Higher desiccation resistance can develop under cold conditions over short-range, altitudinally varying, geographical areas (250 km) compared with our previously reported long-range (>2000 km), latitudinal variations under tropical climatic conditions. However, significant starvation tolerances are favoured by small body size, higher dispersal rate and higher ambient temperature of the site of origin of populations. Significant correlations of two climatic factors (the mean monthly coefficients of variation of temperature and relative humidity) with these two physiological traits can best explain the observed altitudinal clinal variations under natural conditions.

The relative contributions of developmental plasticity and adult acclimation to physiological variation in the tsetse fly,Glossina pallidipes(Diptera, Glossinidae)

“…This is true of D. melanogaster from the east coast of Australia, where in several populations in response to summer acclimation temperatures, individuals showed greater desiccation resistance than flies exposed to constant or winter temperatures (Hoffmann et al, 2005b). Similar declines in desiccation resistance with increasing treatment temperature have also been found for D. takahashii and D. nepalensis (Parkash et al, 2005). Here, we found that when exposed to 29°C, either as adults or as pupae, adult G. pallidipes had significantly reduced rates of water loss compared to flies held at 21°C or 25°C (and similar to results described in Terblanche et al, in press).…”

Species and genetic diversity in the genus Drosophila inhabiting the Indian subcontinent

“…Thus, the findings recorded for D. ananassae provide evidence that the quality and quantity of nutrients consumed by organisms have strong impact on stress resistance. Studies on resistance to different kinds of stress in different species of Drosophila occurring in India have also been reported by Parkash and coworkers (Parkash and Shamina 1994;Parkash and Munjal 1999;Parkash et al 2005;. The desiccation tolerance and starvation resistance exhibit opposite latitudinal clines and significant differentiation among Indian geographical populations of D. kikkawai.…”

Impact of Darker, Intermediate and Lighter Phenotypes of Body Melanization on Desiccation Resistance inDrosophila melanogaster

“…Observed variations in the investigated physiological traits show regular clines along latitude as well as altitude. The occurrence of latitudinal clines for various traits (morphological, cytological and ecophysiological) on different continents is often considered to be adaptive evolutionary responses to climatic conditions of the origin of populations (Dobzhansky 1948; Stalker and Carson 1948; Mettler et al 1977; Prevosti et al 1985; Watada 1986; Parkash and Munjal 1999; Parkash et al 2005). However, climatic conditions are complex and it can be difficult to identify environmental selective factors.…”