Resistance of Species of the Drosophila Melanogaster Subgroup to Environmental Extremes.

Abstract

Resistance to the extreme stresses of high temperature-desiccation and low temperature were compared among six species of the melanogaster species subgroup of Drosophila. D. melanogaster was the most resistant to all stresses. The cosmopolitan species, D. melanogaster and D. simulans, were more resistant to cold stresses than the four endemic species, D. mauritiana, D. teissieri, D. yakuba and D. erecta. D. simulans, D. mauritiana and D. teissieri showed similar resistance to heat and desiccation, while D. yakuba and especially D. erecta were sensitive to these stresses. A prerequisite for the spread of the cosmopolitan species into temperate zones thus appears to have involved a level of resistance to cold stress exceeding that of the endemics. A greater resistance to heat and desiccation stresses, such as that found in D. melanogaster, may also be necessary for the invasion of more extreme environments. All species with the exception of D. erecta and to a lesser extent D. yakuba can survive 6 h at the extreme temperature of 34�C at 95% RH, and in addition most of those flies surviving stresses of this type are fertile. This suggests that these species can survive short stress periods in a humid microhabitat in the wild.

History and Structure of Sub-Saharan Populations ofDrosophila melanogaster

“…Importantly, our data do not rule out an ancestral range that includes the western rift mountains, which could be compatible with an origin in the ''East Central refugia'' of tropical forest, a possibility suggested by Lachaise et al (1988) and Lachaise and Silvain (2004). Alternatively, given that D. melanogaster has greater resistance to desiccation (van Herrewege and David 1997) and to high and low temperatures (Stanley et al 1980) than any of its close relatives, this species may have evolved in a relatively less humid region of eastern Africa. It is also possible that the geographic range of this species has changed through time in response to climate change and other factors.…”

Alternative smooth or stepped altitudinal cline of fecundity in Drosophila teissieri and D. yakuba in the Ivory Coast.

“…This can be connected with the greater tolerance of the former species to the physiological stresses (desiccation, cold temperature stresses, high temperature stresses at 95 or 0% RH) than the latter (Stanley et al, 1980). It is also worth noting that Tantawy and E1 Helw (1970) comparing Scottish and Egyptian populations of D. melanogaster also observed enhanced fecundity when at 15°C in the Scottish populations but when at 28°C in the Egyptian populations, that is in conditions similar to those found in the wild.…”

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

“…Although a more pronounced acclimation effect on lower than on upper limits is not universal [e.g. the converse has been found the caterpillars of the moth Embryonopsis halticella (Klok and Chown, 1998)], it does seem to be typical of most ectotherms (Kingsolver and Huey, 1998 Metabolic rate difference (ml CO 2 h -1 ) * * geographic variation in thermal limits, and in the responses of these limits to selection (Addo-Bediako et al, 2000;Chen et al, 1990;Chown, 2001;Gaston and Chown, 1999;Gilchrist et al, 1997;Hercus et al, 2000;Hoffmann et al, 1997;Kimura, 2004;Stanley et al, 1980;Terblanche et al, 2005b). Increases in metabolic rate of the G. pallidipes adults with adult exposure to low temperature seems to be typical of this group of tsetse flies because it has also been found in Glossina morsitans.…”