What have two decades of laboratory life-history evolution studies onDrosophila melanogaster taught us?

SUMMARY We studied larval development and acquisition of metabolic resources in Drosophila melanogaster selected for adult desiccation resistance. Desiccation-selected (D) flies had longer developmental times in comparison with control populations, resulting in significantly higher body mass. No differences were found in larval growth rates, suggesting that increased body mass results from the extended larval feeding period. Larvae from both D and control lines molted from second to third instar 81-84 h after egg laying,whereas D larvae pupated 5-6 h later than controls. This indicates that selecting adults for desiccation resistance results in longer third larval instar. Newly eclosed D flies had higher carbohydrate and water contents in comparison with control populations. No differences were found in body mass,water or metabolite contents of newly eclosed selected and control flies after larvae were prevented from further feeding from 96 h after egg laying onwards. This shows that differences in accumulated carbohydrate and water stores are a result of evolved differences in the duration of third larval instar. The contribution of third instar feeding to desiccation resistance of adult selected flies is higher than that of controls. Thus, selection for adult stress resistance has resulted in correlated changes in larval physiology.

Section: Discussionmentioning

confidence: 99%

Selection for desiccation resistance in adultDrosophila melanogasteraffects larval development and metabolite accumulation

Gefen

Marlon

Gibbs

2006

“…Hence, the unit of replication in any study addressing evolutionary questions should be population, not individuals. Therefore, it is not possible to rule out that the changes in circadian phenotypes reported in early selection studies may be a consequence of genetic drift or inbreeding that the populations may have undergone (reviewed by Prasad and Joshi, 2003;David et al, 2005;Miller and Hedrick, 2001).…”

Section: Evolution Of Circadian Clocksmentioning

confidence: 99%

Selection on the timing of adult emergence results in altered circadian clocks in fruit flies Drosophila melanogaster

Kumar

Paranjpe

et al. 2007

SUMMARY To investigate whether circadian clocks in fruit flies Drosophila melanogaster evolve as a consequence of selection on the timing of adult emergence, we raised four replicate populations each of early(early1..4) and late (late1..4)emerging flies by selecting for adults that emerged during the morning and the evening hours. We estimated the percentage of flies that emerged during the two selection windows to evaluate the direct response to selection, and the circadian phenotypes of adult emergence and locomotor activity rhythms under light/dark (LD) and constant darkness (DD) to assess the correlated response to selection. After 55 generations, the percentage of flies emerging during the morning window increased in the early populations, but decreased in the late populations. The percentage of flies emerging during the evening window increased in the late populations, but decreased in the early populations. The time course and waveform of emergence and locomotor activity rhythms of the selected populations diverged from each other as well as from the controls. Further, the circadian periodicity of the early populations was significantly shorter than the controls, while that of the late populations was significantly longer than the controls. The light-induced phase response curve of the selected populations differed significantly within groups as well as from the controls. Such modifications in the circadian phenotypes of the selected populations due to heritable changes in genetic architecture, in response to imposed selection pressure, suggest that the circadian clocks underlying emergence and locomotor activity rhythms in D. melanogaster evolve as a correlated response to selection on the timing of adult emergence.

“…In nature, insect populations including those of the fruit fly Drosophila melanogaster are subjected to directional selection for faster development because they inhabit ephemeral habitats such as rotting fruits (Prasad and Joshi, 2003). Several studies on life history traits in different model organisms, including Drosophila, led to the development of life history theory, which posits that natural selection enhances organismal fitness, and that the trait combinations under selection are constrained by trade-offs (see Prasad and Joshi, 2003).…”

Section: Introductionmentioning

confidence: 99%

“…Several studies on life history traits in different model organisms, including Drosophila, led to the development of life history theory, which posits that natural selection enhances organismal fitness, and that the trait combinations under selection are constrained by trade-offs (see Prasad and Joshi, 2003). Trade-offs are observed at phenotypic as well as genetic levels; hence assessment of trade-offs is necessary at both levels.…”

Section: Introductionmentioning

confidence: 99%

Correlated changes in life history traits in response to selection for faster pre-adult development in the fruit fly Drosophila melanogaster

Yadav

Sharma

2014

Insects including the fruit fly Drosophila melanogaster are under intense pressure to develop rapidly because they inhabit ephemeral habitats. We have previously shown that when selection for faster development was artificially imposed on D. melanogaster in the laboratory, reduction of pre-adult development time and shortening of the clock period occurs, suggesting a role for circadian clocks in the regulation of life history traits. Circadian clocks in D. melanogaster have also been implicated in the control of metabolic pathways, ageing processes, oxidative stress and defense responses to exogenous stressors. In order to rigorously examine correlations between pre-adult development time and other life history traits, we assayed pre-adult survivorship, starvation and desiccation resistance, body size and body weight, fecundity and adult lifespan in faster developing populations of D. melanogaster. The results revealed that selection for faster pre-adult development significantly reduced several adult fitness traits in the faster developing flies without affecting pre-adult survivorship. Although overall fecundity of faster developing flies was reduced, their egg output per unit body weight was significantly higher than that of controls, indicating that reduction in adult lifespan might be due to disproportionate investment in reproduction. Thus our results suggest that selection for faster preadult development in D. melanogaster yields flies with higher reproductive fitness. Because these flies also have shorter clock periods, our results can be taken to suggest that pre-adult development time and circadian clock period are correlated with various adult life history traits in D. melanogaster, implying that circadian clocks may have adaptive significance.