Reproductive strategy in Drosophila melanogaster: Significance of a genetic divergence between temperate and tropical populations

Abstract

Reproductive capacities of tropical and temperate populations of D. melanogaster were compared using three complementary techniques: (1) measure of egg production by females grown in the laboratory under uncrowded conditions and provided as adults with abundant food; (2) study of egg production of flies of unknown ages, collected in nature and then kept in similar conditions; and (3) analysis of ovarian activity of wild females dissected just after their capture.Tropical populations showed a lower fecundity in the laboratory and this was also observed in laboratory reared adults. On the average, flies also appeared to be older in the tropics than in temperate countries. These data, together with ecological observations showing that tropical populations live in a more predictable and stable environment, suggest that temperature populations are r-selected, while tropical ones are K-selected. The study of ovarian activity of wild females failed however to confirm this expectation. Tropical flies, which have a lower genetic fecundity, generally appeared to produce more propagules than did temperate flies. Such a contradiction shows how the ideas of r- and K-selection are difficult to apply to natural populations of Drosophila. Population density and interindividual competition are probably not the main selective forces in nature. Attention must also be paid to the necessity of exploring the environment to find resources, to the role of predation and parasitism, and to the occurrence in temperate countries of seasonal fluctuations with different selective pressures on successive generations.

Evolutionary Optimality Applied to Drosophila Experiments: Hypothesis of Constrained Reproductive Efficiency

“…We assume that the patterns presented in Figure 1 are observed in a close to optimal environment. The numerous experimental data on egg laying in Drosophila do not contradict the assumption in a wide sense (Partridge et al 1987;Boulétreau-Merle 1988;Le Bourg et al 1988;Fowler and Partridge 1989;Pretzlaff and Arking 1989;Partridge and Fowler 1992;Chippindale et al 1993;Zwaan et al 1995 Figure 1C. These characters are taken to describe a representative Wayne State female fly.…”

“…Indeed, ovariole number variation W* r in Drosophila has been observed to be positively correlated with fecundity (Boulétreau-Merle et al 1982) and is thought to be associated with different reproductive potential (Markow 1996). Experimental observations show that the ovaries of mated Drosophila females are significantly larger than those of virgins and unfavorable conditions such as low dietary treatment result in a smaller ovary weight (Chippindale et al 1997).…”

“…Exponential decay arises at older ages with time constant 2 k 1 . (A) Daily fecundity in mutant Drosophila strain (Boulétreau-Merle 1988). RC ϭ 82.41 eggs/day, T ϭ 29 days, 1 ϭ 1.33 days, 2 ϭ 11.1 days.…”

Genetics of egg production in Drosophila sechellia

“…D. sechellia also appears to have evolved a slower rate of egg production than its sister species after it split from its presumably D. simulans-like ancestor (Coyne et al, 1991;R'Kha et al, 1997). Given that egg production is closely related to female fitness in Drosophila (Boulétreau-Merle et al, 1982), the persistence of a low rate of egg production in D. sechellia is surprising. One possible explanation for the low rate of egg production is that it is a deleterious pleiotropic effect of genes involved in specializing on Morinda.…”

Quantitative Trait Loci Affecting Phenotypic Plasticity and the Allometric Relationship of Ovariole Number and Thorax Length in Drosophila melanogaster

“…In D. melanogaster, interpopulation variation in 1 ovariole number is correlated with differences in fecundity (Boulétreau-Merle et al 1982, but see also Schmidt et al 2005), and intrapopulation variation is correlated with maximum fecundity (David 1970), but not necessarily total fitness (Wayne et al 1997). Artificial selection on ovariole number elicits a correlated response in fecundity; among selection lines there is a positive correlation between ovariole number and fecundity (Robertson 1957;Engstrom 1971).…”