Abstract
BackgroundPopulations of Drosophila melanogaster show differences in many morphometrical traits according to their geographic origin. Despite the widespread occurrence of these differences in more than one Drosophila species, the actual selective mechanisms controlling the genetic basis of such variation are not fully understood. Thermal selection is considered to be the most likely cause explaining these differences.ResultsIn our work, we investigated several life history traits (body size, duration of development, preadult survival, longevity and productivity) in two tropical and two temperate natural populations of D. melanogaster recently collected, and in a temperate population maintained for twelve years at the constant temperature of 18°C in the laboratory. In order to characterise the plasticity of these life history traits, the populations were grown at 12, 18, 28 and 31.2°C. Productivity was the fitness trait that showed clearly adaptive differences between latitudinal populations: tropical flies did better in the heat but worse in the cold environments with respect to temperate flies. Differences for the plasticity of other life history traits investigated between tropical and temperate populations were also found. The differences were particularly evident at stressful temperatures (12 and 31.2°C).ConclusionOur results evidence a better cold tolerance in temperate populations that seems to have been evolved during the colonisation of temperate countries by D. melanogaster Afrotropical ancestors, and support the hypothesis of an adaptive response of plasticity to the experienced environment.
Highlights
Populations of Drosophila melanogaster show differences in many morphometrical traits according to their geographic origin
Temperate populations were bigger than the tropical ones over the whole thermal range in spite of significant differences between populations within location (P < 0.001), and flies reared at colder temperatures were bigger than flies reared at warmer temperatures for all populations (P < 0.001)
On the basis of our observations, we found that some adaptive differences in life history traits among natural populations persist in spite of laboratory adaptation [40] or inbreeding effects; other life history traits change only their mean values and not their plastic response over a thermal range
Summary
Populations of Drosophila melanogaster show differences in many morphometrical traits according to their geographic origin. BMC Evolutionary Biology 2006, 6:67 http://www.biomedcentral.com/1471-2148/6/67 enced by such variations. In this sense, the response curves of fitness traits to the environmental changes need to be investigated. A major problem in ecological genetics is to understand the evolutionary responses to stressful variations. If a given stress is really exceptional in its intensity, it is likely to result in the extinctionof a population without eliciting an adaptive response. Milder and more repetitive stresses, on the other hand, are expected to induce an adaptive change, and the role of stress in shaping the genetic architecture of life history traits is a regular problem in evolutionary biology [5,6]
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