Thermal plasticity in Drosophila melanogaster: a comparison of geographic populations.
BACKGROUND
Populations 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.


RESULTS
In 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 degrees 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 degrees 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 degrees C).


CONCLUSIONS
Our 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.
Trotta
Vincenzo
V
Alma Mater Studiorum, Università di Bologna, Dipartimento di Biologia Evoluzionistica Sperimentale, via Selmi 3, 40126 Bologna, Italy. vtrotta@alma.unibo.it
Calboli
Federico C F
FC
Ziosi
Marcello
M
Guerra
Daniela
D
Pezzoli
Maria C
MC
David
Jean R
JR
Cavicchi
Sandro
S
D000704:Analysis of Variance; D000818:Animals; D002980:Climate; D004331:Drosophila melanogaster / Q000254:growth & development* / Q000502:physiology; D005260:Female; D005298:Fertility; D005602:France; D005843:Geography; D007558:Italy; D008136:Longevity; D008297:Male; D013045:Species Specificity; D013696:Temperature; D014921:Wings, Animal / Q000254:growth & development