Thoracic trident pigmentation in Drosophila melanogaster : Differentiation of geographical populations

Abstract

SummaryA phenotypic classification of trident pigmentation allowed the characterization ol any natural population by a pigmentation score, ranging from 0 to 3. After some training, independent observers could produce very

Phenotypic plasticity of abdomen pigmentation in two geographic populations of Drosophila melanogaster: male–female comparison and sexual dimorphism

“…Body pigmentation is also very plastic in relation to growth temperature (David et al 1990;Gibert et al 1996) and both clinal and plastic variations produce darker flies in a cold environment. Such a phenomenon, observed also in other insects, is generally explained by the thermal budget hypothesis: a dark color is beneficial in the cold for collecting the energy of solar radiations and increasing body temperature (Watt 1969;Gibson and Falls 1979;David et al 1985David et al , 1990Kingsolver and Wiernasz 1991;Gibert et al 1996;Majerus 1998;True 2003).…”

“…In D. melanogaster, latitudinal clines have been observed for various morphometrical traits such as body size, brisle numbers, ovariole number or body pigmentation (see David and Capy 1988;Gibert et al 2004a, for reviews). In the case of pigmentation, latitudinal clines have been demonstrated for a dark trident pattern on the mesonotum (David et al 1985Munjal et al 1997). A genetic difference, i.e.…”

Phenotypic plasticity of body pigmentation in Drosophila: correlated variations between segments

“…In the latter case, darker individuals are generally observed at low temperatures [1,8,9,15,16,18,19,22,25,40]. Increased melanization at lower temperatures is generally thought to be adaptive for thermoregulation: being darker will favor the absorption of light radiation and thus improve metabolic activity at low temperature; the reverse being true at high temperature.…”

“…In Drosophila melanogaster and related species, phenotypic plasticity of pigmentation can be quantified on the mesothorax (a dark pattern with a trident shape) [2,8] [8] while abdomen pigmentation is variable in females only. In the present work, only females were analysed.…”

“…For the thoracic trident, only four phenotypic classes were used, ranging from 0 (no visible trident) to 3 (dark trident) (see David et al. [8] It was suggested [37] that in many cases r m could be used as an approximation of the genetic correlation rg. By simulation, Roff and Preziosi [30] showed however that equating r m to rg would be biased unless family size n would be sufficiently large (> 20 (table IB and figure 2).…”