Department of Ecology and Evolution, University of Lausanne, Lausanne, Switzerland.
J Evol Biol. 2011 Apr;24(4):897-903. doi: 10.1111/j.1420-9101.2010.02225.x. Epub 2011 Jan 31.
Both development and evolution under chronic malnutrition lead to reduced adult size in Drosophila. We studied the contribution of changes in size vs. number of epidermal cells to plastic and evolutionary reduction of wing size in response to poor larval food. We used flies from six populations selected for tolerance to larval malnutrition and from six unselected control populations, raised either under standard conditions or under larval malnutrition. In the control populations, phenotypic plasticity of wing size was mediated by both cell size and cell number. In contrast, evolutionary change in wing size, which was only observed as a correlated response expressed on standard food, was mediated entirely by reduction in cell number. Plasticity of cell number had been lost in the selected populations, and cell number did not differ between the sexes despite males having smaller wings. Results of this and other experimental evolution studies are consistent with the hypothesis that alleles which increase body size through prolonged growth affect wing size mostly via cell number, whereas alleles which increase size through higher growth rate do so via cell size.
在慢性营养不良的情况下，发育和进化都会导致果蝇成年个体体型减小。我们研究了大小变化与表皮细胞数量变化对因幼虫食物不良而导致的翅膀大小可塑性和进化性减小的贡献。我们使用了来自六个对幼虫营养不良具有耐受性的选择种群和六个未选择的对照种群的果蝇，这些种群分别在标准条件下或在幼虫营养不良的情况下饲养。在对照种群中，翅膀大小的表型可塑性是由细胞大小和细胞数量共同介导的。相比之下，在标准食物上观察到的翅膀大小的进化变化则完全是由细胞数量减少引起的。在选择种群中，细胞数量的可塑性已经丧失，尽管雄性翅膀较小，但雌雄之间的细胞数量没有差异。本研究和其他实验进化研究的结果与以下假设一致，即通过延长生长来增加体型的等位基因主要通过细胞数量来影响翅膀大小，而通过更高的生长速度来增加体型的等位基因则通过细胞大小来实现。
