Data from: Temperature-size rule is mediated by thermal plasticity of critical size in Drosophila melanogaster

Most ectotherms show an inverse relationship between developmental temperature and body size, a phenomenon known as the temperature size rule (TSR). Several competing hypotheses have been proposed to explain its occurrence. According to one set of views, the TSR results from inevitable biophysical effects of temperature on the rates of growth and differentiation, whereas other views suggest the TSR is an adaptation that can be achieved by a diversity of mechanisms in different taxa. Our data reveal that the fruit fly, Drosophila melanogaster, obeys the TSR using a novel mechanism: reduction of critical size at higher temperatures. In holometabolous insects, attainment of critical size initiates the hormonal cascade that terminates growth, and hence, Drosophila larvae appear to instigate the signal to stop growth at a smaller size at higher temperatures. This is in contrast to findings from another holometabolous insect, Manduca sexta, in which the TSR results from the effect of temperature on the rate and duration of growth. This contrast suggests that there is no single mechanism that accounts for the TSR. Instead, the TSR appears to be an adaptation that is achieved at a proximate level through different mechanisms in different taxa.

绝大多数外温动物（ectotherms）均表现出发育温度与体型间的负相关关系，这一现象被称为温度体型法则（temperature size rule, TSR）。学界已提出多种竞争性假说来阐释该现象的成因。其中一类观点认为，TSR源于温度对生长与分化速率不可避免的生物物理效应；而另一类观点则提出，TSR是一种适应性特征，可通过不同类群间的多样机制实现。本研究数据表明，黑腹果蝇（Drosophila melanogaster）通过一种全新机制遵循TSR：在高温环境下降低临界体型（critical size）。在全变态昆虫（holometabolous insects）中，临界体型的达成会启动终止生长的激素级联反应，因此果蝇幼虫会在高温条件下以更小的体型触发生长停止信号。这与另一类全变态昆虫——烟草天蛾（Manduca sexta）的研究发现相悖，后者的TSR源于温度对生长速率与生长时长的影响。这一差异表明，TSR并无统一的解释机制。相反，TSR似乎是一种适应性特征，在近因层面上可通过不同类群的差异化机制得以实现。