Department of Biology, University of North Carolina, Greensboro, NC 27402, USA.
Am Nat. 2012 Sep;180(3):342-53. doi: 10.1086/666987. Epub 2012 Jul 19.
To better understand the evolution of phenotypic plasticity and thermoregulation and their potential value for ectotherms in the face of global warming, we conducted field experiments to measure their effects on fitness and their association with reproductive phenology in Plantago lanceolata in a thermally variable environment. We measured the reproductive timing and success of genotypes varying in thermoregulation, as mediated by floral-reflectance plasticity. Results were consistent with the hypothesis that thermoregulation is more adaptive when thermally variable reproductive seasons are shorter and cooler. Strong thermoregulation/plasticity increased reproductive success during the cool portion of the reproductive season but not during the warm portion. Directional selection that favored strongly thermoregulating genotypes early in the season shifted to stabilizing selection that favored genotypes with weaker thermoregulation later in the season. Thermoregulation and reproductive phenology were negatively correlated. Although reproductive onset and duration were similar between genotypes, strong thermoregulators produced more and larger spikes (clutches) early; weak thermoregulators produced more spikes late. Results suggest that with atmospheric warming, the benefit of raising body temperature via thermoregulation when it is cool should decline in extant populations. The negative correlation between thermoregulation and phenology should accelerate the evolutionary shift toward thermoconformity, that is, reduced plasticity.
为了更好地理解表型可塑性和体温调节的进化及其在全球变暖背景下对外温动物的潜在价值，我们在一个温度变化的环境中，通过植物斑兰的花反射率可塑性来测量其对适合度的影响及其与生殖物候的关系，进行了野外实验。我们测量了在温度变化的生殖季节中，通过热调节而变化的基因型的生殖时间和成功率。结果与假设一致，即当生殖季节较短且较凉爽时，热调节更具适应性。强烈的热调节/可塑性增加了生殖季节凉爽部分的生殖成功率，但不增加温暖部分的生殖成功率。有利于季节早期强热调节基因型的定向选择转变为有利于季节后期弱热调节基因型的稳定选择。热调节和生殖物候呈负相关。尽管基因型之间的生殖起始和持续时间相似，但强热调节者早期产生更多和更大的穗（簇）；弱热调节者后期产生更多的穗。结果表明，随着大气变暖，在凉爽时通过热调节来提高体温的益处应该会在现存种群中下降。热调节与物候之间的负相关应该会加速向热顺应性（即降低可塑性）的进化转变。
