Semlitsch Raymond D
Institute of Zoology, University of Zürich, CH-8057 Zürich, Switzerland.
Evolution. 1993 Dec;47(6):1805-1818. doi: 10.1111/j.1558-5646.1993.tb01271.x.
The distribution and proportion of the sexual species Rana lessonae to the hemiclonal hybrid R. esculenta among natural habitats suggests that these anurans may differ in adaptive abilities. I used a half-sib design to partition phenotypic and quantitative genetic variation in tadpole responses at two food levels into causal variance components. Rana lessonae displays strong phenotypic variation across food levels. Growth rate is strictly determined by environmental factors and includes weak maternal effects. Larval period and body size at metamorphosis both contain moderate levels of additive genetic variance. The sire x food interactions and the lack of environmental correlations indicate that adaptive phenotypic plasticity is present in both of these traits. In contrast, R. esculenta displays less phenotypic variation across food levels, especially for larval period. Variation in body size at metamorphosis is underlain by genetic variation as shown by high levels of additive genetic variance, yet growth rate and larval period are not. Significant environmental correlations between larval period at high food level and growth, larval period, and body size at low food, indicate phenotypic plasticity is absent. A positive phenotypic correlation between body size at metamorphosis and larval period for R. lessonae at both food levels suggests a trade-off between growing large and metamorphosing quickly to escape predation or pond drying. The lack of a similar correlation for R. esculenta at the high food level suggests it may be less constrained. Different levels of adaptive genetic variation among larval traits suggest that the sexual species and the hybridogenetic hemiclone differ in their abilities to cope with temporally and spatially heterogeneous environments.
在自然栖息地中，有性物种莱氏蛙（Rana lessonae）与半克隆杂种食用蛙（R. esculenta）的分布及比例表明，这些无尾两栖动物在适应能力上可能存在差异。我采用半同胞设计，将两个食物水平下蝌蚪反应的表型和数量遗传变异划分为因果方差成分。莱氏蛙在不同食物水平下表现出强烈的表型变异。生长速率严格由环境因素决定，且母体效应较弱。变态时的幼体期和体型均含有中等水平的加性遗传方差。父本与食物的相互作用以及缺乏环境相关性表明，这两个性状都存在适应性表型可塑性。相比之下，食用蛙在不同食物水平下的表型变异较小，尤其是幼体期。变态时体型的变异由高水平的加性遗传方差所显示的遗传变异决定，但生长速率和幼体期并非如此。高食物水平下的幼体期与低食物水平下的生长、幼体期和体型之间存在显著的环境相关性，表明不存在表型可塑性。两个食物水平下，莱氏蛙变态时的体型与幼体期之间呈正表型相关，这表明在长得大与快速变态以逃避捕食或池塘干涸之间存在权衡。高食物水平下食用蛙缺乏类似的相关性，这表明它可能受到的限制较小。幼体性状之间不同水平的适应性遗传变异表明，有性物种和杂交半克隆在应对时空异质环境的能力上存在差异。
