Centre for Invasion Biology, Department of Botany and Zoology, Stellenbosch University, Stellenbosch, 7602 South Africa.
Univ Lyon, Université Claude Bernard Lyon 1, CNRS, ENTPE, UMR 5023 LEHNA, F-69622, Villeurbanne, France.
J Exp Biol. 2021 Apr 1;224(7). doi: 10.1242/jeb.233031. Epub 2021 Apr 15.
Environmental temperature variation generates adaptive phenotypic differentiation in widespread populations. We used a common garden experiment to determine whether offspring with varying parental origins display adaptive phenotypic variation related to different thermal conditions experienced in parental environments. We compared burst swimming performance and critical thermal limits of African clawed frog (Xenopus laevis) tadpoles bred from adults captured at high (∼2000 m above sea level) and low (∼ 5 m above sea level) altitudes. Maternal origin significantly affected swimming performance. Optimal swimming performance temperature (Topt) had a >9°C difference between tadpoles with low altitude maternal origins (pure- and cross-bred, 35.0°C) and high-altitude maternal origins (pure-bred, 25.5°C; cross-bred, 25.9°C). Parental origin significantly affected critical thermal (CT) limits. Pure-bred tadpoles with low-altitude parental origins had higher CTmax (37.8±0.8°C) than pure-bred tadpoles with high-altitude parental origins and all cross-bred tadpoles (37.0±0.8 and 37.1±0.8°C). Pure-bred tadpoles with low-altitude parental origins and all cross-bred tadpoles had higher CTmin (4.2±0.7 and 4.2±0.7°C) than pure-bred tadpoles with high-altitude parental origins (2.5±0.6°C). Our study shows that the varying thermal physiological traits of Xenopus laevis tadpoles are the result of adaptive responses to their parental thermal environments. This study is one of few demonstrating potential intraspecific evolution of critical thermal limits in a vertebrate species. Multi-generation common garden experiments and genetic analyses would be required to further tease apart the relative contribution of plastic and genetic effects to the adaptive phenotypic variation observed in these tadpoles.
环境温度变化会导致广泛分布的种群产生适应性表型分化。我们使用一个共同的花园实验来确定具有不同亲本起源的后代是否表现出与亲本环境中经历的不同热条件相关的适应性表型变异。我们比较了从海拔较高（约 2000 米以上）和较低（约 5 米以上）的成年非洲爪蟾（Xenopus laevis）中繁殖的蝌蚪的爆发式游泳性能和临界热极限。母体起源显著影响游泳性能。低海拔母体起源（纯系和杂交系，35.0°C）和高海拔母体起源（纯系，25.5°C；杂交系，25.9°C）的蝌蚪的最佳游泳性能温度（Topt）有超过 9°C的差异。母体起源显著影响临界热（CT）极限。低海拔母体起源的纯系蝌蚪的 CTmax（37.8±0.8°C）高于高海拔母体起源的纯系和所有杂交系的蝌蚪（37.0±0.8 和 37.1±0.8°C）。低海拔母体起源的纯系蝌蚪和所有杂交系的蝌蚪的 CTmin（4.2±0.7 和 4.2±0.7°C）高于高海拔母体起源的纯系蝌蚪（2.5±0.6°C）。我们的研究表明，非洲爪蟾蝌蚪的变化的热生理特征是对其父母热环境的适应性反应的结果。这项研究是少数几个证明在脊椎动物物种中临界热极限潜在种内进化的研究之一。需要进行多代共同花园实验和遗传分析，以进一步区分这些蝌蚪中观察到的适应性表型变异的可塑性和遗传效应的相对贡献。
