Department of Botany and Zoology, Faculty of Sciences, Masaryk University, Brno, Czech Republic.
Czech Academy of Sciences, Institute of Vertebrate Biology, Brno, Czech Republic.
J Therm Biol. 2021 Apr;97:102896. doi: 10.1016/j.jtherbio.2021.102896. Epub 2021 Feb 26.
Tonic immobility (TI) is an important antipredator response employed by prey in the last stages of a predation sequence. Evolution by natural selection assumes consistent individual variation (repeatability) in this trait. In ectotherms, which experience variable body temperatures, TI should be repeatable over a thermal gradient to be targeted by natural selection; however, information on thermal repeatability of this trait is missing. We examined thermal repeatability of TI in juveniles of two sympatric amphibians, smooth (Lissotriton vulgaris) and alpine (Ichthyosaura alpestris) newts. Both species showed disparate TI responses to body temperature variation (13-28 °C). While the proportion of TI response was repeatable in both taxa, it increased with body temperature in alpine newts but was temperature independent in smooth newts. Duration of TI decreased with body temperature in both taxa but was only repeatable in smooth newts. Our results suggest that a warming climate may affect population dynamics of sympatric ectotherms through asymmetry in thermal reaction norms for antipredator responses.
紧张不动状态（TI）是猎物在捕食序列的最后阶段采取的一种重要的抗捕食反应。自然选择进化假设这种特征具有一致的个体变异（可重复性）。在变温动物中，TI 应该在热梯度上具有可重复性，才能成为自然选择的目标；然而，关于这种特征的热可重复性的信息是缺失的。我们研究了两种同域两栖动物——光滑（Lissotriton vulgaris）和高山（Ichthyosaura alpestris）蝾螈幼体的 TI 对温度变化（13-28°C）的热可重复性。这两个物种对体温变化的 TI 反应不同（13-28°C）。虽然 TI 反应的比例在两个分类群中都是可重复的，但在高山蝾螈中，它随体温的升高而增加，而在光滑蝾螈中，它与体温无关。TI 的持续时间在两个分类群中都随体温的升高而降低，但在光滑蝾螈中是可重复的。我们的结果表明，气候变化可能会通过抗捕食反应的热反应规范的不对称性影响同域变温动物的种群动态。
