Halliday William D, Blouin-Demers Gabriel
Department of Biology, University of Ottawa, 30 Marie Curie, Ottawa, ON, Canada K1N 6N5.
Department of Biology, University of Ottawa, 30 Marie Curie, Ottawa, ON, Canada K1N 6N5.
J Therm Biol. 2015 Aug;52:108-16. doi: 10.1016/j.jtherbio.2015.06.002. Epub 2015 Jun 16.
Whole-organism performance depends on body temperature and ectotherms have variable body temperatures. The thermal coadaptation hypothesis posits that thermal reaction norms have coevolved with thermal preference such that organisms attain optimal performance under a narrow range of body temperatures commonly experienced in the wild. Since thermal reaction norms are often similar, researchers interested in the effects of temperature on fitness often use one easily measured thermal reaction norm, such as locomotor performance, and assume it is a good proxy for fitness when testing the thermal coadaptation hypothesis. The extent to which this assumption holds, however, is often untested. In this study, we provide a stringent test of the thermal coadaptation hypothesis in red and in confused flour beetles by comparing the thermal reaction norm for reproductive output to the preferred body temperature range. We also test the assumption that locomotor performance can serve as a proxy for the thermal reaction norm for reproductive output, a more ultimate index of fitness. In both species, we measured the number of eggs laid, righting time, and sprint speed at eight temperatures, as well as the thermal preference in a thermal gradient. The number of eggs laid increased with female sprint speed and with male righting time, and all three performances had similar thermal reaction norms, with 80% of the maximum achieved between 23 and 37°C. Red flour beetles had preferred body temperatures that matched the optimal temperature for performance; confused flour beetles had lower preferred body temperature than the optimal temperature for performance. We found support for the assumption that locomotor performance can serve as a proxy for reproductive output in flour beetles, but we only found evidence for thermal coadaptation in one of the two species.
生物体的整体表现取决于体温,而变温动物的体温是可变的。热协同适应假说认为,热反应规范与热偏好共同进化,使得生物体在野外通常经历的较窄体温范围内达到最佳表现。由于热反应规范通常相似,对温度对适应性影响感兴趣的研究人员经常使用一种易于测量的热反应规范,如运动表现,并在检验热协同适应假说时假定它是适应性的良好指标。然而,这一假设成立的程度往往未经检验。在本研究中,我们通过比较生殖输出的热反应规范与偏好体温范围,对赤拟谷盗和杂拟谷盗的热协同适应假说进行了严格检验。我们还检验了运动表现可作为生殖输出热反应规范的指标这一假设,生殖输出是一个更能反映适应性的最终指标。在这两个物种中,我们在八个温度下测量了产卵数、翻身时间和冲刺速度,以及在热梯度中的热偏好。产卵数随雌性冲刺速度和雄性翻身时间的增加而增加,并且这三种表现都有相似的热反应规范,在23至37°C之间达到最大值的80%。赤拟谷盗的偏好体温与表现的最佳温度相匹配;杂拟谷盗的偏好体温低于表现的最佳温度。我们发现运动表现可作为拟谷盗生殖输出指标的假设得到了支持,但我们仅在两个物种中的一个中发现了热协同适应的证据。