Kuyucu Arda Cem, Sahin Mehmet Kursat, Caglar Selim Sualp
Hacettepe University, Department of Biology, Faculty of Science, Ankara, Turkey.
Hacettepe University, Department of Biology, Faculty of Science, Ankara, Turkey.
J Therm Biol. 2018 Jan;71:212-220. doi: 10.1016/j.jtherbio.2017.11.017. Epub 2017 Nov 29.
According to the thermal melanism hypothesis, darker coloured melanic individuals heat up faster and to higher temperatures than lighter coloured individuals due to lower skin reflectance. Consequently, it is assumed that darker melanic types may be advantageous compared to light coloured types in colder regions. As temperature gradually decreases with elevation and latitude the degree of melanism is expected to increase along these gradients in ectothermic species. Isophya rizeensis, a colour polymorphic bush cricket species endemic to Northeastern Turkey is an interesting case since the degree of melanism decreases with elevation, contrary to the thermal melanism hypothesis. In order to investigate the relation between colouration and thermal biology of this species, body temperatures (T) of crickets from different colour morphs, environmental temperatures (T), solar radiation and vegetation height were measured to test the relation between these variables and thermoregulation. Field results showed that solar radiation was the most effective factor on temperature excess (T), the difference between body and ambient temperature. Additionally, T values showed negative correlation with vegetation height. Although T values did not differ significantly between colour morphs, paired experiments under sunlight showed that darker morphs heated up faster and attained higher body temperatures than light morphs. We conclude that, since higher T values at alpine short swards might also increase the risk of facing deleterious temperatures at high elevations, protection against overheating might be one of the factors responsible for this polymorphism.
根据热黑化假说，由于皮肤反射率较低，颜色较深的黑化个体比颜色较浅的个体升温更快且温度更高。因此，据推测，在较寒冷地区，与浅色类型相比，深色黑化类型可能具有优势。随着海拔和纬度的升高温度逐渐降低，预计变温动物的黑化程度会沿着这些梯度增加。伊索菲亚·里泽ensis是一种颜色多态的灌丛蟋蟀物种，原产于土耳其东北部，是一个有趣的例子，因为黑化程度随海拔升高而降低，这与热黑化假说相反。为了研究该物种颜色与热生物学之间的关系，测量了不同颜色形态蟋蟀的体温（T）、环境温度（T）、太阳辐射和植被高度，以测试这些变量与体温调节之间的关系。野外结果表明太阳辐射是对体温过剩（T，即体温与环境温度之差）影响最大的因素。此外，T值与植被高度呈负相关。虽然不同颜色形态的T值没有显著差异，但在阳光下进行的配对实验表明，深色形态比浅色形态升温更快且体温更高。我们得出结论，由于高山短草地区较高的T值也可能增加在高海拔地区面临有害温度的风险，防止过热可能是导致这种多态性的因素之一。
