Hulbert A J, MacMillen Richard E
Department of Ecology and Evolutionary Biology, University of California, 92717, Irvine, CA, USA.
Oecologia. 1988 May;75(4):521-526. doi: 10.1007/BF00776415.
The water balance of three different sized coexisting species of heteromyid rodents (Dipodomys merriami ca. 39 g;Perognathus fallax ca. 23 g;Perognathus longimembris ca. 9 g) was assessed while consuming two different diets (either wheat or hulled sunflower) at ambient temperatures of 15-30°C. The metabolism of wheat as the sole food source was calculated to provide a greater metabolic water production (MWP) than the consumption of sunflower seed because of their different composition. The state of water balance was assessed by measuring urine concentrations and body weight maintenance on each diet at each temperature. Both measures showed that (i) all species were able to maintain a more positive water on the higher MWP seed, (ii) for all species there was an ambient temperature above which water balance could no longer be maintained, (iii) that this temperature was higher with the higher MWP food source and (iv) water regulatory efficiency was negatively correlated with body mass.Dipodomys showed a reduced digestive efficiency compared toPerognathus. When presented with both seedsDipodomys showed no preference for either seed irrespective of the state of water balance whilst thePerognathus species showed a tendency for an increased preference for the high MWP food source at the higher ambient temperatures. The ecological implications of these findings are discussed.
在15 - 30°C的环境温度下，研究人员评估了三种不同体型、共存的更格卢鼠科啮齿动物（美氏更格卢鼠约39克；淡色林鼠约23克；长尾林鼠约9克）在食用两种不同食物（小麦或去壳向日葵）时的水平衡情况。由于小麦和向日葵种子的成分不同，经计算，以小麦作为唯一食物来源时，其代谢水产量（MWP）比食用向日葵种子更高。通过测量每种温度下每种食物的尿液浓度和体重维持情况来评估水平衡状态。这两项测量结果均表明：（i）所有物种在代谢水产量较高的种子上能够维持更正向的水平衡；（ii）对于所有物种而言，存在一个高于该温度便无法再维持水平衡的环境温度；（iii）该温度在代谢水产量较高的食物来源情况下更高；（iv）水分调节效率与体重呈负相关。与林鼠相比，更格卢鼠的消化效率较低。当同时提供两种种子时，无论水平衡状态如何，更格卢鼠对两种种子均无偏好，而林鼠物种在较高环境温度下表现出对代谢水产量高的食物来源偏好增加的趋势。文中讨论了这些发现的生态意义。
