根田鼠几种觅食功能反应模型的比较

Comparisons of the models for functional responses of foraging in root voles (Microtus oeconomus)

植物组织空间排列对植食性哺乳动物功能反应的作用,是觅食生态学的热点问题之一。以新鲜紫花苜蓿叶片为食物,改变苜蓿叶片大小调控根田鼠口量,改变叶片间距调控叶片密度,设置叶片空间异质性斑块。在空间异质性斑块上测定根田鼠的觅食行为及其参数,检验植食性哺乳动物4种功能反应模型的预测性。除复合模型参数Rmax、h和Vmax及口量模型参数Rmax的最大似然估计值与测定值近似外,其它模型参数的估计值与测定值均存在较大差异。根田鼠摄入率测定值与4种模型预测值的线性回归均显著(P<0.01),但与复合模型预测值的线性拟合效果最佳。表明,复合模型能很好地解释根田鼠觅食与行走的竞争对摄入率调节的动态。根田鼠复合模型存在调节其功能反应机制转变的距离临界值(d)。叶片间距大于该值时,叶片密度调节摄入率;叶片间距小于该值时,口量调节摄入率。结果充分地验证了提出的特定假设:在植物密集条件下,植物大小能调节植食性小型哺乳动物根田鼠的摄入率;在植物稀疏条件下,植物密度调节其摄入率。

The effect of variation in the spatial arrangement of plant tissues on the functional response of mammalian herbivores is one of the key parts of the foraging theory.In this study,4 models for the intake rate of root voles （ Microtus oeconomus） foraging in the pathes of fresh alfalfa （ Medicago satival ） leaves were evaluated.Each trial included observations of root voles in a single patch type,characterized by a different arrangement of leaf size and leaf density which represented spatially heterogeneous leaf patches.The size of the leaf offered to root voles was varied to control their bite mass,and plant spacing was varied to control leaf density within the patches.The composite model depicting the combined effects of bite mass and plant density fitted the data more properly than the other models.The maximal likelihood estimate of the parameters,Rmax,h and Vmax from the combined model represented the independent and direct estimates more closely than the other models.Although significantly linear regressive relationships existed between observed and predicted intake rates of root voles by the 4 models （P0.01） ,the composite model fitted best to the observations,indicating that the composite model described the dynamics of intake rates regulated by competing between foraging and walking of root voles.The composite model predicted a distance threshold （d ） distinguishing the mechanisms for functional responses：the vole＇s intake rate was regulated by bite size when the leaf spacing was lower than the threshold,but once the leaf spacing exceeded the threshold,the vole＇s intake rate was then regulated by the leaf density.The validating tests of these models provided a strong support to the hypotheses about intake rates to be regulated by dual mechanisms in small mammalian herbivores：the plant size regulated the intake rate of root voles in plant-abundant patches,while the plant density regulated their intake rates in plant-sparse patches.