泽陆蛙和饰纹姬蛙蝌蚪不同热驯化下选择体温和热耐受性

用泽陆蛙（Fejervarya limnocharis）蝌蚪和饰纹姬蛙（Microhyla ornata）蝌蚪做研究模型，检测热驯化（20 、25 和30 C）对选择体温（Tsel）、低温耐受性（CTMin）和高温耐受性（CTMax）的影响。结果显示，两种蝌蚪的Tsel既不受驯化温度的影响，也不存在种间差异；泽陆蛙蝌蚪的CTMin显著小于饰纹姬蛙蝌蚪，而CTMax和VTR则显著大于饰纹姬蛙蝌蚪；CTMin和CTMax随驯化温度的升高而升高，VTR则随驯化温度的升高而减小。研究结果表明，热驯化显著影响两种蝌蚪的CTMin、CTMax和VTR，而对两种蝌蚪的体温调定点无显著影响；这些热生物学特征对两种蝌蚪有效适应环境温度变化、利用资源、减少种间竞争具有重要的生态学意义。

Selected body temperature and thermal tolerance of tadpoles of two frog species (Fejervarya limnocharis and Microhyla ornata) acclimated under different thermal conditions

We collected six clutches of the Cricket Frog Fejervarya limnocharis and 10 clutches of the Ornate Narrow-mouthed Frog Microhyla ornata in late June 2010 from Fuyang,Zhejiang,East China,and incubated eggs of the two species at a constant temperature of 25 ℃.We raised 30 tadpoles from each clutch and released the remaining ones to the site where the clutches were collected.We randomly selected 90 tadpoles from those raised in the laboratory,and acclimated them at three constant temperatures(20,25 and 30 ℃),30 individuals at each temperature,for two weeks to examine the influence of thermal acclimation on selected body temperature(Tsel,a measure of thermal preference) and thermal tolerance critical thermal minimum(CTMin) and critical thermal maximum(CTMax)] and viable temperature range(VTR),and whether tadpoles of these two sympatric species differ in thermal preference and thermal tolerance.Tsel was measured by recording the water temperature where the tadpole stayed in a thermal gradient ranging from 15 ℃ to 38 ℃.We cooled(for CTMin determination) at the rate of 0.2 ℃/min or heated(for CTMax determination) tadpoles from 25 ℃ at the rate of 0.6 ℃/min.Body temperatures associated with a transient loss of the righting response at the lower and the upper limits of the thermal tolerance were considered to be the endpoints for CTMin and CTMax,respectively.Tadpoles of the two species did not differ in Tsel,and neither in F.limnocharis nor in M.ornata were body temperatures selected by tadpoles affected by thermal acclimatio.CTMim was greater in tadpoles of M.ornata,whereas CTMax and VTR were greater in tadpoles of F.limnocharis.CTMin and CTMax increased as acclimation temperature increased,and VTR decreased as acclimation temperature increased,in both species.Our data show that tadpoles of the two species do not differ in thermal preference but in thermal tolerance,and that thermal acclimation plays an important role in influencing thermal tolerance but not in thermal preference.Temperature is among the most important abiotic factors influencing biological processes in organisms and has consequences on their habitat requirements and hence spatial distribution,and is therefore a part of an organism′s multidimensional niche that should be treated as an ecological resource.Theoretically,species cannot coexist without a quantitative partitioning of resources along the axes of diet,space,time and thermal requirement.That sympatric species respond differently to variation in temperature at the spatial scale of the local community by using microhabitats with different thermal regimes may facilitate their coexistence.Our finding that tadpoles of F.limnocharis and M.ornata differ in thermal tolerance may have an implication for their differences in microhabitat use in nature,which may promote the coexistence of these two sympatric frog species.