Spatial Variation Of Morphological And Ecological Characteristics Of Brachionus Calyciflorus (Rotifera) From East China

The differences in morphometry, life history characteristics and reproductive characteristics among eight geographic populations of Brachionus calyciflorus collected from East China in March 2008 (in winter) were investigated, and the main results were presented as the following:1. Morphometric differences among eight geographic populations of B. calyciflorus were investigated by means of ANOVA, cluster analysis, principal component analysis and discriminant analysis. The results showed that the response in each of morphometric parameters to increasing temperature differed with geographic population. The results of two-way ANOVA showed that geographic population affected significantly all the morphometric parameters, temperature and interaction between temperature and geographic population both affected all the morphometric parameters except the posterior lateral spine length. The results of cluster analyses showed that Nanchang, Anqing and Nanjing populations were clustered into one clade, Ganzhou, Wuhu, Xuzhou, Dezhou and Tianjin populations were clustered into another clade. Principal component analysis on morphometric parameters showed that each of morphometric parameters affected morphometric characteristics of all the geographic populations. Discriminant analysis showed that the discriminant analysis I was more accurate than the discriminant analysis II, but their discriminant accuracies for the eight geographic populations were lower. The morphometric characteristics used in this study is unsuitable to accurately identify different geographic populations. The morphometric parameters were significantly correlated with water temperature, annually mean temperature and latitude of the habitats of the rotifers, which might be regarded as the results of adaptation to the different environmental conditions faced by them in the field.2. Differences in the life history characteristics among eight geographic populations of B. calyciflorus cultured at 10?C, 15?C and 20?C with 3.0×10~6cells ml-1 of alga Scenedesmus obliquus were investigated by means of life table demographic approach. The results showed that the response in each of the life table demographic parameters to increasing temperature differed with geographic population. Both temperature and geographic population affected significantly all the life table demographic parameters of B. calyciflorus, and their interaction affected significantly all the life table demographic parameters, except the generation time. Among the three temperatures, the life expectancy at hatching and generation time of the rotifers shortened with increasing temperature; the gross reproductive rate at 20?C was the highest; net reproductive rate, intrinsic rate of population increase and proportion of sexual offspring produced by rotifers increased with the rise of temperature. Among the eight geographic populations, the life expectancies at hatching, generation times and net reproductive rates of Anqing, Xuzhou and Tianjin populations were all the highest; the gross reproductive rate of Tianjin population was higher than those of Nanchang, Wuhu, Nanjing and Dezhou populations; the intrinsic rates of population increase of Anqing, Xuzhou and Tianjin populations were higher than that of Dezhou population; the proportions of sexual offspring produced by Nanchang, Anqing, Wuhu, Nanjing and Dezhou populations were the highest, and that produced by Ganzhou population was the lowest. Life expectancy at hatching, generation time, gross reproductive rate, net reproductive rate and intrinsic rate of population increase were all significantly correlated with both body size and egg volume of the rotifers, indicating that they were indirectly affected by the changes in body size and egg volume of the rotifers. The differences in life table demographic parameters among eight geographic populations, and their significant correlations with water temperature, annually mean temperature and latitude might be attributed to adaptation to local environment.3. Differences in reproductive characteristics among eight geographic populations of B. calyciflorus cultured at 10?C, 15?C and 20?C with 3.0×10~6cells ml-1 of alga Scenedesmus obliquus were investigated. The response in each of the reproductive parameters to increasing temperature differed with geographic population. Two-way ANOVA showed that temperature, geographic population and their interaction affected significantly population growth rate, average mixis and fertilization rates. Among the three temperatures, the population growth rate and the average mixis rate of B. calyciflorus increased with the rise of temperature; the average fertilization rate at 10?C was the lowest. Among the eight geographic populations, the population growth rate of Anqing population was higher than those of Wuhu and Tianjin populations; the average mixis rates of Ganzhou, Xuzhou and Tianjin populations were the lowest; the average fertilization rate of Wuhu population was the highest. Population growth rate, average mixis and fertilization rates of the rotifers were significantly correlated with water temperature, annually mean temperature and latitude, which might be regarded as the results of adaptation to the local environmental conditions faced by them in the field.