Abstract Competition and predation are the two major biotic interactions in zooplankton community. Various rotifer species exhibit polymorphism in lorica and spine morphology in the presence of predators and competitors, which effectively increases their defence competition capacity. This study compared life-history parameters between long-spined morph (LSM) and short-spined morph (SSM) of Keratella tropica at three temperatures. The results showed that both morphs showed significantly higher intrinsic rate of population increase at 25 °C than those at 20 °C and 30 °C. The intrinsic rate of population increase was significantly lower in LSM than SSM at 25 °C and 30 °C, and the net reproductive rate was significantly lower in LSM than SSM at 30 °C. These results suggested that K. tropica had cost on development of long spines, which, however, was dependent on temperature. Moreover, the competition outcome of LSM and SSM with Moina macrocopa were investigated at three densities of Scenedesmus obliquus (0.5 × 106, 1.0 × 106 and 2.0 × 106 cells/mL) and three initial densities of M. macrocopa (0.1, 0.3 and 0.9 in./mL), revealing that both LSM and SSM populations decreased significantly at all tested algal densities and Moina levels. LSM showed higher population growth rate than SSM at lower algal density (0.5 × 106 cells/mL) and higher Moina densities (0.3 and 0.9 in./mL), which suggested that LSM could be more effective to defend M. macrocopa. Three-way analysis of variance showed no significant effects of algal density on population growth rate of K. tropica, but interaction between algal density and M. macrocopa density significantly affected its population growth rate.

中文翻译：

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两种热带喀拉特藻变种的生活史参数和与大蝾螈竞争的有效性比较

摘要 竞争和捕食是浮游动物群落中两种主要的生物相互作用。各种轮虫在捕食者和竞争者的存在下表现出lorica和棘突形态的多态性，有效地提高了它们的防御竞争能力。本研究比较了热带喀拉特藻在三种温度下的长刺变形 (LSM) 和短刺变形 (SSM) 的生活史参数。结果表明，与 20°C 和 30°C 相比，这两种形态在 25°C 下的内在种群增长率显着更高。25°C和30°C时LSM的内在种群增长率显着低于SSM，而LSM的净繁殖率在30°C时显着低于SSM。这些结果表明 K. tropica 在长刺的发育上有代价，然而，取决于温度。此外，在三种密度的栅藻（0.5 × 106、1.0 × 106 和 2.0 × 106 细胞/mL）和三种初始密度的 M. macrocopa（0.1、0.3 和 0.9）下研究了 LSM 和 SSM 与 Moina macrocopa 的竞争结果in./mL)，表明 LSM 和 SSM 种群在所有测试的藻类密度和 Moina 水平下均显着下降。在较低的藻类密度（0.5 × 106 个细胞/mL）和较高的 Moina 密度（0.3 和 0.9 in./mL）下，LSM 显示出比 SSM 更高的种群增长率，这表明 LSM 可以更有效地保护 M. macrocopa。三元方差分析表明，藻密度对K. tropica种群增长率没有显着影响，但藻密度与M. macrocopa密度之间的相互作用对其种群增长率有显着影响。