Invasion biologists have attempted to reveal intraspecific variability of biological traits of non-native species at large spatial scales, but the knowledge of the intraspecific variability of invasive species within a single population (such as resource polymorphism) is still limited. In this study, we report the intraspecific variability in life-history traits of a non-native largemouth bass (LMB) population in a subtropical reservoir and discuss the causes and mechanisms of this novel resource polymorphism in relation to ontogenetic diet shift (ODS) and growth rate of prey fish. A polymorphic LMB population was characterized as the sympatric occurrence of “normal” and “dwarf” forms. The normal form showed evident ODS in their diet from smaller gobies to larger prey such as bluegill (BG). In contrast, the majority of dwarfs preyed on gobies throughout their life, because the BG population rapidly grew out of the predation window of dwarfs under the subtropical warm climate. Analysis of the first-year life-history of LMB suggested that the shift of individuals to normal form is irreversibly determined by first-year growth and that the largest size class of the young-of-the-year cohort reaching 180–200 mm standard length and experiencing ODS can shift to the normal form. In conclusion, scarcity of alternative prey and rapid escape of BG from the predation window prevents ODS in dwarfs, creating distinct resource use patterns and diverging life-history traits between the two forms. Novel resource polymorphism in LMB is likely a response to food limitation, and whether this response is based on phenotypic or genetic plasticity should be clarified.

入侵生物学家试图在大空间尺度上揭示外来物种生物学特性的种内变异性，但对单个种群内入侵物种的种内变异性（如资源多态性）的认识仍然有限。在这项研究中，我们报告了亚热带水库中非本地大口黑鲈 (LMB) 种群生活史特征的种内变异性，并讨论了这种新的资源多态性与个体遗传饮食转变 (ODS) 和猎物鱼的生长速度。多态性 LMB 种群的特征是“正常”和“矮化”形式的同域发生。正常形式在从较小的虾虎鱼到较大的猎物如蓝鳃鱼 (BG) 的饮食中显示出明显的 ODS。相比之下，大多数矮人一生都在捕食虾虎鱼，因为在亚热带温暖气候下，BG 种群迅速超出了矮人的捕食窗口。对 LMB 第一年生活史的分析表明，个体向正常形态的转变是由第一年的生长不可逆转地决定的，并且达到 180-200 毫米标准的年幼人群的最大体型类别长度和经历 ODS 可以转变为正常形式。总之，替代猎物的稀缺和 BG 从捕食窗口的快速逃脱阻止了矮人的 ODS，从而在两种形式之间创造了不同的资源使用模式和不同的生活史特征。LMB 中新的资源多态性可能是对食物限制的反应，这种反应是基于表型还是遗传可塑性，应该加以澄清。