Data from: A new mechanistic approach for the further development of a population with established size bimodality

Usually, the origin of a within-cohort bimodal size distribution is assumed to be caused by initial size differences or by one discrete period of accelerated growth for one part of the population. The aim of this study was to determine if more continuous pathways exist allowing shifts from the small to the large fraction within a bimodal age-cohort. Therefore, a Eurasian perch population, which had already developed a bimodal size-distribution and had differential resource use of the two size-cohorts, was examined. Results revealed that formation of a bimodal size-distribution can be a continuous process. Perch from the small size-cohort were able to grow into the large size-cohort by feeding on macroinvertebrates not used by their conspecifics. The diet shifts were accompanied by morphological shape changes. Intra-specific competition seemed to trigger the development towards an increasing number of large individuals. A stage-structured matrix model confirmed these assumptions. The fact that bimodality can be a continuous process is important to consider for the understanding of ecological processes and links within ecosystems.

学界通常认为，同群个体内的双峰体型分布，其成因不外乎初始体型差异，或是种群中部分个体经历了单次离散的加速生长阶段。本研究旨在探究：在双峰年龄群中，是否存在更为连续的路径，可实现小型个体群体向大型个体群体的转变。为此，研究团队针对一个已形成双峰体型分布、且两个体型群存在资源利用分化的欧亚鲈鱼（Eurasian perch）种群开展了调查。研究结果表明，双峰体型分布的形成可作为一个连续过程发生。小型体型群的鲈鱼可通过取食同种个体未利用的大型无脊椎动物，完成向大型体型群的生长过渡。这类食性转变同时伴随有形态体型的变化。种内竞争（intra-specific competition）似乎触发了种群向更多大型个体发展的过程。阶段结构矩阵模型（stage-structured matrix model）验证了上述假设。双峰分布可通过连续过程形成这一结论，对于理解生态系统内部的生态过程与相互关联具有重要意义。