Data from: Classification tree methods provide a multifactorial approach to predicting insular body size evolution in rodents

Many hypotheses have been proposed to explain size changes in insular mammals, but no single variable suffices to explain the diversity of responses, particularly within Rodentia. Here in a dataset on insular rodents we observe strong consistency in the direction of size change within islands and within species, but (outside of Heteromyidae) little consistency at broader taxonomic scales. Using traits of islands and of species in a classification-tree analysis we find the most important factor predicting direction of change to be mainland body mass (large rodents decrease, small ones increase); other variables (island climate, number of rodent species, and area) were significant although their roles as revealed by the classification tree were context-dependent. Ecological interactions appear relatively uninformative, and on any given island the largest and smallest rodent species converged or diverged in size with equal frequency. Our approach provides a promising framework for continuing examination of insular body-size evolution.学界已提出诸多假说来解释岛屿哺乳动物（insular mammals）的体型变化规律，但尚无单一变量能够全面阐释其响应的多样性，尤以啮齿目（Rodentia）类群为甚。本研究针对岛屿啮齿类构建的数据集显示，单个岛屿内及同一物种间的体型变化方向具有高度一致性，但在异鼠科（Heteromyidae）之外的类群中，更高级分类学尺度下的一致性则较为薄弱。通过结合岛屿与物种特征开展分类树分析（classification-tree analysis），本研究发现预测体型变化方向的最重要因素为大陆种群的体型大小：体型较大的啮齿类在岛屿上体型会缩小，而体型较小的啮齿类则会增大；其余变量（岛屿气候、啮齿类物种数与岛屿面积）虽同样具有统计学显著性，但其在分类树模型中展现的作用具有情境依赖性。生态相互作用（ecological interactions）对体型变化的解释力相对较弱；且在任意一座岛屿上，体型最大与最小的啮齿类物种出现体型趋同或趋异的频率大致相当。本研究提出的分析框架为后续开展岛屿体型演化研究提供了极具前景的研究路径。