Ecological niche differentiation is a process that accompanies lineage diversification and community assembly. Traditionally, the degree of niche differentiation is estimated by contrasting niche hypervolumes of two taxa, reconstructed using ecologically relevant variables. These methods disregard the fact that niches can shift in different ways and directions. Without means of discriminating between different types of niche differentiation, important evolutionary and ecological patterns may go unrecognized. Herein, we introduce a new conceptual and methodological framework that allows quantification and classification of niche differentiation and divergence between taxa along single niche axis. This new method, the Niche Divergence Plane, is based on species' responses to an underlying environmental gradient, from which we derive a two-dimensional plane defined by two indices, niche exclusivity and niche dissimilarity. These two indices identify the proportion of the environmental gradient that is unique to each species, that is, how much of the environmental gradient species do not share (niche breadth exclusivity) and how different the species' responses are along the environmental gradient (niche dissimilarity). Thus, the latter can also be seen as a measure of the differences in niche preference or importance, even when there is significant overlap in niche breadth (i.e., low niche exclusivity). Based on the position of the two indices on the divergence plane, we can distinguish niche conservatism from four other general types of niche divergence: hard, soft, weighted, and nested. We demonstrate that the Niche Divergence Plane complements traditional measures of niche similarity (e.g., Schoener's D or Hellinger's I). Additionally, we show an empirical comparison using the Niche Divergence Plane framework on two Ambystoma salamanders. Overall, we demonstrate that the Niche Divergence Plane is a versatile tool that can be used to complement and expand previous methods of ecological niche comparisons and the study of ecological niche divergence.

中文翻译：

---

用于量化和分类生态位分化的新理论和分析框架


生态位分化是伴随着谱系多样化和群落组装的过程。传统上，生态位分化的程度是通过对比两个分类群的生态位超体积来估计的，并使用生态相关变量重建。这些方法忽视了利基市场可以以不同的方式和方向转变的事实。如果没有区分不同类型的生态位分化的方法，重要的进化和生态模式可能无法被识别。在此，我们引入了一个新的概念和方法框架，该框架允许沿单个生态位轴对分类群之间的生态位分化和分歧进行量化和分类。这种新方法，即生态位发散平面，是基于物种对潜在环境梯度的反应，我们从中得出一个由两个指数定义的二维平面，即生态位排他性和生态位不相似性。这两个指数确定了每个物种独有的环境梯度的比例，即物种不共享的环境梯度的程度（生态位广度排他性）以及物种对环境梯度的反应有多大差异（生态位不相似性）。因此，后者也可以被视为衡量利基偏好或重要性差异的指标，即使利基广度存在显着重叠（即低利基排他性）。根据两个指数在背离平面上的位置，我们可以将利基保守性与其他四种一般类型的利基背离区分开来：硬、软、加权和嵌套。我们证明 Niche Divergence Plane 补充了传统的 Niche 相似性度量（例如，Schoener 的 D 或 Hellinger 的 I）。 此外，我们展示了使用 Niche Divergence Plane 框架对两只 Ambystoma 蝾螈进行实证比较。总体而言，我们证明了生态位分歧平面是一种多功能工具，可用于补充和扩展以前的生态位比较方法和生态位分歧研究。