Data from: The effect of range overlap on ecological niche divergence depends on spatial scale in monkeyflowers

Patterns of niche divergence and geographical range overlap of closely related species provide insights into the evolutionary dynamics of ecological niches. When ranges overlap, shared selective pressures may preserve niche similarity along coarse‐scale macrohabitat axes (e.g., bioclimates). Alternatively, competitive interactions may drive greater divergence along local‐scale microhabitat axes (e.g., micro‐topographical features). We tested these hypotheses in 16 species pairs of western North American monkeyflowers (Erythranthe and Diplacus, formerly Mimulus) with species’ niches, geographic ranges and a robust phylogeny. We found that macrohabitat niche divergence decreased with increasing range overlap, consistent with convergent selection operating at a coarse scale. No significant relationship was detected for microhabitat niches. Additionally, niche divergence was greater for young pairs along all macrohabitat niche axes, but greater for old pairs along one microhabitat axis related to vegetation cover. For a subset of species pairs with partially overlapping ranges, greater microhabitat divergence was detected in sympatry than in allopatry for at least one niche axis for three pairs, consistent with character displacement in sympatry. Thus, coarse‐ and local‐scale niche divergence show dissimilar patterns in relation to range overlap and evolutionary time, perhaps because the relative importance of convergent versus divergent selection depends on spatial scale.

近缘物种的生态位（niche）分化格局与地理分布重叠模式，可为生态位进化动态的研究提供关键洞见。当物种分布范围发生重叠时，共同的选择压力可能会在粗尺度大生境（macrohabitat）维度（如生物气候因子）上维持生态位的相似性；反之，种间竞争相互作用则可能驱动局部尺度小生境（microhabitat）维度（如微地形特征）上的生态位分化程度加剧。我们以北美西部的16对近缘沟酸浆类群（Erythranthe属与Diplacus属，原隶属于广义沟酸浆属Mimulus）为研究对象，结合各物种的生态位数据、地理分布范围以及稳健的系统发育（phylogeny）数据，对上述假说开展了检验。研究结果显示，大生境维度的生态位分化程度随分布重叠范围的扩大而降低，这与粗尺度下的趋同选择作用模式相符；而在小生境维度的生态位上则未检测到显著的相关关系。此外，在所有大生境维度上，分化时间较短的物种对的生态位分化程度更高；但在与植被覆盖相关的某一小生境维度上，分化时间较长的物种对的生态位分化程度反而更高。针对部分分布范围存在重叠的物种对子集，我们在其中3对物种的至少一个生态位维度上发现，同域分布（sympatry）种群的小生境分化程度显著高于异域分布（allopatry）种群，这与同域分布下的性状替换（character displacement）现象相符。综上，粗尺度与局部尺度的生态位分化，在与分布重叠范围及进化时间的关联模式上存在显著差异，这或许是因为趋同选择与趋异选择的相对重要性取决于空间尺度。