Data from: Ecological niche differentiation in peripheral populations: a comparative analysis of eleven Mediterranean plant species

Aim: The “central-peripheral” hypothesis has provided a baseline for many studies of population dynamics and genetic variability at species distribution limits. Although peripheral populations are often assumed to occur in ecologically marginal conditions, little is known about whether they effectively occur in a distinct ecological niche. Location: Western Mediterranean basin. Time Period: 2013-2014. Major taxa studied: A cross-taxa analysis of 11 Mediterranean vascular plants. Methods: We quantified variation in the ecological niche between populations at the northern range limits of species in Mediterranean France and those in the central part of the distribution in continental Spain or Italy. We analyzed both the macro-ecological niche where populations occur in terms of broad habitat and altitudinal range and the micro-ecological niche where individual plants grow in terms of soil and structural biotic and abiotic characteristics. Results: Most species occur in a single broad habitat type common to central and peripheral populations and have a narrower altitudinal range in the latter. In contrast, for the micro-ecological niche we detected marked variation in several niche parameters among central and peripheral populations. Although many differences are species-specific some are common to several species. We found a trend towards narrower micro-niche breadth in peripheral populations. Main conclusions: Our results illustrate the importance of studying the precise ecological characteristics where plants grow and the pertinence of a multi-species approach to correctly assess niche variation. The ecological originality of peripheral populations underlines their evolutionary potential and conservation significance.

研究目的：中心-边缘假说（central-peripheral hypothesis）已为诸多针对物种分布极限处种群动态与遗传变异的研究奠定了理论基础。尽管学界通常认为边缘种群多处于生态边缘生境中，但目前尚未明确其是否真正占据独特的生态位（ecological niche）。
研究区域：西地中海盆地（Western Mediterranean basin）。
研究时段：2013—2014年。
研究类群：针对11种地中海维管植物开展跨类群分析。
研究方法：本研究量化了地中海法国境内物种分布北界的边缘种群，与西班牙本土或意大利本土分布区中部种群之间的生态位差异。分别从两个维度展开分析：其一为大生态位（macro-ecological niche）维度，基于宽泛生境类型与海拔范围界定种群的分布空间；其二为微生态位（micro-ecological niche）维度，以单个植株生长所处的土壤、生物与非生物结构特征为衡量标准。
研究结果：多数物种的中心种群与边缘种群共享同一种宽泛生境类型，且边缘种群的海拔分布范围更窄。与之相对，微生态位维度下，多个生态位参数在中心与边缘种群间呈现显著差异。尽管多数差异具有物种特异性，但也有部分差异在多个物种中普遍存在。本研究还发现，边缘种群的微生态位宽度整体呈现收窄趋势。
主要结论：本研究结果证实了针对植株生长的精确生态特征开展研究的重要性，以及采用多物种方法准确评估生态位变异的必要性。边缘种群的生态独特性，凸显了其进化潜力与保护价值。