Background

The Iberian Peninsula comprises one of the largest boundaries between Mediterranean and Eurosiberian vegetation, known as sub-Mediterranean zone. This ecotone hosts many unique plant species and communities and constitutes the low-latitude (warm) margin of numerous central European species which co-occur with Mediterranean vegetation. Two of the main species found in this region are the Eurosiberian European beech (Fagus sylvatica L.) and the Mediterranean Pyrenean oak (Quercus pyrenaica Willd.). It remains unclear how the different physiological and adaptive strategies of these two species reflect their niche partitioning within a sub-Mediterranean community and to what extent phenotypic variation (intraspecific variability) is driving niche partitioning across Eurosiberian and Mediterranean species.

Methods

We quantified functional niche partitioning, based on the n-dimensional hypervolume to nine traits related to resource acquisition strategies (leaf, stem and root) plus relative growth rate as an additional whole-plant trait, and the environmental niche similarity between Pyrenean oak and European beech. Further, we analyzed the degree of phenotypic variation of both target species and its relationship with relative growth rates (RGR) and environmental conditions. Plant recruitment was measured for both target species as a proxy for the average fitness.

Results

Species’ functional space was highly segregated (13.09% overlap), mainly due to differences in niche breadth (59.7%) rather than niche replacement (25.6%), and beech showed higher trait variability, i.e., had larger functional space. However, both species shared the environmental space, i.e., environmental niches were overlapped. Most plant traits were not related to abiotic variables or RGR, neither did RGR to plant traits.

Conclusions

Both target species share similar environmental space, however, show notably different functional resource-use strategies, promoting a high complementarity that contributes to maintaining a high functionality in sub-Mediterranean ecosystems. Therefore, we propose that conservation efforts be oriented to preserve both species in these habitats to maximize ecosystem functionality and resilience.

中文翻译：

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Fagus sylvatica 和 Quercus pyrenaica：两个几乎没有共同点的邻居

背景

伊比利亚半岛是地中海和欧西伯利亚植被之间最大的边界之一，被称为次地中海地区。该生态交错带拥有许多独特的植物物种和群落，构成了与地中海植被共生的众多中欧物种的低纬度（温暖）边缘。在该地区发现的两个主要物种是欧洲西伯利亚欧洲山毛榉 ( Fagus sylvatica L.) 和地中海比利牛斯橡树 ( Quercus pyrenaica)威尔德）。目前尚不清楚这两个物种的不同生理和适应策略如何反映它们在亚地中海群落中的生态位划分，以及表型变异（种内变异）在多大程度上推动了欧西伯利亚和地中海物种的生态位划分。

方法

我们基于与资源获取策略（叶、茎和根）相关的九个性状的 n 维超体积，加上作为额外的全植物性状的相对生长率，以及比利牛斯橡树和欧洲橡树之间的环境生态位相似性，量化了功能性生态位划分山毛榉。此外，我们分析了两个目标物种的表型变异程度及其与相对生长率 (RGR) 和环境条件的关系。对两种目标物种的植物补充进行了测量，作为平均适合度的代表。

结果

物种的功能空间高度分离（13.09% 重叠），主要是由于生态位宽度的差异（59.7%）而不是生态位替代（25.6%），并且山毛榉表现出更高的性状变异性，即具有更大的功能空间。然而，这两个物种共享环境空间，即环境生态位重叠。大多数植物性状与非生物变量或 RGR 无关，RGR 也与植物性状无关。

结论

两个目标物种共享相似的环境空间，然而，显示出明显不同的功能性资源利用策略，促进高度互补性，有助于维持亚地中海生态系统的高功能性。因此，我们建议保护工作的方向是保护这些栖息地中的这两个物种，以最大限度地提高生态系统的功能和恢复力。