J Plant Ecol ›› 2020, Vol. 13 ›› Issue (3): 273-280.DOI: 10.1093/jpe/rtaa011

• Research Articles • Previous Articles     Next Articles

The assembly of plant-patch networks in Mediterranean alpine grasslands

David S. Pescador1, *, José María Iriondo1, Gianalberto Losapio2,3 and Adrián Escudero1   

  1. 1 Departamento de Biología y Geología, Física y Química Inorgánica, Escuela Superior de Ciencias Experimentales y Tecnología, Universidad Rey Juan Carlos, Móstoles, Spain, 2 Department of Environmental Systems Science, ETH Zurich, Zurich, Switzerland, 3 Department of Biology, Stanford University, Stanford, CA, USA

    *Corresponding author. E-mail: david.sanchez@urjc.es
  • Received:2019-08-27 Revised:2020-02-18 Accepted:2020-03-10 Online:2020-03-14 Published:2020-06-01

Abstract:

Aims

Harsh environmental conditions in alpine ecosystems shape vegetation structure into patches, where many different plant species cluster and grow together. Yet, which factors are important for the structure and dynamics of such plant–patch networks remains poorly understood. We aim to assess which and how environmental and biotic factors predict the assembly of plant–patch networks along a mountain range.

Methods

We examined the distribution of plant species in more than 5500 vegetation patches in 37 Mediterranean alpine grasslands distributed along a 500 m altitudinal gradient (National Park of Sierra Guadarrama, Spain). We established a plant–patch network for each grassland community and analyzed how nestedness and modularity vary with environmental (altitude, insolation and soil conditions) and biotic factors (number of species per plot, mean patch area and total pasture area).

Important Findings

Plant–patch networks showed consistent, non-random patterns characterized by a nested, but not modular, structure, which suggests that positive associations among co-occurring specialists promote their growth within patches as subsets of a pool with more generalist species. Both nestedness and modularity of plant–patch networks varied among grasslands. Specifically, nestedness decreased with increasing species per plot and increased with mean patch area, while it was independent of environmental variables; modularity increased with increasing pasture area and species per plot. The negative relationship between species per plot and nested patterns may be linked to the restricted number of species that can coexist within the same patch at a given size. Moreover, the positive relationship between patch size and nestedness indicates that the growth of rare plant species within vegetation patches occupied by more abundant species is facilitated in bigger rather than smaller patches. Furthermore, these results indicate that the nested assembly of vegetation patches may be independent of abiotic conditions. These findings suggest that large and unfragmented vegetation patches are fundamental for the maintenance of plant diversity in alpine grasslands. Looking at species distribution at fine spatial scales may shed new light on the biotic processes underlying plant network assembly and provide novel ways for conserving biodiversity.

Key words: alpine ecosystems, community assembly, ecological networks, metacommunity, modularity, nestedness, patch dynamics

摘要:

高寒生态系统中恶劣的环境条件导致其植被结构的斑块化,即不同植物物种聚集并共同生长。然而,我们对驱动植物-斑块网络的结构和动态的重要因素仍知之甚少。本研究旨在通过研究沿山脉分布的植物-斑块网络,评估哪些环境和生物因素能够预测植物-斑块网络形成。我们调查了沿海拔500米分布的37个地中海高寒草原(位于西班牙Sierra Guadarrama国家公园)中的5500多个植被斑块的植物物种分布。我们为每个草地群落建立植物-斑块网络,分析环境因素(海拔、日照和土壤条件)和生物因素(每块草地的物种数量、平均斑块面积和总牧场面积)对其嵌套结构和模块化程度的影响。研究发现,植物-斑块网络呈现出一致的、非随机的模式(其特征是嵌套而非模块化的结构),这表明共生的专性植物之间的正向联系促进其在斑块内的生长,这些斑块是具有更多广域性物种种群的子集。草地植物-斑块网络的嵌套结构和模块化程度各不相同。具体而言,嵌套结构随每个样地物种数的增加而减少,而随平均斑块面积的增加而增大,但其与环境变量无关;模块化程度随草地面积和每个样地物种数的增加而增强。每个样地的物种数和嵌套模式之间的负相关关系可能与在面积给定的斑块中可共存的物种数量有限有关。此外,斑块大小与嵌套结构之间的正相关关系表明,在物种丰富的植被斑块内,较大的斑块更有利于稀有植物的生长。此外,研究结果表明,植被斑块的嵌套组配可能与非生物条件无关。这些结果说明,大而完整的植被斑块是维持高寒草原植物多样性的基础。研究在精细空间尺度上的物种分布,可能为植物网络聚集的生物过程提供新思路,并为保护生物多样性提供新方法。

关键词: 高寒生态系统, 群落聚集, 生态网络, 集合群落, 模块化, 嵌套结构, 斑块动态