Dispersal syndromes are poorly associated with climatic niche differences in the Azorean seed plants

Aim: Environmental niche tracking is linked to the species ability to disperse. While well investigated on large spatial scales, dispersal constraints also influence small-scale processes and may explain the difference between the potential and the realized niche of species at small-scales. Here we test whether niche size and niche fill differ systematically according to dispersal syndrome within isolated oceanic islands. We expect species with higher dispersal abilities (anemochorous or endozoochorous) will have a higher niche fill, despite of their environmental niche size.

Location: Azores archipelago

Taxon: Native seed plants

Methods: We combined a georeferenced database of the species distribution within the archipelago (Azorean Biodiversity Portal/GBIF) with an expert-based dispersal syndrome categorization and a high-resolution climatic grid (CIELO model). Using four climatic variables (Annual Mean Temperature, Mean Diurnal Range, Annual Precipitation, Precipitation Seasonality), we calculated a 4-dimensional hypervolume to estimate the niche size of each species. Niche fill was quantified as the suitable climatic space of the island that was occupied by the focal species.

Results: Endozoochorous species display higher niche fill compared to epizoochorous and hydrochorous species, and larger niches than anemochorous and epizoochorous. Differences among the remaining groups are not significant neither for niche fill nor for niche size.

Main Conclusions: Although endozoochorous species track their niche more efficiently at small-scales than other dispersal syndromes, the differences between dispersal syndromes are not consistent. The ability of a species to track its niche at small-scales is not tightly related to its dispersal syndrome. Although intuitively appealing, dispersal syndrome classifications might not be the most appropriate tools for understanding dispersal processes at small-scales.

Methods
Data collection and processing are described in detail in the article. R scripts are available at https://github.com/neckera/niche-Azores.

研究目的：生态位追踪与物种的扩散能力密切相关。尽管学界已在大空间尺度上对该关联开展了充分研究，但扩散限制同样会影响小尺度生态过程，或可解释小尺度下物种潜在生态位与现实生态位（realized niche）之间的差异。本研究旨在检验：在孤立大洋岛屿中，物种的生态位大小与生态位填充度是否会依据传播综合征（dispersal syndrome）呈现系统性差异。我们推测，扩散能力更强的物种（风播（anemochorous）或内动物传播（endozoochorous）物种），即便其环境生态位大小各异，也会拥有更高的生态位填充度。
研究地点：亚速尔群岛（Azores archipelago）
研究类群：本土种子植物
研究方法：本研究将群岛内物种分布的地理参考数据库（亚速尔生物多样性门户网站/全球生物多样性信息设施（GBIF））、基于专家经验的传播综合征分类体系，以及高分辨率气候网格（CIELO模型）进行整合。选取年均温、昼夜温差均值、年降水量、降水季节性4个气候变量，通过计算四维超体积（4-dimensional hypervolume）来估算每个物种的生态位大小；生态位填充度则以目标物种所占据的岛屿适宜气候空间进行量化。
研究结果：内动物传播物种的生态位填充度高于外动物传播（epizoochorous）与水媒传播（hydrochorous）物种，且其生态位规模大于风播与外动物传播物种。其余类群间的生态位填充度与生态位规模差异均不显著。
主要结论：尽管内动物传播物种在小尺度上的生态位追踪效率高于其他传播综合征类群，但不同传播综合征间的差异并不具有一致性。物种在小尺度上的生态位追踪能力与其传播综合征并无紧密关联。尽管传播综合征分类体系在直觉上颇具吸引力，但它或许并非理解小尺度扩散过程的最优工具。
补充方法：数据采集与处理流程详见原文。R脚本可在https://github.com/neckera/niche-Azores获取。