Biotic homogenisation in bird communities leads to large-scale changes in species associations

This is the dataset used for the manuscript Biotic homogenisation in bird
communities leads to large-scale changes in species associations Aim: The
impact of global change on biodiversity is commonly assessed in terms of
changes in species distributions, community richness and community
composition. Whether and how much associations between species, i.e. the
degree of correlation in their spatial co-occurrence, are also changing is
much less documented and mostly limited to local studies of ecological
networks. In this study, we quantify changes in large-scale patterns of
species associations in bird communities in relation to changes in species
composition. Location: France. Time period: 2001-2017. Major taxa studied:
Common breeding birds. Methods: We use network approaches to build three
community-aggregated indices reflecting complementary aspects of species
association networks. We characterise the spatio-temporal dynamics of
these indices using a large-scale and high-resolution dataset of bird
co-abundances of 109 species monitored for 17 years (2001-2017) from 1,969
sites across France. We finally test whether spatial and temporal changes
in species association networks are related to species homogenisation
estimated as the spatio-temporal dynamics of β-diversity and the
proportion of habitat generalists. The consistency of these relationships
is tested across three main habitats, namely woodland, grassland and human
settlements. Results: We document a directional change in
association-based indices in response to modifications in β-diversity and
in the proportion of generalists in space and time. Weaker associations
and sparser networks were related to lower β-diversity and a higher
proportion of generalists, suggesting an overlooked aspect of biotic
homogenisation affecting species associations. We report that this overall
pattern is not constant across habitats, with opposite relationships
between biotic homogenisation and change in species association networks
in urban versus forest communities suggesting distinct homogenisation
processes. Main Conclusions: Although species association contain only
partial signatures of species interactions, our study highlights that
biotic homogenisation translates to finer changes in community structure
by affecting the number, strength and type of species associations.

本数据集用于支撑题为《鸟类群落生物均质化引发物种关联（species associations）的大规模变化》的研究手稿。
研究目的：当前学界评估全球变化对生物多样性的影响时，通常以物种分布、群落丰富度及群落组成的变化作为核心评估指标。然而，物种间的关联——即二者空间共现的相关程度——是否发生变化、变化幅度如何，相关研究仍较为匮乏，且大多局限于生态网络的局部尺度研究。本研究旨在量化鸟类群落中物种关联的大规模格局变化，并探讨其与物种组成变化的关联。
研究区域：法国
时间跨度：2001年至2017年
研究类群：常见繁殖鸟类
研究方法：本研究采用网络分析方法，构建三类反映物种关联网络不同互补维度的群落综合指数（community-aggregated indices）。我们依托覆盖法国全境1969个监测样点、历时17年（2001-2017年）的109种鸟类共现丰度大规模高分辨率数据集，对上述指数的时空动态进行刻画。最终，我们检验物种关联网络的时空变化是否与以β多样性（β-diversity）和广适性物种（habitat generalists）占比的时空动态所表征的生物均质化（biotic homogenisation）相关，并在林地、草地和人类聚居区三类主要生境中验证上述关联的一致性。
研究结果：本研究发现，基于物种关联的指数会随β多样性和广适性物种占比的时空变化发生定向改变。较弱的物种关联与更稀疏的网络结构，与更低的β多样性及更高的广适性物种占比相关，这表明生物均质化存在一个被忽视的维度——其会对物种关联产生影响。本研究同时指出，这一整体格局在不同生境中并不一致：城市群落与森林群落中，生物均质化与物种关联网络变化的关联方向相反，这提示不同生境的均质化过程存在差异。
研究结论：尽管物种关联仅能反映物种互作的部分特征，本研究仍表明，生物均质化会通过改变物种关联的数量、强度与类型，引发群落结构的精细化变化。