Data from: Compensatory dynamics maintain bird phylogenetic diversity in fragmented tropical landscapes

1.Tropical forest loss can drive the extinction of forest-dependent species. Yet, non-forest species can proliferate in deforested landscapes, thus enabling community-level attributes (e.g., total abundance and richness) to be maintained in the remaining forest patches. Such compensatory dynamics have been, however, poorly investigated regarding the phylogenetic dimension of species diversity. Here, we assessed whether compensatory dynamics can stabilize the phylogenetic richness, divergence and structure of bird communities in response to forest loss in two regions in the Brazilian Atlantic forest, each under with different levels of land use intensification.

2.We surveyed birds in 40 forest sites, and assessed the response of five phylogenetic metrics to forest cover measured in local (600-m radius) landscapes. We separately assessed the entire community, forest-dependent and non-forest-dependent species and used information-theoretic criteria to assess the effect of forest cover on each response variable. In particular, we evaluated the plausibility of four models: a null model (no effect of forest cover), a linear model, a power law model (nonlinear effect), and an analysis of covariance model (to assess whether the effect of forest cover differed between regions).

3.Forest cover varied from 7% to 98%, and was positively related to the phylogenetic richness of forest-dependent species, but negatively related to the phylogenetic richness and divergence of non-forest birds, particularly in the more disturbed region. As consequence, the phylogenetic richness and divergence of the entire community were weakly related to forest cover.

4.Forest birds were less phylogenetically clustered in sites surrounded by lower forest cover, but the phylogenetic structure of non-forest birds was independent of forest cover.

5.Synthesis and applications. The phylogenetic impoverishment of forest-dependent birds is offset by the phylogenetic enrichment and divergence of non-forest-dependent birds in severely tropical deforested landscapes. These compensatory dynamics suggest that both bird groups are important for safeguarding bird evolutionary diversity in human-modified landscapes. Although deforested landscapes are reservoirs of bird phylogenetic diversity, suggesting that ecosystem functioning may be maintained in these sites, preventing further deforestation is urgently needed to preserve forest birds and their key ecological roles in the ecosystem.

1. 热带森林丧失可引发依赖森林物种（forest-dependent species）的灭绝。然而，非森林物种（non-forest species）可在已砍伐的景观中增殖，从而使剩余森林斑块中的群落水平属性（如总个体丰度与物种丰富度）得以维持。不过，针对物种多样性的系统发育维度（phylogenetic dimension），这类补偿动态（compensatory dynamics）的相关研究仍较为匮乏。本研究于巴西大西洋沿岸森林的两个区域（两地土地利用强度水平各异），探究了补偿动态是否能够稳定鸟类群落在森林丧失压力下的系统发育丰富度（phylogenetic richness）、分化度（phylogenetic divergence）与结构（phylogenetic structure）。
2. 我们对40个森林样地开展了鸟类调查，并针对局地（600米半径）景观中测得的森林覆盖率，分析了5项系统发育指标（phylogenetic metrics）的响应特征。我们分别针对整个鸟类群落、依赖森林物种与非依赖森林物种进行分析，并采用信息论准则（information-theoretic criteria）评估森林覆盖率对各响应变量的影响。具体而言，我们评估了4类模型的合理性：零模型（null model，无森林覆盖率效应）、线性模型（linear model）、幂律模型（power law model，非线性效应）以及协方差分析模型（analysis of covariance model，用于探究不同区域间森林覆盖率的效应差异）。
3. 本次研究的森林覆盖率介于7%至98%之间，其与依赖森林物种的系统发育丰富度呈正相关，而与非森林鸟类的系统发育丰富度及分化度呈负相关，这一现象在受干扰程度更高的区域尤为显著。因此，整个鸟类群落的系统发育丰富度与分化度与森林覆盖率仅存在微弱关联。
4. 当样地周边森林覆盖率较低时，森林鸟类的系统发育聚集（phylogenetically clustered）程度更低，但非森林鸟类的系统发育结构与森林覆盖率并无关联。
5. 总结与应用。在受严重破坏的热带砍伐景观中，依赖森林物种的系统发育贫乏（phylogenetic impoverishment）现象可被非依赖森林物种的系统发育丰富化（phylogenetic enrichment）与分化过程所抵消。这类补偿动态表明，两类鸟类群落在人为改造的景观（human-modified landscapes）中，对于保护鸟类演化多样性均具有重要意义。尽管砍伐景观可作为鸟类系统发育多样性的储存库，提示此类样地的生态系统功能（ecosystem functioning）或可得以维持，但仍需紧急制止进一步的森林砍伐，以保护森林鸟类及其在生态系统中发挥的关键生态功能。