Data from: Biodiversity extinction thresholds are modulated by matrix type

Biodiversity extinction thresholds are abrupt declines in biological diversity that occur with habitat loss, associated with a decline in habitat connectivity. Matrix quality should influence the location of thresholds along habitat loss gradients through its effects on connectivity; however these relationships have seldom been explored empirically. Using field data from 23 independent 1,254 ha landscapes in the Brazilian Atlantic Forest, we evaluated how tropical avian biodiversity responds to native forest loss within habitat patches embedded either in homogeneous pasture matrix context (with a high proportion of cattle pastures), and heterogeneous coffee matrix context (with high abundance of sun coffee plantations). We considered taxonomic, functional, and phylogenetic diversity, and tested if matrix type and choice of diversity metric influenced the location of biodiversity thresholds along the forest cover gradient. We found that matrix type postponed the abrupt loss of taxonomic diversity, from a threshold of 35% of forest cover in homogeneous pasture matrix to 19% in heterogeneous coffee matrix. Phylogenetic diversity responded similarly, with thresholds at 30% and 24% in homogeneous-pasture and heterogeneous-coffee matrices, respectively, but no relationship with forest cover was detected when corrected for richness correlation. Despite the absence of a threshold for functional diversity in either matrix types, a strong decline below 20% of habitat amount was detected. Finally, below 20% native habitat loss, all diversity indices demonstrated abrupt declines, indicating that even higher-quality matrices cannot postpone diversity loss below this critical threshold. These results highlight that taxonomic diversity is a more sensitive index of biodiversity loss in fragmented landscapes, which may be used as a benchmark to prevent subsequent functional and phylogenetic losses. Furthermore, increasing matrix quality appears an efficient conservation strategy to maintain higher biodiversity levels in fragmented landscapes over a larger range of habitat loss.

生物多样性灭绝阈值（Biodiversity extinction thresholds）是指伴随生境丧失而发生的生物多样性骤降现象，其与生境连通性的下降密切相关。基质（matrix）质量可通过影响连通性，进而调控生境丧失梯度上临界阈值的位置；然而此类关系鲜少得到实证探索。
本研究依托巴西大西洋森林中23处独立的1254公顷景观样地的野外调查数据，评估了热带鸟类生物多样性对原生林丧失的响应——这些景观样地的生境斑块（habitat patch）分别嵌入两类基质：均质牧场基质（以高比例肉牛牧场为主）与异质咖啡基质（以大量全日照咖啡种植园为主）。研究涵盖了分类多样性（taxonomic diversity）、功能多样性（functional diversity）与系统发育多样性（phylogenetic diversity）三类指标，并检验了基质类型与多样性指标的选择是否会改变森林覆盖梯度上生物多样性阈值的位置。
研究发现，基质类型可延缓分类多样性的骤降发生：在均质牧场基质中，分类多样性阈值对应的森林覆盖占比为35%，而在异质咖啡基质中则降至19%。系统发育多样性呈现相似响应规律，均质牧场与异质咖啡基质对应的阈值分别为30%与24%；但在校正物种丰富度相关性后，未检测到森林覆盖与系统发育多样性的关联。尽管两类基质中均未检测到功能多样性的阈值，但当生境占比低于20%时，功能多样性出现显著下降。最终，当原生生境丧失比例低于20%时，所有多样性指数均出现骤降，表明即便是高质量基质也无法将多样性丧失延缓至该临界阈值以下。
本研究结果表明，分类多样性是破碎化景观中生物多样性丧失的更敏感指标，可作为预防后续功能与系统发育多样性丧失的基准参考。此外，提升基质质量似乎是一种高效的保护策略，能够在更广的生境丧失范围内维持破碎化景观中的较高生物多样性水平。