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）是伴随生境丧失（habitat loss）出现的生物多样性急剧下降现象，与生境连通性（habitat connectivity）下降密切相关。基质质量（matrix quality）应通过影响连通性，进而调控生境丧失梯度（habitat loss gradients）上阈值的位置，但此类关系鲜有实证性探索。本研究依托巴西大西洋森林（Brazilian Atlantic Forest）中23处独立的1254公顷景观的实地调查数据，评估了热带鸟类生物多样性（tropical avian biodiversity）对两类生境斑块内原生林丧失的响应：一类斑块嵌入以高比例牛牧场为主的均质牧场基质（homogeneous pasture matrix），另一类则嵌入以大量全日照咖啡种植园为主的异质咖啡基质（heterogeneous coffee matrix）。研究考量了分类多样性（taxonomic diversity）、功能多样性（functional diversity）与系统发育多样性（phylogenetic diversity），并检验了基质类型与多样性指标选择是否会影响森林覆盖梯度（forest cover gradient）上生物多样性阈值的位置。研究结果显示，基质类型延缓了分类多样性的急剧丧失：均质牧场基质中的阈值为森林覆盖占比35%，而异质咖啡基质中的阈值则降至19%。系统发育多样性呈现相似响应：均质牧场与异质咖啡基质中的阈值分别为30%和24%，但在校正丰富度相关性（richness correlation）影响后，未检测到其与森林覆盖的关联。尽管两种基质类型中均未检测到功能多样性的阈值，但当生境留存量低于20%时，出现了显著的多样性下降。最终，当原生生境留存比例低于20%时，所有多样性指数均出现急剧下降，表明即便是高质量基质也无法将多样性丧失延缓至这一临界阈值以下。这些结果表明，分类多样性是破碎化景观（fragmented landscapes）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。此外，提升基质质量似乎是一种高效的保护策略（conservation strategy），可在更大范围的生境丧失区间内维持破碎化景观中的较高生物多样性水平。