Tropical forest loss and fragmentation and the associated loss in species diversity are increasing in both magnitude and scope. Much attention has been paid to how attributes of forest fragments, such as area and forest structure, impact the diversity and functional composition of vertebrate communities, while more recent work has begun to consider the importance of landscape-level variables, such as surrounding tree cover. Yet, the relative impacts of these factors on species diversity and functional composition remain unclear, particularly among under-studied taxonomic groups. We quantified how species richness, community composition, and functional traits of terrestrial birds and mammals are associated with variation in fragment area, elevation, habitat structure and surrounding tree cover. Our goal was to determine the degree to which these diverse explanatory variables contribute to species diversity. We used motion-activated camera traps to sample terrestrial birds and mammals in 22 forest fragments in northwestern Ecuador. We used a hierarchical multi-species occupancy model accounting for imperfect species detection to estimate species richness and species composition differences among fragments, weighted multiple regression and distance matrix regression to assess covariates of richness and composition, and an RLQ ordination to assess co-variation of environmental conditions and species traits. Terrestrial mammals and birds exhibited similar relationships to key environmental variables, but also showed guild-specific differences. Elevation was significantly associated with differences in species richness and community composition for both groups. Forest cover in the surrounding matrix was associated with higher species richness and changes in community composition in mammals, but not terrestrial birds. Canopy openness showed a positive association with mammalian species richness but no relationship with bird species richness. There was no association between density of large trees and richness for either group. We found no significant associations between environmental variation and functional composition among forest fragments. This work highlights the general importance of elevation and forest cover in shaping patterns of species diversity and composition in forest fragments and suggests heightened sensitivity to matrix conditions in mammals relative to terrestrial birds.

中文翻译：

---

破碎的热带景观中陆生鸟类和哺乳动物的丰富度、群落组成和功能特征的环境相关性

热带森林的丧失和破碎化以及相关的物种多样性丧失在规模和范围上都在增加。人们非常关注森林碎片的属性，如面积和森林结构，如何影响脊椎动物群落的多样性和功能组成，而最近的工作已经开始考虑景观层面变量的重要性，如周围的树木覆盖. 然而，这些因素对物种多样性和功能组成的相对影响仍不清楚，特别是在研究不足的分类群中。我们量化了陆生鸟类和哺乳动物的物种丰富度、群落组成和功能特征如何与碎片面积、海拔、栖息地结构和周围树木覆盖的变化相关联。我们的目标是确定这些不同的解释变量对物种多样性的贡献程度。我们使用运动激活相机陷阱对厄瓜多尔西北部 22 个森林碎片中的陆生鸟类和哺乳动物进行采样。我们使用分层多物种占用模型来考虑不完善的物种检​​测来估计片段之间的物种丰富度和物种组成差异，使用加权多元回归和距离矩阵回归来评估丰富度和组成的协变量，并使用 RLQ 排序来评估环境条件和物种特征。陆生哺乳动物和鸟类与关键环境变量表现出相似的关系，但也表现出特定于公会的差异。海拔与两组的物种丰富度和群落组成的差异显着相关。周围基质中的森林覆盖与哺乳动物更高的物种丰富度和群落组成的变化有关，但与陆生鸟类无关。冠层开放度与哺乳动物物种丰富度呈正相关，但与鸟类物种丰富度无关。任何一组的大树密度与丰富度之间都没有关联。我们发现环境变化与森林碎片之间的功能组成之间没有显着关联。