Data from: Defaunation and fragmentation erode small mammal diversity dimensions in tropical forests

Forest fragmentation and defaunation are considered the main drivers of biodiversity loss, yet the synergistic effects of landscape changes and biotic interactions on assemblage structure have been poorly investigated. Here, we use an extensive dataset of 283 assemblages and 105 species of small mammals to understand how defaunation of medium and large mammals and forest fragmentation change the community composition and diversity of rodents and marsupials in tropical forests of South America. We used structured equation models to investigate the relationship between small mammal species, functional and phylogenetic diversity with forest size, forest cover and the occurrence of medium and large mammals. The best-fit model showed that defaunation reduced functional diversity, and that species diversity of small mammals increased with forest patch size. Forest cover did not affect functional and phylogenetic diversity. Our results indicate that occurrence of medium and large sized mammals (probably acting as predators, or competitors of small mammals) and forest patch size help to retain species and functional diversity in small mammal communities. Further, the number of species in a small mammal community was critical to the maintenance of phylogenetic diversity, and may have a pronounced influence on the ecological functions played by small mammals. Identifying how phylogenetic and functional diversity change in function of human pressures allows us to better understand the contribution of extant lineages to ecosystem functioning in tropical forests.森林破碎化与动物区系耗竭被视为生物多样性丧失的核心驱动因素，然而景观变化与生物间相互作用对物种集合群落结构的协同效应却尚未得到充分研究。本研究依托涵盖283个物种集合群落、105种小型哺乳动物的大型数据集，旨在解析南美热带森林内，大中型哺乳动物的动物区系耗竭与森林破碎化如何改变啮齿类与有袋类的群落组成及多样性。研究采用结构方程模型（Structured Equation Model），探究小型哺乳动物的物种多样性、功能多样性与系统发育多样性分别与森林斑块面积、森林覆盖率以及大中型哺乳动物出现情况之间的关联。最优拟合模型结果显示，动物区系耗竭会降低功能多样性，而小型哺乳动物的物种多样性随森林斑块面积增大而提升；森林覆盖率则对功能多样性与系统发育多样性无显著影响。本研究结果表明，大中型哺乳动物的存在（其可能充当小型哺乳动物的捕食者或竞争者）与森林斑块面积，有助于维持小型哺乳动物群落的物种多样性与功能多样性。此外，小型哺乳动物群落的物种丰富度对维持系统发育多样性至关重要，且可能对小型哺乳动物所承担的生态功能产生显著影响。明确系统发育多样性与功能多样性如何随人类活动压力发生变化，有助于我们更好地理解现存演化支系对热带森林生态系统功能的贡献。