Tropical mammal functional diversity increases with productivity but decreases with anthropogenic disturbance

A variety of factors can affect the biodiversity of tropical mammal communities, but their relative importance and directionality remain uncertain. Previous global investigations of mammal functional diversity have relied on range maps instead of observational data to determine community composition. We test the effects of species pools, habitat heterogeneity, primary productivity and human disturbance on the functional diversity (dispersion and richness) of mammal communities using the largest standardized tropical forest camera trap monitoring system, the Tropical Ecology Assessment and Monitoring (TEAM) Network. We use occupancy values derived from the camera trap data to calculate occupancy-weighted functional diversity and use Bayesian generalized linear regression to determine the effects of multiple predictors. Mammal community functional dispersion increased with primary productivity, while functional richness decreased with human-induced local extinctions and was significantly lower in Madagascar than other tropical regions. The significant positive relationship between functional dispersion and productivity was evident only when functional dispersion was weighted by species' occupancies. Thus, observational data from standardized monitoring can reveal the drivers of mammal communities in ways that are not readily apparent from range map-based studies. The positive association between occupancy-weighted functional dispersion of tropical forest mammal communities and primary productivity suggests that unique functional traits may be more beneficial in more productive ecosystems and may allow species to persist at higher abundances.

多种因素均可影响热带哺乳动物群落的生物多样性，但其相对重要性与作用方向仍不明确。此前针对哺乳动物功能多样性的全球研究，均通过分布范围地图而非实地观测数据来确定群落组成。本研究依托当前规模最大的标准化热带森林红外相机监测系统——热带生态评估与监测（Tropical Ecology Assessment and Monitoring, TEAM）网络，检验物种库、生境异质性、初级生产力与人类干扰对哺乳动物群落功能多样性（功能离散度（functional dispersion）与功能丰富度（functional richness））的影响。我们利用红外相机数据得到的物种占用（occupancy）值，计算基于占用加权的功能多样性，并采用贝叶斯广义线性回归分析多预测变量的影响效应。研究结果显示，哺乳动物群落的功能离散度随初级生产力提升而升高，而功能丰富度则因人类活动诱导的本地物种灭绝而降低，且马达加斯加的功能丰富度显著低于其他热带区域。仅当以物种占用值对功能离散度进行加权时，功能离散度与生产力之间的显著正相关关系才会显现。由此可见，标准化监测的实地观测数据，能够揭示基于分布范围地图的研究难以察觉的哺乳动物群落驱动机制。热带森林哺乳动物群落基于占用加权的功能离散度与初级生产力呈正相关，这表明独特的功能性状在生产力更高的生态系统中可能更具优势，并可帮助物种维持更高的种群丰度。