Structure of the leaf litter frog community in an area of Atlantic Forest in southeastern Brazil

ABSTRACT Different spatial and temporal factors can influence the species richness and abundance of leaf anurans that are fundamental for the ecosystem functioning, as they act as predators and integrate the trophic chain as prey of other animals. There are relatively few studies that aimed to understand the spatio-temporal variation and the influence of environmental factors on leaf litter communities. We studied parameters of the anuran community living in the forest leaf litter in the Duas Bocas Biological Reserve (DBBR), Espírito Santo, Brazil. We sought to understand the extent to which richness, abundance, biomass and density varied between two locations with different stages of preservation (primary and secondary forest). In addition, we tested the effect of temperature and local humidity on abundance. We conducted the samplings monthly from October 2017 to September 2018, establishing 98 4 x 4 m plots (16 m2 each) demarcated on the DBBR forest leaf litter. We measured temperature (°C) and relative air humidity (%), and each plot was carefully surveyed by four observers. We tested for differences in anuran density between the two sampled locations and estimated the effects of environmental variables in the community. We recorded 102 individuals of anurans from 11 species belonging to eight families. The DBBR anuran community parameters significantly differed between the two studied locations, with the highest values of anuran richness and abundance occurring in the area covered by primary forest, probably due to differences in the preservation of each area. However, temperature and humidity did not affect the abundance of anurans in the sampled areas. Our results provide the first information about spatial variation and influence of environmental factors, directed to the community of leaf litter anurans in DBBR, and represents the second study on this group of anurans in the state of Espírito Santo.

摘要：不同时空因子可影响叶栖无尾类（leaf anurans）的物种丰富度与种群丰度；这类动物兼具捕食者与猎物双重身份，可整合食物链结构，对生态系统功能至关重要。目前针对森林凋落物群落的时空变异及其环境影响因子的研究相对匮乏。

我们于巴西圣埃斯皮里图州杜阿斯博卡斯生物保护区（Duas Bocas Biological Reserve，DBBR）开展了森林凋落物栖息无尾类群落参数的相关研究。本研究旨在明确两个不同保护演替阶段（原始林与次生林）样地间，无尾类的丰富度、丰度、生物量及密度的差异程度；同时检验了环境温度与局部湿度对种群丰度的影响。

采样工作于2017年10月至2018年9月每月开展一次，在DBBR的森林凋落物生境中共划定98个4×4米（单块面积16㎡）的样方。我们测定了样地的环境温度（℃）与空气相对湿度（%），并由4名调查人员对每个样方进行细致普查。

本研究检验了两个采样样地间无尾类密度的差异，并评估了环境变量对群落结构的影响。本次调查共记录到隶属于8个科、11个物种的102只无尾类个体。结果显示，DBBR的无尾类群落参数在两个样地间存在显著差异，原始林区域的无尾类丰富度与丰度均更高，这可能与两处样地的保护状态差异密切相关。不过，温度与湿度并未对采样区域内的无尾类丰度产生显著影响。

本研究首次提供了DBBR叶栖无尾类群落的空间变异及环境因子影响的相关数据，同时也是圣埃斯皮里图州针对该类无尾类的第二项专项研究。