Effects of small-scale anthropogenic alterations in Euglossini bees at eastern Amazon forest

ABSTRACT In this study, through a rapid assessment, we evaluated differences in richness, abundance, species composition and beta diversity of Euglossini bees in preserved areas and areas altered by riverine human populations in the Caxiuanã National Forest (northern Amazon). Our hypotheses were: i) the species richness, diversity, abundance and composition of Euglossini bees differ between the preserved and altered areas because many species are intolerant to small anthropic disturbances; and ii) areas altered by riverine populations have higher values of beta diversity (species dissimilarity between sites) than preserved areas, due to local changes in habitat and increased heterogeneity between sites. We sampled two areas (preserved and altered) and, in each area, four transects were sampled with odorous baits. We used a Student’s t test to evaluate differences in richness, abundance, and Shannon-Wiener diversity index. We also evaluated differences in composition and differences in beta diversity between areas. We collected 102 specimens, identified in 18 species and three genera, 63 individuals (61.8% of the total) in preserved areas and 39 individuals (38.2%) in altered areas. Euglossa liopoda (Dressler, 1982) was the most abundant in altered areas and Euglossa imperialis (Cockerell, 1922) the most abundant in preserved areas. Species richness was 2.5 times greater in the transects of preserved areas, and species composition also differed between the sampled areas. In contrast, species abundance did not differ between transects of both areas. Despite our small sample size, this study demonstrated that the richness, composition and beta diversity of Euglossini bees can be potentially affected by local changes in habitat caused by small-scale activities provided by traditional Amazonian groups. Our results indicate the urgency for more comprehensive studies aimed to investigate these relationships.

摘要：本研究通过快速评估，对亚马逊北部卡希乌阿纳国家森林（Caxiuanã National Forest）内原生保护区域与沿河人类活动干扰区域的兰花蜂族（Euglossini）物种丰富度、多度、物种组成及β多样性（beta diversity）的差异进行了分析。本研究提出两项假说：其一，鉴于多数兰花蜂物种对小型人为干扰不耐受，原生保护区域与受干扰区域的物种丰富度、多样性、多度及物种组成将存在显著差异；其二，受沿河人类活动影响的区域因生境局部改变及样点间异质性提升，其β多样性（样点间物种相异性）将高于原生保护区域。

本研究设置两类采样区域（原生保护区域与受干扰区域），每类区域布设4条样带，利用气味诱饵开展采样。我们采用学生t检验（Student’s t test）评估物种丰富度、多度及香农-威纳多样性指数（Shannon-Wiener diversity index）的组间差异，并同时分析两类区域间的物种组成与β多样性差异。

本次研究共采集到102号标本，隶属于3属18个物种；其中原生保护区域内采集到63头个体，占总样本量的61.8%，受干扰区域采集到39头个体，占比38.2%。受干扰区域的优势物种为唇兰蜂（Euglossa liopoda (Dressler, 1982)），原生保护区域的优势物种为帝王兰蜂（Euglossa imperialis (Cockerell, 1922)）。原生保护区域样带的物种丰富度为受干扰区域的2.5倍，且两类区域的物种组成亦存在显著差异；相较之下，两类区域样带的物种多度并无显著差异。

尽管本研究样本量较小，但研究结果表明，亚马逊传统族群开展的小型人类活动所引发的生境局部改变，可能会对兰花蜂族的物种丰富度、组成及β多样性产生潜在影响。本研究结果凸显了开展更全面相关研究的紧迫性，以进一步厘清二者间的关联机制。