A large-scale assessment of ant diversity across the Brazilian Amazon Basin: integrating geographic, ecological, and morphological drivers of sampling bias

Tropical ecosystems are often biodiversity hotspots, and invertebrates represent the main underrepresented component of diversity in large-scale analyses. This problem is partly related to the scarcity of data widely available to conduct these studies and the lack of systematic organization of knowledge about invertebrates’ distributions in biodiversity hotspots. Here, we introduce and analyze a comprehensive data compilation of Amazonian ant diversity. Using records from 1817 to 2020 from both published and unpublished sources, we describe the diversity and distribution of ant species in the Brazilian Amazon Basin. Further, using high-definition images and data from taxonomic publications, we build a comprehensive database of morphological traits for the ant species that occur in the region. In total, we recorded 1,067 nominal species in the Brazilian Amazon Basin, with sampling locations strongly biased by access routes, urban centers, research institutions, and major infrastructure projects. Large areas where ant sampling is non-existent represent about 52% of the basin and are concentrated mainly in the North, Southeastern, and Western Brazilian Amazon. We found that distance to roads is the main driver of ant sampling in the Amazon. Contrary to our expectations, morphological traits had lower predictive power in predicting sample bias than purely geographic variables. However, when geographic predictors were controlled, habitat stratum and traits contribute to explain the remaining variance. More species were recorded in better-sampled areas, but species richness estimation models suggest that areas in South Amazonian edge forests are associated with especially high species richness. Our results represent the first trait-based, large-scale study for insects in Amazonian forests and a starting point for macroecological studies focusing on insect diversity in the Amazon Basin.

热带生态系统多为生物多样性热点区域，而无脊椎动物是大尺度多样性分析中受关注不足的核心类群。该问题的部分成因在于，开展此类研究所需的公开可用数据较为匮乏，且生物多样性热点区域内关于无脊椎动物分布的相关知识缺乏系统性整理。本研究针对亚马逊蚂蚁多样性构建并分析了一套综合性数据汇编：研究整合了1817年至2020年间已发表及未发表的各类记录，以此描述巴西亚马逊流域内蚂蚁物种的多样性与分布格局；此外，借助高清影像与分类学文献数据，本研究为该区域分布的蚂蚁物种构建了涵盖形态性状的完整数据库。本次研究共记录巴西亚马逊流域内1067种已定名蚂蚁物种，且采样点位存在显著偏向性，主要集中于通行路线、城市中心、科研机构及重大基础设施项目周边。完全未开展蚂蚁采样的区域约占该流域总面积的52%，主要集中在巴西亚马逊北部、东南部与西部区域。研究发现，距道路的距离是影响亚马逊地区蚂蚁采样活动的核心驱动因素。与研究预期相悖的是，相较于纯地理变量，形态性状对采样偏差的预测能力较弱；但在控制地理预测变量后，栖息地层与形态性状可对剩余方差做出部分解释。采样程度更高的区域记录到的蚂蚁物种数量更多，但物种丰富度估算模型结果显示，亚马逊南部边缘森林区域的物种丰富度尤其偏高。本研究成果是首个针对亚马逊森林昆虫的基于性状的大尺度研究，同时也是聚焦亚马逊流域昆虫多样性的宏生态学研究的重要起点。