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 Using records from 1817 to 2020 from both published and unpublished sources, we describe the diversity and distribution of ant species in the Brazilian Amazon Basin.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.

We obtained all records available in the literature for the Brazilian Amazon (from 1817 to 2020) through the Global Ant Biodiversity Informatics (GABI - Guénard et al. 2017) project. Then, we compiled additional data on ant occurrences in the Brazilian Amazon from online databases and scientific repositories in Brazil. We also included checklists from non-published sources, mainly dissertations, master’s theses, field expeditions, and environmental assessment reports, to compile the most comprehensive information on ant occurrences in the Brazilian Amazon. We obtained these checklists from Brazil’s leading research centers on taxonomy, systematics, and ant biology.

We constructed the database of morphological traits based on five continuous measurements for all ant species recorded in the Brazilian Amazon Basin. These traits were selected because they are classified as priority information in functional aspects of ant ecology. Our database was based on more than 3,000 high-definition images, including lateral, frontal, and dorsal views. For species without high-definition images available, we obtained morphological traits from the taxonomic literature when possible, leading to data extracted from over 40 publications. We employed ImageJ software to record the measurements (http://imagej.nih.gov/ij). Whenever possible, we used the minor workers to standardize the measurements, as is routinely done in studies of the morphological diversity of ants. However, when these were not available, we used major workers to obtain morphological measurements. Further, some ant species have vestigial or absent eyes, making it impossible to measure some morphological traits. We assigned the following rule for these species: when the species did not show eyes, we assigned a value equal to 0 (zero) for “maximum eye size”. The same procedure was adopted for morphological traits related to eyes, such as “interocular distance”. This protocol allows keeping such species in the analyses and maintains their unique morphological characteristics.