DOI: 10.5061/dryad.ht76hdrj8
title: A large-scale assessment of ant diversity across the Brazilian Amazon Basin: integrating geographic, ecological, and morphological drivers of sampling bias

description: 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 published and unpublished sources, we describe the diversity and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.
description: 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.