DOI: 10.5061/dryad.w6m905qsx
title: Global biogeography of ant social parasites: Exploring patterns and mechanisms of an inverse latitudinal diversity gradient

description: Aim: One of the most consistent global biogeographic patterns is the
 latitudinal diversity gradient where species richness peaks within the
 equatorial tropics and decreases towards the poles. Here, we explore the
 global biogeography of socially parasitic ants, which comprises the most
 diverse group of social parasites in the Hymenoptera. We test the
 biogeographic hypothesis that ant social parasites are distributed along
 an inverse latitudinal diversity gradient by peaking in diversity outside
 of the equatorial tropics. Location: Global Taxon: Ants (Hymenoptera:
 Formicidae) Methods: We assembled a comprehensive biogeographic dataset
 for all 371 taxonomically described socially parasitic ant species. We
 used phylogenetic and taxonomic studies to compare species richness with
 the number of species representing independent evolutionary origins of
 social parasitism across a latitudinal gradient. In addition, we compared
 ant social parasite diversity across biogeographic regions using
 rarefaction to account for different sampling efforts. Finally, we tested
 for a correlation between latitude and the proportion of ant social
 parasite species within regional ant faunae. Results: The geographic
 distribution records and the inferred 91 origins of socially parasitic
 life histories show that both species richness and the number of species
 representing independent evolutionary origins of social parasitism peak in
 the northern hemisphere outside of the equatorial tropics. Based on
 rarefaction curves, northern latitude regions harbour the most ant social
 parasite species, but the diversity of independent evolutionary origins is
 not significantly different between northern and southern hemispheres. The
 proportion of ant social parasite species within regional faunae is
 correlated with latitude only in the northern hemisphere. Main
 conclusions: The inverse latitudinal diversity gradient of ant social
 parasites contrasts with the biogeographic pattern observed in
 free-living, non-parasitic ant species and appears to be driven by large
 species radiations as well as by the presence of specialized life
 histories exclusive to the northern hemisphere.
description: We assembled a biogeographic dataset consisting of 6001
 occurrence records for all 371 taxonomically described socially parasitic
 ant species. Geographic occurrence records were assembled from the Global
 Ant Biodiversity database (GABI) via antmaps.org (Janicki et al., 2016;
 Guénard et al., 2017), AntWeb (antweb.org), the Museum of Comparative
 Zoology database (mczbase.mcz.harvard.edu), specimen records in our
 personal collections, personal communication with colleagues, and the
 primary literature. For each social parasite species, we gathered
 occurrence records at each latitudinal and longitudinal degree for every
 country the parasite was reported from. In the case of countries with
 greater than 2.78x10<sup>6</sup> km<sup>2</sup>
 land area, which includes Russia, Canada, China, the United States,
 Brazil, Australia, India, and Argentina, we used occurrence records at
 each latitudinal degree at the scale of first-level administration to
 achieve a more detailed biogeographic resolution in our dataset, which is
 consistent with first-level administration data from GABI. For all
 occurrence data, we recorded the accuracy based on the precision of the
 occurrence record: country, first-level administrative division, locality,
 or GPS.
description: The raw data and metadata used in this study are in an Excel
 Workbook format. To use the raw data one should export only the
 "raw_data" sheet of the Excel Workbook. Note: the raw data
 includes special characters such as (?) and spaces that were filtered out
 during analyses.