On the diversity of Neotropical Hymenoptera

Hymenoptera is globally one of the most diverse groups of insects. There are no recent estimates nor sound data on the size of the fauna of this order in the Neotropical Region. Based on printed or digital catalogs, lists, as well as reviews of monographs, and other sources, the Neotropics comprises 26 su-perfamilies, 92 families, 3162 genera, and over 33 640 species of Hymenoptera. Hymenoptera diversity in the Neotropics is greater than in the Nearctic, Palearctic and Australian regions. The Neotropics is probably the richest region in the World in families, genera, and species of the order, with the majority of taxa endemic to this region.

Wasps, bees and ants, order Hymenoptera, are one of the most diverse and important groups of insects in terrestrial ecosystems. The vast majority of species are parasitoid wasps that exert a natural control over populations of other insects, many of them phytophagous. Bees are important pollinators of many plants. Ants are key players in the structure and dynamics of forests. Their wealth of behavioral patterns (solitary, communal, subsocial, social, and parasitic) is an obligatory source for the study of the evolution of sociability. In addition, some species are agricultural pests, or may cause veterinary or medical problems. In contrast to the importance of the order, knowledge of its diversity at the global and regional level is key. Knowing how many species there are, what names they have, and where they are found is vital for studies in systematics, phylogeny, biogeography, ecology and conservation.
As Hymenoptera is one of the four hyper-diverse insect orders, it is not easy to establish precise numbers of the described species in the group. It is even more challenging to have estimates of undescribed species, a task that has become increasingly difficult in face of the decline of biological collections and curators, mainly taxonomists. In Hymenoptera, 111 families, 8423 genera (Aguiar et al. 2013) and 154 000 living species (Huber 2017) have been described, making it the most diverse order after Coleoptera and Lepidoptera, and close to Diptera. Estimates of total species richness are also variable, generally exceeding one million (Ulrich 1999). One recent study suggests a hidden high diversity of parasitoid wasps (Forbes et al. 2018). If true, this planet is flooded not with beetles, but with wasps.
For Coleoptera there is at least one checklist to the Neotropical Region published by Blackwelder between 1944 and1957 and reprinted by the Smithsonian. In Lepidoptera there are innumerable catalogs with an emphasis on butterflies, being J.B. Heppner the editor of a series that covers most superfamilies and families of the order, with the exception of Geometroidea and Noctuoidea which are covered in other sources (e.g. Scobble 1999 for Geometridae). Nelson Papavero during several decades published the serial catalog of Diptera of the Neotropical region (Klassa and dos Santos 2014).
For Neotropical Hymenoptera there are printed or digital catalogs for specific groups such as sawflies (Taeger et al. 2010), ants (Kempf 1972, Bolton 1995, c2022, Bolton et al. 2007, bees (Moure et al. 2007) and non-bee apoids (Amarante 2002(Amarante , 2005, or online resources, such as for Chalcidoidea (Noyes c2020). But there are no printed or digital resources that list the entire fauna of Hymenoptera described for the Neotropics. How many species of Hymenoptera have been described for the Neotropics? Fernández (2000) offers a rough assessment, indicating 20 super families, 77 families, 2527 genera and around 24 000 species, estimating the number of species for the region at 60 000. These numbers are now out of date due to the many taxonomic developments since then, but also due to better access to publications and databases with information on poorly known groups at that time (such as Ceraphronoidea) or very rich groups with old and inaccessible literature (such as Chalcidoidea).
A new assessment of the size of Neotropical Hymenoptera fauna has improved from access to more sources of information, either in old checklists now available online, new lists, or the extraction of information from online catalogs, such as those dealing with bees and chalcidoids. Here is offered the list of Hymenoptera superfamilies and families known in the Neotropical region with the number of genera and described species with the sources before each family (Table 1). In most cases, the numbers are taken from the original references. In most taxa, the data from each list was verified for country or, as in the case of Johnson (1992), for region. Here we report the number of families, genera and species for each superfamily (Table 1). From the Noyes Chalcidoidea database, the names for each family, genus and species were consulted under the "Neotropical" restriction, and lists were compiled for each family. This procedure was followed for the online catalog of bees of the Neotropical Region, which was last updated in 2013.
According to table 1 there are 26 superfamilies, 92 families, 3162 genera and 33645 species for the Neotropics (see also supplementary Figs. S1-4). These figures imply a notable increase regarding the numbers presented in Fernández (2000). Part of these differences are explained by new studies in phylogeny that have created new suprageneric categories (Pilgrim et al. 2008, Sann et al. 2018, Chen et al. 2021, Zhang et al. 2022).
The number of described genera and species can be considered reliable for groups in which there is recent, revised and constantly updated information, such as the Chalcidoidea database of Noyes or Bolton's catalog of ants (Bolton c2022).  De Santis 1979, 1983, Noyes 2020 Agaonidae 7  However, in key groups such as bees or microhymenoptera (excluding Chalcidoidea) there is no updated information.
In some cases (such as Diaprioidea and Platygastroidea), It is striking that the Neotropics are home to a rich fauna, with a high number of endemism, but at the same time it is facing serious problems that threaten the future of biological diversity (Mundy 2020

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