Entomological collections hold significant scientific potential, especially understudied taxa of historical collections from important biogeographical regions, such as bees in Portugal. The Science Museum of the University of Coimbra (MCUC) holds the largest historical collection of Portuguese bees, primarily because M.A. Diniz, one of the few Portuguese bee experts, was based in this institution during the 20^th century, and several historical collections are stored there from that period and before. Nevertheless, most of the records were unpublished and unrevised. In this work, we revised and databased (via GBIF) 13,374 Portuguese bee records (11,053 unpublished), covering 464 species, of which 11 are new to Portuguese fauna. All 9 type specimens from Portuguese species (1 holotype, 2 syntypes, 5 paratypes and 1 dismissed type) were reported and photographed. We also provide an update of the Anthophila checklist for continental Portugal, with three additional unreported species from other institutions (for a total of 14 new species) and removal or confirmation of exclusion of 19 previously reported species, producing a revised total for the Portuguese continental bee fauna of 736 species.

Biodiversity, digitization, natural history collections, pollinators, wild bees

Entomological collections are crucial to significantly improving our knowledge of the entomofauna (Short et al. 2018). Our understanding of national bee fauna is particularly dependent on these collections due to the challenge of morphological identification without collected specimens (Reverté et al. 2023). Through verified specimens, entomological collections allow the confident exploration of the distribution, phenology, morphological variability and biological material sources, directly feeding most taxonomic and ecologic studies (i.e., Scheper et al. 2014; Oliveira et al. 2016; Rasmussen et al. 2016; Dorchin 2023). Portugal is the 9^th most bee species-rich European country (Reverté et al. 2023), benefiting from its geographic position, with Mediterranean influence in most of the continental territory and an Atlantic influence in the north-western part, as well as insular territories in the Macaronesia territories (Michener 2007; Reverté et al. 2023).

Due to the vital role of bees in the sustainability of terrestrial ecosystems, playing an important role in multiple ecosystem services (most noticeably, pollination) (Klein et al. 2007; Willmer et al. 2017), there has been a significant shift in the research investment across Europe (Reverté et al. 2023). This has uncovered deficiencies in data sources and taxonomic work (amongst others) all over the continent (Ghisbain et al. 2023). The knowledge of the bees of Portugal is moderate as the first comprehensive checklist was only published in 2018 by Baldock and collaborators, gathering data from published literature and additional collections, mostly held internationally by private collectors (Baldock et al. 2018). This work was a milestone that triggered the study of new data sources, historical and contemporary. The European movement involves Portugal in several European initiatives to improve bee taxonomic capacity, monitoring and reference collections, such as projects “SPRING - Strengthening Pollinator Recovery through INdicators and monitorinG” (2021–23) and “TETTRIs - Transforming European Taxonomy through Training, Research and Innovations” through the third-party project “ARCADE - Aligning Reference Collections with tAxonomic Development Efforts for pollinator conservation in Portugal”, (2024–25).

The Portuguese bee collection at the Science Museum of the University of Coimbra (MCUC, Portugal) was actively built and studied intermittently for more than 100 years from the late 19^th century to the early 21^st century, most noticeably by its main curator and collector, the hymenopterist M.A. Diniz, based in Coimbra (Diniz 1959, 1960, 1961a, 1961b, Diniz 1989). In this collection, the most noticeable sources of Portuguese material include a mixed collection, the so called “Old Collection”, from naturalist expeditions made by the staff of the University of Coimbra (based in Coimbra) and São Fiel College (based in Castelo Branco), up to the beginning of the 20^th century; the private collection of N.F. d’Andrade (based in Estoril), and collections from M.A. Diniz and associates - these last two mostly from mid-20^th century. Besides the bee specimens collected in Portugal, there are specimens from many countries (primarily European reference material) that were exchanged by M.A. Diniz with the museums of Madrid (Spain) and Paris (France) during collaborations in the 1960s and the 1980s, respectively (M.A. Diniz, pers. comm.), that significantly improved reference material for the identification of Portuguese bee species.

Mostly in the second half of the 20^th century, several bee taxonomists visited the MCUC entomological collection or exchanged a portion of the material. This resulted in several literature references to the collection or the exchanged material (literature list presented in the results). Baldock et al. 2018 did not revise this collection. They highlighted the need to do so, especially considering that it is the most extensive collection of Portuguese historical material after the loss of the collection from the National Museum of Natural History and Science (Lisbon, Portugal) in a fire in the late 1970s (Mendes et al. 2021). Despite its immense scientific potential, by the time the current work was started in 2022, the MCUC bee collection was not centralized, and no additional documentation (catalogue, material exchanges, visiting schedules) was available beyond the published literature.

With these considerations on the MCUC Bees of Portugal collection in mind, the main objective of the current work was to revise this historical collection and update the current knowledge of Portuguese bee fauna. In particular, we aimed: 1) to provide a taxonomic revision of the bee collection, contributing with novel georeferencing of the specimens and specimen-record links to published literature through the creation of a GBIF dataset; 2) to provide an insight on bee species representation, geographic coverage, phenology and historical periods at a country-level context within this collection; and 3) to provide an updated list of bee species, with new records and photographs of new species additions to the Portuguese bee fauna (including also a few external sources), and existing type material of Portuguese species. This work brings new data on the Portuguese bee fauna and an insight into a neglected but vital collection, promoting the overall potential of future works on Portuguese and Iberian bees.

All available bee specimens collected in Portugal and held in the MCUC collection were studied for this work. These specimens are referred to as the MCUC Bees of Portugal collection. Only material confirmed to have been collected in Portugal is reported in the present work, comprising 13,374 specimens, of which all but 61 were determined to the species level. However, 3,136 additional specimens were worked separately (i.e., were not included in the dataset) because of unknown geographic origin or because they do not belong to Portuguese Anthophila or Anthophila overall. Among the specimens excluded from the dataset, we nonetheless report the type material housed in the MCUC, belonging to Portuguese species.

Several steps were necessary to revise the MCUC Bees of Portugal collection, including specimen indexing, organization and taxonomic revision. For this, first, the original arrangement of the specimens in the original boxes was documented, and an individual code was assigned to each specimen. Additionally, all the information from the existing labels was databased (May 2022 to August 2023). Afterwards, we started indexation, and the specimens received a new catalogue label and were moved to new boxes (August 2023 to October 2023). Then, the taxonomic revision process started and consisted of observing each specimen under the stereomicroscope (Wild Heerbrugg M5, with 10× oculars and 6 to 50× middle selector), comparing each specimen with reference material and using the most appropriate dichotomous keys to species level (October 2023 to May 2024). The taxonomic nomenclature follows Ghisbain et al. 2023. A total of 86 specimens were revised by bee experts, namely Thomas James Wood (Andrena Fabricius, 1775 and Melitta Kirby, 1802), Simone Flaminio (Lasioglossum Curtis, 1833 and Halictus Latreille, 1804), Achik Dorchin (Eucera Scopoli, 1770), Jakub Straka (Nomada Scopoli, 1770), Petr Bogush (Coelioxys Latreille, 1809), Pierre Rasmont and Guillaume Ghisbain (Bombus Latreille, 1802), and Romain Le Divelec (Hylaeus Fabricius, 1793). All the tasks done directly on the MCUC collection material required individual protection (facial mask 3M 4279+ and protective clothing) to reduce exposition to previous chemical treatments.

All the records with information about the collection site were georeferenced and added to a GBIF dataset – “Bees of Portugal Collection, Science Museum of the University of Coimbra” (Gaspar et al. 2025). Georeferencing each specimen was done on Google Earth using the toponyms provided on the specimen label. Toponyms not found in current maps were also searched in Portuguese toponyms databases (http://mapcarta.com and http://nominatim.openstreetmap.org). It also included personal insights on most frequent collection sites from M.A. Diniz (M.A. Diniz, pers. comm.). Variable levels of precision were obtained, ranging mostly from 10 m to 2.5 km. Additionally, in the GBIF database, we also linked some specimens to published literature based on the compilation of records made by Baldock et al. 2018. We linked the data by accepting the same identifier, locality and date (label on the specimen), in compatible time frames, depending on the paper details.

Relevant specimens were photographed, namely, male and female (when available) representative specimens from new species to Portugal (all species except two were photographed) and all the existing type material from Portuguese species. Photographs of each specimen were associated with its labels. The images were acquired with a Leica DMC4500 camera attached to a Leica Z6 APO microscope on a motorized focus stand to produce raw photo stacks processed to single montage images with Leica LAS X (v5.2.2.28326).

Additionally, 10 specimens from six collections harbouring bee specimens collected in Portugal were also considered for producing the updated list of bee species, namely: the FLOWer lab collection, São Bento College, University of Coimbra, Coimbra, Portugal (FLOW); the National Museum of Natural History and Science collection, Lisbon, Portugal (MUHNAC); the University of Mons collection, Department of Zoology, University of Mons, Mons, Belgium (UMONS); the Naturalis Biodiversity Center collection, Leiden, the Netherlands (RMNH); the A. Livory private collection, France; and K. Janssen private collection, Belgium.

The current continental Portugal bee fauna checklist was reviewed using literature revision and supporting information to our knowledge. Besides the new additions, we provided a list of removed species (with respective explanations) and compiled an updated fauna checklist.

The MCUC Bees of Portugal collection is now confirmed as one of the most relevant national historical collections still existing in Portugal, comprising the most extensive recorded collection in number of species and specimens of bees for Portugal from the late 19^th century and mid-20^th century.

The known Portuguese bee fauna is once again increasing in the number of species, following the trend since the publication of the first comprehensive checklist of Baldock et al. 2018 (which reported 355 new species out of 680 species) and of subsequent publications which increased the diversity of bee fauna or made nomenclatural changes (Wood et al. 2020, 2021; Litman et al. 2021; Gaspar et al. 2022, 2023; Praz et al. 2022; Soares et al. 2022; Wood and Le Divelec 2022; Wood and Ortiz-Sánchez 2022; Bogusch 2023; Cross 2023; Reverté et al. 2023; Wood 2023). Most of the newly reported species here come from the MCUC collection, setting another example of the importance and contribution of historical collections to national checklists (i.e., Herrera Mesías and Weigand 2021). The current number of continental species is set at 736, and it is likely to continue growing due to future revisions to national collections, extensive sampling and monitoring efforts. A further 10 species not present on the mainland are found on the Portuguese islands (Wood et al. 2020).

This study also reveals that the presence of type material of bees in Portugal, particularly in the MCUC, is relatively limited, as most material is stored in centralized European institutions with easier access for further studies, and which had well-developed taxonomic infrastructure historically, most clearly seen in France. While most of the type materials currently held at the MCUC are associated with taxonomic work done on the collection, some also originated from material exchanges. The MCUC collection includes material of one of the two bee species currently endemic to continental Portugal - Colletes (Colletes) dinizi Kuhlmann, Ortiz & Ornosa, 2001 (the other being Protosmia (Protosmia) lusitanica Le Goff & Gonçalves, 2018) (Reverté et al. 2023). The most remarkable potential type material is that of Anthophora (Pyganthophora) romandii, collected in 1842, the oldest confirmed record in the MCUC collection, that may have been acquired through an unknown exchange of material.

The MCUC Bees of Portugal collection provides a unique data source, largely contributing to filling some gaps in the representation of species, geographic scope, phenology and historical periods. The collection provided new additions to the bee fauna and holds some of the type materials existing in Portugal. It is a vital reference collection for developing bee taxonomy and reinforces the need to preserve, value and expand historical collections.

We are grateful to the museum director, Paulo Trincão, for facilitating access and promoting better physical conditions of the collection. We are also grateful to Manuel Assunção Diniz for the availability to revisit the MCUC collection and provide personal insight on the collection context and to Raúl Nascimento Ferreira and Maria Pires (granddaughter of Nuno Freire d’Andrade) for additional personal insights. We dedicate this work to all the collectors and specialists who made this collection as relevant as it is.

We also thank Paulo Borges (University of the Azores, Açores, Portugal) for helping in the GBIF dataset preparation; Patrícia Ferreira for the help during the labelling of the MCUC’s specimens; and the additional bee experts who identified some of the material: Achik Dorchin, Guillaume Ghisbain, Jakub Straka, Petr Bogush, Pierre Rasmont, and Romain Le Divelec.

We also thank Martim Batista and Roberto Keller (National Museum of Natural History and Science, Lisbon, Portugal) for providing technical support to acquire the photographs from new species records and type material. The LEICA equipment used for such a task was acquired under the project PORBIOTA - E-Infraestrutura Portuguesa de Informação e Investigação em Biodiversidade, reference 22127-PORBIOTA.

We also thank Javier Ortiz-Sánchez, Piluca Álvarez Fidalgo and Jack Neff for reviewing the submitted work.

This work was funded by the Portuguese Foundation for Science and Technology – FCT – through the fellowship 2023.01736.BD to Hugo Gaspar, and by the 3PP project ARCADE that has received funding from the European Union’s Horizon Europe Research and Innovation programme within the framework of the TETTRIs Project funded under Grant Agreement Nr 101081903.