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Biodiversity Data Journal :
Data Paper (Biosciences)
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Corresponding author: Albena Lapeva-Gjonova (gjonova@gmail.com)
Academic editor: Francisco Hita Garcia
Received: 12 Aug 2025 | Accepted: 20 Oct 2025 | Published: 04 Nov 2025
© 2025 Albena Lapeva-Gjonova, Monika Pramatarova, Lech Borowiec, Ilia Gjonov, Rumyana Kostova, Rostislav Bekchiev, Simeon Borissov
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Lapeva-Gjonova A, Pramatarova M, Borowiec L, Gjonov I, Kostova R, Bekchiev R, Borissov S (2025) DNA barcoding of Messor ants of Bulgaria with insights into their taxonomic diversity. Biodiversity Data Journal 13: e168586. https://doi.org/10.3897/BDJ.13.e168586
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Despite ongoing efforts to catalogue European ant species, studies focusing on the genetic diversity of Balkan ants remain limited. An integrative approach combining morphology, genetics, ecology and biogeography is preferable for accurately identifying species and resolving taxonomic uncertainties, particularly amongst challenging insect taxa, such as the ants in the genus Messor (Hymenoptera, Formicidae).
In this study, we analyse ants of the genus Messor using DNA barcode sequences, with a particular focus on the Bulgarian fauna. A total of 85 COI sequences were examined, including 84 from Messor specimens and one from Aphaenogaster, which was used as an outgroup. Of these, 81 sequences were newly generated, while four were retrieved from GenBank. The majority of specimens were collected in Bulgaria (61), with additional samples from Greece (13), Türkiye (4), Albania (1) and North Macedonia (2), providing broader genetic and geographic representation.
Althogether, 11 Messor morphospecies were identified, based on specimens used for molecular analysis. To assess the degree of congruence between morphological and molecular data, six species delimitation analyses were conducted: RESL, GMYC, ASAP, ABGD, bPTP and mPTP. In addition, haplotype network analysis of all sequences identified 35 distinct and coherently clustered haplotypes, providing insights into genetic diversity.
The COI barcode region successfully distinguished Messor wasmanni Krausse, 1910, M. oertzeni Forel, 1910 and M. ibericus Santschi, 1931. In contrast, species pairs, such as M. atanassovii Atanassov, 1982 and M. creticus Salata & Borowiec, 2019, as well as M. ponticus Steiner et al., 2018 and M. hellenius Agosti & Collingwood, 1987, could not be reliably differentiated using COI data. Furthermore, Messor structor (Latreille, 1798) showed high intraspecific genetic diversity. Finally, the structor and instabilis species groups were recovered with moderate to high support in both Maximum Likelihood and Bayesian Inference analyses, confirming that M. oertzeni and M. hellenius belong to the structor group.
Our results provide a reference for future research and underscore the value of integrative taxonomic approaches in ant biodiversity studies.
the Balkans, COI, species delimitation, Formicidae, Myrmicinae
The genus Messor, commonly known as harvester ants, consists of typically granivorous species involved in seed dispersal, nutrient cycling and microclimate modification in surface soil layers (
Comprehensive modern studies on the species composition and distribution of Messor species in Bulgaria remain insufficient. Two recent species revisions have addressed some species within the genus found in the country. One such revision, focusing on the European species of the structor group (
The scarcity of historical descriptions, coupled with high morphological variability within species and occurrences of hybridisation and even xenoparity, makes the genus Messor taxonomically and biologically challenging (
DNA barcoding using mitochondrial cytochrome c oxidase I (COI) gene fragments has proven to be an efficient method for species identification and biodiversity assessment, including ants of Messor genus (
Accordingly, expanding barcoding efforts in underexplored regions, such as the Balkans, is crucial for improving our understanding of species diversity and evolutionary relationships. While a large-scale barcoding project of European ants is underway (Menchetti et al., unpublished), further research specifically targeting the genetic diversity of Balkan Messor ants will provide valuable insights into taxonomy and phylogeny.
Specimens for DNA barcoding were primarily selected, based on morphology and their origin from diverse collection sites across the country. Morphological identifications followed
Molecular analyses: DNA extraction, amplification and sequencing of the standard 658 bp COI barcode region were performed by the Canadian Centre for DNA Barcoding (CCDB) using the primers LepF1 and LepR1 (
To assess the degree of congruence between morphological identification conducted prior to the molecular data, multiple species delimitation approaches were applied to the molecular dataset. Sequence alignment and trimming were performed using MEGA v.12 (
Phylogenetic reconstruction was performed using both Maximum Likelihood (ML) and the Bayesian Inference (BI) analyses. ML analysis was performed in IQ-TREE (
A map of sequence sampling sites was created in QGIS version 3.34.12-Prizren, based on the Cross Blended Hypsometric map layer (https://www.naturalearthdata.com).
Latitude: min. 34.931 max. 43.768; Longitude: min. 19.577 max. 27.794.
| Rank | Scientific Name |
|---|---|
| subfamily | Myrmicinae Lepeletier de Saint-Fargeau, 1835 |
| genus | Aphaenogaster Mayr, 1853 |
| species | Aphaenogaster festae Emery, 1915 |
| genus | Messor Forel, 1890 |
| species | Messor atanassovii Atanassov, 1982 |
| species | Messor creticus Salata & Borowiec, 2019 |
| species | Messor hellenius Agosti & Collingwood, 1987 |
| species | Messor ibericus Santschi, 1931 |
| species | Messor mcarthuri Steiner, Csősz, Markó, Gamisch, Rinnhofer, Folterbauer, Hammerle, Stauffer, Arthofer & Schlick-Steiner, 2018 |
| species | Messor oertzeni Forel, 1910 |
| species | Messor ponticus Steiner, Csősz, Markó, Gamisch, Rinnhofer, Folterbauer, Hammerle, Stauffer, Arthofer & Schlick-Steiner, 2018 |
| species | Messor structor (Latreille, 1798) |
| species | Messor wasmanni Krausse, 1910 |
| species | Messor cf. structor |
| species | Messor sp. 1 |
| species | Messor sp. 2 |
The dataset constitutes a collection of sequences pertaining to Bulgarian species of the genus Messor (Hymenoptera, Formicidae). This dataset comprises all attributes and metadata in accordance with the BOLD rules and are available to the public via a Digital Object Identifier (DOI).
A total of 84 COI sequences, representing 11 morphospecies and 10 to 15 molecular lineages (depending on the species delimitation method used), were analysed, including 80 newly-generated sequences. The lengths of the DNA barcodes ranged from 579 to 658 bp, with the majority (59 sequences) being 658 bp long (Fig.
Results of species delimitation methods, based on DNA barcoding. Each vertical colour bar represents different delimitation schemes obtained with ASAP, RESL, ABGD, bPTP and mPTP methods, with the corresponding number of specimens. The tree is based on ASAP analysis, with nodes colour coded depending on their p-value (black: p < 0.001, red: p < 0.05, yellow: p > 0.1, grey: not applicable).
Messor instabilis species group
The morphological similarity between Messor atanassovii and M. creticus is supported by low genetic distance observed in the delimitation analyses (K2P 1.92%) (Suppl. material
Specimens from four nest samples — one from Central Macedonia in Greece and three from south-western Bulgaria — designated in this study as Messor sp. 1, exhibited morphological traits characteristic of both Messor atanassovii and M. wasmanni, specifically the setosity of the former and the larger size of the latter. However, all species delimitation analyses strongly supported their separation from both species and indicated a closer genetic affinity to M. wasmanni, with K2P distances of 6.28% and 5%, respectively (Suppl. material
The most widespread species of the instabilis group, Messor wasmanni, is represented in this study by a larger number of specimens (13) from the widest geographical range — spanning Bulgaria, Türkiye and Greece (including Crete). It exhibits an intraspecific genetic distance up to 0.81% (mean: 0.18%) (Suppl. material
Messor structor species group
Species delimitation analyses were consistent in supporting the distinctiveness of Messor oertzeni, M. mcarthuri and unidentified species close to M. oertzeni (named Messor sp. 2), as well as one molecular lineage within Messor structor represented by four sequences — three from western Bulgaria and one from North Macedonia. Further evaluation is also needed for a single sequence (BGANT032-23) obtained from a nest sample in the western Balkan Mountains (Vrachanski Balkan). Although this specimen is morphologically similar to M. structor and clearly separated from all recognised taxa in the analyses, the small sample size and absence of reproductive specimens make its taxonomic affinity still unclear.
Messor ibericus was consistently recognised in distance-based methods (ASAP, RESL, ABGD) and the coalescent-based method GMYC, exhibiting an intraspecific genetic distance up to 0.46% (mean 0.2%), but not in the tree-based methods bPTP and mPTP. This discrepancy can be attributed to differences in methodological assumptions and sensitivity to genetic variation (
Previous studies investigating Messor structor across its broad geographic distribution — spanning Austria, Bulgaria, Czechia, France, Hungary, Romania and Slovenia — revealed the existence of multiple mitochondrial lineages within the species (
Only the GMYC method succeeded in separating M. hellenius and M. ponticus (Suppl. material
The examined species fall into two well-defined species groups, instabilis and structor (Fig.
Within the instabilis group, Messor creticus — included in the study to enhance both geographic and phylogenetic representation — was recovered as a sister taxon to M. atanassovii (1.00 PP, 92% BS), with very strong support, a finding that aligns well with morphological observations. Additionally, Messor sp. 1, which exhibits morphological traits intermediate between M. atanassovii and M. wasmanni, clusters closely with M. wasmanni with very strong support (1.00 PP, 96% BS).
In the structor group, Messor hellenius and M. oertzeni are nested within the clade, with M. oertzeni occupying a basal position (0.97 PP, 82% BS) supported by moderate to strong values. Their assignment to the structor group is in agreement with previous studies (
The taxon labelled as "Messor sp. 2" is placed as sister to M. oertzeni (1.00 PP, 95% BS), supported with very strong confidence, consistent with morphological characteristics observed in the nest sample.
Messor structor itself exhibits considerable genetic diversity, reflected in the phylogenetic analyses by multiple well-supported lineages within its clade. Such diversity is expected given the species’ broad distribution across Europe and likely corresponds to population-level differentiation.
The recently described M. mcarthuri (0.93 PP, 84% BS) is recovered as sister to the clade comprising M. hellenius, M. ponticus and M. ibericus, consistent with the topology of the latter two species reported in
Our results provide valuable reference material for future research and highlight the importance of applying integrative taxonomic approaches to studies of ant biodiversity. Furthermore, DNA barcoding can contribute to elucidating the phylogenetic relationships within the genus, offering insights into evolutionary lineages.
However, caution should be exercised when inferring species identification solely on morphology or solely on the COI sequence data for taxonomically challenging species, without taking into account biological and ecological data (e.g. interactions between neighbouring colonies of different morphospecies, differences in nest structure, foraging systems or diurnal activity). Deeper genetic studies are required to explain the observed tendency of some species to form hybridogenetic populations with distinct morphology, which may lead to the description of new species.
This study was supported by the National Science Fund of the Republic of Bulgaria under grant No. KP-06-N-51/6, dated 11.11.2021. We greatly appreciate the valuable comments and suggestions from the reviewers and the Section Editor Francisco Hita Garcia, which have been very helpful in revising and improving the manuscript.
Conceptualisation: AL-G, MP; Methodology: AL-G, MP, SB; Field data collection: AL-G, IG, RK, RB; Species identification: AL-G, LB; Data curation: AL-G, MP, IG; Formal analysis: AL-G, MP, LB, SB; Visualisation: AL-G, MP, RK, SB; Writing: original draft: AL-G, MP; Writing: review and editing: AL-G, MP, LB, IG, RK, RB, SB; Funding acquisition and project administration: AL-G.