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Eumerus is one of the most diverse genera of hoverfly worldwide. Species delimitation within genus is considered to be difficult due to: (a) lack of an efficient key; (b) non-defined taxonomical status of a large number of species; and (c) blurred nomenclature. Here, we present the first molecular study to delimit species of the genus by using a fragment of the mitochondrial cytochrome-c oxidase subunit I gene (COI) gene. We assessed 75 specimens assigned to 28 taxa originating from two biogeographic zones: 22 from the western Palaearctic and six from the Afrotropical region. Two datasets were generated based on different sequence lengths to explore the significance of availability of more polymorphic sites for species delimitation; dataset A with a total length of 647 bp and dataset B with 746 bp. Various tree inference approaches and Poisson tree processes models were applied to evaluate the putative 'taxonomical' vs. 'molecular' taxa clusters. All analyses resulted in high taxonomic resolution and clear species delimitation for both the dataset lengths. Furthermore, we revealed a high number of mitochondrial haplotypes and high intraspecific variability. We report two major monophyletic clades, and seven 'molecular' groups of taxa formed, which are congruent with morphology-based taxonomy. Our results support the use of the mitochondrial COI gene in species diagnosis of Eumerus.

Understanding tumor progression and metastatic potential are important in cancer biology. Metastasis is the migration and colonization of clones in secondary tissues. Here, we posit that clone migration events between tumors resemble the dispersal of individuals between distinct geographic regions. This similarity makes Bayesian biogeographic analysis suitable for inferring cancer cell migration paths. We evaluated the accuracy of a Bayesian biogeography method (BBM) in inferring metastatic patterns and compared it with the accuracy of a parsimony-based approach (metastatic and clonal history integrative analysis, MACHINA) that has been specifically developed to infer clone migration patterns among tumors. We used computer-simulated datasets in which simple to complex migration patterns were modeled. BBM and MACHINA were effective in reliably reconstructing simple migration patterns from primary tumors to metastases. However, both of them exhibited a limited ability to accurately infer complex migration paths that involve the migration of clones from one metastatic tumor to another and from metastasis to the primary tumor. Therefore, advanced computational methods are still needed for the biologically realistic tracing of migration paths and to assess the relative preponderance of different types of seeding and reseeding events during cancer progression in patients.

This study provides an overview of the Eumerus minotaurus taxon group, diagnosing a new species, E. anatolicus Grković, Vujić and Radenković sp. n. (Muğla, Turkey), and unraveling three cryptic species within E. minotaurus: E. karyates Chroni, Grković and Vujić sp. n. (Peloponnese, Greece), E. minotaurus Claussen and Lucas, 1988 (Crete and Karpathos, Greece) and E. phaeacus Chroni, Grković and Vujić sp. n. (Corfu and Mt Olympus, Greece; Mt Rumija, Montenegro). We applied an integrative taxonomic approach based on molecular, morphological and wing geometric morphometric data to corroborate and delimit cryptic species within the complex. In addition, we discuss the latent biogeographic patterns and speciation processes leading to configuration of the E. minotaurus group based on palaeogeographic evolution of the Aegean. Mitochondrial phylogeographic analysis suggested that speciation within the E. minotaurus group is attributable to formation of the mid-Aegean Trench and Messinian Salinity Crisis, and was integrated at the Pleistocene. We show that more accurate estimates of divergence times may be based on geological events rather than the standard arthropod mtDNA substitution rate.