Usage of Different Molecular Markers in Delimitation of Cryptic Taxa in Merodon avidus Species Complex (Diptera: Syrphidae)

Three populations of Merodon avidus species complex from two geographical areas in the Danube River region (Djerdap and Fruska Gora) were used in this study with the aim to delimitate cryptic taxa within the complex. According to the diagnostic morphological characters, as well as to the season of their adult activity, samples were presumably identified as M. avidus Rossi or M. moenium Wiedemann. In order to reveal genetic differentiation between these taxa and to evaluate their current taxonomic status, two differ- ent types of molecular markers were used, allozymes and mtDNA. The analysis of 5 enzyme loci revealed the clear presence of two separate taxa, with presence of unique alleles in AAT (EC number 2.6.1.1) and ME (EC number 1.1.1.40) loci in M. avidus and M. moenium populations. The UPGMA dendogram based on Nei's genetic distance showed the presence of M. avidus and M. moenium cluster. On the other hand, the parsimony tree based on cytochrome c oxidase subunit I (COI) mtDNA sequences failed to discrimi- nate these two taxa. The haplotype analysis revealed that one haplotype was shared between M. avidus and M. moenium. This led us to the conclusion that the allozyme data with species-specific alleles are more informative for resolving taxonomic questions in M. avidus species complex compared to the mtDNA marker. Moreover, the allozymes confirmed different seasonal preferences of the two taxa when they exist at the same locality. Since the studies of taxonomically diverse and challenging taxa are important for identification of areas of genetic endemism, we highly recommend integrative usage of allozyme and morphological markers.