Abstract
The jewel beetle genus Agrilus (Buprestidae), with approximately 2880 recognized species, is taxonomically challenging due to the great similarity of species. An example of taxonomic ambiguity is the Agrilus viridis species group, particularly the viridis complex that comprises many varieties differing both ecologically and morphologically. The status of these varieties has remained largely unresolved and no consensus exists on their status. We used geometric morphometrics in combination with the DNA barcode marker sequence in order to evaluate the possible distinction among populations of A. viridis feeding on Alnus, Betula and a variety of Salix species in Finland. We found that morphology supports the existence of two species, one feeding on Betula and Alnus, the other feeding on Salix. The findings based on DNA barcodes are more complex, suggesting possible introgression events in the species' his- tory. Our results suggest that the Betula/Alnus and Salix feeding forms of A. viridis represent distinct species that have, while maintain- ing their morphological integrity, probably experienced repeated hybridization events in the past. DNA barcoding provides valuable additional information for taxonomic studies based on careful morphological study and information on their ecology, but drawing taxonomic conclusions from barcode data alone can lead to considerable confusion.
Highlights
Since the establishment of binomial nomenclature and modern taxonomy by Carolus Linnaeus in the 1750s, more than 1.5 million eukaryotic species have been described
Based on the MANOVA analysis, A. sulcicollis, A. paludicola and A. viridis specimens reared from Betula and Salix differed significantly from each other in terms of all four morphological structures studied (Table 3)
The clear morphometric distinction of A. sulcicollis from other species studied was expected as the shape differences are obvious even to the naked eye
Summary
Since the establishment of binomial nomenclature and modern taxonomy by Carolus Linnaeus in the 1750s, more than 1.5 million eukaryotic species have been described. Species delimitation was largely based on subjective visual evaluation and linear measurements of morphological characters. After the initial proposition of Hebert et al (2003) to use a ~ 650 bp fragment of the mitochondrial COI gene as a universal “barcode” for identification and possibly even species delimitation in animals, DNA barcoding has become a massive global enterprise targeting almost all living organisms. Several authors have observed incongruence between species delimitations derived from barcode sequences and those based on other evidence (Monaghan et al, 2005; Astrin et al, 2012) and a notable increase in variation within species with increasing geographical scale (Bergsten et al, 2012)
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