Systematics and biogeography of the Holarctic dragonfly genus Somatochlora (Anisoptera: Corduliidae)

The striped emeralds (Somatochlora Selys) are a Holarctic group of medium-sized metallic green dragonflies that mainly inhabit bogs and seepages, alpine streams, lakes, channels and lowland brooks. With 42 species they are the most diverse genus within Corduliidae (Odonata: Anisoptera). Systematic, taxonomic and biogeographic resolution within Somatochlora remains unclear, with numerous hypotheses of relatedness based on wing veins, male claspers (epiproct and paraprocts) and nymphs. Furthermore, Somatochlora borisi was recently described as a new genus (Corduliochlora) based on 17 morphological characters, but its position with respect to Somatochlora is unclear. We present a phylogenetic reconstruction of Somatochlora using Anchored Hybrid Enrichment (AHE) sequences of 40/42 Somatochlora species (including Corduliochlora borisi). Our data recover the monophyly of Somatochlora, with C. borisi recovered as sister to the remaining Somatochlora. We also recover three highly supported clades and one of mixed support; this lack of resolution is most likely due to incomplete lineage sorting, third-codon position saturation based on iterative analyses run on variations of our dataset and hybridization. Furthermore, we constructed a dataset for all species based on 20 morphological characters from the literature which were used to evaluate phylogenetic groups recovered with molecular data; the data support the validity of Corduliochlora as a genus distinct from Somatochlora. Finally, divergence time estimation and biogeographic analysis indicate Somatochlora originated in the Western North Hemisphere during the Miocene, with three dispersal events to the Eastern North Hemisphere (11, 7 and 5 Ma, respectively) across the Beringian Land Bridge.