Pyrrhosoma and its relatives: a phylogenetic study (Odonata: Zygoptera)

The placement and relationships of the red-and-black zygopteran Pyrrhosoma, currently considered to be part of the Teinobasinae, has long been uncertain. DNA fragments (COI and ITS) reveal that Pyrrhosoma s.s. is restricted to the West Palaearctic, with two morphologically distinct name-bearing clades (nymphula, elisabethae), and with a morphologically indistinct third clade in the Middle Atlas, Morocco, that might be close to the common ancestor of all three. Chromagrion, the closest relative of Pyrrhosoma, is found in North America, not in South Asia. Two isolated Chinese taxa (tinctipenne and latiloba) are morphologically similar to Pyrrhosoma, but their molecular distance is so large that a new genus, Huosoma, is required to accommodate them. Past climate change is suggested as the driver of the biogeography and evolution of this group of zygopterans. The origin of the Moroccan isolate and of elisabethae might predate the glaciations, and be of Pliocene age. The much wider disjunction between the American and South Asian groups and the western group suggests an older, perhaps Miocene age.