Clarifying the identity of two resembling hoverfly species, Betasyrphus serarius and B. nipponensis (Diptera: Syrphidae: Syrphini), based on morphology and DNA barcoding

Abstract

• Identity of resembling Betasyrphus serarius and B. nipponensis is investigated. • Additional diagnostic characters are proposed for B. serarius and B. nipponensis. • Betasyrphus nipponensis is recorded for the first time in Korea. • Nine available Betasyrphus species are recognized as a robust barcode cluster. • Australian, Pakistan and Malaysian barcodes as distinct species near serarius. The two Palaearctic members of the hoverfly genus Betasyrphus , B. serarius (Wiedemann, 1830) and B. nipponensis (Goot, 1964), closely resemble each other, except for their male genitalic characters. For this reason, these two species have been often mistaken for each other. In Korea, only B. serarius has been recognized as a sole species based on mixed specimens from these two species. In the present study, we attempted to define B. serarius and B. nipponensis more precisely and identify additional diagnostic characteristics to distinguish these species. We examined external morphological characters including the genitalic structures, the wing microtrichia distributions (WMDs), as well as the wing interference patterns (WIPs). In addition, we analyzed the DNA barcode sequences of individuals, covering as many morphological variants as possible, to distinguish the females of these two species. As a result, we found some additional diagnostic male genitalic and WMD characters. Unfortunately, despite our efforts, females of these two species remain undistinguishable. DNA barcoding analysis did not reveal any significant differences between B. serarius and B. nipponensis . Our analysis based on 20 Korean samples and 486 Syrphidae sequences retrieved from BOLD Systems (ver. 4) and GenBank showed that the nine available Betasyrphus species including the type species formed a robust barcode cluster. Betasyrphus serarius and B. nipponensis together with three unidentified species from Pakistan, Australia and Malaysia also formed a strong sub-cluster. In addition, we provide an identification key, diagnoses, and descriptions with color photographs.