Abstract
Oulema melanopus (Linnaeus, 1758) and Oulema duftschmidi (Redtenbacher, 1874) (Coleoptera: Chrysomelidae) are two native West Palaearctic species developing on various cultivated and wild grasses. Along with O. obscura they are considered to be secondary pests of cereal crops. However, local outbreaks have been recorded recently and their status as secondary pests may evolve, especially as the use of broad-spectrum insecticides is now greatly reduced. Oulema melanopus and O. duftschmidi are considered to be sibling species. They are morphologically very close and difficult to distinguish from each other, which makes it difficult to study them. We tested the reliability of the standard barcode fragment (COI) for distinguishing between these species. A total of 92 samples of the two species, covering the majority of their natural range, was sequenced for the barcode fragment and inter- and intraspecific genetic distances were estimated. Our results confirm those of BezdÄk & Baselga (2015, Acta Entomol. Mus. Nat. Prag. 55: 273-304) in that this marker cannot differentiate between all the species of the Oulema melanopus complex, which in the Mediterranean basin contains several described and possibly some undescribed cryptic species. However, this marker may be useful in an agricultural context in areas where only O. melanopus and O. duftschmidi occur (such as in cereal crops in France) where it can be used to reliably and rapidly separate all stages of these two taxa and can therefore help in studying their ecology and dynamics.
Highlights
Cereal leaf beetles belong to Coleoptera of the subfamily Criocerinae within the family Chrysomelidae and their larvae feed and develop on various cultivated or wild grasses (Venturi, 1942; Jolivet, 1997)
With the exception of O. tristis, which has not been reported on crops since three species of Oulema are regularly observed in crops and are likely to damage them in France and Europe: O. obscura, O. melanopus, and O. duftschmidi, which was confused with the previous species until 1989 and is still not included in plant protection manuals
This study showed that the standard COI barcode can be used to distinguish between some Oulema species, including O. melanopus and O. duftschmidi, but cannot distinguish some other species in the melanopus complex, suggesting that further analyses might be needed to validate their taxonomic status
Summary
Cereal leaf beetles belong to Coleoptera of the subfamily Criocerinae within the family Chrysomelidae and their larvae feed and develop on various cultivated or wild grasses (Venturi, 1942; Jolivet, 1997). Two species of Oulema are frequently cited as cereal pests in the Palearctic region: O. melanopus and O. obscura (Balachowsky & Mesnil, 1935; Bonnemaison, 1962; Labeyrie, 1963; Chambon et al, 1983; ACTA, 2016). With the exception of O. tristis, which has not been reported on crops since three species of Oulema are regularly observed in crops and are likely to damage them in France and Europe: O. obscura, O. melanopus, and O. duftschmidi, which was confused with the previous species until 1989 and is still not included in plant protection manuals. O. melanopus and O. duftschmidi are considered to be sibling species, as they are very similar both in their internal (genitalia) and external morphology Their identification requires the dissection of the flagellum located in the penis of the males
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