Research Article |
Corresponding author: Michael Schmitt ( michael.schmitt@uni-greifswald.de ) Academic editor: Caroline Chaboo
© 2017 Michael Schmitt, Gabriele Uhl.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Schmitt M, Uhl G (2017) Oulema septentrionis and O. erichsonii are neither conspecific nor melanic variants of O. melanopus as assessed by micro CT analysis of their lectotypes (Insecta, Coleoptera, Chrysomelidae, Criocerinae). In: Chaboo CS, Schmitt M (Eds) Research on Chrysomelidae 7. ZooKeys 720: 121-130. https://doi.org/10.3897/zookeys.720.19760
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The investigation of the type series of Oulema septentrionis (Weise, 1880) and Oulema erichsonii (Suffrian, 1841) using Micro-computed X-ray tomography (µCT) revealed that neither species is a melanic variant of Oulema melanopus (Linnaeus, 1758) as has been suggested previously. Lectotypes of Oulema septentrionis (Weise, 1880) and Oulema erichsonii (Suffrian, 1841) are designated based on the study of type material. The male genitalia of O. septentrionis and O. erichsonii differ to an extent in the shape of the median lobe and flagellum that their status as separate species is – cautiously – confirmed by the present study.
Taxonomy, lectotype designation, 3D-reconstruction, aedeagus, flagellum, morphology
In the western Palearctic there are Oulema species with a red and with a blue pronotum. The discussion as to how many species we should accept is ongoing. In catalogues (e.g.
On the website of the NERC- Centre for Ecology & Hydrology the hypothesis was published that specimens identified as Oulema septentrionis in Ireland could actually be melanic forms of O. melanopus: “The taxonomic status of O. septentrionis in Ireland is currently under review as there is evidence from dissections of the aedeagal flagellum that specimens from Ireland and Normandy are a melanic form of O. melanopus. The final outcome of this work is awaiting publication” (http://www.coleoptera.org.uk/species/oulema-septentrionis, last accessed 11.05.2017). We examined the type specimens of O. septentrionis and O. erichsonii non-distructively under microCT in order to inspect the median lobe and flagellum of the aedeagus and compare them with the those in the red-necked Oulema species O. melanopus and O. duftschmidi - as these two latter can hardly be separated by external morphological characters. With this investigation we attempt to assess two hypotheses: first, that O. septentrionis is a melanic form of O. melanopus and second that O. septentrionis and O. erichsonii are conspecific. The latter assessment is based on a morphological species concept (“morphospecies”). As long as there is no sound information at hand as to possible cross-breeding (“biospecies”) and ecological relationships (“ecospecies”), we use morphospecies as a proxy for bio- and ecospecies.
From the collection of the Museum für Naturkunde Berlin (
The set of TIFF-files from the microCT scan of the three (former) syntype specimens of Oulema erichsonii is deposited at the MLUH, that of Oulema septentrionis at ZMHU, copies are accessible through MorphDBase (https://www.morphdbase.de/ – OULEERIC_1, OULEERIC_2, OULESEPT_1).
Of the 11 syntype specimens – all of them pinned - of O. septentrionis we scanned three specimens, among them one male that we designate here lectotype (Fig.
The 3D reconstruction revealed that the tip of the apex of the median lobe is pointing straight forward. Seen from the side, the apex of the median lobe has a wedge-like shape with upper and lower outline forming an angle of 40° (Fig.
The scanned syntype of O. erichsonii specimens was a male. This we designated here lectotype (Fig.
Material examined: The specimens do not bear a locality label but only tiny labels in different colours showing an individual number. In the book of records maintained by Christian Wilhelm Ludwig Eduard Suffrian (1805–1876), the localities for each numbered specimen are listed. These are:
Lectotype male, pinned, No. 3180 Elberfeld (Fig.
The 3D reconstruction revealed that the tip of the apex of the median lobe is slightly bent downwards (“ventrally”). Seen from the side, the apex of the median lobe has a wedge-like shape with upper and lower outline forming an angle of 30° (Fig.
We compared the flagella of the above species with those of the species of which they were suspected melanic forms. One male of O. melanopus: GERM. RHEINL. / UNKEL / 29.93.92 SIEDE // BACHTÄLCHEN / KAHLSCHLAG / UNT. VERBASCUM // LEMA MELANOPUS (L.) S.STR. / SIEDE DET. 92. One male of O. duftschmidi: same data as before, but LEMA DUFT- / SCHMIDI REDT. / SIEDE DET. 92.
The flagella differ clearly from each other and from those of O. erichsonii and O. septentrionis. The flagellum of O. melanopus is short, stout, and only slightly curved, with a proportion of length/diameter=4.8. The flagellum of O. duftschmidi is long, slender, nearly semi-circular, without an inflexion point, and ca. 40 times longer than wide. Since the rim of the distal opening is complete, it is certain that the tips are not broken (Fig.
Our study shows that Oulema septentrionis is not a melanic form of Oulema melanopus. The specimens from Ireland and Normandy identified as Oulema septentrionis by the authors of the website www.coleoptera.org.uk must belong to a different species, provided that the shape of the flagella differ between the supposed O. septentrionis and the specimens we investigated.
The outer morphology of Oulema melanopus (Linnaeus, 1758) and of O. duftschmidi (Redtenbacher, 1874) is extremely similar. Until Nicole Berti’s thorough investigation (1989) taxonomists treated the two forms as conspecific. Therefore, we used dissected specimens of both species for comparison with O. septentrionis and O. erichsonii (Fig.
The morphological differences in the aedeagus of the lectotypes of Oulema septentrionis and O. erichsonii concur with the differences in external morphology found in the literature (e.g.,
Our study corroborates that Micro-computed X-ray tomography (µCT) can be used successfully for non-invasive, non-destructive investigation of internal structures of dried beetle specimens, e.g. old type material, as was e.g. demonstrated for Lepidoptera (
We thank the curators of MLUH, Karla Schneider, and of ZMHU, Johannes Frisch, for the loan of the syntype material, Peter Michalik (Greifswald) for taking the photograph stacks, Philip Steinhoff (Greifswald) for his assistance with the 3D-reconstruction, Dieter Siede (Retterath, Germany) for providing dissected specimens of Oulema duftschmidi and O. melanopus, Michael L. Cox (Grays, Essex, UK) for initially stimulating our investigation, Si-Qin Ge (Beijing), Konstantin Nadein (Müncheberg), Geoffrey Morse (San Diego), and Sofia Muños-Tobar (Clemson) for helpful comments on our manuscript, and the Deutsche Forschungsgemeinschaft for funding the acquisition of the Zeiss XradiaXCT-200 (DFG INST 292/119-1 FUGG; DFG INST 292/120-1 FUGG).
Contribution to the 9 th International Symposium on the Chrysomelidae, Orlando, FL, USA, September 28, 2016