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Three synonyms of the coastal Phucobius sharp species (Coleoptera: Staphylinidae) are proposed based on morphological and molecular characters

https://doi.org/10.1016/j.aspen.2020.12.015Get rights and content

Highlights

  • Three synonyms of the coastal Phucobius Sharp species are proposed.

  • The molecular analyses support the validity of Phucobius pectoralis.

  • Description with diagnostic features of Phucobius pectoralis is presented.

Abstract

A taxonomic reappraisal of four marine littoral Phucobius Sharp species along the western Pacific Ocean including the South China Sea is presented based on morphological and molecular characters (COI and 28S). Specimens of the four species, each having its own distinct geographic distribution, are extremely similar to each other including the structures of the median lobe of the aedeagus, and may be regarded as conspecific. Also, the molecular analyses support the validity of P. pectoralis with three synonymies based on morphological characters. Genetic divergence of COI using uncorrected p-distance among all individuals of Phucobius species ranged from 0.11% to 3.21%. Three distinct geographical clusters (Russia, Korea and Japan, and Vietnam) are found in the NJ and PA trees and we treat all of them as a single species. Three new synonyms are proposed for Phucobius pectoralis (Boheman): P. simulator Sharp syn. nov., P. tricolor Bernhauer syn. nov., and P. densipennis Bernhauer syn. nov. Phucobius pectoralis is redescribed with illustrations of diagnostic characters. Also, the intraspecific variation among the populations of P. pectoralis is briefly discussed.

Introduction

The marine littoral staphylinine genus Phucobius Sharp was established based on Phucobius simulator Sharp (1874) from Japan and contains eight species occurring along the coasts of the Western Pacific and Indian Oceans (Frank and Ahn, 2011). They are known to be predators in decaying seaweeds on beaches.

During an ongoing study toward a world revision of the Cafius Stephens complex, we found that some Phucobius species from the western Pacific Ocean including the South China Sea are superficially similar to each other in external structure and male genital structure. These findings motivated us to study species delimitation of these Phucobius species using an integrative approach (Dayrat, 2005, Song and Ahn, 2014, Will et al., 2005, Yeates et al., 2011), with multiple lines of evidence for consistent species identification.

We studied about 150 Phucobius specimens, collected from the broad geographic regions (see below) and they are compared with the type specimens. In addition, we used molecular characters (genetic divergence data and gene tree monophyly) for species delimitation based on two loci (COI and 28S) in order to test the accuracy of the morphologically assigned four Phucobius species.

In this paper, three new synonyms are proposed for Phucobius pectoralis (Boheman, 1858): P. simulator Sharp, 1874, syn. nov., P. tricolor Bernhauer, 1917, syn. nov., and P. densipennis Bernhauer, 1931, syn. nov. Phucobius pectoralis is redescribed with illustrations of diagnostic characters. Also, the intraspecific variation among the populations of P. pectoralis is briefly discussed.

Section snippets

Materials and methods

For the study of morphological characters, we selected numerous specimens with different geographic distribution for the study of intraspecific variation, and dissected and cleared the whole body for examining microstructures. Habitus and scanning electron microscope (SEM) photographs followed the methods described by Yoo and Ahn, 2020, Lee and Ahn 2016, respectively.

Depository of specimens examined is as follows: The Natural History Museum, London, United Kingdom (BMNH); Bernice Pauahi Bishop

Molecular character analysis

In total, 53 new sequences from the Russian Far East thorough Korea and Japan to Vietnam [26 individuals of 3 Phucobius species and 2 individuals of Cafius vestitus (Sharp)] were generated (856 bp of partial COI gene region and 1004 bp of partial 28S). All new sequences were deposited in GenBank (accession numbers: MT937197–MT937224 and MT937255–MT937279 in Table 1).

Genetic divergence of COI using uncorrected p-distance among three Phucobius species ranged from 0.23% (between P. simulator from

Discussion

Eight Phucobius species have been recorded in the world (Frank and Ahn, 2011) and their diagnostic characters include body color and shape and structure of male genitalia. However, three of these had been suspected in their identifications. Bernhauer (1932) first pointed out that the type of P. pectoralis (Boheman) is similar to P. simulator. Later, Naomi (1984) also noted that three species (Phucobius simulator, P. densipennis Bernhauer, and P. tricolor Bernhauer) resembled each other in

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

We thank A. F. Newton and M. K. Thayer (FMNH), R. Booth (BMNH), J. Hájek and M. Fikáček (NMPC), J. Bergsten (NHRS), S. Blank (SDEI) S. Myers (BPBM), A. Davies (CNC), and Z.-H. Zhou (IZ-CAS) for providing us with many specimens including type series, and H. Hoshina (Fukui University, Japan), N. Kobayashi (Saitama Prefectural University, Japan), H. Kojima (Tokyo University of Agriculture, Japan), and T. Ban (Natural History Museum and Institute, Chiba, Japan) for the productive collecting trips

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