Mitochondrial divergence suggests unexpected high species diversity in the opsariichthine fishes (Teleostei: Cyprinidae) and the revalidation of Opsariichthys macrolepis.

Xue Wang,Huanzhang Liu,Fei Liu,Dan Yu

doi:10.1002/ece3.4933

Abstract

Opsariichthine (sensu Oceanologi Et Limnologia Sinica, 1982, 13, 293–298) is a cyprinid group consisting of five genera and endemic to East Asia. Previous studies suggested that there may be many possible cryptic species in this group, but this has not been confirmed. In this study, using mitochondrial cyt b sequences on 1,388 samples and 739 haplotypes, we showed very high species diversity within this group. The results showed that phylogenetic relationships of the opsariichthine group were as ([Nipponocypris‐Parazacco‐Candidia] + [Zacco + Opsariichthys]), and there were multiple deep lineages within several species, flagging putative cryptic species. When a 3% genetic distance was used as a threshold for species delimitation, 35 haplogroups were found, nine haplogroups in Candidia‐Parazacco‐Nipponocypris group, six haplogroups in the Zacco group, and 20 haplogroups in the Opsariichthys group. We consider all of them to be putative until determination of distinct species based on the tree topology, geographic distributions, or a combination of both. In addition, two kinds of species delimitation tools, ABGD and PTP, were applied to construct molecular operational taxonomic units (MOTUs). The ABGD method revealed nine MOTUs in Candidia‐Parazacco‐Nipponocypris group, two MOTUs in the Zacco group, and 17 MOTUs in the Opsariichthys group. And the PTP method revealed 10 MOTUs in Candidia‐Parazacco‐Nipponocypris group, 10 MOTUs in the Zacco group, and 29 MOTUs in the Opsariichthys group. Therefore, there should be more species in the opsariichthine group than presently described. Based on the molecular data and morphological characteristics, we proposed Opsariichthys macrolepis as a valid species and described its morphological diagnostic characters.

Highlights

The identification and delimitation of species, one of the main ob‐ jectives of taxonomy, are important in evolutionary biology be‐ cause species remain the fundamental unit and operational entity in most disciplines (Durand & Borsa, 2015)
Such as, (a) three new species were identified, Opsariithchys duchuunguyeni from northern Vietnam, Opsariithchys kaopingensis and Candidia pingtungensis from southern Taiwan, (b) Zacco evolans from southern China and Taiwan, Zacco acutipinnis from southern China, and Zacco pachycephalus from Taiwan were suggested as members of Opsariichthys, (c) Opsariichthys minutus from central and southern China and Opsariichthys hainanenisi from Hainan were considered as valid, (d) Opsariichthys heini and Opsariichthys bea were unrelated to Opsariichthys, but closely related to genus Rasbora and Parazacco, respectively, by morphological description
The result showed that, when a 3% genetic distance was used as a threshold for species delimitation, there were 35 haplogroups in the mito‐ chondrial phylogeny of the opsariichthine fishes, nine haplogroups in Candidia‐Parazacco‐Nipponocypris group, six haplogroups in the Zacco group, and 20 haplogroups in the Opsariichthys group

Summary

| INTRODUCTION

The identification and delimitation of species, one of the main ob‐ jectives of taxonomy, are important in evolutionary biology be‐ cause species remain the fundamental unit and operational entity in most disciplines (Durand & Borsa, 2015). A series of reports on the taxonomy of opsariichthine based on morphological and ge‐ netic analyses was published, and the reports proposed the new classification of these Asian minnows (Chen & Chang, 2005; Chen, Huang, Jang‐Liaw, Shen, & Wu, 2008; Chen, Wu, & Huang, 2009; Huynh & Chen, 2013) Such as, (a) three new species were identified, Opsariithchys duchuunguyeni from northern Vietnam, Opsariithchys kaopingensis and Candidia pingtungensis from southern Taiwan, (b) Zacco evolans from southern China and Taiwan, Zacco acutipinnis from southern China, and Zacco pachycephalus from Taiwan were suggested as members of Opsariichthys, (c) Opsariichthys minutus from central and southern China and Opsariichthys hainanenisi from Hainan were considered as valid, (d) Opsariichthys heini and Opsariichthys bea were unrelated to Opsariichthys, but closely related to genus Rasbora and Parazacco, respectively, by morphological description. We used molecular approach to conduct a comprehensive investigation of

| MATERIAL AND METHODS

| Laboratory methods

Findings

| DISCUSSION