Eight in One: Hidden Diversity of the Bagrid Catfish Tachysurus albomarginatus s.l. (Rendhal, 1928) Widespread in Lowlands of South China

Abstract

There is increasing evidence that species diversity is underestimated in the current taxonomy of widespread freshwater fishes. The bagrid species T. albomarginatus s.l. is mainly distributed in the lowlands of South China, as currently identified. A total of 40 localities (including the type locality), which covers most of its known range, were sampled. Molecular phylogenetic analyses based on concatenated mtDNA and nuclear genes recover nine highly supported lineages clustering into eight geographic populations. The integration of molecular evidence, morphological data, and geographic distribution demonstrates the delineation of T. albomarginatus s.l. as eight putative species. Four species, namely, T. albomarginatus, T. lani, T. analis, and T. zhangfei sp. nov. and the T. similis complex are taxonomically recognized herein. Moreover, T. zhangfei sp. nov. comprises two genetically distinct lineages with no morphological and geographical difference. This study also reveals aspects of estimation of divergence time, distribution, and ecological adaption within the T. albomarginatus group. The unraveling of the hidden species diversity of this lowland bagrid fish highlights the need for not only the molecular scrutiny of widely distributed species of South China but also the adjustment of current biodiversity conservation strategies to protect the largely overlooked diversity of fishes from low-elevation rapids.

Complete mitochondrial genomes of two catfishes (Siluriformes, Bagridae) and their phylogenetic implications

“…4), which is consistent with the previous study of Liu et al (2019). The traditional genera Leiocassis, Pseudobagrus, Pelteobagrus, and Tachysurus were not each monophyletic (Hardman 2005;Ku et al 2007;Liu et al 2019), but instead were grouped into Tachysurus as found in recent research (Cheng et al 2021;Shao et al 2021). Our results supported that the species in Leiocassis, Pseudobagrus, Pelteobagrus, and Tachysurus belong to the same genus, which by taxonomic priority should be Tachysurus.…”

“…However, the phylogenetic relationships between different genera of Bagridae are not well understood, such as the monophyly or the validity of Leiocassis , Pseudobagrus , Pelteobagrus , and Tachysurus . Recently, Leiocassis , Pseudobagrus , Pelteobagrus , and Tachysurus were classified into Tachysurus according to morphological analysis ( Cheng et al 2021 ; Shao et al 2021 ).…”

Updated species checklist of fishes from Lake Dongting in Hunan Province, South China: Species diversity and conservation

“… Tachysurus sinensis is a senior subjective synonym of T. fulvidraco (Richardson, 1846) ( Ng and Kottelat 2007 ). Specimens, previously recognised as T. albomarginatus (Rendahl, 1928), from Lake Dongting represent an undescribed species, which was named as T. zhangfei ( Shao et al 2021 ). Possibly, Ru’s (2012) specimens, under the name of T. tenuis (Günther, 1873), from Lake Dongting were misidentified as it is hitherto known merely from the type locality, Chongming Island, Shanghai City ( Kottelat 2013 ; Cheng et al 2021 ).…”