Systematic Taxonomy Of The Genus Oreonectes And Troglonectes

The genus Oreonectes Günther 1868 and the genus Troglonectes Zhang,Zhao et Tang 2016 belong to the order Cypriniformes,Nemacheilidae,and are small benthic fishes,mainly distributed in Guangxi,Guangdong,Hong Kong,Guizhou and Previous studies on these two genera mainly used morphological methods and rarely involved molecular biological methods.These two genera,except for Oreonectes platycephalus,which belongs to the surface species,live in dark karst caves and have evolved convergently to such extreme environments,which adds many difficulties to the effective classification of the genus Oreonectes and the genus Troglonectes.In this paper,the validity and systematic taxonomic status of the existing species are explored through morphological and molecular phylogenetic studies,and the results are as follows.1.In this study,334 samples of Nemacheilidae were collected,representing 45 species.Morphology was based on Mann–Whitney U test and Principal component analysis to prove the validity of Troglonectes.Meanwhile,species of the genus Troglonectes and Oreonectes were collated.(1)Oreonectes donglanensis,Oreonectes duanensis and Oreonectes anophthalmus conform to the characteristics of the genus Troglonectes and are synonyms,renamed Troglonectes anophthalmus comb.nov.Zhang,Zhao ? Zhang,2006;(2)the morphological characters of the Oreonectes anophthalmus and Oreonectes acridorsalis are different from the genus Oreonectes or Oreonectes.Therefore,the two species may not belong to either of these two genera.(3)Yunnannilus retrodorsalis of the genus Yunnannilus should belong to the genus Troglonectes,renamed as Troglonectes retrodorsalis comb.nov.Lan,Yang ? Chen,1995;(4)Triplophysa lihuensis are similar to the genus Troglonectes in terms of genus-level characteristics,and the belong to the genus Troglonectes,renamed Triplophysa lihuensis comb.nov.Wu,Yang ? Lan,2012;(5)Troglonectes jiarongensis Lin,Chao ? Kun,2012,Triplophysa dongganensis and Troglonectes elongatus Tang,Zhao ? Zhang,2012 morphologically similar,the long-whiskered blind cave loach and the Triplophysa dongganensis are synonyms of the long-bodied cave loach,respectively,and are proposed to be renamed as Troglonectes longibarbatus comb.nov.Tang,Zhao ? Zhang,2012.2.Based on mitochondrial genome data,the molecular phylogenetic relationships of the fishes of the genus Oreonectes and the genus Troglonectes were studied by molecular systematics,and phylogenetic trees were constructed by maximum likelihood method(ML)and Bayesian method(BI).The results are basically consistent with morphological classification system:(1)Species of Ridge Loach are divided into two branches(Oreonectes(I)and Oreonectes(II)sensu stricto.Oreonectes(I)includes the model species,and a new genus of Oreonectes(II)is suggested,To accommodate Oreonectes anophthalmus,Oreonectes acridorsalisand Heminoemacheilus parva.(2)the monophyly of the genera Oreonectes and Troglonectes is supported,and the validity of species within each genus and their taxonomic status are re-defined and re-evaluated;(1)Oreonectes donglanensis,Oreonectes duanensis,and Oreonectes transparent are genetically clustered into a monophyletic lineage with minimal genetic differences,and Oreonectes donglanensis and Oreonectes duanensis are synonyms of Oreonectes transparent;(2)Triplophysa lihuensis and Yunnannilus retrodorsalisare genetically clustered into a single line with minimal genetic differences;Triplophysa lihuensis and Yunnannilus retrodorsalis should be divided into the genus Troglonectes;(3)Troglonectes jiarongensis,Troglonectes elongatus and Triplophysa dongganensis poly are a monophyletic lineage with minimal genetic differences,and in accordance with international nomenclature regulations,T.jiarongensis and T.dongganensis are all synonyms of Troglonectes elongatus;3.Using the mitochondrial genome to estimate the divergence time of the genera Oreonectes and Troglonectes,we show that the formation and genus-level divergence of the loach genera Oreonectes and Troglonectes in the karst region of southwest China are closely related to the multilevel uplift of the Himalayan/Qinghai-Tibetan Plateau,lateral extrusion in Indochina,karst geomorphology and cave formation,small regional orogeny,and East Asian monsoonal changes,which occurred from the late Oligocene to early Miocene.The phylogenetic tree of this study not only confirms the previous taxonomic hypothesis based on morphological inference traditionally,but also provides new insights into the phylogenetic relationships of many cave loaches at the genus and species levels,and offers suggestions for the current taxonomy of the cave loaches in China.4.The results in the phylogenetic tree of this study do not support the monophyletism of the tribe,and need to be further revised to restore the monophyletism.In this paper,Yunnanilini and Lefuini,based on the results of this study on Yunnanilini and Lefuini,are considered valid for further redistribution of the genera included in the two groups in combination with geographical distribution,including Troglonectes(clade A),Paranemachilus(B clade)Yunnannilus(II)(C clade),Oreonectes(II)sensu Stricto(D clade),Micronemacheilus(clade E),Yunnannilus(I)(F clade),,Oreonectes(I)(G clade)and were added to Yunnanilini.Lefua was the only member of Lefuini.And a new family,Traccatichthyini Nov.