Phylogenetic relationships of Simpsonichthys subgenera (Cyprinodontiformes, Rivulidae), including a proposal for a new genus

Abstract

The systematic knowledge of Simpsonichthys has changed substantially in recent years, with five subgenera having been elevated to the genus category. In view of these taxonomic changes, the aim of the present study was to identify the phylogenetic relationships among this group in order to test a hypothesis of the division of Simpsonichthys. The ATPase 8 and 6 gene sequences of 53 specimens of Simpsonichthys, Xenurolebias, Ophthalmolebias, Spectrolebias and Hypsolebias genera were assessed. The final topology divided the Simpsonichthys subgenera into five clades: clade I (Hypsolebias antenori group and Ophtalmolebias), clade II (Simpsonichtys and Spectrolebias), clade III (Hypsolebias flammeus and H. magnificus groups), clade IV (H. notatus group) and clade V, which included the Xenurolebias genus as a sister group to all the other Simpsonichthys subgenera. Simpsonichthys, Spectrolebias and Hypsolebias could therefor not be described as monophyletic groups, as has been proposed in some hypotheses. The H. antenori, H. notatus and H. magnificus groups, however, were monophyletic. The molecular results also suggested that H. ocellatus belongs to the Hypsolebias flammeus group. The phylogenetic position of H. fasciatus suggested a new group within Hypsolebias, or possibly even a new genus. The characteristics of the Hypsolebias antenori group and their phylogenetic position suggested that only the species of this group should be included in the Hypsolebias genus. The basal position of the Hypsolebias notatus group and its morphological character may represent a new genus. Although the monophyletism of Simpsonichtys could not be recovered, the branches supported the division of the western and eastern clades, possibly due to allopatric speciation. These facts suggest the division of the genus into at least two major clades. In addition, the study of morphological and molecular data is suggested to obtain a better understanding of such complex organisms, and a major taxonomic review is required.

Rivulids (Rivulidae: Cyprinodontiformes) of Bolivia: knowledge status and updated inventory

“…Concluye que Simpsonichthys es parafilético mientras que los subgéneros propuestos anteriormente por Costa (2006c), entre ellos Spectrolebias, son todos monofiléticos y en consecuencia los reclasificó como géneros válidos. Sin embargo, Ponzetto et al (2016), basándose en análisis moleculares, indican que los géneros Simpsonichthys, Spectrolebias y Hypsolebias Costa no pudieron ser recuperados como grupos monofiléticos, y por tanto era necesaria una revisión taxonómica mayor para redefinir su situación. A pesar de estos resultados, hasta el momento no se ha realizado ninguna revisión y, por consiguiente, Spectrolebias continúa siendo considerado un género válido (Fricke et al 2023b).…”

Review of the family Rivulidae (Cyprinodontiformes, Aplocheiloidei) and a molecular and morphological phylogeny of the annual fish genus Austrolebias Costa 1998

“…According to a recent molecular phylogenetic analysis (Costa et al, 2017a), Nematolebias + Xenurolebias are the sister clade of the remaining genera, which relate to each other as follows: Spectrolebias, (((Austrolebias, ((Simpsonichthys, Cynolebias), (Opthalmolebias, Hypsolebias))). However, Ponzetto et al (2016), in a phylogenetic analysis based on one mitochondrial marker, had recently challenged the monophyly of Hypsolebias, with some species more closely related to Ophtlamolebias than to other Hypsolebias.…”