A Century after! Rediscovery of the ancient catfish Diplomystes Bleeker 1858 (Siluriformes: Diplomystidae) in coastal river basins of Chile and its implications for conservation

Carlos P Muñoz-Ramírez,Raul Briones,Nicole Colin,Konrad Górski,Alfonso Jara,Pablo Fierro,Aliro Manosalva

doi:10.1590/1982-0224-2019-0073

Abstract

ABSTRACT The ancient catfish family Diplomystidae, with seven species endemic to rivers of southern South America, represents one of the oldest branches of the diverse order Siluriformes. With most species endangered, new reports of these species become extremely valuable for conservation. Currently, it is assumed that Diplomystes species inhabit only Andean (large) basins, and that they are extinct from coastal (small) basins from which their presence have not been recorded since 1919. Here, we document new records of the family Diplomystidae in the Laraquete and Carampangue basins, two coastal basins from the Nahuelbuta Coast Range, Chile, with no previous reports. This finding represents the rediscovery of the genus in coastal basins in more than a Century. Based on analysis of mitochondrial DNA sequences, the collected specimens were found to be closely related to Diplomystes nahuelbutaensis from the Andean Biobío Basin, but sufficiently differentiated to suggest that coastal basin populations are a different management unit. These populations are important because, contrary to previous thoughts, they prove these catfish can survive in small river networks, providing unique opportunities for research and conservation. The conservation category of Critically Endangered (CE) is recommended for the populations from the Laraquete and Carampangue basins.

Highlights

Conservation of rare, ancient species is fundamental because they contribute disproportionately more to biodiversity (Faith, 1992) and their extinction would cause a severe loss of important branches of the tree of life
Despite their genetic proximity with the Biobío populations, the haplotype network shows these coastal populations represent a separate genetic group, with haplotypes not shared with any previously analyzed Biobío populations (Fig. 3B). This result was confirmed by the randomization test (Fig. 4) which shows that the genetic differentiation between the coastal and Biobío samples was significantly larger than chance, as shown by the comparison of the Fst value relative to the null distribution of Fst values expected under a panmictic population model
The only previous reference of Diplomystes from a coastal basin is provided by early material collected in the Andalién Basin by Eigenmann in 1919, studied later by several authors (e.g., Arratia, 1987; Arratia, Quezada-Romegialli, 2017)

Summary

Introduction

Conservation of rare, ancient species is fundamental because they contribute disproportionately more to biodiversity (Faith, 1992) and their extinction would cause a severe loss of important branches of the tree of life. The strictly freshwater catfish family Diplomystidae is one of such groups of species. It forms one of the earliest branching groups of the diverse order Siluriformes, with extensive morphological evidence placing Diplomystidae as the sister group of all other catfish worldwide (Lundberg, Baskin, 1969; Arratia, 1987; Grande, 1987; Mo, 1991; de Pinna, 1998; Diogo, 2004; Hardman, 2005). Despite the importance of the family for understanding catfish evolution, most species face conservation issues, with three species (Diplomystes chilensis (Molina, 1782), D. nahuelbutaensis Arratia, 1987, and D. camposensis Arratia, 1987) considered Endangered by the Chilean Government (MINSEGPRES, 2008), one of these (D. chilensis) has been assumed Extinct by some authors (Muñoz-Ramírez et al, 2010, 2014; Arratia, Quezada-Romegialli, 2017).

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