From taxonomic deflation to newly detected cryptic species: Hidden diversity in a widespread African squeaker catfish

Abstract

Cryptic genetic diversity and erroneous morphological species determination represent frequent problems in biodiversity research. Here, examination of 138 specimens of Synodontis (Mochokidae, Siluriformes) from the Nile River and Lake Turkana revealed the presence of both S. schall-like and S. frontosus-like morphotypes, with a phenotypic gradient between them. We concluded phylogenetic and population genetic analyses based on two mitochondrial and one nuclear marker including 131 coxI (565 bp), 96 cytb (973 bp) and 19 RAG2 (896 bp) sequences from the Nile-Turkana population, plus additional GenBank data of Synodontis spp. Whilst nuclear data were inconclusive, mitochondrial sequences suggested that both morphotypes and intermediate forms are conspecific. The results imply probable synonymy of S. frontosus with S. schall. Conversely, a strong biogeographical signal was revealed among widely distributed and supposedly conspecific S. schall-like catfish of the Nilo-Sudanian ichthyological province. Synodontis schall sensu stricto (=Eastern clade), as defined by type locality in the Nile, is apparently restricted to the eastern part of the Nilo-Sudanian ichthyological province (e.g. Nile, Turkana, Chad). Synodontis schall Western clade (Senegambia, Niger, Chad) most probably represents a cryptic taxon, unrecognized thus far due to the absence of distinctive morphological differences.

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

“…Two or more distinct species are regarded to be cryptic if they are erroneously classified under one species name ( Bickford et al, 2007 ). In most cases, cryptic species are those species that represent distinct lineages under molecular scrutiny but have been classified as a single species owing to failure to detect their subtle morphological differences ( Jirsová et al, 2019 ). However, species of this kind should be referred to as pseudocryptic species ( Matsuda and Gosliner, 2018 ) and cryptic species are truly represented by those species recently diverged, sympatrically occurring, and distinguishable only by DNA data ( Brickford et al, 2007 ; Schnurr et al, 2018 ).…”

Trophic Structure of the Fish Community in the Samandeni Reservoir—Burkina Faso

“…The competition for food between certain species in the reservoir could partly explain this situation. This is the case between Synodontis schall and Synodontis nigrita, two sympatric species, phylogenetically close [21] and with very similar feeding habits. This also applies to Chrysichthys auratus and Chrysichthys nigrodigitatus.…”

Keeping up with the status of freshwater fishes: A California (USA) perspective

“…Thus, genomic analysis revealed that a widespread cyprinid, the California roach ( Hesperoleucus symmetricus ) is a complex that includes six species, four subspecies, and several distinct population segments (Baumsteiger & Moyle, 2019) (Figure 3a). In assessments of freshwater fish diversity, documentation of cryptic diversity is accelerating (Bartáková et al, 2019; Jirsová, Štefka, et al, 2019; Li, Jiang, et al, 2020; Ramirez, Birindelli, Carvalho, et al, 2017; Shelley et al, 2018). Assessments of freshwater fishes often have no alternative but to rely on incomplete or old data, restricting our ability to accurately assess their status.…”