A New South American Freshwater Turtle of the Genus Mesoclemmys from the Brazilian Amazon (Testudines: Pleurodira: Chelidae)

Where to set the bar? Recent descriptions inflate species number in South American toad-headed turtles ( Mesoclemmys )

“…Phylogenetic analysis. Cunha et al (2021Cunha et al ( , 2022 justified the formal description of M. jurutiensis and M. sabiniparaensis with the putative phylogenetic distinctness in two mitochondrial gene fragments, namely 16S (16S ribosomal RNA gene) and the barcoding gene COI (cytochrome c oxidase subunit I). The downsides of using only mtDNA to delineate species are widely known: mtDNA is uniparentally inherited, considered a single genetic locus, has the propensity to introgress across species borders and to transfer into the nuclear genome, has little use in detecting hybridization, and often yields topologies that do not represent species trees (Moore 1995;Toews & Brelsford 2012;Allendorf 2017;Hillis 2019).…”

“…While we agree that the genus deserves scientific attention and likely comprises additional unrecognized taxa (Ettmar 2019), the evidence presented in these two descriptions was neither strong nor robust, and the conclusions drawn from their extremely limited datasets were very weakly supported. Here, we point out the inconsistencies and methodological shortcomings of Cunha et al (2021Cunha et al ( , 2022 and discuss why M. jurutiensis and M. sabiniparaensis were described prematurely and should not be recognized until more robust and reliable data are presented to corroborate their validity. We specifically focus on phylogenetic and morphological evidence.…”

“…Two recent articles by Cunha et al (2021Cunha et al ( , 2022 each described a newly discovered Brazilian freshwater turtle species: Mesoclemmys jurutiensis and M. sabiniparaensis, respectively. The South American genus Mesoclemmys (family Chelidae) is a poorly studied group of sideneck turtles that has been subject to frequent taxonomic discussions and revisions (McCord et al 2001;Bour & Zaher 2005;Cunha et al 2019;Ettmar 2019;Thomson et al 2021;TTWG 2021).…”

“…The South American genus Mesoclemmys (family Chelidae) is a poorly studied group of sideneck turtles that has been subject to frequent taxonomic discussions and revisions (McCord et al 2001;Bour & Zaher 2005;Cunha et al 2019;Ettmar 2019;Thomson et al 2021;TTWG 2021). In the descriptions of M. jurutiensis and M. sabiniparaensis, Cunha et al (2021Cunha et al ( , 2022 used similar morphological, statistical, and molecular analyses to provide what they described as "strong and robust scientific evidence" to support the validity of their two new species. While we agree that the genus deserves scientific attention and likely comprises additional unrecognized taxa (Ettmar 2019), the evidence presented in these two descriptions was neither strong nor robust, and the conclusions drawn from their extremely limited datasets were very weakly supported.…”

“…Therefore, the exclusive use of mtDNA sequences to delineate species is highly discouraged in modern taxonomy (e.g., TTWG 2007a;Padial et al 2010). In addition, the analyses by Cunha et al (2021Cunha et al ( , 2022 were based on very restricted taxon sampling, and relevant sequences available from GenBank were not included, even some of their own (GenBank accession numbers MZ707096, MZ707098). Their datasets also suffer from a severe mismatch in species assemblages for the two mitochondrial gene fragments, so that their concatenated alignment represents a patchwork of mostly incomplete sequences (Table 1).…”