Phylogenetic relationships of a new genus and species of stevardiine fish (Characiformes: Characidae: Stevardiinae) from the Río Amazonas basin, Peru

Abstract

Varicharax nigrolineatus, a new genus and species of stevardiine fish, is described from the Río Amazonas basin, Peru, based on a comprehensive phylogenetic comparison with other characids. Two data sets (A: combined morphological and molecular matrix, 474 species and 6,653 characters; B: morphological matrix, 216 species and 524 characters) were used to estimate the phylogenetic relationships of the new genus. Morphological and molecular data from these data sets were taken from two previously published matrices on characids. Varicharax nigrolineatus is phylogenetically diagnosed by 18 autapomorphies in total (from both data sets), which are related to different anatomical characteristics of the neurocranium, body, and fins. Furthermore, V. nigrolineatus can be easily differentiated from all characids (except Acrobrycon in part) by the following combination of characters: the presence of a hypertrophied caudal-fin squamation on the lower caudal-fin lobe forming a remarkable pouch-like structure, consisting of multiple series of large adjacent scales (being almost similar or slightly more pronounced in males than in females), the presence of caudal-fin bony hooks on the lower lobe in adult males, complete lateral line, and a dark mid-lateral stripe that extends from the posterior border of the head to caudal peduncle. In the resulting topologies from both data sets, the phylogenetic placement of V. nigrolineatus was well supported within Stevardiinae. Additionally, V. nigrolineatus was resolved within the tribe Stevardiini as sister group of a clade formed by Chrysobrycon + Pseudocorynopoma and Corynopoma + Gephyrocharax in the final hypothesis from the combined data set, whereas in the final topology from the morphological data set, V. nigrolineatus was placed as sister group of a clade comprised of Acrobrycon and the Stevardiini without Argopleura. K E Y W O R D SNeotropical freshwater fish, sexual dimorphism, Stevardiini, Varicharax gen. nov., Varicharax nigrolineatus sp. nov. Bryconops affinis Günther, MHNG 2184.28, 2 c&s, 29.0-32.0 mm SL, French Guiana, Balatée creek, Río Maroni basin. Bryconops melanurus (Bloch), MCP 15807, 3 c&s, 41.2-83.4 mm SL, Brazil, Mato Grosso, Barra do Bugres, stream crossing the Tangara da Sierra road, 13 km S of Nova Limpia, tributary of Rio Paraguai. Carlana eigenmanni Meek, LACM 9230.020, 2 c&s, 45.2-57.6 mm SL, Costa Rica, Heredia, Río Puerto Viejo. Carlastyanax aurocaudatus (Eigenmann), CI-FML 5015, 15, 31.3-48.1 mm SL (2 c&s 39.4-40.1 mm SL), Colombia, Upper Cauca, Río La Vieja basin, La Siria creek. Chalceus macrolepidotus Cuvier, MHNG 2189.13, 2 c&s, 64.0-67.0 mm SL, French Guiana, Litany Maripasoula at its confluence with le Tampoe, upper Río Maroni. Charax stenopterus (Cope), CI-FML 3878, 1 c&s, 39.2 mm SL, Argentina, Corrientes, Guayquiraró, Río Corrientes. Cheirodon interruptus (Jenyns), Argentina: CI-FML 3825, 2 c&s, 32.9-33.4 mm SL, Santiago del Estero, Río Hondo basin, dam at Río Hondo.

Expanding the Distribution and Phylogenetic Insights ofChrysobrycon mojicaiin the Peruvian Amazon: Morphological and Molecular Analyses with Taxonomic Corrections

“…Recent phylogenetic research combining molecular and morphological data has supported the monophyly of Stevardiini, including Hysteronotus [9], aligning with earlier morphological studies [10,49]. However, it is noteworthy that both Thomaz et al [8] and Ferreira et al [9] did not include molecular data for Hysteronotus.…”

Molecular and morphological evidence revalidates Acrobrycon tarijae (Characiformes, Characidae) and shows hidden diversity

“…Further studies based on morphological data recovered Acrobrycon as separate from the Hemibryconini , as the sister clade of the Stevardiini ( Vanegas-Ríos 2018 ). Later, based on a combined phylogenetic analysis, Mirande (2019) corroborated a sister-group relationship between Acrobrycon and Hemibrycon , including both genera within Hemibryconini , a result also shown in Vanegas-Ríos et al (2020) .…”

Morphology and phylogenetic significance of the pelvic articular region in elasmobranchs (Chondrichthyes)

“…Nevertheless, it is important to stress that the monophyly of this group is not under dispute and it has been corroborated by several phylogenetic analyses (Didier, 1995; Inoue et al., 2010; Licht et al., 2012). As proposed in previous studies (Mirande, 2017, 2019; Vanegas‐Ríos et al., 2020), the analysis was also performed under extended implied weighting, using the command “xpiwe (*”, to handle missing information for molecular characters (Goloboff, 2014). Four weighting schemes were defined to explore the most parsimonious trees among distinct approaches on character homoplasy for the NADH2 sequences following Mirande (2019): SEP – each character weighted according to its own homoplasy; COD – sequences divided in sets of three contiguous sites (codons) and each character weighted by the average homoplasy of its set; BLK – each character weighted by the average homoplasy of entire data partition (markers); and POS – sets formed by codon positions for each partition and each character weighted according to its position.…”