Abstract
Genetic and phylogenetic relationships among seven piranha species of the genera Serrasalmus and Pygocentrus from the Paraná-Paraguay, São Francisco and Tocantins River basins were evaluated in the present study by partial sequences of two mitochondrial genes, Cytochrome b and Cytochrome c Oxidase I. Phylogenetic analysis of Maximum-Likelihood and Bayesian inference were performed. Results indicated, in general, greater genetic similarity between the two species of Pygocentrus (P. nattereri and P. piraya), between Serrasalmus rhombeus and S. marginatus and between S. maculatus, S. brandtii and S. eigenmanni. Pygocentrus nattereri, S. rhombeus and S. maculatus showed high intraspecific genetic variability. These species have each one, at least two different mitochondrial lineages that, currently, occur in sympatry (S. rhombeus) or in allopatry (P. nattereri and S. maculatus). Species delimitation analysis and the high values of genetic distances observed between populations of S. rhombeus and of S. maculatus indicated that each species may corresponds to a complex of cryptic species. The non-monophyletic condition of S. rhombeus and S. maculatus reinforces the hypothesis. The geographic distribution and the genetic differentiation pattern observed for the piranha species analyzed herein are discussed regarding the geological and hydrological events that occurred in the hydrographic basins.
Highlights
Piranhas and closely related genera of pacus and tambaquis comprise the family Serrasalmidae (Ostariophysi: Characiformes), currently with 98 valid species in 16 genera (Fricke et al, 2019)
Concatenated cytb and c Oxidase subunit I (coI) sequences were efficient in discriminating the piranha species, revealing high bootstrap or posterior probabilities values supporting clades in both dendrograms (Figure 2) as well as consistent p-distance values (Table 2)
Single-gene topologies obtained with cytb or coI sequences were similar with each other and with the topology based on the concatenated sequences
Summary
Piranhas and closely related genera of pacus and tambaquis comprise the family Serrasalmidae (Ostariophysi: Characiformes), currently with 98 valid species in 16 genera (Fricke et al, 2019). The largest group of Serrasalmidae is comprised by the piranhas. According to Freeman et al (2007), “piranhas” or the “true piranhas” are a group of fishes that traditionally includes the genera Serrasalmus (24, perhaps 28 species), Pristobrycon (5), Pygocentrus (3 or 4) and Pygopristis (1). Piranhas are freshwater Neotropical fish endemic from South America, occurring in the rivers of the Amazon, Orinoco, Guiana, Araguaia-Tocantins, Paraná-Paraguay and São Francisco basins (Jégu, 2003). Despite their ecological and economic importance, the taxonomy and systematic classification of piranhas and other serrasalmids are confusing. Species identification and phylogenetic placement of many taxa are problematic (Freeman et al, 2007; Thompson et al, 2014)
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