Abstract
Steindachneridion scriptum is an important species as a resource for fisheries and aquaculture; it is currently threatened and has a reduced occurrence in South America. The damming of rivers, overfishing, and contamination of freshwater environments are the main impacts on the maintenance of this species. We accessed the genetic diversity and structure of S. scriptum using the DNA barcode and control region (D-loop) sequences of 43 individuals from the Upper Uruguay River Basin (UUR) and 10 sequences from the Upper Paraná River Basin (UPR), which were obtained from GenBank. S. scriptum from the UUR and the UPR were assigned in two distinct molecular operational taxonomic units (MOTUs) with higher inter-specific K2P distance than the optimum threshold (OT = 0.0079). The COI Intra-MOTU distances of S. scriptum specimens from the UUR ranged from 0.0000 to 0.0100. The control region indicated a high number of haplotypes and low nucleotide diversity, compatible with a new population in recent expansion process. Genetic structure was observed, with high differentiation between UUR and UPR basins, identified by BAPS, haplotype network, AMOVA (FST = 0.78, p < 0.05) and Mantel test. S. scriptum from the UUR showed a slight differentiation (FST = 0.068, p < 0.05), but not isolation-by-distance. Negative values of Tajima’s D and Fu’s Fs suggest recent demographic oscillations. The Bayesian skyline plot analysis indicated possible population expansion from beginning 2,500 years ago and a recent reduction in the population size. Low nucleotide diversity, spatial population structure, and the reduction of effective population size should be considered for the planning of strategies aimed at the conservation and rehabilitation of this important fisheries resource.
Highlights
Freshwater ecosystems are among the most endangered ecosystems (Dudgeon et al, 2006)
The Cytochrome Oxidase subunit I (COI) inter-molecular operational taxonomic units (MOTUs) between S. scriptum from the Uruguay River (UUR) and S. scriptum from the Upper Paraná River (UPR) showed values larger than the optimum threshold (OT), while intra-MOTU values for fishes from both basins were lower than the average OT (UUR = 0.000 to 0.010; UPR = 0.000) (Table 1)
The DNA barcode confirmed the identification of all the individuals of S. scriptum from UUR as a single MOTU
Summary
Freshwater ecosystems are among the most endangered ecosystems (Dudgeon et al, 2006). The understanding of the genetic diversity and structure of wild populations of fish species are important to the regulation of fisheries and conservation management strategies (Carvalho and Hauser, 1994; Iervolino et al, 2010). Steindachneridion scriptum (Miranda Ribeiro, 1918) is a large catfish belonging to the family Pimelodidae. This potamodromous fish species presents restricted distribution in the Upper Uruguay River (UUR) and Upper Paraná River (UPR) basins (Marques et al, 2002). S. scriptum is an important fishing resource to the riverine fishermen (Schork et al, 2013); it was recently classified as an endangered species according to the Chico Mendes Institute for Biodiversity Conservation (ICMBIO, 2014). Human activities (e.g., damming of rivers, illegal fishing, and industrial waste) are the main threats to S. scriptum in the UUR (Fontana et al, 2003) and are the principle reason for population reduction in this basin (Beux and Zaniboni-Filho, 2008)
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