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Keywords:

  • Biogeography;
  • biogeographical units;
  • Brazil;
  • coastal basins;
  • freshwater fish;
  • Neogene;
  • phylogeography;
  • São Francisco Basin

Abstract

Aim

The aim of this study was to test the hypothesis that the Brazilian coastal populations of Hoplias malabaricus were subject to the same geomorphological and palaeohydrological factors that resulted in endemic fish regions, by characterizing the mitochondrial DNA, nuclear sequences and cytogenetic data of these populations.

Location

Seventeen coastal basins in north-eastern, eastern and south-eastern Brazil, plus the São Francisco Basin.

Methods

Forty-two specimens were analysed. Mitochondrial ATP synthase 6 (ATPase-6) and nuclear recombination activating gene 2 (RAG2) gene sequences were used for Bayesian inference and maximum parsimony analyses. Molecular models were selected using MrModeltest.

Results

Molecular analyses indicated four haplogroups (Northeastern, Eastern A, Eastern B and Southeastern) for ATPase-6 and three clades for RAG2. All topologies were congruent with Hoplias malabaricus diploid numbers, with most regions of proposed endemism and coastal geomorphological units.

Main conclusions

Deep genetic divergence between the Northeastern and the other haplogroups was interpreted as evidence of the vicariant effect of the Abrolhos Formation, which effectively isolates 2= 40 and 2= 42 coastal populations. To the south, the Cabo Frio Magmatic Lineament also isolates the Eastern and Southeastern 2n = 42 populations. In the Northeastern haplogroup, stream piracy was probably involved in chronologically varied dispersal events between coastal and continental basins. All haplogroups also included haplotypes that dispersed in recent times. Results show an older vicariant pattern and recent dispersal events congruent with the occurrence of temporary connections along the coast caused by eustatic sea level variations and the occurrence of stream piracy involving either continental or coastal basins, and suggest these processes contributed to the current distribution patterns of Brazilian coastal freshwater fish.