Materials and Methods

Tissue Samples were collected in the locations indicated on the map (Fig. 1) and were preserved in 95% ethanol. The DNA was extracted following the protocol for extraction by phenol-chloroform of Sambrook et al. (1989). The region of the gene for ATPase was amplified via PCR, with the use of primers specifically developed by Sivasundar et al., (2001). The sequencing reactions were performed in accordance with the recommendations of the manufacturers utilizing the Terminator Cycle Sequencing Kit (Amersham Bioscience), and analized in the MegaBACE 1000 automatic sequencer.

Intra and Inter-populational Analyses

The genetic structure of the populations was analyzed using AMOVA (Analysis of Molecular Variance) (Excoffier et al., 1992), and pairwise FsT (Cockerham & Weir, 1993), implemented by the program Harlequin 2.0 (Schneider et al., 2000). Indices of genetic diversity and tests of selective neutrality of mutations were accessed using the program Harlequin 2.0. The haplotype network was constructed with the program TCS versão 1.18 (Clement et al., 2000).

No indication of genetic difference was demonstrated in the two populations of C. temensis, an indication of elevated genetic flux. () (Tab. 3b).

The results of AMOVA also show this pattern. In the populations of C. orinocensis, 37,26% of the genetic variation occurred between the two populations (Fst=0,372; P=0). While in C. temensis, the variation between the two populations was -0,97% (Fst=-0,0096; P=0.7575). Fst and AMOVA indicate population fragmentation in C. orinocensis.

These results demonstrate that a distance of ~100 Km between tributaries of the Rio Negro can function as a barrier to the dispersion of some species of fish as seen in C. orinocensis, but not in others as in C. temensis. Species of peacock bass, for example, can exhibit different patterns of migration, reflecting different life strategies.

Bibliography and References

Funding