Harvard University Press, Cambridge, MA, 602 pp.). Genes in conflict: the biology of selfish genetic elements. Burt and Trivers, 2006 Burt A and Trivers R (2006). Repetitive DNA represents a large portion of fish genomes and may play a role in genome structure maintenance, chromosomal physiology and possibly local adaptations processes ( Charlesworth et al., 1994 Charlesworth B, Snegowski P and Stephan W (1994) The evolution dynamics of repetitive DNA in eukaryotes. The understanding of how fish genomes interact to provide local adaptations to specific environmental conditions and their fluctuation is a frontier of scientific knowledge. Mol Phylogenet Evol 49:32-43., observed restriction of gene flow between 'brown' discus and 'Heckel' discus ( Symphysodon) populations from the Amazonas and Negro rivers, which was interpreted as result of local adaptation to distinct environments. Farias and Hrbek (2008) Farias IP and Hrbek T (2008) Patterns of diversification in the discus fishes (Symphysodon spp. Genetic divergence is also expected from populations occurring in such distinct environment conditions. Netherlands, Dordrecht, pp 127-166.).Īn enormous diversity of fishes and other aquatic organisms inhabits the Amazon basin, where they interact with equally diverse, heterogeneous and dynamic habitats ( Val and Almeida-Val, 1995 Val AL and Almeida-Val VMF (1995) Fishes of the Amazon and their environments. The Amazon: limnology and landscape ecology of a mighty tropical river and its basin.
Negro) having an acidic pH of < 5 and a brownish water color ( Sioli, 1984 Sioli H (1984) The Amazon and its main effluents: Hydrography, morphology of the river courses, and river types. Tapajós) a pH variable between 5 to 8 and a greenish water color, and black water rivers ( e.g. Amazonas) having a neutral pH and turbid water, clear water rivers ( e.g. This classification system has been formally considered since the 1950s and is supported based on differences in water chemical properties, with white water rivers ( e.g. Brasília: Sociedade Civil Mamirauá/CNPq/Rainforest Alliance, 208 pp.). Traditionally, these rivers are recognized as white, clear and black water types ( Goulding, 1997 Goulding M (1997) História natural dos rios amazônicos. The rivers in the Amazon basin, South America, are usually categorized based on the appearance of their water color type. Minor differences detected in the amount of repetitive DNA markers are interpreted as possible signatures of local adaptations to distinct aquatic environments.Ĭytogenomics FISH rDNA REX 3 Tapajós river Heteromorphism in pair 14 was detected as evidence for the initial differentiation of an XX/XY system. We found a conserved karyotypic macrostructure with a diploid number of 40 chromosomes (20 metacentrics + 20 submetacentrics) in all the samples. We investigated the chromosomal localization of repetitive DNA markers (constitutive heterochromatin, rDNA and the transposable element REX-3) in populations from the Amazonas river (white water), the Negro river (black water) and the Tapajós river (clear water), in order to address the variation/association of cytogenomic features and environmental conditions. Its large distribution across distinct aquatic environments can pose stressful conditions for dispersal and creates possibilities for the emergence of local adaptive profiles. Hoplias malabaricus is a common fish species occurring in white, black and clear water rivers of the Amazon basin.
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