I just read an interesting research paper called Deep Phylogenic Divergance in Species of Astronautus...in Cichlid Evolution 2012
Below is the conclusion
The strong phylogeographic structure and the discovery of potentially new species of Astronotus are not necessarily surprising. Astronotus species are sedentary and territorial, have low power of dispersion, and therefore are likely to be influenced by climatic and geomorphological events. Perhaps the most interesting observation is that the division between the group East and West (not considering the Borba locality) parallels the division between the cichlid fishes Symphysodon sp. 2 (phenotype blue) and Symphysodon tarzoo (phenotype green) [16, 17, 47]. Also intriguing is that all but one specimen from the Borba locality in the lower Madeira River share haplotypes with the group West, which again parallels haplotype sharing between lower Madeira River and western Amazon observed by Ready et al. [47] in Symphysodon. The differentiation of the Bolivia group from all other Astronotus is potentially explained by the presence of the series of rapids on the Madeira River. These series of rapids are thought to delimit the geographic distributions of such diverse taxa as Inia geoffrensis and I. boliviensis[48, 49], Cichla monoculus and C. pleiozona [50], or they act as barriers, restricting gene flow in Colossoma macropomum [13] and Podocnemis expansa [51]. The physiochemical composition of the Negro River has also been suggested to act as a barrier between and within species [16, 17, 52, 53]. The patterns observed in Astronotusare likely to be general, implying that multiple additional species in broadly distributed Amazonian taxa are almost inevitably to be discovered.
Below is the conclusion
The strong phylogeographic structure and the discovery of potentially new species of Astronotus are not necessarily surprising. Astronotus species are sedentary and territorial, have low power of dispersion, and therefore are likely to be influenced by climatic and geomorphological events. Perhaps the most interesting observation is that the division between the group East and West (not considering the Borba locality) parallels the division between the cichlid fishes Symphysodon sp. 2 (phenotype blue) and Symphysodon tarzoo (phenotype green) [16, 17, 47]. Also intriguing is that all but one specimen from the Borba locality in the lower Madeira River share haplotypes with the group West, which again parallels haplotype sharing between lower Madeira River and western Amazon observed by Ready et al. [47] in Symphysodon. The differentiation of the Bolivia group from all other Astronotus is potentially explained by the presence of the series of rapids on the Madeira River. These series of rapids are thought to delimit the geographic distributions of such diverse taxa as Inia geoffrensis and I. boliviensis[48, 49], Cichla monoculus and C. pleiozona [50], or they act as barriers, restricting gene flow in Colossoma macropomum [13] and Podocnemis expansa [51]. The physiochemical composition of the Negro River has also been suggested to act as a barrier between and within species [16, 17, 52, 53]. The patterns observed in Astronotusare likely to be general, implying that multiple additional species in broadly distributed Amazonian taxa are almost inevitably to be discovered.
