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Patterns of diversification in the discus fishes (Symphysodon spp. Cichlidae) of the Amazon basin.
Mol Phylogenet Evol. 2008 Oct; 49(1):32-43.MP

Abstract

We carried out a phylogeograhic and population genetic analysis of fishes of the taxonomically contentious genus Symphysodon from the Amazon basin in order to test hypotheses of relationships among taxonomic units, and potential processes driving diversification within this genus. We sampled 334 individuals of the genus Symphysodon from 24 localities that span the complete geographic distribution of this genus. The sampling scheme included all known phenotypic groups, species and subspecies. Analyses were based on 474 bp of the mitochondrial control region and 1443 bp of the exon 3 of RAG1 gene. We observed 102 mtDNA haplotypes defined by 89 segregating sites, and 5 nuDNA alleles defined by three segregating sites. Maximum-likelihood, Bayesian-inference and statistical parsimony analyses revealed three well defined monophyletic groups. These clades corresponded to the 'green' and 'blue' groups of Symphysodon aequifasciatus, and to a previously morphologically unrecognized clade from the Xingu River drainage. These three clades were nested within a paraphyletic assemblage consisting of the 'brown' group of S. aequifasciatus and of both described subspecies of S. discus, the 'Heckel' and the 'abacaxi' discus. Nuclear allele sharing was observed among groups, but there were significant differences in frequencies. We inferred several processes including past fragmentation among groups, and restricted gene flow with isolation by distance within the paraphyletic 'brown+Heckel+abacaxi' groups, and suggest that differences among the 'blue', 'Heckel' and 'brown' groups are potentially maintained by differences in water chemistry preferences. We further inferred colonization of the western Amazon basin by an ancestor of the 'green' clade. The 'green' group was the only group with a pattern of haplotype distribution consistent of a demographic expansion, and the divergence of this clade from other groups of discus was consistent with recent geologic evidence on the breach of the Purus Arch which separates western Amazon from eastern Amazon. We further hypothesized that the differentiation of the 'Xingu' clade could be due to vicariance events resulting from Pleistocene sea level, and thus Amazon River level fluctuations. We discuss the bearings of our results on the current taxonomy of this group, and on the biological reality of the different forms, subspecies and species of Symphysodon concluding that we are probably observing a process of diversification, and therefore taxonomy will remain contentious.

Authors+Show Affiliations

Universidade Federal do Amazonas, Departamento de Biologia, Laboratório de Evolução e Genética Animal, Av. Rodrigo Octávio Jordão Ramos, 3000, 69077-000 Manaus, AM, Brazil.No affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

18762435

Citation

Farias, Izeni Pires, and Tomas Hrbek. "Patterns of Diversification in the Discus Fishes (Symphysodon Spp. Cichlidae) of the Amazon Basin." Molecular Phylogenetics and Evolution, vol. 49, no. 1, 2008, pp. 32-43.
Farias IP, Hrbek T. Patterns of diversification in the discus fishes (Symphysodon spp. Cichlidae) of the Amazon basin. Mol Phylogenet Evol. 2008;49(1):32-43.
Farias, I. P., & Hrbek, T. (2008). Patterns of diversification in the discus fishes (Symphysodon spp. Cichlidae) of the Amazon basin. Molecular Phylogenetics and Evolution, 49(1), 32-43. https://doi.org/10.1016/j.ympev.2008.05.033
Farias IP, Hrbek T. Patterns of Diversification in the Discus Fishes (Symphysodon Spp. Cichlidae) of the Amazon Basin. Mol Phylogenet Evol. 2008;49(1):32-43. PubMed PMID: 18762435.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Patterns of diversification in the discus fishes (Symphysodon spp. Cichlidae) of the Amazon basin. AU - Farias,Izeni Pires, AU - Hrbek,Tomas, Y1 - 2008/06/03/ PY - 2007/09/21/received PY - 2008/05/17/revised PY - 2008/05/20/accepted PY - 2008/9/3/pubmed PY - 2008/12/17/medline PY - 2008/9/3/entrez SP - 32 EP - 43 JF - Molecular phylogenetics and evolution JO - Mol Phylogenet Evol VL - 49 IS - 1 N2 - We carried out a phylogeograhic and population genetic analysis of fishes of the taxonomically contentious genus Symphysodon from the Amazon basin in order to test hypotheses of relationships among taxonomic units, and potential processes driving diversification within this genus. We sampled 334 individuals of the genus Symphysodon from 24 localities that span the complete geographic distribution of this genus. The sampling scheme included all known phenotypic groups, species and subspecies. Analyses were based on 474 bp of the mitochondrial control region and 1443 bp of the exon 3 of RAG1 gene. We observed 102 mtDNA haplotypes defined by 89 segregating sites, and 5 nuDNA alleles defined by three segregating sites. Maximum-likelihood, Bayesian-inference and statistical parsimony analyses revealed three well defined monophyletic groups. These clades corresponded to the 'green' and 'blue' groups of Symphysodon aequifasciatus, and to a previously morphologically unrecognized clade from the Xingu River drainage. These three clades were nested within a paraphyletic assemblage consisting of the 'brown' group of S. aequifasciatus and of both described subspecies of S. discus, the 'Heckel' and the 'abacaxi' discus. Nuclear allele sharing was observed among groups, but there were significant differences in frequencies. We inferred several processes including past fragmentation among groups, and restricted gene flow with isolation by distance within the paraphyletic 'brown+Heckel+abacaxi' groups, and suggest that differences among the 'blue', 'Heckel' and 'brown' groups are potentially maintained by differences in water chemistry preferences. We further inferred colonization of the western Amazon basin by an ancestor of the 'green' clade. The 'green' group was the only group with a pattern of haplotype distribution consistent of a demographic expansion, and the divergence of this clade from other groups of discus was consistent with recent geologic evidence on the breach of the Purus Arch which separates western Amazon from eastern Amazon. We further hypothesized that the differentiation of the 'Xingu' clade could be due to vicariance events resulting from Pleistocene sea level, and thus Amazon River level fluctuations. We discuss the bearings of our results on the current taxonomy of this group, and on the biological reality of the different forms, subspecies and species of Symphysodon concluding that we are probably observing a process of diversification, and therefore taxonomy will remain contentious. SN - 1095-9513 UR - https://www.unboundmedicine.com/medline/citation/18762435/Patterns_of_diversification_in_the_discus_fishes__Symphysodon_spp__Cichlidae__of_the_Amazon_basin_ L2 - https://linkinghub.elsevier.com/retrieve/pii/S1055-7903(08)00271-6 DB - PRIME DP - Unbound Medicine ER -