Browsing Department of Biochemistry by Author "Anderson, Chanelle"
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- ItemA molecular phylogenetic study of the South American fish genus Pterophyllum(Stellenbosch : Stellenbosch University, 2016-03) Anderson, Chanelle; Bellstedt, D. U.; Stellenbosch University. Faculty of Science. Dept. of Biochemistry.ENGLISH ABSTRACT: The South American fish genus Pterophyllum, commonly referred to as Angel Fish, contains three recognized species namely Pterophyllum leopoldi, Pterophyllum altum and Pterophyllum scalare. In addition, morphological variants, particularly of Pt. scalare and Pt. altum, occur in their natural habitat. However, uncertainty regarding the taxonomy and the phylogenetic relationships between the three species of the genus Pterophyllum within the tribe Heroini, still remains. In the first part of this study three mitochondrial (Cytochrome b, 16S rRNA and NADH dehydrogenase subunit 4) and two nuclear (Recombinase Activator Gene 2 and ribosomal S7 intron 1) markers were amplified and sequenced for 27 Pterophyllum samples. Along with this, 166 nucleotide reference sequences, representing six outgroups and 160 Neotropical cichlid taxa, were downloaded for each of the five molecular markers from GenBank. In addition to maximum likelihood and parsimony analyses, a BEAST analysis was performed on the Cytochrome b sequence matrix. This study was the first to conclusively show that the genus Pterophyllum is a monophyletic group of which Pt. leopoldi is the basal lineage whilst Pt. altum and Pt. scalare form a derived sister association. Furthermore, it appears that the evolution of the genus Pterophyllum corresponds to the historical geographical changes of the Amazonian landscape. In addition, the study also provides phylogenetic evidence for the reconnection of the Amazon and Orinoco river systems by means of the Casiquiare channel. In the second part of this study the sequence variability of 13 additional nuclear markers were investigated in order to expand the five-gene analysis with the aim of enhancing the resolution of the phylogeny. In conjunction with this, the number of Pterophyllum taxa included in the ND4 sequence matrix were increased from two to six representatives for each population of the three species in order to elucidate intraspecies and population variability. The two nuclear genes Mitfb and RpL8 were identified as the most variable of the 13 nuclear genes investigated. The inclusion of these two nuclear genes in the five-gene data matrix, improved the ratio of mitochondrial to nuclear variable characters from 79:21 to 67:33 in the seven-gene phylogeny. Distinction between Pt. altum of the upper Rio Negro and Upper Rio Orinoco was repeatedly confirmed with full statistical support. Variation within Pt. scalare retrieved three groups of which Pt. scalare Santa Isabel and Pt. scalare Manacapuru were the basal lineages. This study offers no phylogenetic evidence to support a hybrid origin for the latter.