title: Intraspecific concerted evolution of the rDNA ITS1 in Anopheles farauti sensu stricto (Diptera: Culicidae) reveals recent patterns of population structure.
abstract: We examined the intraindividual variation present in the first ribosomal internal transcribed spacer (ITS1) of Anopheles farauti to determine the level of divergence among populations for this important malarial vector. We isolated 187 clones from 70 individuals and found regional variation among four internal tandem repeats. The data were partitioned prior to analysis given the presence of a paralogous ITS2 sequence, called the 5'-subrepeat, inserted in the ITS1 of most clones. A high level of homogenization and population differentiation was observed for this repeat, which indicates a higher rate of turnover relative to the adjacent 'core' region. Bayesian analysis was performed using several substitutional models on both a combined and a partitioned data set. On the whole, the ITS1 phylogeny and geographic origin of the samples appear to be congruent. Some interesting exceptions indicate the spread of variant repeats between populations and the retention of ancestral polymorphism. Our data clearly demonstrate concerted evolution at the intraspecific level despite intraindividual variation and a complex internal repeat structure from a species that occupies a continuous coastal distribution. A high rate of genomic turnover in combination with a high level of sequence divergence appears to be a major factor leading to its concerted evolution within these populations.
authors.affiliation: Biological Sciences, University of Wollongong, Northfields Avenue, Wollongong, NSW 2522, Australia.
authors.forename: James E
authors.initials: JE
authors.lastname: Bower
authors.forename: Mark
authors.initials: M
authors.lastname: Dowton
authors.forename: Robert D
authors.initials: RD
authors.lastname: Cooper
authors.forename: Nigel W
authors.initials: NW
authors.lastname: Beebe
mesh_terms: D000818:Animals; D000852:Anopheles / Q000235:genetics*; D001482:Base Composition; D001499:Bayes Theorem; D002999:Clone Cells; D021903:DNA, Ribosomal Spacer / Q000235:genetics*; D019143:Evolution, Molecular; D005843:Geography; D010802:Phylogeny; D011157:Population Dynamics; D012091:Repetitive Sequences, Nucleic Acid / Q000235:genetics; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D013045:Species Specificity
chemical_list: D021903:DNA, Ribosomal Spacer