Parasitology



Deep divergence among subgenera of Gyrodactylus inferred from rDNA ITS region


M. S.  ZIETARA  a1 a2 a3 c1 , T.  HUYSE  a1 , J.  LUMME  a3 and F. A.  VOLCKAERT  a1
a1 Laboratory of Aquatic Ecology, Katholieke Universiteit Leuven, Ch. de Bériotstraat 32, B-3000 Leuven, Belgium
a2 Biological Station, Gdansk University, Ornitologów 26, PL-80-680 Gdansk-Górki Wsch., Poland
a3 Department of Biology, University of Oulu, POB 3000, Fi-90014 Oulun Yliopisto, Finland

Article author query
zietara m   [PubMed][Google Scholar] 
huyse t   [PubMed][Google Scholar] 
lumme j   [PubMed][Google Scholar] 
volckaert f   [PubMed][Google Scholar] 

Abstract

This paper adds new insight to a molecular phylogeny of Gyrodactylus, based on a complete sequence of the ITS rDNA region of 4 subgenera and a more detailed molecular analysis. We propose a hierarchical approach in elucidating the phylogeny of this species-rich genus. A total of 37 sequences (915–1239 bp) from 10 representative species from 4 out of 6 subgenera, as defined by Malmberg (1970), are included in the analysis. Genetic differences observed at the 5.8S locus provide objective criteria to separate (sub)genera, while deep genetic differences of the spacers form a sound basis for species-specific identification. We demonstrate that each Gyrodactylus subgenus possesses a unique sequence of the 5.8S gene. Thus, there is concordance between the 5.8S gene and the excretory system used by Malmberg (1970) as a diagnostic character of subgenus status. At the species level, there is a discrepancy between morphological and molecular variation. Whereas the morphological variation, expressed in the shape and size of the attachment apparatus, is very low, the molecular variation, expressed at the ITS1 and ITS2 regions, is very high. This can be attributed either to the fast evolving ITS region or to the fact that the genus consists of groups of a higher taxonomic level than previously recognized. Perspectives and limitations of using the ITS rDNA region for a molecular phylogeny of this genus are discussed.

(Received April 27 2001)
(Revised August 6 2001)
(Accepted August 6 2001)


Key Words: ITS; 5.8S rRNA gene; Monogenea; phylogeny; Gyrodactylus.

Correspondence:
c1 Corresponding author: Gdansk University, Biological Station, 80-680 Gdansk, Ornitologów 26, Poland. Tel: +48 58 3080714. Fax: +48 58 3080703. E-mail: zietara@biotech.univ.gda.pl


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