Intraspecific and interspecific genome size variation in Iberian Cyprinidae and the problem of diploidy and polyploidy, with review of genome sizes within the family

Intra- and interspecific genome size variations of all the cyprinid taxa of Portuguese fresh waters belonging to distinct karyotype groups - diploid ( 2n = 50), triploid (3n = 75) and tetraploid (2n = 100) - were compared. Nuc lear DNA content measurements by flow cytometry gave identical magnitudes o f genome size variation within and among populations of the two diploid (Ch ondrostoma polylepis and Rutilus macrolepidotus both with 2n = 50) and the polyploid (Barbus bocagei with 2n = 100) species analysed. No apparent corr elation could be found between DNA content and karyotype groups. The diploi d Gobio gobio has a typical polyploid DNA content and Barbus comiza, with 2 n = 100, exhibited a typical diploid value. This reinforces the lack of cor relation of this parameter with the generally assumed karyotype evolution f rom the diploid to polyploid levels. Changes in genome size could be affect ed by many small, independent cumulative changes, rather than through numer ical changes in karyotypes. The high genome size variation within the famil y really questions the traditional recognition of Cyprinidae as monophyleti c. A complete taxonomic survey using all available data, including chromoso mal and molecular markers, is needed to the definition of the primitive cyt otaxonomic condition. It is hypothesized that only a revised taxonomic conc ept of Cyprinidae will definitely allow clarification of the diploid-polypl oid relationships within the family.