A critical review and a new proposal of karyotype asymmetry indices

In literature seven different methods of evaluating karyotype asymmetry - the TF%, the As K%, Stebbins' classification, the Rec and the Syi, the A(1) and the A(2), the DI, and the A - are used for the elucidation of phylogenetic relationships and taxonomic treatments within a particular group or taxon. The investigation of these seven methods reveals that the intervals used by Stebbins to separate the different types of karyotype asymmetry are very broad and only one quantitative parameter, the A(2) index, correctly describes the variation in chromosome length in a complement. A new asymmetry index (AI) is proposed to measure karyotype asymmetry and a new parameter, the CVCI, is offered, that precisely assesses the relative variation in centromere position in a complement. The AI index, the CVCI and the CVCL (= A(2) x 100) have the potential to display even minor karyotypic variations. Thus, these three indices together increase the precision of results in comparison with other existing methods. All this has important consequences as regards the interpretation of the results of karyological studies.