The use of chromosome studies (i.e. number, structure, and behaviour) in taxonomic work. Chromosome number is probably the most frequently quoted feature of the * karyotype used by taxonomists. Chromosome counts are usually made on sporophytic tissue at mitosis and are therefore the diploid number (2n). When dealing with a polyploid series, the base number (i.e. the number of chromosomes present in the original haploid * genome) may be given. The position of the centromere is a reliable feature of chromosome structure and consequently makes a good * taxonomic character. More detailed studies of meiotic behaviour can reveal, for example, the heterozygosity of some * inversions. Such a feature may be consistent for a particular taxon, thus providing additional taxonomic evidence. Cytological data is sometimes thought to be of special significance, and may be ascribed more weight (see weighting) than other taxonomic evidence. |
