Phyletic hot spots for B chromosomes in angiosperms.
We determined whether supernumerary B chromosomes were nonrandomly distributed among major angiosperm lineages and among lineages within families, as well as the identity of lineages with unusually high B-chromosome frequencies (hot spots). The incidence of B chromosomes for each taxon was gathered from databases showing species with and without these chromosomes (among species with known chromosome numbers). Heterogeneity was found at all ranks above the species level. About 8% of monocots had B chromosomes versus 3% for eudicots; they were rare in nonmonocot basal angiosperms. Significant heterogeneity in B-chromosome frequency occurred among related orders, families within orders, and major taxa within families. There were many B-chromosome hot spots, including Liliales and Commelinales at the order level. At the family level, there was a trend suggesting that B-chromosome frequencies are positively correlated with genome size.
Levin
Donald A
DA
Section of Integrative Biology, University of Texas, Austin, Texas 78713, USA. dlevin@uts.cc.utexas.edu
Palestis
Brian G
BG
Jones
R Neil
RN
Trivers
Robert
R
D032461:Chromosomes, Plant / Q000235:genetics*; D019143:Evolution, Molecular; D018745:Genome, Plant; D019684:Magnoliopsida / Q000235:genetics*; D010802:Phylogeny; D013045:Species Specificity