First Nuclear DNA C-values for 25 Angiosperm Families.

DNA amount is a widely used biodiversity character. As known DNA C-values represent the global angiosperm flora poorly, better coverage of taxonomic groups is needed, including at the familial level. A workshop, sponsored by Annals of Botany , was held at the Royal Botanic Gardens, Kew in 1997. Its key aim was to identify major gaps in our knowledge of plant DNA C-values and recommend targets for new work to fill them by international collaboration. In 1997 C-values were known for approx. 150 families, meaning there was no estimate for most angiosperm families (approx 68%). The workshop recommended a goal of complete familial representation by 2002, as a main target for angiosperms. Bennett et al . ( Annals of Botany86 : 859-909, 2000) presented a fifth supplementary list of angiosperm C-values from 70 original sources which included first C-values for 691 species. Only 12 (1.7%) of these were first C-values for unrepresented families, so the need to improve familial representation was substantially unmet. We began new work to address this in September 1999, and now report first DNA C-values for 25 angiosperm families. Such targeting seems essential to achieve the goal of familial coverage set by the 1997 workshop within 5 years. 4C values range from 0.67 pg (similar to Arabidopsis thaliana ) in Amoreuxia wrightii (Cochlospermaceae) to 7.49 pg in Deutzia prunifolia (Hydrangeaceae). These data support the view that ancestral angiosperms almost certainly had small genomes (defined as 1C ⩽ 3.5 pg). Chromosome counts are reported for 19 taxa, including first records for three genera plus four species.