Nuclear DNA C-values complete familial representation in gymnosperms

Abstract

The gymnosperms are a monophyletic yet diverse group of woody trees with approx. 730 extant species in 17 families. A recent survey showed that DNA C-values were available for approx. 16% of species, but for only 12 of the 17 families. This paper completes familial representation reporting first C-values for the five remaining families: Boweniaceae, Stangeriaceae, Welwitschiaceae, Cephalotaxaceae and Sciadopityaceae. C-values for nine Ephedra and two Gnetum species are also reported. C-values are now available for 152 (21%) species. Analysis confirms that gymnosperms are characterized by larger C-values than angiosperms (modal I C of gymnosperms = 15.8 pg compared with 0.6 pg in angiosperms) although the range (IC = 2.25-32.20 pg) is smaller than that in angiosperms (IC = 0.05-127.4 pg). Given complete familial coverage for C-values and increasing consensus in gymnosperm phylogeny, the phylogenetic component of C-value variation was also investigated by comparing the two datasets. This analysis revealed that ancestral gymnosperms (represented by cycads and/or Ginkgo; mean genome size = 14.71 pg) probably had larger genomes than ancestral angiosperms. © 2001 Annals of Botany Company.