Nuclear DNA Amounts in Pteridophytes

Abstract

DNA amounts (C-value and genome size) are much-used biodiversity characters. A workshop held at Kew in 1997 identified major gaps in our knowledge of plant DNA amounts, recommending targets for new work to fill them. Murray reviewed non-angiosperm plants noting that representation of pteridophyte species (approx. 0.42%) was poor, while locating C-value data for them was very difficult. The workshop confirmed the need to make data for other groups besides angiosperms accessible for reference purposes. This paper pools DNA C-values for 48 pteridophyte species from eight original sources into one reference source, and fulfils a key workshop recommendation for this group. Comparing these data shows that nuclear 1C-values in pteridophytes vary approx. 1000-fold, from 0.055pg in Selaginella species to about 55pg in Ophioglossum petiolatum. Genome size estimates for 25 pteridophytes vary approx. 200-fold from 0.055 to 10.7pg, and the mean genome sizes in diploids and polyploids (5.15 and 4.59pg, respectively) are not significantly different. Wider comparisons show that ranges of genome sizes in the major groups of land plants are very different. Those in bryophytes and pteridophytes are narrow compared with those in gymnosperms and angiosperms. The data indicate that the origin of land plants possibly involved a first major increase in genome size in the evolution of vascular plants, while a second such increase occurred later in gymnosperms. C-values for pteridophytes remain very few, but conversely opportunities for new work on them are many.