State of the art in cytogenetics, insights into chromosome number evolution, and new C-value reports for the fern family Gleicheniaceae.

ABSTRACT

Studies concerning the cytogenetics of Gleicheniaceae have been scarce, especially those employing evolutionary approaches. Two chromosome number evolutionary models have been hypothesized for Gleicheniaceae. One proposes that ancestral haploid numbers were small and that the chromosome numbers of extant species evolved through polyploidy. The other model proposes that, at the genus level, fern chromosome evolution occurred from ancestors with essentially the same high chromosome numbers seen in living lineages. Neither of those hypotheses has been tested based on phylogenetic frameworks. We sought to (i) present the state of the art of Gleicheniaceae chromosome numbers; (ii) test the two evolutionary models of chromosome numbers within a phylogenetic framework; (iii) test correlations between DNA contents and chromosome numbers in the family. We report here DNA C-values for five species, which increases the number of investigated taxa nearly twofold and report two new genera records. Ancestral state chromosome reconstruction corroborates the hypothesis that ancestral chromosome numbers in Gleicheniaceae were as high as those of extant lineages. Our results demonstrate the possible role of dysploidy in the evolutionary chromosome history of Gleicheniaceae at the genus level and suggest that the relationship between chromosome number and DNA content does not appear to be linear.