Summary of plastid and nuclear sequence support for parentage of the allopolyploids in the North American Dryopteris complex. Colored lines connect diploids progenitors with allopolyploid offspring according to the “semicristata” hypothesis [12,14]. Warm colors (yellows, oranges, and pinks) denote support from the nuclear phylogenies, and cool colors (greens and blue) denote support from the plastid phylogeny. Maternal and paternal lineages are indicated by symbols. Outlines of pinnae from each species are given for comparison. Fraser-Jenkins  and Stein et al.  (based on work by Werth and Kuhn ) have produced reconstructions of D. semicristata that depict it as more similar to D. cristata or D. carthusiana, respectively.
Sessa et al. BMC Evolutionary Biology 2012 12:104 doi:10.1186/1471-2148-12-104