Various hypotheses of the parentage of the Dryopteris polyploids in North America.A) The “semicristata” hypothesis [12,14]. B) The “reinterpretation” hypothesis . CF) Alternate hypotheses for the putative offspring of “D. semicristata” that employ only extant taxa [29,40,43,49]. G) Alternate hypothesis for D. campyloptera. H) Alternate hypothesis for D. celsa. IK) Hypotheses for D. filix-mas[30,33,50]. G and I indicate proposed instances of autopolyploidy. Diploids are depicted as solid circles, tetraploids as open squares, and hexaploids as open hexagons. Lines connect polyploids with their putative parental taxa. Inferred genomes are indicated as letters below taxon names. For ease of comparison, all diagrams use the same labeling scheme (e.g. II = D. intermedia, etc.), although several of the original publications employed an A, B, C, etc. labeling scheme for the various genomes. See Table 1 for additional references to hypotheses.
Sessa et al. BMC Evolutionary Biology 2012 12:104 doi:10.1186/1471-2148-12-104