Genetic Evidence for Allopolyploidy in the Neotropical Fern Hemionitis pinnatifida (Adiantaceae) and the Reconstruction of an Ancestral Genome

Abstract

Genetic evidence from enzyme electrophoresis and restriction site analyses of cpDNA was employed to explore the origin of the tetraploid Hemionitis pinnatifida by determining the role of diploid species of Hemionitis in contributing to the tetraploid genome. The results clearly supported the hypothesis that H. pinnatifida is an allotetraploid with H. palmata as one of its diploid progenitors. The other diploid parent was not identified among the existing species of Hemionitis and is either extinct or exceedingly rare. Genetic identity analyses compared the extant diploid genomes with the divergent diploid genomes combined in tetraploids. One of these divergent genomes was shown to be a good approximation of that of H. palmata, and the other is a reconstruction of that of the missing diploid parent. These analyses demonstrated that the missing ancestor was genetically more similar to H. palmata than either of these species is to the other diploid species surveyed. Such greater genetic similarity may have been important in allowing hybridization between the two diploid progenitors of H. pinnatifida. The data also suggest that tetraploid individuals may have been synthesized de novo at least five times among the three populations surveyed.