Diversification and reticulation in the circumboreal fern genus Cryptogramma

• Published in: Molecular phylogenetics and evolution 2013-06, Vol.67 (3), p.589-599
• Main Authors: Metzgar, Jordan S., Alverson, Edward R., Chen, Sinian, Vaganov, Alexey V., Ickert-Bond, Stefanie M.
• Format: Article
• Language: English
• Subjects: alleles; allopolyploidy; backcrossing; Chromosomes, Plant; Coniogramme; Cryptogramma; data collection; DNA; Evolution, Molecular; Ferns - classification; Ferns - genetics; ferns and fern allies; gapCp; Genetic Variation; Haploidy; Introgression; loci; Molecular Sequence Data; monophyly; nucleotide sequences; parsley; Phylogeny; Phylogeography; Plastids - genetics; Polyploidy; Pteridaceae; Tetraploidy
• ISSN: 1055-7903; 1095-9513
• DOI: 10.1016/j.ympev.2013.02.020

[Display omitted] ► Cryptogramma is monophyletic based on plastid sequence data. ► Most described Cryptogramma species are taxonomically valid monophyletic lineages. ► European Cr. crispa is an ancient autotetraploid. ► New World tetraploid Cr. sitchensis formed by Cr. acrostichoides and Cr. raddeana. ► Nuclear sequence data in Cr. acrostichoides complex exhibit signs of introgression. We investigated the evolutionary complexity that resulted from cryptic diversification and polyploidy in parsley ferns (Cryptogramma). A total of 14 species were included in our data set, with six outgroup species and eight Cryptogramma species. DNA sequence data from six plastid loci (rbcL, rbcL–accD, rbcL–atpB, rps4–trnS, trnG–trnR and trnP–petG) were analyzed using maximum likelihood and Bayesian methods to provide the first rigorous assessment of diversification in the genus, including testing the monophyly of the genus and sections. Cryptogramma and Coniogramme are recovered as reciprocally monophyletic sister genera. We established the monophyly of both sections within Cryptogramma. Furthermore, our sequence data reveal that described species reflect mostly allopatric reciprocally monophyletic lineages that are independent evolutionary trajectories. Using sequence data from the nuclear locus (gapCp) we find that the European C. crispa is an autotetraploid with a partially diploidized genome, while the North American tetraploid Cryptogramma sitchensis is an allopolyploid derived from C. acrostichoides and C. raddeana. Subsequent backcrossing between C. sitchensis and C. acrostichoides has allowed the introgression of C. raddeana alleles into northern populations of C. acrostichoides.