Metzgar, Jordan , Ickert-Bond, Stefanie M. .
Diversification and reticulation in the circumboreal parsley ferns (Cryptogramma).
We investigated the evolutionary complexity that resulted from cryptic diversification and polyploidy in parsley ferns (Cryptogramma) and clarified the origin of polyploid lineages by integrating evidence from multiple biosystematic approaches. Within Pteridaceae, Cryptogramma is in the basal cryptogrammoid clade (Llavea-Coniogramme-Cryptogramma) and the genus consists of nine species found in boreal habitats across the world, as well as southern South America. Forty samples from a total of 14 species were included in our data set, including 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 parsimony, maximum likelihood and Bayesian inference 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. Species boundaries have been contested, with estimates ranging from two essentially circumboreal species to nine geographically discrete species. Our sequence data reveal that most described species reflect mostly allopatric reciprocally monophyletic lineages that are independent evolutionary trajectories. We also use sequence data from the nuclear locus (gapCp) to reconstruct the history of polyploid taxa, including the identification of their diploid progenitors. 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. Chromosome number evolution is reconstructed across the phylogeny using an explicit maximum likelihood modeling approach. The base chromosome number for Cryptogramma is inferred to be x=30, with two polyploidization events shown to be the only chromosome changes in the genus.
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1 - University Of Alaska Fairbanks, Museum Of The North, 907 Yukon Drive, Fairbanks, AK, 99775, USA
2 - University Of Alaska Museum Of The North, Herbarium (ALA) And Dept. Of Biology And Wildlife, University Of Alaska Fairbanks, 907 Yukon Dr., Fairbanks, AK, 99775, USA
Presentation Type: Oral Paper:Papers for Sections
Location: Union E/Hyatt
Date: Monday, July 9th, 2012
Time: 10:45 AM