Folk, Ryan , Freudenstein, John .
Reticulate Evolution and Phylogenetic Relationships in the Genus Heuchera (Saxifragaceae).
Heuchera (Saxifragaceae) is an endemic and widely distributed North American herbaceous genus of about 40 species, well-known for its confusing patterns of reticulation both ancient and recent, as well as a frequent occurrence of autopolyploidy. With a view to elucidating the significance and pattern of these two processes, we have improved upon previous efforts at estimating the phylogeny of Heuchera using sequences from trnL-F, rpl32-trnL, ITS, and GBSSI-B (approx. 4,050 bp total) and more extensive taxonomic and infraspecific sampling as well as chromosome counts for all accessions. All loci demonstrate comparatively limited variation consistent with a recent and rapid radiation of the genus. Our parsimony and model-based phylogenetic analyses show a strong incongruence between nuclear and chloroplast trees, revealing three highly distinct chloroplast haplotypes and suggesting at least 3 chloroplast capture events with moderate to strong support: one from the genus Tiarella to a clade consisting of geographically broadly distributed subsections Micranthae, Pilosissimae, Villosae, and Cylindricae (the Euheuchera clade), another from the Euheuchera clade to the eastern subsection Americanae, and a third from the Mitella nuda/diphylla lineage to all but two species of the southwestern subsection Caespitosae. Within the Caespitosae chloroplast clade the tetraploid and northernmost species H. caespitosa has moderate support as sister to the diploid remainder of the group, and direct sequencing of GBSSI-B has shown clear evidence of allopolyploid origin for this taxon. Nuclear trees divide the genus into two sister clades, one consisting of the Euheuchera clade and the second consisting of all other species. Within the latter of these, section Rhodoheuchera is supported as monophyletic and the new and enigmatic H. woodsiaphila is clearly placed within. A clade consisting of Rocky Mountain endemics, previously considered unrelated, was also recovered.
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1 - The Ohio State University, 1315 Kinnear Road, Columbus, OH, 43220, USA
2 - Ohio State University, MUSEUM OF BIOLOGICAL DIVERSITY, 1315 KINNEAR RD, COLUMBUS, OH, 43212-1157, USA
Presentation Type: Oral Paper:Papers for Sections
Location: Delaware B/Hyatt
Date: Wednesday, July 11th, 2012
Time: 5:30 PM