Abstract Detail

Phylogenomics

Stitzer, Michelle [1], Lindsley, Dale [1], Hall, Benjamin [2].

Phylogenomic reconstructions in Rhododendron subgenus Hymenanthes.

Rhododendron is a large (~1000 species) and diverse genus of woody plants native to the Northern Hemisphere, with major species richness in Southeast Asia. Taxonomic revisions throughout the 20^th century put differing emphasis on key morphological characters, including inflorescence placement, evergreen or deciduous habit, and the presence of leaf scales. Phylogenetic inquiries based on DNA sequences have revealed conflicting relationships, with chloroplast and multiple nuclear markers each supporting a different taxonomic organization. Although individual analyses broadly agree on the monophyly of major subgenera and sections, each marker studied strongly supports divergent subsectional relationships within the evergreen broadleaf elepidote subgenus Hymenanthes. It is unclear to what degree this discordance arises from hybridization between species or incomplete lineage sorting after rapid radiation into novel ecological environments. To accumulate a genomic perspective on these processes, we sampled approximately 2% of the 660 Mb rhododendron genome in 96 species using RAD-seq, focusing the majority of our sampling on subgenus Hymenanthes. RAD-seq isolates regions surrounding a restriction enzyme recognition site, and combined with paired-end Illumina sequencing, generates sequences that can be clustered into thousands of orthologous loci. Our approach samples the nuclear and chloroplast genomes, and we have analyzed each separately. We have used concatenated and species-tree based approaches to reconstruct the history of the genus, although computational limitations require subsampling for some nuclear analyses. Chloroplast and nuclear phylogenies both resolve the earliest divergence in the subgenus to be subsection Pontica, the only subsection found today outside of SE Asia. Four monotypic subsections are nested within established monophyletic subsections, supporting their reassignment. The two genomes present conflicting evidence for both the monophyly of and relationships between the remaining 19 morphologically defined subsections. Approximately half of all nuclear loci support the consensus topology, and further analyses will consider the causes. Biogeographic reconstruction and divergence dating based on the nuclear genome suggests an origin for Hymenanthes rhododendrons in central China in the Oligocene, followed by Miocene diversifications in Western China and Tibet, and upon entrance to the Himalayas. This reduced representation survey of the rhododendron genome presents support for taxonomic reclassification and evolutionary interpretations of this morphologically diverse and ecologically complex native of SE Asia.

Broader Impacts:

1 - University of Washington, Department of Biology, Box 351330, Seattle, WA, 98195, United States
2 - University of Washington, Department of Biology, BOX 35-1330, Seattle, WA, 98195-1330, USA

Keywords:
Rhododendron
next generation sequencing
RAD-seq
Phylogenomics.

Presentation Type: Oral Paper:Papers for Topics
Session: 36
Location: Magnolia/Riverside Hilton
Date: Tuesday, July 30th, 2013
Time: 5:15 PM
Number: 36015
Abstract ID:876
Candidate for Awards:Margaret Menzel Award