Systematics Section / ASPT
Jakob, Sabine S. , Blattner, Frank R. .
Chloroplast haplotype analysis and phylogeography of Hordeum (Poaceae).
The barley genus Hordeum L. occurs with 31 species in the meridional and temperate regions of the World. The center of diversity is southern South America with 16 di- and polyploid species. Phylogenetic analysis of the ITS region revealed a rapid and relatively recent radiation within this group during the last 2 Myr, while the immediate sister clade from European coastal habitats consists of only a single species. To uncover speciation mechanisms underlying this rapid radiation we first analyzed the phylogeographic structure of the South American and the related European species. About 1000 bp of the trnL-F chloroplast region of 500 individuals from all Hordeum species were sequenced and a chloroplast haplotype network for the entire genus was constructed. After the exclusion of hypervariable mononucleotide repeats, we got 56 haplotypes, which form geographically justified clades within this network. In Eurasia all species possess their own haplotypes and a relatively high number of interior haplotypes were undefined (empty). In the New World species the pattern was quite different with only few empty haplotypes and a high number of shared chloroplast types among different species. These differences were interpreted as the result of different phylogenetic and palaeoclimatic histories of the major clades, resulting in the loss of old types in Eurasia vs. preservation of nearly all types in the New World. The phylogeographical structures within the haplotype network supported the proposed migration routes of the genus throughout the world and show also a high degree of interspecific chloroplast exchange and, therefore, still permeable species boundaries in the Americas.
1 - Inst. of Plant Genetics and Crop Plant Research, Dept. of Taxonomy, Corrensstr. 3, Gatersleben, D-06466, Germany
Presentation Type: Paper
Location: Cottonwood A (Snowbird Center)
Date: Wednesday, August 4th, 2004
Time: 8:15 AM