J Syst Evol ›› 2009, Vol. 47 ›› Issue (5): 402-415.DOI: 10.1111/j.1759-6831.2009.00041.x

• Reviews & Research Articles • Previous Articles     Next Articles

Molecular phylogeny of Solms-laubachia (Brassicaceae) s.l., based on multiple nuclear and plastid DNA sequences, and its biogeographic implications

1,5Ji‐Pei YUE 1Hang SUN 2David A. BAUM 3Jian‐Hua LI 4Ihsan A. AL‐SHEHBAZ 5Richard REE*   

  1. 1 (Key Laboratory of Biodiversity and Biogeography, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming 650204, China)
    2 (Department of Botany, University of Wisconsin, Madison, Wisconsin 53706, USA)
    3 (Arnold Arboretum and Harvard University Herbaria, 22 Divinity Avenue, Massachusetts 02318, USA)
    4 (Missouri Botanical Garden, P.O. Box 299, St. Louis, Missouri 63166-0299, USA)
    5 (Department of Botany, The Field Museum, 1400 S. Lake Shore Drive, Chicago, Illinois 60605, USA) * Authors for correspondence. E-mail: .
  • Received:2009-03-10 Published:2009-09-24


The Hengduan Mountains region of south-west China is a noted biodiversity hotspot, but the geographic origins and historical assembly of its rich endemic flora, including the sky-island species of Solms-laubachia Muschl. (Brassicaceae), have been little studied. Previous molecular studies on the phylogeny of Solms-laubachia showed it to be paraphyletic, leading to considerable expansion not only of its taxonomic limits, but also its geographic range, with the inclusion of taxa from outside the Hengduan region. However, these studies provided little resolution of interspecific relationships, preventing inferences about historical biogeography within the clade. In this study, new sequence data from two nuclear genes (LEAFY and G3pdh) and two chloroplast intergenic spacers (petN-psbM and psbM-trnD) were combined with existing markers to increase phylogenetic signal. Phaeonychium villosum (Maxim.) Al-Shehbaz was found to be nested within Solms-laubachia s.l. In general, phylogenetic relationships appear to be a good predictor of geography, with the Hengduan Mountain endemics embedded in a paraphyletic grade of species from the western Himalayas and central Asia, but also imply morphological homoplasy. Incongruence was detected between the nuclear and chloroplast gene trees, perhaps resulting from incomplete lineage sorting of ancestral polymorphisms. The crown age of Solms-laubachia s.l. was estimated to be around 1.42–3.68 million years ago, using Bayesian relaxed molecular clock analysis. Historical biogeographic analysis using a parametric dispersal-extinction-cladogenesis model inferred central Asia and the western Himalayas as most probable ancestral range of Solms-laubachia s.l., and estimated higher rates of eastward expansion than westward during the diversification of descendant lineages. In sum, our results suggest that Solms-laubachia s.l. originated during the Pliocene in central Asia, and subsequently migrated eastward into the Hengduan Mountains, colonizing sky-island, alpine scree-slope habitats that may have provided novel ecological opportunity and accelerated speciation, ultimately establishing this region as the present center of diversity of the genus.

Key words: Hengduan Mountains, biogeography, Brassicaceae, phylogeny, Solms-laubachia s.l.