J Syst Evol ›› 2010, Vol. 48 ›› Issue (3): 161-174.DOI: 10.1111/j.1759-6831.2010.00077.x

• Research Articles • Previous Articles     Next Articles

Molecular phylogenetic analysis of Leibnitzia Cass. (Asteraceae: Mutisieae: Gerbera-complex), an Asian-North American disjunct genus

1Kristen E. BAIRD 2Vicki A. FUNK 2Jun WEN 1Andrea WEEKS*   

  1. 1(Department of Environmental Science and Policy, George Mason University, Fairfax, Virginia 22030, USA)
    2(US National Herbarium, Smithsonian Institution, MRC 166, P.O. Box 371012, Washington, DC 20013-7012, USA)
  • Received:2009-12-09 Published:2010-05-18

Abstract: Leibnitzia comprises 6 species of perennial herbs that are adapted to high elevation conditions and is one of only two Asteraceae genera known to have an exclusively disjunct distribution spanning central to eastern Asia and North America. Molecular phylogenetic analysis of Leibnitzia and other Gerbera-complex members indicates that Leibnitzia is monophyletic, which is contrary to our expectation that American Leibnitzia species, L. lyrata and L. occimadrensis, would be more closely related to another American member of the Gerbera-complex, Chaptalia. Ancestral area reconstructions show that the historical biogeography of the Gerbera-complex mirrors that of the entire Asteraceae, with early diverging lineages located in South America that were followed by transfers to Africa and Eurasia and most recently to North America. Intercontinental transfer of Leibnitzia appears to have been directed from Asia to North America. Independent calibrations of nuclear (rDNA internal transcribed spacer region) and chloroplast (trnL-rpl32 intron) DNA sequence data using relaxed clock methods and either mean rate or fossil-based priors unanimously support Miocene and younger divergence times for Gerbera-complex taxa. The ages are not consistent with most Gondwanan vicariance episodes, and thus the global distribution of Gerberacomplex members must be explained in large part by long-distance dispersal. American species of Leibnitzia are estimated to have diverged from their Asian ancestor during the Quaternary (ca. 2 My) and either migrated overland to North America via Beringia and retreated southwards along high elevation corridors to their present location in southwestern North America or were dispersed long-distance.

Key words: Beringia, biogeography, Gerbera-complex, Mutisieae.