The phylogenetics and biogeography of Leibnitzia (Asteraceae: Mutiseae): American species in an Asian genus
Date
2009-09-29T14:12:17Z
Authors
Baird, Kristen
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Abstract
Evolutionary relationships among the seven genera of the Gerbera daisy complex (Asteraceae) remain largely untested due to their well-acknowledged need for taxonomic revision. Here I present a phylogenetic analysis of the Gerbera-complex that tests the monophyly of one constituent genus, Leibnitzia Cass. (6 spp.). Historically Leibnitzia comprised four species distributed from the Himalayan Plateau to eastern Asia. Two montane southwestern North America species, Leibnitzia lyrata (Sch.Bip.) Nesom and L. occimadrensis Nesom, were subsequently placed in Leibnitzia based on the similarity of their achene trichomes. The distribution of these two species overlaps with that of Chaptalia Vent., a morphologically similar New World genus of the Gerbera-complex. Nuclear (ITS) and chloroplast (trnL-rpl32 intron) DNA sequence data from accessions of Leibnitzia, Chaptalia, and other Gerbera-complex genera were analyzed in order to test the hypothesis that American Leibnitzia are more closely related to Chaptalia than to Asian Leibnitzia. Our findings confirm the monophyly of Leibnitzia and its remarkable biogeographic disjunction. Asian-American disjunctions are typically observed in temperate forest taxa distributed between eastern Asia and eastern North America. Leibnitzia, by contrast, occupies open, semi-arid temperate to sub-tropical montane habitat and is distributed widely across Asian and Central America. To our knowledge, this disjunction is unique in the flowering plant family Asteraceae and provides an interesting new example of the Asian-American disjunction pattern.
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Keywords
Phylogenetics, Biogeography, Asteraceae, Leibnitzia, Gerbera, Systematics