Systematics Section / ASPT
Refulio-Rodriguez, Nancy F. , Columbus, J. Travis .
Phylogenetic Relationship of the Recently Rediscovered Dissanthelium californicum (Poaceae: Pooideae).
DISSANTHELIUM californicum (Poaceae: Pooideae) is exceptional in the genus because it grows in the Northern Hemisphere near sea level in a Mediterranean climate. The only other low-elevation species in the genus of ca. 20 species is D. patagonicum which is found in southern Argentina. The remaining species all grow at high elevations (generally > 4000 m) in the Andes. Based on its morphology and geographic distribution, Hitchcock (1923) and O. Tovar (pers. comm.) speculated that D. californicum may be misplaced in the genus. Prior to 2005 the species was last collected in 1903 from the California Channel Islands and was the only native California grass considered presumed extinct. Its exciting rediscovery on Santa Catalina Island in 2005 permitted studies based on fresh material, including cytology and molecular phylogenetics. Using DNA sequences from two nuclear markers, ITS and Adh1, and two chloroplast markers, trnT–L–F and rpoB–trnCGCA, we investigated the phylogeny of Dissanthelium and its position in Pooideae. The results show that Dissanthelium is not monophyletic, because the monotypic Andean genera Anthochloa and Tovarochloa and species of Poa are nested within. Furthermore, D. californicum resolves in the clade, although there is insufficient sequence variation in these molecular markers to indicate its closest relative. A strong candidate is D. patagonicum, which shares with D. californicum spikelets sometimes with three (rather than two) florets, and pubescent lemmas. The data suggest that the presence of D. californicum in California is the result of a past long-distance dispersal event from South America.
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1 - Rancho Santa Ana Botanic Garden, 1500 North College Avenue, Claremont, California, 91711, USA
Presentation Type: Oral Paper:Papers for Sections
Date: Wednesday, August 2nd, 2006
Time: 4:30 PM