Sigel, Erin M. , Windham, Michael D. , Pryer, Kathleen M. .
To have or have not: Using farina to delineate major clades within the false cloak ferns (Argyrochosma).
Among ferns, the xeric-adapted cheilanthoids (Pteridaceae), provide a prime example of convergent evolution. Genera in this group have been circumscribed using a suite of morphological characters (e.g., leaf dissection and pubescence, presence or absence of a false indusium) that directly relate to the plant’s ability to survive in arid environments. Dependence on such easily observed, but potentially homoplastic, characters to define taxa in this group has resulted in a taxonomic conundrum: nearly every major genus has been shown to be polyphyletic. Here we present the first plastid multigene (rbcL, atpA, and trnG-trnR) phylogeny of the strictly New World cheilanthoid genus Argyrochosma, the false cloak ferns. Our data strongly support the monophyly of this group and its exclusion from Notholaena sensu lato. We use our phylogeny to assess patterns of morphological evolution in the genus through character mapping and ancestral state reconstruction. Our data indicate that Argyrochosma is divided into two major clades– one exclusively non-farinose, and the other primarily farinose. Within the latter clade, at least two separate losses of farina have occurred in the polyphyletic A. nivea var. tenera. In addition to clarifying patterns of morphological evolution, the phylogenetic hypotheses presented here provide a critical context for addressing the ecology and geographic distribution of Argyrochosma species in North and South American deserts.
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1 - Duke University, Department of Biology, 139 Biological Sciences Building, PO Box 90338, Durham, North Carolina, 27708, USA
Presentation Type: Oral Paper:Papers for BSA Sections
Location: Alpine B/Snowbird Center
Date: Monday, July 27th, 2009
Time: 10:30 AM