Systematics/Phytogeography / Taxonomie/ Section
Villarreal A., Juan Carlos , McFarland, Kenneth D. , Goffinet, Bernard .
Phylogenetic relationships within the Nothoceros alliance: the origin of the asexual Appalachian endemic Megaceros aenigmaticus.
Phylogenetic inferences from rbcL, nad5 and 18S sequences resolved the genus Megaceros (Dendrocerotaceae) as paraphyletic with all new world Megaceros nested within the austral genus Nothoceros. The definition and the relationships of the twenty-one American species of Megaceros within this complex remain ambiguous in the absence of critical taxonomic and phylogenetic treatments for this group, for which most species are poorly known, and often only from the type specimen. Here we present a phylogeny using three chloroplast loci, a portion of the nad5-4 mitochondrial spacer and the nuclear ITS region for the Nothoceros alliance (which includes American Megaceros plus Nothoceros). Our reconstruction confirms the polyphyly of Megaceros. The New Zealand N. giganteus and the Austral American N. endiviaefolius makes up a sister-group to the Austral American M. fuegiensis. The other five species of Megaceros form a monophyletic group that diverged from a common ancestor with the previous clade. The asexual Southern Appalachian endemic Megaceros aenigmaticus has a Neotropical origin and probably originated from cloud forest ancestors. Megaceros aenigmaticus shares a common ancestor with Paramo populations from the Neotropics suggesting a recent origin of the species (2-5MYA) coinciding with the availability for plant colonization of the high tropical alpine areas during the Plio-Pleistocene. Presence/absence of pyrenoid, a key morphological feature to define genera within the family Dendrocerotaceae, seems to be homoplastic within the Nothoceros alliance and invites a re-evaluation of this trait from an ultrastructural/physiological perspective.
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1 - University of Connecticut, Ecology and Evolutionary Biology, 75 North Eagleville Road, Storrs, CT, 06269, united States
2 - University of Tennessee, Department of Botany, 437 Hesler Biology Bldg, 1406 Circle Drive, Knoxville, Tennessee, 37996-1100, USA
3 - University of Connecticut, Ecology & Evolutionary Biology, 75 North Eagleville Road, U-3043, Storrs, Connecticut, 062693043, USA
Presentation Type: Poster:Posters for Sections
Location: Ball Room & Party Room/SUB
Date: Monday, July 28th, 2008
Time: 12:30 PM