Systematics/Phytogeography / Taxonomie/ Section
Price, Taina M. .
Molecular phylogeny of Phemeranthus Raf. (Portulacaceae), a North American xerophytic plant genus.
The genus Phemeranthus Raf. (Portulacaceae) comprises about 27 species of succulent, herbaceous perennials with terete leaves, most of which are found in patchy xeric habitats such as rock outcrops and sand barrens. Like other elements of the so-called Madro-Tertiary Geoflora, its center of diversity is in northern Mexico and the southwestern United States. However, xeric habitats in North America are not restricted to the desert Southwest. In the glade and flat-rock ecosystems of the interior highlands and southeastern United States, local patches of desert-like conditions host numerous species with western affinities. Among these, Phemeranthus species stand out for their extreme xerophytic adaptation, actively growing and flowering in the shallowest soils throughout the height of summer. Phemeranthus species exhibit wide variation in geographic range size and habitat specificity. Some are widespread in North America, while others are endemic to one or a few localities. Some appear to be edaphic specialists, while others occur on a relatively wide range of soil types. This variation makes the genus an ideal system to study the patterns and processes involved in the evolution of speciesí distributions. Originally erected in 1801, Phemeranthus was long included in Talinum. However, Phemeranthus species are distinguished from Talinum by numerous morphological characters, and molecular data indicate that the two groups are not closely related. Preliminary phylogenetic analyses of multiple chloroplast, mitochondrial, and nuclear sequence regions indicate that Phemeranthus [excluding Talinum aurantiacum] is monophyletic and contains two monophyletic subgenera: a southern clade distributed primarily in Mexico, and a northern clade distributed primarily in the United States. The molecular phylogeny will provide a foundation to address a variety of questions regarding the evolution of this xerophytic plant group.
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1 - Washington University in St. Louis, Biology, Campus Box 1137, 1 Brookings Drive, St. Louis, MO, 63130, United States
Presentation Type: Oral Paper:Papers for Sections
Location: Room 1/Woodward
Date: Monday, July 28th, 2008
Time: 9:45 AM