Systematics Section / ASPT
Wen, Jun , Lee, Chunghee .
Evolution of intercontinental biogeographic disjunctions between Asia and the New World: insights from the ginseng plant family.
The disjunct distributions of plants between Asia and North America have been actively studied recently. Many taxa were supported to have migrated from Asia into the New World, and their divergence times were estimated to be mostly in the Miocene and the Pliocene with molecular methods. Most recent phylogenetic studies of the disjuncts have a sampling bias toward north temperate taxa. We herein use the Araliaceae, which have at least five major lineages showing disjunctions between Asia and the New World, as a biogeographic model to examine the diversification dynamics. We report results from Aralia, Panax, and Oplopanax from temperate Asia and North America; and Dendropanax, and the Oreopanax – Sinopanax clade from tropical/subtropical Asia and the neotropics, using nuclear ribosomal ITS, and chloroplast trnL-F and ndhF sequences. A rapid early evolutionary radiation was supported for a major clade (20 genera) of Araliaceae in Asia. Even though the Aralia – Panax clade has higher species richness in Asia (66 species, vs. 16 species in the New World), the dispersal-vicariance analysis found the New World as the ancestral area of the clade. Four intercontinental disjunctions were supported within the clade and were estimated to have occurred 10, 25, 26, and 36 million years ago (mya) using the penalized likelihood method. A strong biogeographic barrier between mainland Asia and Australasia was suggested. An ancient divergence was suggested between the tropical Asian and neotropical disjunct lineages in Dendropanax (46 mya) and in the Oreopanax – Sinopanax clade (35 mya). The Asian and North American disjunction in the cold temperate Oploplanax was estimated to be recent ca. 5 mya. Our Araliaceae studies demonstrate the complex and sometimes highly nonparsimonious migration history of plants between Asia and the New World in the Tertiary, and also support the more ancient disjunctions in tropical than temperate lineages.
1 - University of California, Botany and Plant Sciences, Riverside, California, 92521
2 - Field Museum, Botany Department, 1400 S. Lake Shore Dr., Chicago, Illinois, 60605-2496, USA
Presentation Type: Paper
Location: Cottonwood A (Snowbird Center)
Date: Wednesday, August 4th, 2004
Time: 8:45 AM