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Abstract Detail


Systematics/Phytogeography / Taxonomie/ Section

Schenk, John J. [1], Hufford, Larry [2].

Age Estimates of Clade Diversification in Loasaceae.

Analyses of clade diversification in Loasaceae have been limited by the paucity of fossils for the family and unknown divergence times for clades.  In contrast to Loasaceae, its sister family Hydrangeaceae and other Cornales have relatively rich fossil records.  In order to infer divergence times in Loasaceae using molecular dating, we reconstructed a phylogeny for Cornales and outgroups that allowed the incorporation of 16 fossil calibration points.  Penalized likelihood was used to analyze sequences from the plastid matK region.  Our results indicate Loasaceae and Hydrangeaceae diverged 92-58 million year before present (MYBP).  Crown group diversification in Loasaceae, including the origin of Eucnide, began 87-51 MYBP.  Mentzelia, which has been hypothesized to be of recent origin, diverged from Gronovioideae 70-35 MYBP, and the crown Mentzelia were estimated to have diverged during the Paleocene-Oligocene (60-27 MYBP); however, five of its six sections diverged only in the Oligocene-Pliocene (26-3 MYBP).  The five genera of Gronovioideae diverged 61-11 MYBP.  Subfamily Loasoideae, which has its greatest species richness in South America, was estimated to have a stem lineage originating in the Late Cretaceous-Eocene (74-41 MYBP) with diversification of the crown lineage in the Eocene-Miocene (54-21 MYBP).  North and South America were separated prior to the Late Cretaceous, the earliest time when Loasoideae could have diverged, and the concordant formation of a volcanic archipelago connecting North and South America at this earliest possible time for the origin of Loasoideae lead us to favor dispersal of the clade southward at that time, although long distance dispersal cannot be ruled-out.  The separation of Africa and South America well before the origin of Kissenia (46-17 MYBP), an African endemic, makes dispersal rather than vicariance the likely cause of its current distribution.


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1 - Washington State University, School of Biological Sciences, 312 Abelson Hall, PO Box 644236, Pullman, WA, 99164-4236, United States
2 - Washington State University, School of Biological Sciences, Po Box 644236, Pullman, Washington, 99164-4236, USA

Keywords:
Cornales
Molecular clock
penalized likelihood
Relaxed clock
intercontinental migration.

Presentation Type: Oral Paper:Papers for Sections
Session: 16
Location: Room 3/Woodward
Date: Monday, July 28th, 2008
Time: 1:00 PM
Number: 16001
Abstract ID:266


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