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Abstract Detail


Systematics Section / ASPT

Oh, Sang-Hun [1], Tripp, Erin A. [1], Stone, Donald E. [1], Manos, Paul S. [1].

Phylogeny and biogeography of Juglans (Juglandaceae) based on nuclear DNA sequences.

With a rich fossil history and disjunct distribution, the economically important genus Juglans provides an excellent case to investigate historical biogeography. This genus of 20 species has been divided into four sections based on leaf, fruit, and seedling characteristics, but their relationships are unclear. Members of sect. Rhysocaryon (black walnut, 16 species) are distributed in North and South America and the West Indies; J. cinerea, the sole member of sect. Trachycaryon (American butternut) is native to eastern North America; and the two species of sect. Cardiocaryon (Asian butternut) occur in eastern Asia. Juglans regia (Persian walnut) in the monotypic sect. Juglans occupies mountain slopes extending from southeastern Europe to western Asia. Phylogenetic analyses of the combined nucleotide sequences of the ITS and ETS regions of nrDNA and the second intron of LEAFY supported the monophyly of four sections: sect. Rhysocaryon is sister to (sect. Juglans - (sect. Trachycaryon + sect. Cardiocaryon)). The data support a vicariance and subsequent dispersal scenario suggesting that the most recent common ancestor of Juglans was widely distributed in North America and Eurasia and that the ancestor of butternuts originated in Eurasia and spread to North America. The divergence between J. cinerea and Asian butternuts was estimated to be very recent (2 ± 0.4 MYBP) based on the penalized likelihood method. Two major clades were resolved within sect. Rhysocaryon, one that includes South American and Caribbean species, the other containing species from the US and adjacent areas in northern Mexico. Mesoamerican species, specifically ones from southern Mexico and Guatemala, form a clade with South American species. Age estimation of the South American black walnut clade (6 ± 1.2 MYBP) suggests that southward dispersion likely occurred prior to the closure of the Isthmian marine portal, consistent with fossilized walnuts from the Late Miocene of Ecuador.


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1 - Duke University, Department of Biology, 139 Biological Sciences Building, PO Box 90338, Durham, North Carolina, 27708, USA

Keywords:
Juglans
biogeographty
ITS
ETS
LEAFY.

Presentation Type: Oral Paper:Papers for Sections
Session: CP43
Location: Stevens 3/Hilton
Date: Wednesday, July 11th, 2007
Time: 10:15 AM
Number: CP43008
Abstract ID:2034


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