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Molecular divergence between disjunct taxa in eastern Asia and eastern North America
Author(s) -
Lee Nam Sook,
Sang Tao,
Crawford Daniel J.,
Yeau Sung Hee,
Kim SeungChul
Publication year - 1996
Publication title -
american journal of botany
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.218
H-Index - 151
eISSN - 1537-2197
pISSN - 0002-9122
DOI - 10.1002/j.1537-2197.1996.tb13926.x
Subject(s) - biology , disjunct , taxon , divergence (linguistics) , evolutionary biology , genetic divergence , disjunct distribution , vicariance , phylogenetic tree , botany , phylogeography , genetics , genetic diversity , population , gene , linguistics , philosophy , demography , sociology
Eastern Asian‐eastern North American disjuncts in four genera were examined for allozyme divergence and sequence divergence of the internal transcribed spacers (ITS) of nuclear ribosomal DNA. The disjunct pairs of taxa include Caulophyllum robustum‐C. thalictroid.es, Menispermum dauricum‐M. canadense, Penthorum chinense‐P. sedoides , and Phryma leptostachya var. asiatica‐P. leptostachya var. leptostachya. Allozyme divergence was comparable in Caulophyllum and Penthorum (genetic identities of 0.534 and 0.546) and was considerably higher than between pairs of taxa in Menispermum (0.273) and Phryma (0.291). Caulophyllum and Penthorum , which have the highest genetic identities at allozyme loci, also have low ITS sequence divergences (1.30 and 1.65%, respectively). Phryma , which has low isozyme identity, also has the highest ITS sequence divergence (4.46%). The two taxa of Menispermum have low ITS sequence divergence (0.93%) despite having a low identity (0.273) at allozyme loci. The results suggest that divergence between the taxa in the four genera are not the result of a single historical event. Estimated divergence times are reasonably consistent with a late Miocene disjunction for Caulophyllum and Penthorum , whereas the age of the Phryma disjunction is calculated at over 20 million years. The nonconcordant divergences between allozymes and ITS sequences in Menispermum may be caused by concerted evolution in the latter or possibly longer generation time in the woody plants. Additional molecular data are needed to clarify the situation.