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Phylogenetic relationships of diploid and polyploid species in Ludwigia sect. Isnardia (Onagraceae) based on chloroplast and nuclear DNAs
Author(s) -
Hung Kuo-Hsiang,
Schaal Barbara A.,
Hsu Tsai-Wen,
Chiang Yu-Chung,
Peng Ching-I,
Chiang Tzen-Yuh
Publication year - 2009
Publication title -
taxon
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.819
H-Index - 81
eISSN - 1996-8175
pISSN - 0040-0262
DOI - 10.1002/tax.584013
Subject(s) - biology , reticulate evolution , polyploid , chloroplast dna , ploidy , introgression , phylogenetic tree , botany , evolutionary biology , genetics , gene
Ludwigia , a genus with rampant interspecific hybridization, is an ideal model for examining the impact of gene introgression and polyploidization on species diversification. We examined the evolution of the Ludwigia sect. Isnardia , which is a polyploid complex ( x = 8) of five species distributed in North America. The phylogeny of L . sect. Isnardia was reconstructed based on sequences of cpDNA atpBrbcL intergenic spacer and nrITS (internal transcribed spacer). Most L . sect. Isnardia species are polyphyletic at both loci, indicating possible recurrent hybridization, based on maximum likelihood trees rooted at L . sect. Microcarpium . A minimum spanning network was also constructed to examine genealogical relationships among haplotypes. In the cpDNA network, haplotypes of tetraploid L. spathulata are nested at the most interior nodes, suggesting a parental genome origin of an extinct diploid or an unsampled extant diploid with a DD cytotype. Allopolyploid L. arcuata contributed its cpDNA to hexaploid L. repens and L. brevipes. ITS haplotypes of diploid L. palustris were clustered with L. spathulata , suggesting L. palustris as the paternal genome donor. Ludwigia brevipes may have arisen via bi3directional hybridization between L. palustris and L. arcuata followed by polyploidy. Genetic and phylogenetic analyses using molecular markers with different inheritance modes provided sufficient insights into the reticulate evolution of the species of L . sect. Isnardia . Interspecific hybridization and polyploidy play a key role in the species evolution in L . sect. Isnardia .