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ARS Home » Pacific West Area » Davis, California » Nat'l Clonal Germplasm Rep - Tree Fruit & Nut Crops & Grapes » Research » Publications at this Location » Publication #231200
Title: Origin, evolution, and biogeography of Juglans: a phylogenetic perspective

Author
item Aradhya, Mallikarjuna
item POTTER, DANIEL - UCD - PLANT SCIENCE
item FANGYOU, GAO - UCD - PLANT SCIENCE
item Simon, Charles

Submitted to: Tree Genetics and Genomes
Publication Type: Popular Publication
Publication Acceptance Date: 10/23/2006
Publication Date: 2/6/2007
Citation: Aradhya, M.K., Potter, D., Simon, C.J. 2007. Origin, evolution, and biogeography of Juglans: a phylogenetic perspective. Tree Genetics and Genomes. 3: 363-378.

Interpretive Summary: The eastern Asian and eastern North American disjunction in Juglans offers an opportunity to estimate the time since divergence of the Eurasian and American lineages and to compare it with paleobotanical evidences. Five chloroplast DNA non-coding spacer (NCS) sequences: trnT-trnF, psbA-trnH, atpB-rbcL, trnV-16S rRNA, and trnS-trnfM and data from earlier studies (matK, ITS, and nuclear RFLP) were used to reconstruct phylogeny and to estimate the divergence time of major lineages. Seventeen taxa from four sects. of Juglans and two outgroup taxa, Pterocarya stenoptera and Carya illinoiensis were included. NCS data was congruent only with matK data. Both maximum parsimony (MP) and maximum likelihood (ML) cladograms were concordant at the sectional level and revealed three well-supported monophyletic clades corresponding to sectionss. Juglans, Cardiocaryon, and Rhysocaryon in both NCS and combined analyses. The single extant American butternut, J. cinerea was placed within the poorly resolved, but well-supported Rhysocaryon. Placement of taxa within Rhysocaryon and Cardiocaryon were somewhat inconsistent between NCS and combined analyses. Overall, the results suggest that: (1) the NCS sequence divergence levels observed within and between different sects. of Juglans are is low and the addition of matK data only marginally improved resolution within Rhysocaryon; (2) the basal early divergence of placement of the sect. Juglans in both MP and ML analyses of NCS and combined data implies its ancient origin in contrast to fossil evidence, which suggests the earliest divergence of sects. Rhysocaryon and Cardiocaryon; and (3) the extant taxa may not hold the footprints to unravel the evolutionary history reflect the evolutionary history of the genus.

Technical Abstract: The eastern Asian and eastern North American disjunction in Juglans offers an opportunity to estimate the time since divergence of the Eurasian and American lineages and to compare it with paleobotanical evidences. Five chloroplast DNA non-coding spacer (NCS) sequences: trnT-trnF, psbA-trnH, atpB-rbcL, trnV-16S rRNA, and trnS-trnfM and data from earlier studies (matK, ITS, and nuclear RFLP) were used to reconstruct phylogeny and to estimate the divergence time of major lineages. Seventeen taxa from four sects. of Juglans and two outgroup taxa, Pterocarya stenoptera and Carya illinoiensis were included. NCS data was congruent only with matK data. Both maximum parsimony (MP) and maximum likelihood (ML) cladograms were concordant at the sectional level and revealed three well-supported monophyletic clades corresponding to sectionss. Juglans, Cardiocaryon, and Rhysocaryon in both NCS and combined analyses. The single extant American butternut, J. cinerea was placed within the poorly resolved, but well-supported Rhysocaryon. Placement of taxa within Rhysocaryon and Cardiocaryon were somewhat inconsistent between NCS and combined analyses. Overall, the results suggest that: (1) the NCS sequence divergence levels observed within and between different sects. of Juglans are is low and the addition of matK data only marginally improved resolution within Rhysocaryon; (2) the basal early divergence of placement of the sect. Juglans in both MP and ML analyses of NCS and combined data implies its ancient origin in contrast to fossil evidence, which suggests the earliest divergence of sects. Rhysocaryon and Cardiocaryon; and (3) the extant taxa may not hold the footprints to unravel the evolutionary history reflect the evolutionary history of the genus.