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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 #168424
Title: CLADISTIC BIOGEOGRAPHY OF JUGLANS (JUGLANDACEAE) BASED ON CHLOROPLAST DNA INTERGENIC SPACER SEQUENCES

Author
item Aradhya, Mallikarjuna
item POTTER, DANIEL - UNIVERSITY OF CALIFORNIA
item Simon, Charles

Submitted to: Darwin's Harvest: New Approaches to the Origins, Evolution, and Conservation of Crops
Publication Type: Other
Publication Acceptance Date: 8/9/2004
Publication Date: 8/25/2004
Citation: Aradhya, M.K., Potter, D., Gao, F., and Simon, C.J. 2005. Cladistic biodeography of Juglans (Juglandaceae) based on chloroplast DNA intergenic spacer sequences. In: Motley, T.J., Zerega, N., and Cross, H. (Eds.), Darwin's Harvest: Origin, Evolution, and Conservation of Crop Plants. 143-170, Columbia University Press, New York.

Interpretive Summary: Five chlorplast DNA sequences from the intergenic spacer regions were used in the phylogenetic analyses to elucidate the evolutionary relationships within and among the four sections of genus, Juglans. Seventeen ingroup taxa and one outgroup taxon, Pterocarya stenoptera were included in the analyses. There was significant divergence among the sections, Juglans, Rhysocaryon, and Cardiocaryon, except for the section, Trachycaryon containing a single New World butternut taxon, J. cinerea, which was placed into the section, Rhysocaryon. Stratigraphic fossil data were utilized in estimating time since divergence between major phylogenetic lineages. The results suggest that: (1) the cpDNA IGS sequence divergence levels observed within and between different sections of Juglans are low; (2) basal placement of the section Juglans in all the three analyses suggests its ancient origin in contrast to fossil evidence, which suggests the earliest divergence of sections Rhysocaryon and Cardiocaryon; (3) the Asian sections, Juglans and Cardiocaryon, have evolved at different rates as compared to Rhysocaryon; and finally (4) the extant taxa may not represent the entire evolutionary history of the genus.

Technical Abstract: The phylogenetic utility of sequence variation from five chloroplast DNA intergenic spacer (IGS) regions: trnT-trnF, psbA-trnH, atpB-rbcL, trnV-16S rRNA, and trnS-trnfM was examined in the genus Juglans. A total of seventeen taxa representing the four sections within Juglans and an outgroup taxon, Pterocarya stenoptera, were included in the phylogenetic analyses using the maximum parsimony, maximum likelihood, and neighbor-joining methods. The cladograms from all the three analyses were concordent with each other and contained three well-supported monophyletic clades corresponding to the three major sections Juglans, Cardiocaryon, and Rhysocaryon. The cladogenesis within Juglans seems to deviate from the evolutionary hypothesis based on the fossil history and biogeographic evidence. The results suggest that: (1) the cpDNA IGS sequence divergence levels observed within and between different sections of Juglans are low; (2) basal placement of the section Juglans in all the three analyses suggests its ancient origin in contrast to fossil evidence, which suggests the earliest divergence of sections Rhysocaryon and Cardiocaryon; (3) the Asian sections, Juglans and Cardiocaryon, have evolved at different rates as compared to Rhysocaryon; and finally (4) the extant taxa may not represent the entire evolutionary history of the genus.