Systematics Section / ASPT
Rajanikanth, G , Hughes, Colin E. , Bailey, C. Donovan .
Reconstructing species relationships in Leucaena: insights into the origin of polyploids from a low copy nuclear locus.
LEUCAENA (Fabaceae) comprises 22 species of mimosoid legume trees distributed from the southern USA to Peru. The evolutionary history of Leucaena has been influenced by interspecific hybridization, and polyploidy with five polyploid species and a number of putative hybrids identified. Hybrids have apparently occurred spontaneously in south-central Mexico where Leucaena pods are used as an edible crop and extensive sympatry among diploid and polyploid species has occurred following cultivation. Insights into hybrid and polyploid origins from cpDNA and nrDNA ITS data have been limited by lack of well-supported resolution among closely related species prompting a search for more variable nuclear DNA sequence loci. In this study, we have used DNA sequence data derived from an anonymous SCAR-based nuclear locus, 23L, to investigate polyploids. The 23L locus was amplified, cloned, and multiple clones sequenced to screen for divergent copies for 53 accessions representing all 22 species. A total of 148 unique haplotypes were recovered providing 191 parsimony informative characters. The strict consensus tree recovered three major clades that were previously identified using nrDNA ITS and cpDNA data. Comparison of divergent haplotypes across the 23L gene tree provides a number of new insights into polyploid origins. Notably, our findings strongly support an allopolyploid origin for L. diversifolia based on the occurrence of haplotypes that closely match sequences from two distantly related diploid species, L. pulverulenta and L. trichandra. These results are in contrast to previous studies, based on nrDNA ITS and cpDNA, that suggested an autopolyploid origin of L. diversifolia.
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Information on the Luecaena distribution and seed lots
1 - New Mexico State University, Department of Biology, Po Box 30001, Department 3Af, Las Cruces, New Mexico, 88003-8001, USA
2 - University of Oxford, Department of Plant Sciences, South Parks Road, Oxford, Oxfordshire, OX1 3RB, United Kingdom
Presentation Type: Oral Paper:Papers for Sections
Location: 144/Performing Arts Center
Date: Monday, July 31st, 2006
Time: 3:45 PM