Submitted to: American Society of Plant Taxonomists Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 3/6/2006
Publication Date: 7/29/2006
Citation: Whittemore, A.T. 2006. ITS Evolution in Celtis (Cannabaceae). [abstract]. American Society of Plant Taxonomists Annual Meeting. p. 56.
Technical Abstract: Sequencing of nuclear ribososmal internal transcribed spaces (ITS) clones in Celtis subg. Celtis revealed multiple copies with different sequences in all samples examined, even after exclusion of pseudogenes. The subgenera are well separated on the ITS gene tree, and within subg. Celtis the Old World and New World species form two well-separated clades. Within the New World representatives of subg. Celtis, different ITS clones from all the species are scattered through the clade with little discernable pattern. The different sequences did not form multiple phylogenies in parallel, as would be expected from gene duplication followed by independent evolution of the two copies; nor did they cluster geographically, as would be expected if the sharing of alleles is due to recent interspecific hybridization. The pattern is best explained by assuming sequence divergence accompanied by very slow concerted evolution, so that genetic polymorphisms persist beyond recent speciation events.