Systematics of Nicotiana, especially Section Alatae

Anthony Ippolito's first dissertation chapter is a nuclear ribosomal internal transcribed spacer (nrITS) DNA sequence-based phylogeny for the genus Nicotiana. The nrITS sequences were somewhat informative but we found lots of paralogues. See this paper.

The tree for the whole genus is here, along with a color-coded summary page. (both are .pdf files).

A pruned tree is below, showing that the Alatae are a monophyletic group. One N. langsdorfii sequence grouped with the Australian Section Suaveolentes -- we suspect this is a descendent of an allele that was polymorphc in the ancestor of both Sections. There is a small cluster of Alatae sequences elsewere on the big tree (see above) which we suspect represent another major rDNA locus. Within the Alatae, the only well supported clade contains the species with n=10; other Alatae are n=9. Tina Merrels tried to increase resolution using t-RN-L intron sequences but this chloroplast region was nearly invariant. We hope to use allele frequencies from SSR loci to build a distance-based hypothesis for the Section.

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