Title: Phylogenetics and diversification of morning glories based on whole plastome sequences Authors
|Eserman, Lauren -|
|Tiley, George -|
|Leebens-Mack, Jim -|
|Miller, Richard -|
Submitted to: American Journal of Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 8, 2013
Publication Date: N/A
Interpretive Summary: This study was conducted in order to examine the relationships among various species of morning glory. In order to examine these relationships, the DNA from the chloroplasts of 28 species of morning glory were sequenced in their entirety. These whole chloroplast genome sequences, or portions of them, were then compared with one another. Chloroplast DNA sequence information was also used to estimate the antiquity of the species being examined and the timing of their divergence from other groups. Two principle lines, these being the Astripomoeinae and the Argyreiinae, were identified. The data collected also indicated that the Ipomoeaee as a group diverged approximately 38 to 48 million yeas ago (middle Eocene).
Technical Abstract: Phylogenetic studies have demonstrated the largest morning glory genus, Ipomoea, is not monophyletic, and nine other segregate genera are derived from within Ipomoea. Therefore, systematic research is focused on the monophyletic tribe Ipomoeeae (c. 650-900 species). We used whole plastid genomes to infer relationships among exemplar species distributed across Ipomoeeae. Whole plastomes were sequenced, assembled and annotated for twenty-eight morning glory species, representing major Ipomoeeae lineages. Phylogenies were estimated for twenty-eight species sequenced here and one published plastome using alignments of: (a) eighty-two chloroplast genes and (b) whole plastomes. In addition, divergence times were estimated to date key divergence events within the Ipomoeeae. Two nodes were calibrated with fossil pollen for molecular dating analyses. Phylogenies estimated from the two plastome datasets had identical topologies. Phylogenetic results are generally consistent with prior phylogenetic analyses of morning glories. Two major clades, previously named Astripomoeinae and Argyreiinae, are well-supported. There also is support for the monophyly of Ipomoea subgenus Quamoclit. Higher-level relationships with weak support in previous analyses were recovered in this analysis with strong support. Results from the molecular dating analysis suggest a middle Eocene divergence time for the Ipomoeeae. Furthermore, the Argyreiinae clade was found to have diversified before the Astripomoeinae; however, error bars overlap between divergence time estimates of these two clades. Phylogenetic results presented here provide greater confidence in relationships among major lineages of the Ipomoeeae, and divergence time estimation results provide a temporal context for the diversification of this fascinating group of angiosperms.