Disentangling a big genus: unwinding Ipomoeeae s.l. (Convolvulaceae) using an Angiosperms353-guided classical phylogenetic approach

• Background
Taxonomic studies of big plant genera are invariably complex due to their high species diversity. Big genera with tropical species representation exhibit higher taxon descriptions, since tropical and subtropical regions contribute immensely to species diversity. Ipomoea is an example of a large genus, with over 800 species distributed mostly in tropical and subtropical regions and fewer occurring in temperate regions. It is polyphyletic, nesting nine other genera, which collectively form tribe Ipomoeeae. Ipomoea has a long history of taxonomic and nomenclatural confusion, mainly due to a lack of clear morphological delimitation. Phylogenetic studies have greatly contributed to the clarification of taxa within Ipomoeeae. However, sampling biases overlooking Asian and African taxa representation means that these results are still insufficient for advanced generic classification of the group.
• Scope
To improve the understanding of phylogenetic relationships within Ipomoeeae, with a focus on the contribution of newly generated phylogenomic data from 17 African taxa.
• Methods
This study, for the first time, employed the target enrichment strategy with the universal Angiosperms353 probe set. We utilized a single-locus (ITS) constrained-phylogenetic analysis approach for Ipomoeeae, guided by a phylogenomic-generated phylogeny.
• Key Results
The Angiosperms353 tree resolved with strong support and corroborated the monophyly of Ipomoeeae as well as the polyphyly of Ipomoea. Internal branches of the constrained phylogenetic tree exhibited stronger statistical support than in the unconstrained phylogeny. Conflicting gene trees were also observed across the Angiosperms353 phylogeny despite the observed strong support.
• Conclusions
This study emphasizes the need for infrageneric divisions in Ipomoea and a subtribal classification of tribe Ipomoeeae. We also advocate the utilization of phylogenomic data for phylogenetic inference and delimitation of Ipomoeeae. Nuclear molecular data and a multi-species coalescent approach could prove useful in classification of Ipomoeeae, hence increased taxon sampling is recommended to fully understand the tribe