Paulowniaceae

Paulowniaceae are a family of flowering plants within the Lamiales. They are a monophyletic and monogeneric family of trees with currently 7 confirmed species. They were formerly placed within Scrophulariaceae ''sensu lato'', or as a segregate of the Bignoniaceae.

The Paulowniaceae are now resolved as a distinct separate family consisting of the genus ''Paulownia''. They are deciduous trees with large heart shaped leaves and long panicles of white-purple to lavender flowers native to eastern Asia. The most widely distributed and recognized species is ''Paulownia tomentosa'' with common names such as Princess tree, Empress tree, Kiri tree, Foxglove tree, and Phoenix tree.

Taxonomy

There are 7 confirmed species of Paulownia with potentially more as hybrid, variety, or mismatched synonym species.

* ''Paulownia fargesii''
* ''Paulownia fortunei''
* ''Paulownia x taiwaniana''
* ''Paulownia catalpafolia''
* ''Paulownia elongata''
* ''Paulownia tomentosa''
* ''Paulownia coreana'' (''Paulownia tomentosa var. coreana)''
* ''Paulownia kawakamii''

Phylogeny

Paulowniaceae is sister to the Orobanchaceae, a primarily hemi- holoparasitic plant family, except for the clade of herbaceous genera ''Lindenbergia'', ''Rehmannia'', and ''Triaenophora''. Sister to the Orobanchaceae-Paulowniaceae clade is Phrymaceae. Phrymaceae are mostly herbaceous plants with a widespread distribution.

, The Plant List accepted four genera in the family. However of these four genera currently only ''Paulownia'' is a recognized member of Paulowniaceae.

* ''Paulownia''
* ''Brandisia'' is settled in the Orobanchaceae as sister to the '' Pterygiella'' due to molecular data from 9 chloroplast markers and samples from 6 of the 11 ''Brandisia'' species. They are a mostly shrublike family with hemi-parasitic characters that sometimes grow like climbing vines. Morphological similarities between ''Bradisia'' and ''Pterygiella'', such as eglandular hairs on their capsules, reticulate seeds, and similar shaped tricolpate pollen, confirm their close relationship.
* '' Wightia'' is now tentatively positioned as a sister group to Phrymaceae due to many morphological similarities as well as support by chloroplast and mitochondrial DNA analysis. They are a small genus of two species in Southeast Asia, that can grow as a shrub or tree, or as hemiepiphetic pseudo-vine. There are still morphological characters as well as nuclear genome data to support ''Wightia'' as sister to ''Paulownia'' leading it to be of proposed hybrid origin from Phrymaceae and Paulowniaceae. This theory, based on chloroplast genome evidence, would explain its morphological similarities to both families. However the conflicts between the chloroplast, mitochondrial, and nuclear phylogenetic data make it unclear. If these were tested further and proven to be correct it should place ''Wightia'' as a new family Wightiaceae. Though according to Liu et al., 2019, ''Wightia'' should already be its own distinct family as it is highly unlikely that any new study would provide more questionable data against this theory.
* '' Shiuyinghua'' is an accepted genus on The Plant List and is listed under Paulowniaceae, but there is no updated published work on the phylogeny of the genus or its species '' Shiuyinghua silvestrii''. ''Shiuyinghua'' has a history of being placed under the name ''Catalpa silvestrii'' in Bignoniaceae due to its leaf shape, but then as '' Paulownia silvestrii'' in the clade Paulownieae in Scrophulariaceae due to similarities in lateral and terminal inflorescences, and in the five-lobed calyx structure. In 1959 ''S. silvestrii'' was believed to be a distinct species within the Paulownieae tribe due to the overall flower bud shape being significantly different from all other members of ''Paulownia''. The genus was named after Dr. Shiu-ying Hu of Harvard University's Arnold Arboretum. Since then there has been no more evidence or discussion on its placement, nor any available molecular data on a species under the name ''Shiuyinghua silvestrii'' or ''Paulownia silvestrii''.

References

{{Taxonbar, from=Q1896257

Lamiales families
Taxa named by Takenoshin Nakai