AUTHOR=Xia Zhi , Wen Jun , Gao Zhiming 

TITLE=Does the Enigmatic Wightia Belong to Paulowniaceae (Lamiales)?

JOURNAL=Frontiers in Plant Science

VOLUME=10

YEAR=2019

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2019.00528

DOI=10.3389/fpls.2019.00528

ISSN=1664-462X

ABSTRACT=<p>The familial placement of <italic>Wightia</italic> has been controversial in the Lamiales, and the genus is currently placed in Paulowniaceae in APG IV. Phylogenetic analyses of <italic>Wightia</italic> and its close relatives in Lamiales are conducted using sequences of the complete chloroplast genomes as well as sequence data from nine chloroplast DNA regions (<italic>atpB</italic>, <italic>matK</italic>, <italic>ndhF</italic>, <italic>psbBTNH</italic>, <italic>rbcL</italic>, <italic>rps4</italic>, <italic>rps16</italic> intron, <italic>trnL-F</italic>, and <italic>trnV-atpE</italic>) and one mitochondrial gene <italic>rps3</italic>. The maximum likelihood and Bayesian analyses do not support a close relationship between <italic>Wightia</italic> and <italic>Paulownia</italic> of Paulowniaceae; instead the enigmatic <italic>Wightia</italic> is sister to Phrymaceae with strong support in all analyses. Hence <italic>Wightia</italic> should not be placed in Paulowniaceae. Because morphological data show <italic>Wightia</italic>’s affinity to both Phrymaceae and Paulowniaceae and prior nrITS data suggest its sister relationship to <italic>Paulownia</italic> of Paulowniaceae, it is likely that <italic>Wightia</italic> may have had a hybrid origin between early lineages of Phrymaceae and Paulowniaceae. It is therefore the best to exclude <italic>Wightia</italic> from Paulowniaceae and place the genus as unassigned until further nuclear data to test the hybrid hypothesis. The seven species of <italic>Paulownia</italic> constitute a monophyletic group, and Paulowniaceae is supported to be a monogeneric family, consistent with a series of morphological and floral development characters. The genus <italic>Brandisia</italic>, which was sometimes regarded as a close relative of <italic>Wightia</italic>, is supported to be nested within Orobanchaceae, as sister to <italic>Pterygiella</italic>. This sister relationship can be corroborated by fruit, seed and pollen morphological characters.</p>