AUTHOR=Granados Mendoza Carolina , Martínez Salas Esteban Manuel , Goetghebeur Paul , Wanke Stefan , Samain Marie-Stéphanie 

TITLE=Molecular Phylogeny, Character Evolution, and Biogeography of Hydrangea Section Cornidia, Hydrangeaceae

JOURNAL=Frontiers in Plant Science

VOLUME=12

YEAR=2021

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2021.661522

DOI=10.3389/fpls.2021.661522

ISSN=1664-462X

ABSTRACT=<p><bold>Background:</bold><italic>Hydrangea</italic> section <italic>Cornidia</italic> consists of 26 currently accepted species and a yet undefined number of new species and erroneously synonymized taxa. This clade consists of (sub)tropical lianas occurring from northern Mexico to southern Chile and Argentina, and one species from Southeast Asia. Currently, no molecular phylogenetic hypothesis is available that includes more than a few species of this section. Hence, a resolved and well-sampled molecular phylogenetic hypothesis may help to enforce taxonomic decisions. In this study, we present a phylogenetic framework based on sequences from two low copy nuclear genes from a comprehensive taxon sampling of <italic>H</italic>. section <italic>Cornidia</italic> and a selection of outgroups. Our phylogenetic reconstructions prove the non-monophyly of the traditionally recognized subsections <italic>Monosegia</italic> and <italic>Polysegia</italic> and their corresponding series, <italic>Speciosae</italic> and <italic>Aphananthae</italic>, and <italic>Synstyleae</italic> and <italic>Chorystyleae</italic>, respectively. Three morphologically defined species were recovered with high support as monophyletic, namely, <italic>Hydrangea panamensis, Hydrangea serratifolia</italic>, and <italic>Hydrangea tarapotensis</italic>. However, statistical support for some shallow nodes did not allow to refute, with high support, the monophyly of several of the herein recognized species for which more than one individual could be analyzed. Based on the obtained phylogenetic framework, we reconstructed the evolution of selected reproductive characters. <italic>Hydrangea</italic> section <italic>Cornidia</italic> is the only genus section for which dioecism has been extensively documented. Our character reconstruction of sexual dimorphism shows that dioecism is the ancestral state in this section and that this was reversed to monoecy in <italic>Hydrangea seemannii</italic> and <italic>Hydrangea integrifolia</italic>. Character reconstruction for the enlarged marginal flowers recovered their presence as the ancestral character state in <italic>H</italic>. section <italic>Cornidia</italic>, although at least three internal lineages independently lost them; thus, losses were reconstructed to be more likely than gain. With respect to the flower color, more species exhibit white than red flowers, and white is reconstructed as the ancestral state. <italic>Cornidia</italic> also shows an unusual disjunct geographic distribution between Asia and Central Mesoamerica—South America, as it is not present in the USA and Canada. The origin of <italic>Cornidia</italic> is reconstructed to be the New World with higher probability, and the presence of one species in Asia is likely due to long-distance dispersal.</p>