Molecular phylogeny and morphological perianth evolution in Corymbia (Myrtaceae), and the implications for generic delimitation: data and tree files

Premise: Eucalypts (Myrtaceae tribe Eucalypteae) are currently placed in
seven genera. Traditionally, Eucalyptus was defined by its operculum but
when phylogenies placed Angophora, with free sepals and petals, as sister
to the operculate bloodwood eucalypts, the latter were segregated into a
new genus, Corymbia. Yet generic delimitation in the tribe Eucalypteae
remains uncertain. Here we address these problems using phylogenetic
analysis with the largest molecular dataset to date. Methods: We captured
101 low-copy nuclear exons from 392 samples representing 266 species. Our
phylogenetic analysis used maximum likelihood (IQtree) and multi-species
coalescent (Astral). At two nodes critical to generic delimitation, we
tested alternative relationships among Arillastrum, Angophora, Eucalyptus
and Corymbia using Shimodaira's AU test. Phylogenetic mapping was
used to explore the evolution of perianth traits. Results: Monophyly of
Corymbia relative to Angophora was decisively rejected. All alternative
relationships among the seven currently recognised Eucalypteae genera
imply homoplasy in evolutionary origins of the operculum. Inferred
evolutionary transitions in perianth traits are congruent with divergences
between major clades except that expression of separate sepals and petals
in Angophora, which is nested within the operculate genus Corymbia,
appears to be a reversal to the plesiomorphic perianth structure.
Conclusions: Here we formally raise Corymbia subg. Blakella to genus rank
and make the relevant new combinations. We also define and name three
sections within Blakella (B. sect. Blakella, B. sect. Naviculares and B.
sect. Maculatae), and two series within Blakella sect. Maculatae (B. ser.
Maculatae and B. ser. Torellianae). Corymbia is reduced to the red
bloodwoods.