Combined Morphological and Molecular Phylogeny of the Clusioid Clade (Malpighiales) and the Placement of the Ancient Rosid Macrofossil Paleoclusia

Premise of research . The clusioid clade is a member of the large rosid order Malpighiales and contains ∼1900 species in five families: Bonnetiaceae, Calophyllaceae, Clusiaceae sensu stricto (s.s.), Hypericaceae, and Podostemaceae. Despite recent efforts to clarify their phylogenetic relationships using molecular data, no such data are available for several critical taxa, including especially  Hypericum ellipticifolium  (previously recognized in  Lianthus ),  Lebrunia ,  Neotatea ,  Thysanostemon , and the second-oldest rosid fossil (∼90 Ma),  Paleoclusia chevalieri . Here, we (i) assess congruence between phylogenies inferred from morphological and molecular data, (ii) analyze morphological and molecular data simultaneously to place taxa lacking molecular data, and (iii) use ancestral state reconstructions (ASRs) to examine the evolution of traits that have been important for circumscribing clusioid taxa and to explore the placement of  Paleoclusia .

Methodology . We constructed a morphological data set including 69 characters and 81 clusioid species (or species groups). These data were analyzed individually and in combination with a previously published molecular data set of four genes (plastid  matK ,  ndhF , and  rbcL  and mitochondrial  matR ) using parsimony, maximum likelihood (ML), and Bayesian inference. We used ML ASRs to infer the evolution of morphological characters.

Pivotal results . Our phylogeny inferred from morphology alone was poorly supported but largely in agreement with molecular data. Moreover, our combined analyses were much better supported and largely confirm taxonomic hypotheses regarding relationships of extant taxa newly included here. The extinct  Paleoclusia  was placed as a member of stem group Clusiaceae s.s. or within crown group Clusiaceae s.s. as sister to one of its two major subclades.

Conclusions . Despite poor overall bootstrap support for the placement of  Paleoclusia , ancestral character state reconstructions are generally in agreement with our placements. Our recommendation is that  Paleoclusia  be treated as either a minimum stem group or a crown group age constraint of Clusiaceae s.s.