Morphometric, phylogenetic and biogeographic analyses of Pyrularia (Santalales), a parasitic disjunct lineage between eastern Asia and eastern North America
Pyrularia is a small parasitic genus of the Santalales with two to five species exhibiting a well-known classical intercontinental disjunct distribution between eastern Asia (EA) and eastern North America (ENA). Pyrularia and another santalaceous genus Buckleya represent the only two parasitic plant lineages with the EA–ENA disjunction. The present study was carried out to assess the species number and molecular and morphological differentiation in Pyrularia, and to reconstruct the biogeography of the Pyrularia clade (Pyrularia and its close allies) using dating and biogeographic inferences. A phylogenetic analysis based on two nuclear and seven plastid markers strongly supported the monophyly of Pyrularia and revealed two highly distinct subclades corresponding to EA and ENA within the genus. Incongruent topologies within the eastern Asian lineage were found between the nuclear and the plastid datasets, which may be attributed to incomplete lineage sorting. Morphometric and phylogenetic analyses suggest that Pyrularia in eastern Asia may best be treated as a single species, P. edulis. Molecular dating based on four markers suggested that the divergence time between the intercontinental species was in the late Miocene at 5.58 Ma (95% HPD: 2.08–11.72 Ma), which was close to the split of the trans-Pacific clades within the other parasitic EA–ENA disjunct genus Buckleya. The EA–ENA disjunction in the only two parasitic genera may have resulted from the fragmentation of the mesophytic temperate forests in the late Miocene. The Pyrularia clade (including the close allies of Pyrularia) was inferred to have originated in Africa, then dispersed to Asia, and subsequently to North America via the Bering land bridge, resulting in the current intercontinental EA–ENA distribution of Pyrularia.
