Exploring the plant inter-continental distribution is vital for understanding plant origin, diversity, plant protection and utilization. Aponogetonaceae (Alismatales) is an aquatic plant family with peculiar flowers. The family consists of 57 species, disjunctively distributed in Asia, Africa, Madagascar and Australia. Previous studies indicated that this family originated in Australia or Madagascar, and dispersed to other areas. 

 Supervised by Prof. WANG Qingfeng from the Adaptive Evolution of Aquatic Plants Research Group (Wuhan Botanical Garden), CHEN Lingyun worked with Prof.  Susanne S. Renner (a botanist from Munich University) on biogeography of Aponogetonaceae.  

The study obtained nuclear and plastid DNA sequences for 42 species and generated a time-calibrated phylogeny, rooted on appropriate outgroups. Statistical biogeographic analyses were carried out with or without the fossils incorporated in the phylogeny.  

The recent-most common ancestor of living Aponogetonaceae appears to date to the mid-Eocene and to have lived in Madagascar or Africa (but not Australia). Three transoceanic dispersal events from Africa/Madagascar to Asia sometime during the Miocene could explain the observed species relationships. 

As inferred in earlier studies, an ancient Australian species is sister to all other Aponogetonaceae, while the remaining Australian species stem from an Asian ancestor that arrived from Asia about 5 million years ago. The family’s ancient Northern Hemisphere fossil record and deepest extant divergence between a single Australian species and an Africa/Madagascar clade are statistically well-supported and rank among the most unusual patters in the biogeography of flowering plants. 

This study was funded by the Chinese Academy of Sciences (Research Grant XDAO5090305 to QFW), and published on line in Molecular Phylogenetics and Evolution entitled “A phylogeny and biogeographic analysis for the Cape-Pondweed family Aponogetonaceae (Alismatales)”.  

Phylogeny of Aponogetonaceae based on combined ITS, trnK 5’ intron and matK sequences (Image by CHEN Lingyun)