Revised phylogeny and historical biogeography of the cosmopolitan aquatic plant genus Typha (Typhaceae)

Abstract

Typha is a cosmopolitan aquatic plant genus that includes species with widespread distributions. It is a relatively ancient genus with an abundant fossil record dating back to the Paleogene. However, the details of its biogeographic history have remained unclear until now. In this study, we present a revised molecular phylogeny using sequences of seven chloroplast DNA markers from nine species sampled from various regions in order to infer the biogeographic history of the genus. Two clades were recovered with robust support. Typha minima and T. elephantina comprised one clade, and the other clade included the remaining seven species, which represented a polytomy of four robustly supported subclades. Two widespread species, T. angustifolia and T. domingensis, were revealed to be paraphyletic, indicating the need for taxonomic revision. Divergence time estimation suggested that Typha had a mid-Eocene crown origin, and its diversification occurred in the Middle and Late Miocene. Ancestral area reconstruction showed that Typha possibly originated from eastern Eurasia. Both dispersal via the Beringian Land Bridge and recent transoceanic dispersal may have influenced the intercontinental distribution of Typha species.

Figure 1

Bayesian consensus tree for Typha and three Sparganium species. The phylogenetic tree has been reconstructed based on seven chloroplast DNA regions (atpB-rbcL, psbA-trnH, psbD-trnT, rpl32-trnL, rps16 intron, rps16-trnK, and trnL-trnF). Numbers below the branches are Bayesian posterior probabilities (PP), and numbers above the branches are the ML bootstrap values (BS).

Figure 2

Chronogram of Typha, three Sparganium species, and five Bromeliaceae species inferred from BEAST. Blue bars represent the 95% highest posterior density intervals for node ages. Stars indicated three calibration points.

Figure 3

Reconstruction of the ancestral area of Typha. The pie charts at each node were obtained using S-DIVA analysis, and the rectangle charts beside each node were obtained from DEC analysis. The colors of the charts correspond to the most likely ancestral areas inferred. Letters represent the following biogeographic regions: (A) North America, (B) Indo-Pacific, (C) West Eurasia, (D) East Eurasia, (E) Africa, (F) South America, and (G) Australia.