Phylogeny and biogeography of Sagittaria (Alismataceae) revisited: evidence for cryptic diversity and colonization out of South America.

ABSTRACT

Sagittaria is a genus of ca. 40 species in the aquatic plant family Alismataceae with a nearly global distribution, and a center of diversity in the New World. Two thirds of the known species are native to the Americas, while only a few species are distributed in Africa, Asia and Europe. A previous biogeographic analysis of the genus suggested an African origin for the genus with subsequent dispersal to North America and then to East Asia. Here we expanded the taxon sampling with a focus on the New World taxa and applied species delimitation and biogeographic analyses to revise the knowledge of the phylogeny and evolution of the genus. We obtained largely similar topologies from the chloroplast DNA and nuclear DNA (ITS) data sets. The 74 accessions sampled for our analyses were delimited into 29 species and several cryptic taxa were revealed in widely distributed species. Biogeographic analysis supported basal diversification in South America and subsequent colonization to North America and Asia.