Phylogenetic relationships among species of Tamarix (Tamaricaceae) in China

Tamarix is a genus in family Tamaricaceae. The present study inferred phylogenetic trees for sixteen Tamarix species from China, whose status has remained unclear, using the nuclear internal transcribed spacer (ITS) region and four chloroplast DNA regions. Thirty ITS sequences from the GenBank database were added for expanded ITS analysis. The molecular phylogenies divide the Tamarix species into eight clades. Tamarix androssowii, T. gracilis, and T. laxa group together as a subclade closely related to T. gansuensis and T. elongata (clade A). Tamarix austromongolica, T. chinensis, T. hohenackeri, T. ramosissima, and T. sachensis cluster into clade B; T. karelinii from Gansu province is also in this clade. Tamarix leptostachya belongs to clade C, and one population of T. ramosissima from Gansu province is placed in this clade in the expanded ITS tree. Tamarix hispida groups with T. karelinii from Xinjiang province in clade D. Three putative T. hispida individuals from Gansu province and T. hispida from the US cluster into clade E. Finally, Tamarix arceuthoides, T. taklamakanensis, and T. aphylla form separate clades (F, G, and H, respectively). These molecular analyses are consistent with the current classification of certain Tamarix species based on morphological traits.