Out of the Middle East: New phylogenetic insights in the genus Tamarix (Tamaricaceae)

Authors: VILLAR, JOSE - Universidad De Alicante; ALONSO, ANGELES - Universidad De Alicante; JUAN, ANA - Universidad De Alicante; Gaskin, John; CRESPO, MANUEL - Universidad De Alicante

Submitted to: Journal of Systematics and Evolution
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/8/2019
Publication Date: 2/8/2019
Citation: Villar, J.L., Alonso, A.M., Juan, A., Gaskin, J.F., Crespo, M.B. 2019. Out of the Middle East: New phylogenetic insights in the genus Tamarix (Tamaricaceae). Journal of Systematics and Evolution. https://doi.org/10.1111/jse.12478.
DOI: https://doi.org/10.1111/jse.12478

Interpretive Summary: Tamarix is a plant genus that contains USA invasive species. Identification of species in this genus are difficult and we often don’t know how the species are related to each other. Here we present the most complete phylogeny conducted on the genus to date. In total, both nuclear and plastid phylogenetic approaches include more than 70 samples of 39 species from 27 countries, which represents close to 60% of the diversity of the genus. A reticulate evolution is inferred from the trees (the species probably have hybridized over the millennia during their evolution), showing characters such as vaginate leaves to appear at different stages along the evolutionary pathway of the genus. The presence of T. canariensis outside the Canary Islands is cast into doubt, and all such records from NW Africa and Europe are here considered to belong to T. gallica. The results also suggest independence of T. karelinii from T. hispida, and T. parviflora from T. tetrandra. Relationships between a number of species are still unresolved, and additional studies will be needed further refine the complex taxonomy of Tamarix.

Technical Abstract: Tamarix is one of the most taxonomically complex genera among the angiosperms, and there is little consensus regarding its intrageneric classification. Here we present the most complete phylogeny conducted on the genus to date. This includes a nuclear DNA phylogenetic tree, based on nuclear ITS and a plastidial DNA phylogeny, based on three intergenic spacers (trnS-trnG, ndhF-rpl32 and trnQ-rps16). In total, both nuclear and plastid phylogenetic approaches include more than 70 samples of 39 species from 27 countries, which represents close to 60% of the diversity of the genus. Two reduced trees, based only on one plastidial marker, are also included. The first, based on trnS-trnG, was used to increase the number of species related to T. amplexicaulis. The second, based on ndhF-rpl32, was used to check the separation between T. tetrandra and T. parviflora. In combination, these trees produced interesting results. The incongruence between the available infrageneric classifications and the molecular results is confirmed once again. A reticulate evolution is inferred from the trees, showing characters such as vaginate leaves to appear at different stages along the evolutionary pathway of the genus. The presence of T. canariensis outside the Canary Islands is cast into doubt, and all such records from NW Africa and Europe are here considered to belong to T. gallica. The results also suggest independence of T. karelinii from T. hispida, and T. parviflora from T. tetrandra. Relationships between a number of species are still unresolved, and additional studies will be needed further refine the complex taxonomy of Tamarix.