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

Abstract

Tamarix is one of the taxonomically most complex genera among the angiosperms, and there is little consensus regarding its infrageneric classification. Here we present the most complete phylogenetic reconstruction of the genus to date. This includes a DNA phylogenetic tree based on nuclear ribosomal ITS, and a plastid DNA phylogeny based on three intergenic spacers (trnS-trnG, ndhF-rpl32, and trnQ-rps16). In total, both nuclear and plastid phylogenetic analyses include more than 70 samples of 39 species from 27 countries, which represent close to 60% of the diversity of the genus. Two complementary trees, based only on one plastid marker, are also included. The first, based on trnS-trnG, is used to increase the number of species related to T. amplexicaulis. The second, based on ndhF-rpl32, is used to investigate the separation between T. tetrandra and T. parviflora. The incongruence between the available infrageneric classifications and the molecular results is confirmed. A reticulate evolution is inferred from the trees, showing characters such as vaginate leaves appearing at different stages along the evolutionary history 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 not resolved, and additional studies will be needed to further refine the complex taxonomy of Tamarix.

DNA barcodes and microsatellites: How they complement for species identification in the complex genus Tamarix (Tamaricaceae)

“…Cycling conditions for ITS were as follows: an initial step of 3 min at 94 °C; followed by 26 cycles of 1 min at 94 °C, 1 min at 48 °C, and 3 min at 72 °C; and a final extension at 72 °C for 7 min. PCR products were cleaned with ExoSAP-IT™ PCR Product Cleanup Reagent (Thermo Villar et al (2019). Sequences of each region were aligned with ClustalW, followed by minor manual corrections in MEGA v. 7.0.26 (Kumar et al, 2016).…”

“…Previous phylogenetic relationships of Tamarix have shown significant incongruencies between different gene trees (Villar et al, 2019), which might be caused by a rapid radiation of the genus. In this context, the expected presence of incomplete lineage sorting (ILS) and hybridization processes could hinder species identification with DNA barcodes, especially for closely related species.…”

“…DNA barcoding might be a useful tool to aid the taxonomic identification of species of complex genera, such as Tamarix L. This genus comprises between 54 and 90 species of trees and shrubs that grow mainly in salt marshes, ravines and more or less saline rivers (Baum, 1978; Villar et al, 2019). The genus has a natural distribution from Asia to Europe and Africa (Baum, 1978), but it has been introduced in the Americas and Australia, where it is invasive due to high clonal dispersion ability (Brock, 1994; Gaskin & Schaal, 2003).…”

Mediterranean Halophytic Flora and Vegetation in the Iberian Peninsula (Spain and Portugal)

“…Except for the alliance Tamaricion boveano-canariensis (Mediterranean halophytic tamarisk and oleander groves), this class is not exclusively halophytic. In truth, the only characteristic species of this alliance is Tamarix boveanagiven that T. canariensis is not part of the Iberian floraand it is T. gallica (Villar et al 2019) that is accompanied by other halo-tolerant species such as T. africana and Nerium oleander.…”

A new species of Tamarix (Tamaricaceae) from Hormozgan Province, S Iran, supported by morphology and molecular phylogenetics

“…and T. usneoides E. Mey), which was also found by Villar & al. (2015aVillar & al. ( , 2019 based on combined trnGtrnS, ndhF rpl32 and trnQrps16 spacers with high support.…”