Tamarix L.
Genus comprised of about 15 species in North Africa, widely distributed throughout the region. This is one of the most problematic genera in terms of nomenclature due to most species being very similar and extremely polymorphic. For this region more than 30 different species and subspecies and nearly one hundred varieties have been described. Many of these apparently separate taxa are actually sometimes only one taxon, described under different names by different authors or by the same author with insufficient specimens. The clear differentiation in the field between T. pauciovulata, T. trabutii and T. balansae has been impossible, because in all the examined trees characteristics from the three species were observed, and they actually appear to be one species and with a different name: T. amplexicaulis. The monograph on the genus by Baum (1978), already used for the Flora of Libya, Flore de Mauritanie, Catalogue des plantes vasculaires de la Mauritanie et du Sahara occidental and Flora Iberica, constitutes a good basis for a thorough review of the genus in the region.
One of the differentiators characters of Tamarix species is the staminal disk, which according to its shape it can be separated into 3 types. Synlophic, with the disk deeply divided into lobes, from which the stamens are born, as an extension that only just allows to discern where one stamen ends and another one starts; the stamens appear widened at the base on what really is the apex of the lobe. Paralophic, with the disk divided into lobes; from the truncated apex of these lobes the stamens are clearly born. Hololophic, with the disk divided into lobes, stamens are not born on the lobe apexes but they are born between the lobes.
However, an excess of confidence in the stability of the disk’s morphology has led to some of the most important confusions within the genus. The best option seems to be to describe the insertion and to differentiate only between those that have the filaments on the lobes and those that have the filaments in between the lobes. The distinction between synlophic and paralophic often depends on the “inspiration” of the person identifying the specimen. Also, this trait is variable in the majority of the species. Some disks are hard to assign to either the synlophic or the paralophic types, since they do not have lobes. This is especially problematic for the group comprising T. nilotica, T. mannifera, T. arborea, T. arabica, etc., that Zohary grouped under T. nilotica.
Baum, B. R., 1978. The genus Tamarix. The Israel Academy of Sciences and Humanities. Jerusalem.
Bihaoui, A., Haddioui, A & Hammada, S. 2020a. Les erreurs d’identification des espèces du genre Tamarix L. au Maroc, clés non uniformes et espèces polymorphes. Ecologia mediterranea. 46, 1: 49-62
Bihaoui, A., Haddioui, A & Hammada, S. 2020b. Distribution géographique des espèces du genre Tamarix L. (Tamaricaceae) au Maroc. Ecologia mediterranea. 46, 1: 63.74.
Lemmel, C., Bakali, A.H. & Garcin, A. 2021. Matériaux pour la Flore du Sahara: le genre Tamarix. Al Yasmina 2 – Tamarix 1/10.
Villar, J.L. 2016. El género Tamarix en el Mediterráneo occidental y áreas adyacentes: aspectos taxonomicos, filogenéticos y nomenclaturales. Tesis Doctoral. Universidad de Alicante. 171 pp.
Villar, J.L., Alonso, M.A., 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. 9999 (9999): 1–20. doi: 10.1111/jse.12478.
Key to species
1 Leaves very small (c. 2 mm) and spaced apart, with fused margins, forming a ring around the twig, giving the branchlet an articulated leafless aspect Tamarix aphylla
1 Leaves of variable size (1-7 mm) and close to each other, ± triangular, with free margins, never completely surrounding the twig 2
2 Flowers tetramerous or pentamerous, with 4-5 stamens 3
2 Flower pentamerous with (8)10(13) stamens 8
3 Flower pentamerous 4
3 Flowers tetramerous (sometimes pentamerous towards the end of the flowering period or in secondary flowerings) 9
4 Racemes (5)6.8 mm wide, born directly on woody branchesof previous years. Branches black or blackish-purple Tamarix africana
4 Racemes narrower (3-6 mm), usually born on herbaceous young twigs of the current year. Branches purple, brownish or reddish-brown 5
5 Leaves sessile, with a ± narrow base, usually not surrounding more than half of the circumference of the twig Tamarix gallica
5 Leaves amplexicaul or subamplexicaul (surrounding more than half the twig), generally longer than wide 6
6 Filaments on the lobes of the staminal disk. Petals 1.5-1.75 mm long Tamarix arborea
6 Filaments in between the lobes of the staminal disk. Petals 1.2-2 mm long 7
7 Leaves sessile, subamplexicaul (longer than wide), with a narrow to subauriculate base, divaricate, sometimes appressed, not imbricate. Petals 1.5-2 mm long. Throughout NE Africa Tamarix senegalensis
7 Leaves from auriculate to amplexicaul, appressed, ± imbricate. Sepals with entire or subentire margin. Petals 1.1-1.5(2) mm long. Middle East, in North Africa only in Egypt and Sudan Tamarix nilotica
8 Leaves short and wide, often wider than long, surrounding the twig almost entirely at its base. Flowers subsessile. Petals 1.5-2 mm long. Capsule 5-6 mm long Tamarix amplexicaulis
8 Leaves longer and narrower, not amplexicaul. Flowers with petiole 1-1.5 mm. Petals 3-5(6) mm long. Capsule 6-12 mm long Tamarix passerinoides
9 Flowers always tetramerous. Styles 3. Capsule dehiscent in 3 valves Tamarix boveana
9 Flowers tetramerous or sometimes pentamerous, both types together in the same raceme. Styles 4. Capsule dehiscent in 4 valves Tamarix tetragyna
Updated by: J.L. Villar.