Abstract
The genus Tamarix (Tamaricaceae) is a lineage of shrubs and trees with leaves reduced to scales and numerous species adapted to moist and often saline soils in arid and semi-arid climates. Extensive morphological variation and hybridization complicate species delimitation and identification. Based on both morphological and DNA sequence characters, Tamarix humboldtiana Akhani, Borsch & N. Samadi is described as a new species from S Iran. Phylogenetic analysis of plastid rpl16 intron and trnG-trnS spacer sequences depicts a sister group relationship of its unique plastid haplotype to T. tetrandra, whereas nuclear ITS sequence data show close affinities to T. kotschyi. The new species differs from T. kotschyi by distinctly pedicellate, 5-merous flowers and vaginate-amplexicaul leaves. The stem and foliar anatomy and the epidermal micromorphology provide additional characters differentiating the new species from T. kotschyi. The gametic chromosome number of n = 12 reflects that of most of other species of the genus. Tamarix humboldtiana is a rare species living at freshwater riversides in S Iran and is according to current knowledge critically endangered.
Highlights
The genus Tamarix L. constitutes the most speciose lineage of Tamaricaceae and is widely distributed in arid zones of the Old World with major diversity in the IranoTuranian area (Baum 1978; Qaiser 1981)
In an ongoing research project on the evolution and diversity of the genus Tamarix, a population deviating morphologically from the widespread T. kotschyi Bunge was discovered in Hormozgan Province, S Iran
Molecular phylogenetic inference indicated that this entity
Summary
The genus Tamarix L. constitutes the most speciose lineage of Tamaricaceae and is widely distributed in arid zones of the Old World with major diversity in the IranoTuranian area (Baum 1978; Qaiser 1981). The monograph of Baum accepted 54 species, a number that has increased to 62 by newly described species There is great discrepancy in the circumscription of species, and regional accounts of Tamarix often arrive at different treatments in comparison to Baum (1978). Species of Tamarix are difficult to delimit because of high morphological plasticity and frequent hybridization (Rusano vich 1986). In an ongoing research project on the evolution and diversity of the genus Tamarix, a population deviating morphologically from the widespread T. kotschyi Bunge was discovered in Hormozgan Province, S Iran.
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