Format: ORAL

Alejandro Terrones1,2, Joaqun Moreno3, Ana Juan2

1 Estación Experimental de Zonas Áridas (EEZA), CSIC, Almería, Spain 2 University of Alicante, Alicante, Spain 3 Miguel Hernández University of Elche, Elche, Spain

The genus Tamarix comprises trees and shrubs that grow mainly in saline habitats. In the Western Mediterranean region, three different species naturally occur: T. africana, T. boveana and T. gallica. These three species do not form a monophyletic group and some morphological intermediate samples have been mentioned. The species T. gallica is the most common one, and due to its complex morphology, it has been misidentified with T. canariensis, an endemic species from the Canary Islands. The aim of this work is to study the phylogeographic history and genetic diversity of the T. gallica populations in the Western Mediterranean, and to understand the natural hybridization processes between T. gallica and different co-occurring species. For this purpose, fourteen polymorphic nuclear microsatellite markers were analyzed, and two different plastid regions were sequenced for 377 individuals of T. gallica from its complete natural distribution and some individuals from other related species. Our results show that current hybridization processes between co-existing species are much more common than previously reported, even between phylogenetically distant species. The three Western Mediterranean species T. africana, T. boveana and T. gallica hybridize between them with different degrees of introgression in natural populations that do not always involve morphological variability. Besides, T. gallica has a genetically complex relationship with other species, since it shares haplotypes with other geographically distant species from the Eastern Mediterranean region. Nonetheless, the genetic structure of T. gallica population reveals certain clear geographic patterns. In addition, African populations showed a higher genetic diversity, and it diminished towards the north of the Mediterranean Basin. Our results show that incomplete lineage sorting and reticulate evolution have been crucial in the evolution of the genus, and all these processes might be the underlying cause for the morphological confusion between species.