First dated phylogenetic reconstruction of the genus Tamarix (Tamaricaceae): biogeographical implications and hybridization processes in the Mediterranean Basin

Abstract

Abstract The genus Tamarix comprises trees and shrubs that grow mainly in saline habitats. Previous phylogenetic analyses have shown incongruence between different gene trees, which suggest that hybridization processes might have been present in the past. However, the complex pattern of colonization of the Western Mediterranean region has yet to be understood, and no dated phylogeny that reconciles the different gene trees is currently available. The objectives of the study are: (i) to reconstruct the first dated species tree of the genus Tamarix from previously published data, (ii) to evaluate the occurrence of past hybridization, and (iii) to discuss biogeographical implications, mainly focused on the Mediterranean Basin. Our results show that the separation between Tamarix and Myricaria occurred 28.49 Mya, and the crown age of the genus Tamarix is dated at 16.65 Mya. Past hybridization processes might be present in three species: Tamarix amplexicaulis, Tamarix canariensis, and Tamarix minoa. Various colonization events are probable in the Western Mediterranean: a first colonization in the Early Miocene, Tamarix africana during the Late Miocene, and Tamarix boveana and Tamarix gallica during the Pleistocene. In addition, the genus Tamarix migrated to south-western Africa around 5.8 Mya, probably through an ancient arid African corridor, or a long-distance dispersal event.