Late Neogene history of the laurel tree (Laurus L., Lauraceae) based on phylogeographical analyses of Mediterranean and Macaronesian populations

Abstract

Aim The post-glacial range dynamics of many European plant species have been widely investigated, but information rapidly diminishes as one moves further back in time. Here we infer the historical range shifts of Laurus, a paradigmatic tree of the Tethyan flora that has covered southern Eurasia since the Oligo-Miocene, by means of phylogenetic and phylogeographical analyses.Location Mediterranean Basin, Black Sea and Macaronesian archipelagos (Azores, Madeira, Canary Islands).Methods We analysed plastid DNA (cpDNA) sequence (trnK-matK, trnD-trnT) variation in 57 populations of Laurus and three Lauraceae genera. Phylogenetic methods (maximum parsimony and Bayesian inference) and statistical parsimony networks were used to reconstruct relationships among haplotypes. These results were contrasted with the fossil record and bioclimatic niche-based model predictions of past distributions to infer the migration routes and location of refugia. ResultsThe phylogenetic tree revealed monophyly for Laurus. Overall sequence variability was low within Laurus, but six different haplotypes were distinguished and a single network retrieved, portraying three lineages primarily related to geography. A strongly divergent eastern lineage occupied Turkey and the Near East, a second clade was located in the Aegean region and, lastly, a western clade grouped all Macaronesian and central and western Mediterranean populations. A close relationship was observed between the Macaronesian populations of L. azorica and the western populations of L. nobilis. Main conclusionsThe phylogeographical structure of Laurus preserves the imprints of an ancient contraction and break-up of the range that resulted in the evolution of separate cpDNA lineages in its western-and easternmost extremes. Intense range dynamics in the western Mediterranean and multiple glacial refugia contributed to the generation and long-term conservation of this phylogeographical pattern, as shown by the fit between the haplotype ranges and past suitable areas inferred from bioclimatic models. Finally, our results challenge the taxonomic separation of Laurus into two distinct species.

The complex history of the olive tree: from Late Quaternary diversification of Mediterranean lineages to primary domestication in the northern Levant

“…To date, there is no macrofossil for olive LGM persistence in the central Mediterranean basin, but just one piece of anthracological evidence for a presence during the Preboreal at Grotta dell'Uzzo (Sicily), suggesting an early colonization from putative proximal LGM refugia [3]. A similar distribution pattern of genetic diversity and LGM fossils was also reported for Laurus nobilis and Myrtus communis, two other circumMediterranean pre-Pliocene taxa [33,40,41]. The distribution of such species may have thus retracted and expanded in similar ways during the Quaternary glaciations and interglacial periods.…”

Morphological and molecular data from Madeira support the persistence of an ancient lineage ofTaxus baccataL. in Macaronesia and call for immediate conservation actions

“…Although further investigations are in progress, there is a need for a wider samplings, detailed morphological analyses, reproductive tests and additional genetic markers (cf. Shah et al 2008;Rodriguez-Sanchez et al 2009); however, the current evidence appears to support the existence of a new taxon which should be treated, at least, at the same level as the many T. baccata subspecies described on the basis of morphology.…”

Climatic and topographical correlates of plant palaeo- and neoendemism in a Mediterranean biodiversity hotspot

“…1A). Some phylogenetic and phylogeographical studies have proved the validity of such assumption in different lineages (Hampe et al, 2003;Rodr ıguez-S anchez et al, 2009;Liu and Schneider, 2013;Rumsey et al, 2014). This procedure resulted in a siteby-species matrix of 48 ecoregions (Fig.…”