Data from: The building of a biodiversity hotspot across a land-bridge in the Mediterranean

Many of the macroevolutionary processes that have shaped present-day phylogenetic patterns were caused by geological events such as the temporary joining of continents. The study of phylogenetic diversity in space can thus provide information on these events. Here we focus on the western Mediterranean biodiversity hotspot in the southern Iberian Peninsula and northwest Africa, two regions that are separated by the Strait of Gibraltar, and explore the spatial structure of the phylogenetic relationships within and across large-scale plant assemblages. Significant ‘true’ turnover in deep lineages tends to occur within landmasses following a general decreasing precipitation gradient eastward. In contrast, significant ‘true’ turnover in terminal lineages tends to occur between landmasses. Plant assemblages in the western ecoregions of this hotspot tend to be phylogenetically over-dispersed but are phylogenetically clustered on its eastern margins. Phylogenetic patterns are discussed in light of potential scenarios of niche evolution (or conservatism) and lineage diversification. In particular, the significant turnover between landmasses suggests a common scenario of allopatric speciation that could have been facilitated by the intermittent joining of the two continents, which would have constituted an important stimulus for diversification and the emergence of Mediterranean hotspots.