Abstract
Chiliadenus is a small genus in the Inuleae (Asteraceae), consisting of ten species with allopatric distributions along the southern edge of the Mediterranean Sea. The different species have restricted areas of distribution, with only one being more widely distributed. The first molecular phylogenetic study of the genus with complete sampling, as well as a biogeographic analysis of the origin and biogeographic patterns leading to the current diversity of Chiliadenus is presented. Results confirm Chiliadenus as monophyletic and placed as sister to Dittrichia. The ancestor of Chiliadenus is dated to have diverged from that of Dittrichia around 5.45 Ma ago, coinciding with the Messinian salinity crisis, whereas the Chiliadenus crown group is dated to 2.29 Ma, around 3 million years later. Ancestral area reconstructions show the crown group to likely have originated in the area around Morocco and northwestern Algeria, which is also the area where the early divergences have occurred. Chiliadenus has then later diverged and dispersed over the Mediterranean to its current distribution. The evolution of the Chiliadenus crown group coincides with the onset of the Mediterranean climate, and its evolution may be connected to the subsequent climatic changes.
Highlights
The Mediterranean basin is well known for its high plant diversity and its high level of endemism
Chiliadenus is estimated to have diverged from Dittrichia around 5.45 Ma (95% HPD 3.25–8.55 Ma; Fig. 3, node 1), with continental southwestern Europe, Morocco and northwestern Algeria (B) estimated as the most probable ancestral area [with a posterior probability of 0.43 for A, 0.26 for B]
A clade consisting of Chiliadenus saxatilis, C. sericeus, and C. antiatlanticus (PP = 1.0; Fig. 3, node 3), with current distributions in continental southwestern Europe, Morocco and Algeria, respectively, is estimated to 1.03 Ma (0.42–1.91 Ma)
Summary
The Mediterranean basin is well known for its high plant diversity and its high level of endemism. The flora comprises around 24–25.000 plant species, up to around 60% of which are endemic to the area (Greuter 1991). The high diversity has often been explained by a combination of the heterogeneous landscape and the results of important geological events, climatic oscillations, the complex geography, and topography of the area (Thompson 2005; Bonanno and Veneziano 2016). Much remains unknown, and studies of the taxa that together make up the Mediterranean flora are of great interest.
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