Abstract
At the intersection of geological activity, climatic fluctuations, and human
pressure, the Mediterranean Basin – a hotspot of biodiversity – provides an
ideal setting for studying endemism, evolution, and biogeography. Here, we
focus on the Roucela complex (Campanula subgenus Roucela), a group of 13
bellflower species found primarily in the eastern Mediterranean Basin. Plastid
and low-copy nuclear markers were employed to reconstruct evolutionary
relationships and estimate divergence times within the Roucela complex using
both concatenation and species tree analyses. Niche modeling, ancestral range
estimation, and diversification analyses were conducted to provide further
insights into patterns of endemism and diversification through time.
Diversification of the Roucela clade appears to have been primarily the result
of vicariance driven by the breakup of an ancient landmass. We found geologic
events such as the formation of the mid-Aegean trench and the Messinian
Salinity Crisis to be historically important in the evolutionary history of
this group. Contrary to numerous past studies, the onset of the Mediterranean
climate has not promoted diversification in the Roucela complex and, in fact,
may be negatively affecting these species. This study highlights the diversity
and complexity of historical processes driving plant evolution in the
Mediterranean Basin.