Evolution and biogeography of the endemic Roucela complex (Campanulaceae: Campanula) in the Eastern Mediterranean.

Andrew A Crowl,Nico Cellinese,Clayton J Visger,Ralf Hand,Georgia Kamari,Guilhem Mansion,Hsin‐Hui Wu,Dimitrios Phitos

doi:10.1002/ece3.1791

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.

Highlights

Spatial patterns of biological diversity are shaped by numerous factors, including biotic interactions, habitat heterogeneity, area, climatic constraints, isolation, and anthropogenic events (Huston 1994)
We focus on the Roucela complex – referred to as the drabifolia species complex by Carlstro€m (1986) – which includes small, herbaceous, annual Campanula species restricted to the Mediterranean Basin, characterized by the presence of unappendaged calyx lobes (Carlstro€m 1986; Lammers 2007)
Our results provide detailed insights into the evolutionary history of Campanula species in the eastern Mediterranean

Summary

Introduction

Spatial patterns of biological diversity are shaped by numerous factors, including biotic interactions, habitat heterogeneity, area, climatic constraints, isolation, and anthropogenic events (Huston 1994). Uncovering the relative contributions of these factors and evolutionary dynamics responsible for driving endemism is essential to understanding plant diversity and may have important implications for conservation. Endemic species are nonrandomly distributed across terrestrial habitats and appear to be concentrated in specific regions, or “hotspots” of biodiversity (de Candolle 1875; Kruckeberg and Rabinowitz 1985; Myers et al 2000), such as the Mediterranean Basin (e.g., Medail and Quezel 1997; Thompson 2005). The complex, but well understood, climatic and geologic history of this region provides an ideal setting for studying endemism, evolution, and biogeography. While the western Mediterranean Basin has been relatively well studied (e.g., Mansion et al 2008, 2009), the eastern basin remains poorly understood.

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Discussion

Conclusion