Incomplete climate-driven peripatric speciation in Moehringia sect. Moehringia (Caryophyllaceae) in the European Alps

The origin of endemic species in the European Alps is commonly attributed to the climatic oscillations of the Quaternary. Moehringia sect. Moehringia, with 12 of 15 species endemic to the Alps and mostly restricted to well-known glacial refugia, is a prime system for investigating the diversification of a lineage originating in the Alps.

We used all species in this lineage, most of which were represented by multiple accessions, and a target enrichment approach with baits specifically designed for Moehringia to obtain a phylogenetic tree from 829 nuclear loci. We also dated the phylogenetic tree with a molecular clock approach.

Most species originated in the Quaternary. Four regionally distributed species (M. intermedia, M. markgrafii, M. papulosa, M. tommasinii), all nested within the widespread M. muscosa, were found to be between 1.36 and 0.25 million years old. Moehringia muscosa and the four species derived from it differ in habitat, leaf succulence, and glaucousness.

Because the widespread species has not coalesced into monophyly and the regionally distributed species have evolved in glacial refugia, we consider speciation in this lineage incomplete and climate-driven. Divergence in habitat and leaf morphology between the widespread and the derived species suggests a role of adaptive evolution.