Phylogeography of the European rock roseHelianthemum nummularium(Cistaceae): incongruent patterns of differentiation in plastid DNA and morphology

Abstract

Helianthemum nummularium is a morphologically variable species that has been subdivided into several subspecies based on indumentum characters. We investigated four of these subspecies for variation in plastid DNA and leaf and petal shape in Europe. Three size-variable mononucleotide repeat regions were amplified by means of species-specific primers and 18 combined haplotypes were identified. The highest haplotype diversity was found in the Alps and the surrounding lowland areas, whereas marginal areas such as northern Europe and the south-eastern Balkans had a lower diversity. Most of the common haplotypes were shared between subspecies and showed a geographical structuring across the range of the species, whereas geographically restricted haplotypes were found elsewhere (e.g. in the Baltic area). Leaf and petal shape descriptors could not differentiate between subspecies. The role of hybridization and introgression between post-glacial migration lineages is discussed. As an alternative hypothesis to introgression between ancient taxa, we suggest that the poor correspondence between plastid haplotype distribution and subspecies circumscription could be a result of multiple origins of similar morphs (grouped into taxonomic subspecies) in different parts of the distribution range of the complex.

Genetic and morphological differentiation across a contact zone between two postglacial immigration lineages of Helianthemum nummularium (Cistaceae) in southern Scandinavia

“…Using microsatellites, Soubani et al (2014) identified 18 plastid haplotypes that show geographical structuring across the west and south European range of the distribution area of H. nummularium. The mosaic distribution of plastid haplotypes in south and central Europe indicates a complex glacial and post-glacial migration history of the species.…”

“…nummularium is the absence/ presence of a dense cover of stellate hairs on the abaxial surface of the leaf. However, there are no correlation between taxonomic subdivision and distribution of plastid haplotypes within H. nummularium (Soubani et al 2014;Volkova P. A. unpubl. data).…”

“…Helianthemum nummularium shows great morphological variation in leaf shape (length and width) and in indumentum characters (Janchen 1909;Soubani et al 2014;Widén 2010;Widén unpubl. data).…”

“…data). The species reached southern Scandinavia via two migration routes, one from southwest and one from east (Soubani et al 2014;Volkova P. A. unpubl. data).…”

Inheritance of a hair character in Helianthemum oelandicum var. canescens and allele frequencies in natural populations

“…The two species complexes H. nummularium and H. oelandicum with the widest geographical distribution and belonging to different sections of the genus are of special interest. Recent studies based on samples covering large parts of their distributions have shown poor correlations between indumentum and size of leaves and petals (taxon identity) and plastid haplotypes (Soubani 2010;Soubani et al 2014;Volkova et al 2016), indicating extensive hybridization between taxa/morphs in both species. Experimental studies have shown weak crossing barriers within the two species (Widén 1986(Widén , 2015.…”