Phylogeography of the European rock rose Helianthemum nummularium s.l. (Cistaceae) : western richness and eastern poverty

Helianthemum nummularium s.l. is a young, morphologically diverse species distributed from western Europe to the Caucasus and the Southern Urals in the east. We analysed the rps16-trnK plastid intergenic spacer sequences from 85 localities covering most of the range of H. nummularium. Thirteen haplotypes were very unevenly distributed throughout the range of the species, and exhibited a strong phylogeographic signal. The results confirm range expansions of H. nummularium from Mediterranean refugia northwards, but also show the major role of eastern European (the Caucasus and the Southern Urals) refugia in rapid postglacial colonization of east, north and central Europe. The plastid haplotypes form distinct clades, one representing an eastern European lineage with few haplotypes and the other representing a western European lineage with many haplotypes. Parallel to this split in haplotype diversity is the pronounced differentiation in morphological variation displayed by the taxa found in west and east Europe. We discuss the role of topography in generating differences in morphological and genetic diversity between these two groups. We also discuss the taxonomical status of Helianthemum arcticum, which is regarded as an endangered local endemic of the Kola Peninsula. Helianthemum arcticum appears to represent an outlying peripheral population of H. nummularium preserved since the last postglacial major range expansion of this species, and bears the same plastid haplotype as the bulk of east and north European populations

Molecular Phylogeny and Phylogeography of Potentilla multifida L. agg. (Rosaceae) in Northern Eurasia with Special Focus on Two Rare and Critically Endangered Endemic Species, P. volgarica and P. eversmanniana

The results of a molecular genetic study of Potentilla multifida agg. using two plastid markers (ndhC-trnV and psbA-trnH) and a nuclear ITS marker suggested that this group comprises a number of relatively young and incompletely differentiated species widely distributed in Northern Eurasia. The sequences were analyzed using tree-based (maximum likelihood) and network-based (statistical parsimony network) approaches. The plastid data suggested incomplete lineage sorting, characteristic of the group as a whole. The nuclear ITS results demonstrated quite a different pattern, with mostly conspecific accessions shaping monophyletic clades. The majority of the Potentilla sect. Multifidae species studied possess few, usually closely related plastid haplotypes, or are even monomorphic. In contrast, P. volgarica, a narrow endemic from the Volga River valley, presents plastid haplotypes belonging to two distantly related groups. Such a pattern of genetic diversity in P. volgarica may be explained by a long persistence of the species within an extremely small distribution range, on the right bank of the Volga River, most likely representing a contemporary refugium. The genealogy of plastid markers in P. volgarica suggests that this species is ancestral to P.eversmanniana, another narrow endemic from the S Urals

Is Salix fursaevii Mavrodiev (Salicaceae) a palaeoendemic of the Volga River valley or an ecotype of S. triandra L.?

Salix fursaevii, a species endemic to the Volga River flood plain, was described by E. Mavrodiev and co-authors in Byull. Moskovsk. Obshch. Isp. Prir. in 2012. It differs from the closely related and widespread S. triandra by a few quantitative morphological characters and, most of all by its much later flowering time. This late-flowering willow was known and studied before as an ecotype of S. triandra. Our study of a large sample of S. triandra s. l. revealed that 1) S. triandra s. str. and S. fursaevii could not be clearly distinguished using several morphological characters and the time of flowering; 2) specimens morphologically corresponding to S. fursaevii are with a single exception strictly confined to the Volga River flood plain; 3) the populations of S. triandra and S. fursaevii do not differ by nrITS sequences; 4) the populations of S. triandra and S. fursaevii are poorly differentiated by chloroplast atpB-rbcL sequences; 5) representatives of both taxa are tetraploids 2n = 4x = 76. Poor differentiation of populations by chloroplast sequences is indicative of the intraspecific variability, the geographic pattern of which suggests that the Volga River valley was a probable glacial refugium and a source of post glacial spread of S. triandra