Polina A. Volkova

Patterns of plastid DNA differentiation in Erythronium (Liliaceae) are consistent with allopatric lineage divergence in Europe across longitude and latitude

Little attention has been paid so far to the genetic legacy of the oceanic-continental gradient across Europe. Due to this gradient, steppe regions become more extensive and mesic environments become more scattered towards the East. A well-suited system to study the impact of this gradient on lineage differentiation is the temperate mesophilic plant Erythronium dens-canis (Liliaceae), which is widespread in southern Europe with a distribution gap in the Pannonian Plain. Moreover, the large disjunction between E. dens-canis and its sister species E. caucasicum coincides with the Pontic steppe region. By applying range-wide sampling of E. dens-canis and limited sampling of E. caucasicum, we explored their phylogeography using the plastid regions rpl32-trnL and rps15-ycf1. Three major phylogroups were identified: a Caucasian lineage, a highly structured and narrowly distributed Transylvanian lineage, and a more homogenous and widely distributed ‘non-Transylvanian’ lineage. Apparently, both physiographic (mountain) and climatic (steppe) barriers have caused allopatric differentiation in European Erythronium. The Southern Carpathians constitute a latitudinal barrier and the Pannonian Plain a longitudinal barrier between the Transylvanian and ‘non-Transylvanian’ lineages of E. dens-canis. The eastern Carpathian Basin likely functioned as a combination of cryptic eastern (mesic) and cryptic northern refugia for E. dens-canis during glacial periods. The Eastern Carpathians and particularly the Pontic steppe regions acted as a longitudinal barrier between E. dens-canis and E. caucasicum. Steppe-dominated gaps in the distribution range of Erythronium are mirrored by genetic discontinuities along longitudes; this highlights the important role of the oceanic-continental gradient throughout Europe for lineage differentiation.

Colour polymorphism in common primrose (Primula vulgaris Huds.): many colours–many species?

Primula vulgaris exhibits flower colour polymorphism in the eastern part of its range, especially pronounced on the NE coast of the Black Sea. This polymorphism in the Caucasian populations has been taxonomically described and some segregated species are listed as rare and endangered. We used sequence variation in two chloroplast noncoding regions (trnL–trnF and rpll32–trnL) and the complete nuclear internal transcribed spacer (ITS) of ribosomal DNA region to investigate correspondence between flower colour and geographical distribution of both nuclear and chloroplast haplotypes. It appears that variability in these DNA regions does not correlate with flower colour, being, however, clearly structured geographically. We used nested clade analysis to explore this geographical structure. It seems that the territory of the Colchis refugium on the E coast of the Black Sea contains both the highest flower colour and haplotype diversities. The results suggest that common primroses colonized the NE coast of the Black Sea from this refugium, spreading along the coast westward. At the same time, the analysis of ITS haplotypes indicates that P. vulgaris colonized the Crimea from NW Anatolia. This makes it clear that no segregated species can be recognized within flower colour polymorphic P. vulgaris in the Caucasus region. However, its phylogeography needs further detailed study on a broader scale.

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.