We investigate patterns of genetic variation along an east–west transect of Central European populations of Linum flavum and interpret the Quaternary history of its peripheral populations, especially those at the westernmost isolated range edge, discussing their migrations and possible relict status. We defined our peripheral transect across three study regions from Central Hungary, eastern Austria to southwestern Germany. Using AFLP fingerprinting and cpDNA sequence variation (rpL16 intron, atpI‐H), we analyzed 267 and 95 individuals, respectively, representing each study region by four populations. Hierarchical AMOVA (AFLPs) indicated significant variation among study regions (12% of total variance) and moderate differentiation between populations (10%). Population differentiation was high at the westernmost range edge (11.5%, Germany), but also in the east (13.4%, Hungary), compared to the Austrian study region (8.6%). Correspondingly, AFLP diversity was highest in the center of the study transect in eastern Austria. CpDNA haplotypes support a pattern of regional structuring with the strongest separation of the westernmost range edge, and some haplotype sharing among Austrian and Hungarian individuals. Equilibrating nucleotide versus haplotype diversity patterns, the highly diverse populations at the Pannonian range edge (Austria) indicate long‐term persistence, while Central Pannonian populations are obviously effected by recent bottlenecks. Intermediate nucleotide, but high haplotype diversity within the westernmost exclave (Swabian Alb), is indicative of a founder bottleneck during its pre‐LGM or early postglacial migration history, followed by sufficient time to accumulate cpDNA variation. The not obviously reduced genetic diversity and distinctiveness of L. flavum at the westernmost range edge suggest a long‐term persistence (relict status) of populations in this region, where the species has survived probably even the Würm glaciation in extra‐Mediterranean refugia. This genetic relict variation represents an important part of the overall genetic diversity found in the western periphery of this steppe plant and highlights the high conservation priority of respective gene pools.

Aim The steppe grasslands of eastern Central Europe are exceptionally species rich and valuable from a nature conservation point of view. However, their historical biogeography is still poorly understood. Here we use the regional diversity of habitat specialists and chloroplast DNA data to investigate potential long‐term refugia of steppe species in this region. Location Pannonian Basin and adjacent regions; SW Russia. Taxon Vascular plants. Methods After identifying habitat specialists of the three main steppe types (meadow steppes, grass steppes and rocky steppes), we compiled their regional presence–absence in grid cells of 75 km × 75 km. We analysed the dependency of habitat specialist diversity to climate, topographic heterogeneity and geographical distance to potential refugia. For genetic analysis, we sampled three or four habitat specialists of each steppe type and used cpDNA markers to investigate intraspecific diversity and geographical distribution of haplotypes. We also tested for correspondence between the number of habitat specialists and haplotype diversity. Results Climate and topography explained between 40% and 63% of the variance in habitat specialist diversity. Adding geographical distance to potential refugia increased the explained variance in the models for all steppe types. Chloroplast haplotypes featured a complex pattern across the study area. Several species showed a strong geographical differentiation, suggesting migration waves from multiple refugia with only limited subsequent genetic intermixture. Maximum haplotype diversity in a region showed a better correlation with the number of habitat specialists per steppe type than mean haplotype diversity. Main conclusions We can clearly reject the scenario of a late‐Holocene immigration of steppe species from areas outside the Pannonian Basin. Most species must have been present in the region since at least the early Holocene, highlighting the importance of the lower mountain ranges surrounding the Pannonian Basin as long‐term refugia for European steppe species. Dispersal limitation and resulting migration lags seem to have a strong influence on the distribution of steppe species in Central Europe.

Phenotypic polymorphism represents the most obvious type of intraspecific diversity raising scientific interest in its evolution and maintenance. We studied the regional endemic Gentianella bohemica, which exhibits an early- and a late-flowering morph. Genetic variation and structuring were investigated in relation to potential pollination and mating system differences, to verify hypotheses of evolutionary integrity, origin, and reproductive isolation of both flowering morphs. We identified the rarer early-flowering morph as an independent genetic entity, being more selfing, likely stronger pollinator-limited and reproductively isolated. All analysed populations showed strong among population differentiation and low overall genetic diversity due to habitat fragmentation and reduced population sizes. These results indicate likely inbreeding, but we also found evidence for possible outbreeding depression in the late-flowering morph. Both G. bohemica morphs are characteristic of traditionally used, nutrient-poor grasslands, but they represent independent conservation units and need temporally adapted management. We, therefore, also briefly discuss our results in the general context of conservation activities in relation to intraspecific polymorphisms and strongly argue for their formal and consequent consideration.

Many steppe species reach their (north)westernmost distribution limit in western Central Europe. This also applies to Poa badensis , a rare steppe plant of calcareous rock/sand vegetation. To explore potential differences in reproductive success and genetic composition of peripheral populations, we analysed the absolute (north)westernmost occurrences in Western Germany and populations at the western margin (Eastern Austria) and the centre (Central Hungary) of the Pannonicum, representing a part of the continuous range. Specifically, we discuss the genetic and reproductive constitution of the (north)westernmost exclave and draw conclusions on the species’ biogeographical and conservation history in this region. Therefore, we used two independent molecular marker systems (AFLPs, cpDNA sequences) and a set of performance parameters. Overall, lowest regional genetic diversity was found in Western Germany, which is mainly a result of the specific history of two populations. However, this low genetic diversity was not accompanied by reduced reproductive success. The Eastern Austrian populations showed reduced genetic diversity and predominantly reduced performance, interpreted as a consequence of small population sizes. Central Hungarian populations showed the overall highest genetic diversity and comparatively high performance values. We observed high admixture and haplotype sharing between Austrian and Hungarian populations, indicating gene flow among these regions. In contrast, we interpreted the increased population differentiation within, and the clear distinctiveness of the German exclave as a long-term isolation of these (north)westernmost occurrences. Our results, overall, prove the good constitution of these populations and, together with their particular biogeographical history, highlight their conservation value. Electronic supplementary material The online version of this article (10.1007/s10531-019-01722-x) contains supplementary material, which is available to authorized users.

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The Euro-Siberian steppe flora consists of warm- and cold-adapted species, which may have responded differently to Pleistocene glacials and interglacials. Genotyping-by-sequencing individuals from across the distribution range of the pheasant’s eye (Adonis vernalis), we aimed to gain insight into steppe florogenesis based on the species’ evolutionary history. Although the primary area of origin of the species group comprising A. vernalis, A. villosa and A. volgensis is in Asia, our results indicate that recent populations of A. vernalis are not of Asian origin but evolved in the southern part of Europe during the Pleistocene, with Spanish populations clearly genetically distinct from the Southeastern European populations. We inferred that A. vernalis migrated eastwards from the sub-Mediterranean forest-steppes of Southeastern Europe into the continental forest-steppe zone. Eastern European populations had the highest private allelic richness, indicating long-term large population sizes in this region. As a thermophilic species, A. vernalis seems unlikely to have survived in the cold deserts of the Last Glacial Maximum in Western Siberia, so this region was likely (re)colonized postglacially. Overall, our results reinforce the importance of identifying the area of origin and the corresponding ecological requirements of steppe plants in order to understand the composition of today’s steppe flora.