No obvious genetic erosion, but evident relict status at the westernmost range edge of the Pontic‐Pannonian steppe plant Linum flavum L. (Linaceae) in Central Europe

Abstract

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.

Long-term survival and successful conservation? Low genetic diversity but no evidence for reduced reproductive success at the north-westernmost range edge of Poa badensis (Poaceae) in Central Europe

“…Focusing on the Central European distribution of Poa badensis, we defined a study transect (cf. Plenk et al 2017 ) crossing Central Hungary and the eastern parts of Lower Austria in the east, and reaching the (north)westernmost isolated occurrences of the species in Western Germany (Fig. 1 ).…”

“…Depending on the variability of the ancestral gene pool, as well as the probability of and time for accumulation of de novo mutations and/or effects of lineage sorting (Avise 2000 ), these relict populations could hold comparatively high levels of unique genetic diversity (cf. Schmitt and Varga 2012 ; Kajtoch et al 2016 ; Plenk et al 2017 ). The increasing isolation at the distributional periphery and the subsequently increasing genetic differentiation of populations due to genetic drift may have additionally led to high levels of regional genetic diversity; characteristics similar to those described by Hampe and Petit ( 2005 ) for ‘stable’ rear edge populations.…”

“…Besides hypotheses on centrality-marginality phenomena, the existence of extrazonal, small-scale refugia, persisting in situ during the Quaternary or even longer (e.g. Plenk et al 2017 ), must also be considered. In Central Europe, where steppe species today reach their absolute westernmost distribution limit (cf.…”

Formalized classification of semi-dry grasslands in central and eastern Europe

“…In addition to climatic differences, which undoubtedly exist between the regions, historical processes might be responsible for the observed floristic gradients, such as (i) delayed immigration of thermophilous species from glacial refugia in south-eastern Europe (Magyari et al 2010), or (ii) regional extinction of steppe species during the "mid-Holocene bottleneck" due to the spread of deciduous forests in some parts of central Europe, but survival of steppe in other parts (Pokorný et al 2015). Which of these factors plays the main role is not clear, but recent studies on the phylogeography of steppe species indicate that the second process is probably more important than previously thought (Kajtoch et al 2016, Plenk et al 2017.…”

Genetic diversity of Herpetospermum caudigerum (Ser.) Baill using AFLP and chloroplast microsatellites

“…The median-joining model implemented to investigate the evolutionary relationships between haplotypes in NETWORK 4.6.1.2 [31]. To estimate the degree, genetic differentiation was performed by the molecular variance (AMOVA) analysis according to Arlequin V3.5 software [32]. The population genetic structure was analysed as described previously.…”