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.

Kristina Plenk,Katharina Bardy,Maria Höhn,Mike Thiv,Matthias Kropf

doi:10.1002/ece3.2990

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.

Highlights

Glacial and interglacial periods of the Quaternary led to several drastic range shifts of European organisms during the last ca. 2.5 million years, with climatic oscillations being most pronounced starting 800,000 years ago
Population code, category of estimated population size, estimates of genetic diversity based on amplified fragment length polymorphisms (AFLPs)/cpDNA data and number of haplotypes of twelve Linum flavum L. populations sampled in the study regions Swabian Alb (Germany), Lower Austria, and Central Hungary
Results of the AFLP outlier analysis based on 289 amplified fragment length polymorphism (AFLP) fragments, performed using the ARLEQUIN software at the 99% confidence level

Summary

| INTRODUCTION

Glacial and interglacial periods of the Quaternary led to several drastic range shifts of European organisms during the last ca. 2.5 million years, with climatic oscillations being most pronounced starting 800,000 years ago (ya; Lowe & Walker, 2014). The remaining steppe areas are restricted to sites unsuitable for intensive farming (e.g., dry calcareous or sandy grasslands, rocky slopes, gravel, loess or salt soils, and patches in open xerophilous forest communities), leading to fragmented and isolated populations of today often endangered steppe species (Meindl, 2011; Poschlod & WallisDeVries, 2002) Based on this general scenario of steppe vegetation history, thermophilic (nonwoody steppe) species arrived in Central Europe during more than one westward expansion waves in pre-L GM, glacial, or early postglacial times and could have persisted in situ within extreme habitats described above throughout the Holocene (i.e., without interim retreat, indicating their possible relict status; cf Stewart & Lister, 2001; Schmitt & Varga, 2012; Kajtoch et al, 2016; but see Wilmanns, 2005). We will answer the question whether the specific biogeographical history of this species at the (westernmost) range edge covers basically expected patterns regarding peripheral populations (i.e., showing genetic erosion and strong population differentiation within the westernmost Swabian Alb exclave)

| MATERIALS AND METHODS

| DISCUSSION

| CONCLUSIONS ON CONSERVATION GENETIC ASPECTS

DATA ACCESSIBILITY