Low effective population size and high spatial genetic structure of black poplar populations from the Oder valley in Poland

Błażej Wójkiewicz,Weronika B Żukowska,Andrzewj Lewandowski,Monika Litkowiec,Witold Wachowiak

doi:10.1007/s13595-021-01055-2

Abstract

ContextBlack poplar (Populus nigra L.) is a keystone species of European riparian ecosystems that has been negatively impacted by riverside urbanization for centuries. Consequently, it has become an endangered tree species in many European countries. The establishment of a suitable rescue plan of the remaining black poplar forest stands requires a preliminary knowledge about the distribution of genetic variation among species populations. However, for some parts of the P. nigra distribution in Europe, the genetic resources and demographic history remain poorly recognized.AimsHere, we present the first study on identifying and characterizing the genetic resources of black poplar from the Oder valley in Poland. This study (1) assessed the genetic variability and effective population size of populations and (2) examined whether gene flow is limited by distance or there is a single migrant pool along the studied river system.MethodsA total of 582 poplar trees derived from nine black poplar populations were investigated with nuclear microsatellite markers.Results(1) The allelic richness and heterozygosity level were high and comparable between populations. (2) The genetic structure of the studied poplar stands was not homogenous. (3) The signatures of past bottlenecks were detected.ConclusionOur study (1) provides evidence for genetic substructuring of natural black poplar populations from the studied river catchment, which is not a frequent phenomenon reported for this species in Europe, and (2) indicates which poplar stands may serve as new genetic conservation units (GCUs) of this species in Europe.Key messageThe genetic resources of black poplar in the Oder River valley are still substantial compared to those reported for rivers in Western Europe. On the other hand, clear signals of isolation by distance and genetic erosion reflected in small effective population sizes and high spatial genetic structure of the analyzed populations were detected. Based on these findings, we recommend the in situ and ex situ conservation strategies for conserving and restoring the genetic resources of black poplar populations in this strongly transformed by human river valley ecosystem.

Highlights

Black poplar (Populus nigra L.) is a characteristic alluvial forest tree species of great ecological and economic importance in European riparian ecosystems
Key message The genetic resources of black poplar in the Oder River valley are still substantial compared to those reported for rivers in Western Europe
Clear evidence of negative genetic changes in the studied black poplar populations from the Oder valley reflected in the high spatial genetic structure and low effective population sizes was presented in this study

Summary

Introduction

Black poplar (Populus nigra L.) is a characteristic alluvial forest tree species of great ecological and economic importance in European riparian ecosystems. As a pioneer tree species, it dominates at the first stage of succession in riverine forests and contributes to riverbank restoration and flood control. Natural poplar forests, known as Salici-Populetum (willow-poplar forest) or Populetum albae (poplar forest), are centers of biodiversity and host ecosystems of threatened and common animals, including insects. They serve as natural corridors that connect larger forest units (Šiler et al 2014). Black poplar has been used in breeding programs aimed at the development of new highly resistant and fast-growing poplar varieties for years. Due to its high plasticity, the species plays an important role in phytoremediation projects in postindustrial areas (Koskela et al 2004; lsebrands et al 2014)

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