Genetic diversity of Phalaris arundinacea populations in relation to river regulation in the Merkys basin, Lithuania

Abstract

During the 1950s–1960s, the Merkys river basin, the largest protected area of Lithuania,underwent severe anthropogenic regulations. Within the Baltic States, the genetic diversity ofPhalaris arundinacea populations is unknown and how they might be affected by anthropogenicactivities such as river regulation. The objectives of this study were to compare molecularparameters (SSRs or microsatellite loci) within and among populations from natural river fragmentswith populations from regulated river parts. Study populations have greater genetic diversitywithin, rather than among, populations. The upstream portion of the Merkys basin populationshad lower genetic diversity compared with further downstream. The mean number of polymorphicSSR loci was lower for populations from regulated parts of the river basin compared with naturalones. Main principle coordinate analysis revealed populations of regulated rivers at marginal posi-tions. Bayesian clustering showed that current populations are admixtures of 3 distinct geneticgroups, based on STRUCTURE analysis (K = 3 groupings) in geographic subdivisions of (a) down-stream populations (Varėnė, Verseka, Upper Grūda, Lower Grūda, Upper Merkys, Lower Merkys),(b) upstream populations (Upper Šalčia, Beržė, Lower Šalčia, Visinčia, Lower Šaltykščia, Nedilė), and(c) the 2 regulated sites in the distinct geographic area of Taurupis and Upper Šaltykščia.P. arundinacea in the Merkys river basin does not all belong to a single, random‐mating populationencompassing its tributaries or among populations across its geographic scales. In severalinstances, river regulation might impair the genetic diversity of P. arundinacea populations.