Assessing Evolutionary Significant Units (ESU) of the Endangered Freshwater Pearl Mussel (Margaritifera margaritifera) in Southeast Norway on the Basis of Genetic Analysis.

Arne N Linløkken,Silje Garlie,Wenche Johansen,Robert C Wilson

doi:10.3390/genes11091061

Abstract

A total of 312 specimens of freshwater pearl mussel (Margaritifera margaritifera) were sampled from 11 populations, located in four different river systems in Southeast Norway, and analyzed for 11 simple sequence repeat (SSR) (microsatellite) markers. All study populations have landlocked brown trout (Salmo trutta) as the only possible host. Several populations had experienced recruitment failure, probably due to low pH (about 6.0) and calcium concentration. STRUCTURE clustering analysis revealed two genetic clusters, of which one cluster occurred mainly in the western river systems, and totally dominated in one population (Fallselva (A-FAL)) that had higher genetic diversity than the others. Cluster 2 completely dominated in the populations of the eastern river systems, and all of them had low genetic diversity. Bottleneck events were indicated in all populations and the inbreeding coefficient FIS was significant in all populations, except for the southernmost population (Sørkedalselva (B-SØR)), which was the only population with genotypes in Hardy–Weinberg equilibrium. FIS were especially high in the populations of the eastern river systems, and maximum shell length was negatively correlated to FIS. If artificially breeding and stocking should become necessary for future preservation, it should be based on single populations; alternatively, the eastern populations should be based on cross-breeding of populations within the cluster to increase their genetic diversity.

Highlights

Freshwater bivalvia is a group with several endangered species, and the freshwater pearl mussel (Margaritifera margaritifera) is one of the most threatened [1,2,3,4]
Supportive measures must be considered, and this study aimed to explore the genetic structure and diversity by means of simple sequence repeats (SSRs) of mussels from 11 sampling locations situated in four main river systems
Due to an established theory of immigration history of fish in southeast Norway [41], groups of populations may have different ancestry. Conservation measures such as semiartificial infections of host fish and supportive breeding must be based on local strains [28], and this study explored genetic structure to reveal the populations’ ancestry, degree of isolation, and their genetic diversity to assess inbreeding and the populations’ evolutionary potential

Summary

Introduction

Freshwater bivalvia is a group with several endangered species, and the freshwater pearl mussel (Margaritifera margaritifera) is one of the most threatened [1,2,3,4]. It is on the European Red. List [5]. In the management of biological resources, conservation of threatened species is an important issue, and extinction due to habitat loss may be a scenario with survival in captivity as the worst case alternative [16]. Several concepts are used in management and research, such as conservation

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