Strategies for the conservation of endangered freshwater pearl mussels (Margaritifera margaritifera L.): a synthesis of Conservation Genetics and Ecology

Abstract

Freshwater pearl mussels (Margartifera margaritifera L.) are among the most critically threatened freshwater bivalves worldwide. The pearl mussel simultaneously fulfils criteria of indicator, flagship, keystone and umbrella species and can thus be considered an ideal target species for the process conservation of aquatic ecosystem functioning. The development of conservation strategies for freshwater pearl mussels and for other bivalve species faces many challenges, including the selection of priority populations for conservation and strategic decisions on habitat restoration and/or captive breeding. This article summarises the current information about the species' systematics and phylogeny, its distribution and status as well as about its life history strategy and genetic population structure. Based on this information, integrative conservation strategies for freshwater mollusc species which combine genetic and ecological information are discussed. Holistic conservation strategies for pearl mussels require the integration of Conservation Genetics and Conservation Ecology actions at various spatial scales, from the individual and population level to global biodiversity conservation strategies. The availability of high resolution genetic markers for the species and the knowledge of the critical stages in the life cycle, particularly of the most sensitive post-parasitic phase, are important prerequisites for conservation. Effective adaptive conservation management also requires an evaluation of previous actions and management decisions. As with other freshwater bivalves, an integrative conservation approach that identifies and sustains ecological processes and evolutionary lineages is urgently needed to protect and manage freshwater pearl mussel diversity. Such research is important for the conservation of freeliving populations, as well as for artificial culturing and breeding techniques, which have recently been or which are currently being established for freshwater pearl mussels in several countries.

Transcriptomic responses of the endangered freshwater mussel Margaritifera margaritifera to trace metal contamination in the Dronne River, France

“…This species can be found in cool running waters of the Holarctic region. The European population decline was estimated to be 90% by the 1990s, due to pearl harvesting, predation, and habitat degradation, coupled with a decrease of host fish populations necessary for larval growth and dispersion (Geist 2010). Most unionids have indeed a complex reproductive cycle including an ectoparasitic stage on fish; the glochidia are released into the water and attach to the gills or fins of a suitable host fish (Salmo trutta fario for M. margartifera) for several weeks until transformation into juvenile mussels.…”

“…The last estimate of the French population was of a maximum of 100,000 individuals. While most of the populations are small with a maximum of 300 individuals, a large population of about 16,000 is found in the Dronne River (Geist 2010).…”

“…Interestingly, the occurrence of young individuals along the Dronne River may indicate successful recruitment over the last decade. Indeed, according to Geist (2010), the vast majority of European populations are extremely overaged, with the youngest individuals usually being 30-50 years old.…”

Impacts of climate change and land-use scenarios on Margaritifera margaritifera, an environmental indicator and endangered species

“…Freshwater invertebrates received much less attention but inside this group freshwater mussels are among the species frequently used in those studies or programs, because they play an important role in the ecosystem, with some species being classified as indicator or umbrella species, and are one of the most endangered groups of animals on the planet (Bogan, 2008;Galbraith et al, 2010;Geist, 2010;Howard and Cuffey, 2006;Lopes-Lima et al, 2014;Skinner et al, 2003;Sousa et al, 2013). Due to its large size, sedentary, long life span and variable sensitivity to environmental contaminants, freshwater bivalves can also be very useful as indicators of ecological integrity and as sentinels of environmental perturbation (Farris and Van Hassel, 2006).…”

“…The freshwater pearl mussel (M. margaritifera) is one of the most threatened freshwater bivalves worldwide (Geist, 2010). This species is a long-lived bivalve mostly occurring in cool running waters of the Holarctic region.…”