Abstract
Many landscape and biotic processes shape the genetic structure of populations. The genetic structure of species with parasitic stages may also depend on the life history and ecology of their host. We investigated population genetic structure of the mussel Margaritifera margaritifera in Southern Sweden, and in relation to the population size and life history of its hosts, Salmo trutta and S. salar. Mussel populations were genetically differentiated into two clusters, further subdivided into four clusters and distinct conservation units. Regardless of host species, the genetic differentiation was lower among mussel populations sustained by sea-migrating than by resident hosts, while the genetic diversity was higher in mussel populations sustained by sea-migrating than by resident hosts. Genetic diversity of mussel populations was positively related to host abundance. Mussel population size was positively related to high genetic diversity of mussels sustained by resident hosts, while low mussel population size sustained by sea-migrating hosts had a high genetic diversity. The results of our study suggest a combined influence of mussels and host fish on genetic structure of unionoid mussels. We suggest to conserve not only mussel population sizes and host fish species, but also consider host migratory/resident behaviour and abundance when designing conservation programs.
Highlights
Many landscape and biotic processes shape the genetic structure of populations
The present study provides new information on genetic structure among and within drainages, and in relation to variation in life history among host fish populations in southern Scandinavia, with importance for the conservation of unionoid mussels
The generally drainage-independent genetic differentiation was genetically structured into two main clusters, one including the Northern drainages and the other with the most Southern ones (Fig. 1), identified by both the initial STRUCTURE and FST based Neighbour-Joining tree (Fig. 2) analyses
Summary
Many landscape and biotic processes shape the genetic structure of populations. The genetic structure of species with parasitic stages may depend on the life history and ecology of their host. Species with parasitic life stages are dependent on the life history and ecology of the host, where differences in mobility patterns of the host may influence the genetic structure of post-parasitic life stages[6,7,8,9]. Mussel populations sustained by host fish species with a high mobility may show less differentiation and higher genetic diversity compared to mussel populations sustained by stationary host fish species[10,14]. Such genetic structure may be more accentuated between areas with high versus areas with low connectivity between mussel populations. The higher the host fish population size and abundance, the higher potential for high genetic diversity of parasitic mussel larvae on the fish, and for the mussels leaving the host fish entering the benthic mussel population
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