engleski

Molecular genetic differentiation of native Mediterranean mussels, Mytilus galloprovincialis Lamarck, 1819 populations and the relationship with environmental variables

Mussels of the genus Mytilus are important coastal ecosystem services providers and engineers in intertidal and subtidal hard- bottom communities. The distribution of Mytilus mussels is controlled by a number of processes involving both benthic and pelagic environments (e.g. substrate type and availability, water movement, phytoplankton production, physical disturbances) as well as interactions between these processes. The Mediterranean species Mytilus galloprovincialis shows the greatest ability to colonize new geographic regions compared to other Mytilus taxa. Understanding how population genetic variation is related to or caused by environmental variation is important, but has long been a challenge. The present study examined the genetic differentiation of native populations of M. galloprovincialis throughout its entire geographic range in the Mediterranean Sea and adjacent waters using 53 single polymorphism nucleotide (SNP) loci that were genotyped in 1004 mussels collected from 36 locations. Pairwise comparisons of FST values, correspondence analysis (CA) and STRUCTURE analysis all revealed four groups of populations: the Atlantic ; the western Mediterranean ; the Aegean Sea ; and the Azov, Black and Marmara Seas. One population - from Algeria (Oran West) - was situated between two main groups from Mediterranean Sea and Atlantic. No significant genetic differentiation was observed among populations of M. galloprovincialis in the Western Mediterranean Basin, east of the Alboran Front to the coasts of Italy and Tunisia. Using boosted regression tree analysis, site-specific genetic variation was tested for in the context of spatially explicit environmental variation in 13 different variables. The relationship between local environmental variability and the frequencies of SNP alleles was weak. This Blue mussels of the genus Mytilus are important ecosystem engineers in intertidal and subtidal communities. The distribution of Mytilus mussels is influenced by a number of benthic and pelagic environmental variables (e.g., substratum type and availability, water movement, phytoplankton production, physical disturbance) as well as interactions between these variables. Because of its broad tolerance of environmental variation the Mediterranean species, Mytilus galloprovin- cialis, has the greatest ability of all blue mussels to colonise new geographic regions. Understanding how population genetic variation is related to, or caused by, environmental variation is important but has long been a challenge. The present study examined the genetic differentiation of native populations of M. galloprovincialis throughout its entire geographic range in the Mediterranean Sea, the Black Sea and the Sea of Azov using 53 single nucleotide polymorphisms (SNP loci). Mussels, in total 1004 individuals collected from 36 locations, were genotyped and combined with existing SNP data for mussels from 11 reference sites. Pairwise comparisons of FST values, correspondence analysis (CA) and STRUCTURE analysis all revealed four groups of populations: the Atlantic Ocean ; the western Mediterranean ; the Aegean Sea ; and the Azov, Black and Marmara Seas. One population – from Algeria (Oran West) – was intermediate between the two main groups of the Mediterranean Sea and Atlantic Ocean. Seascape genetic analyses using GLM and DistLM analyses were employed to test site-specific genetic variation as a function of 13 environmental variables. The GLM identified five environmental variables that explained variation in site-specific FST values, whilst in the DistLM best-fit model only four were significant. These analyses suggest that a complex mix of environmental variables contribute to explaining genetic variation of M. gallopro- vincialis populations within the Mediterranean Sea, which most likely reflects the complex geological history of formation, isolation and reconnection among the regional sub-basins of the Sea.

Biogeography ; single nucleotide polymorphism ; seascape genetics ; geological formation ; isolation and reconnection

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