Seagrass meadows are among the most important coastal ecosystems  in terms of both spatial extent and ecosystem services but are declining worldwide. Understanding the drivers of seagrass meadow dynamics is essential for designing sound management, conservation  and restoration strategies. However, the  effect of clonality on the population genetics of natural populations understood, severely limiting our comprehension of the dynamics and connectivity of meadows. Here, we revisited population genetics data on 165 meadows of four seagrass species in light of recent theoretical developments, which provide new expectations for the distributions of genotypic and genetic polymorphism under increasing clonal rates . Contrasting shoot life span and rhizome turnover lead to the prediction of a decreasing influence of asexual reproduction  along a gradient from Posidonia oceanica to Cymodocea nodosa, Zostera marinaand Zostera noltii , which should be reflected by decreasing departure from Hardy-Weinberg equilibrium (Fis) and increasing genotypic diversity (R). This meta-analysis provides a nested validation of this hypothesis at the species scale but also at the meadow scale through the emergence of a significant relationship between Fis and R within each species. By empirically demonstrating the theoretical expectations derived from recent modelling approaches, this work calls for the use of Hardy-Weinberg equilibrium (Fis) rather than the strongly sampling-sensitive genotypic index R in studies aiming at understanding the importance of clonal reproduction. We also emphasize the need to revise our perception of the influence of clonality on the dynamics, connectivity and evolutionary trajectory of seagrass meadows to develop the most accurate conservation strategies.
Seagrass meadows are among the most important coastal ecosystems , in terms of both spatial extent and ecosystem services , but they are also declining worldwide. Understanding the drivers of seagrass meadow dynamics is essential for designing sound management, conservation , and restoration strategies. However, the poor knowledge of the effect of clonality on the population genetics of natural populations severely limits our understanding of the dynamics and connectivity of meadows. Recent modelling approaches have described the expected distributions of genotypic and genetic descriptors under increasing clonal rates. Here, in light of these recent theoretical developments, we revisited population genetic data for 165 meadows of four seagrass species . Contrasting shoot life span and rhizome turnover led to the prediction that the influence of asexual reproduction will increase along a gradient from Zostera noltii to Zostera marina, Cymodocea nodosa and Posidonia oceanica , which should be reflected by an increasing departure from Hardy-Weinberg equilibrium (Fis) and decreasing genotypic diversity (R). This meta-analysis provides a nested validation of this hypothesis at both the species and meadow scales through a significant relationship between Fis and R within each species. By empirically demonstrating the theoretical expectations derived from recent modelling approaches, this work calls for the use of Hardy-Weinberg equilibrium (Fis) rather than the strongly sampling-sensitive genotypic index R to assess the importance of clonal reproduction. The results also emphasize the need to revise our appraisal of the extent of clonality and its influence on the dynamics, connectivity and evolutionary trajectory of partial asexuals in general, including in seagrass meadows, to develop the most accurate management strategies.
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