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If similar evolutionary forces maintain intra‐ and interspecific diversity, patterns of diversity at both levels of biological organization can be expected to covary across space. Although this prediction of a positive species‐genetic diversity correlation (SGDC) has been tested for several taxa in natural landscapes, no study has yet evaluated the influence of the community delineation on these SGDCs. In this study, we focused on tropical fishes of the Indo‐Pacific Ocean, using range‐wide single nucleotide polymorphism data for a deep‐sea fish (Etelis coruscans) and species presence data of 4878 Teleostei species. We investigated whether a diversity continuum occurred, for different community delineations (subfamily, family, order and class) and spatial extents, and which processes explained these diversity patterns. We found no association between genetic diversity and species richness (α‐SGDC), regardless of the community and spatial extent. In contrast, we evidenced a positive relationship between genetic and species dissimilarities (β‐SGDC) when the community was defined at the subfamily or family level of the species of interest, and when the Western Indian Ocean was excluded. This relationship was related to the imprint of dispersal processes across levels of biological organization in Lutjanidae. However, this positive β‐SGDC was lost when considering higher taxonomic communities and at the scale of the entire Indo‐Pacific, suggesting different responses of populations and communities to evolutionary processes at these scales. This study provides evidence that the taxonomic scale at which communities are defined and the spatial extent are pivotal to better understand the processes shaping diversity across levels of biological organization. [ABSTRACT FROM AUTHOR]

The sex chromosomes have been hypothesized to play a key role in driving adaptation and speciation across many taxa. The reason for this is thought to be the hemizygosity of the heteromorphic part of sex chromosomes in the heterogametic sex, which exposes recessive mutations to natural and sexual selection. The exposure of recessive beneficial mutations increases their rate of fixation on the sex chromosomes, which results in a faster rate of evolution. In addition, genetic incompatibilities between sex‐linked loci are exposed faster in the genomic background of hybrids of divergent lineages, which makes sex chromosomes contribute disproportionately to reproductive isolation. However, in birds, which show a Z/W sex determination system, the role of adaptation versus genetic drift as the driving force of the faster differentiation of the Z chromosome (fast‐Z effect) and the disproportionate role of the Z chromosome in reproductive isolation (large‐Z effect) are still debated. Here, we address this debate in the bird genus Ficedula flycatchers based on population‐level whole‐genome sequencing data of six species. Our analysis provides evidence for both faster lineage sorting and reduced gene flow on the Z chromosome than the autosomes. However, these patterns appear to be driven primarily by the increased role of genetic drift on the Z chromosome, rather than an increased rate of adaptive evolution. Genomic scans of selective sweeps and fixed differences in fact suggest a reduced action of positive selection on the Z chromosome. [ABSTRACT FROM AUTHOR]

Aim: Evaluating the similarity of diversity patterns across micro‐ to macroevolutionary scales in natural communities, such as species–genetic diversity correlations (SGDCs), may inform on processes shaping community assembly. However, whether SGDCs not only hold across communities but also across lineages has never been explored so far. Here we investigated SGDCs across co‐distributed taxa for different spatial components (α, β, γ), and formally tested the influence of dispersal traits on β‐SGDCs. Location: Western Indian Ocean. Time period: 2016–2017. Major taxa studied: Tropical reef fish species with contrasting dispersal traits. Methods: Using double‐digest restriction‐site associated DNA sequencing (ddRADseq) Single Nucleotide Polymorphism data for 20 tropical reef fishes and distribution data of 2,446 species belonging to 12 families, we analysed the correlations between within‐species genetic diversity and within‐family species diversity (i.e., lineage diversity) for the three spatial components (α, β, γ‐SGDCs). We then related the strength of β‐SGDCs per species to proxies of larval dispersal abilities. Results: We detected positive and significant lineage‐based SGDC only for the β component, that is, the families showing the greatest level of species turnover among sites contain the species with the greatest levels of genetic differentiation. We showed that the Monsoon Drift mainly explained the β‐diversity patterns at both intraspecific and interspecific levels. Higher β‐SGDCs were found for species with short pelagic larval duration and weak larval swimming capacity. Main conclusions: Our study reveals a strong correlation between genetic and species β‐diversity, a result explained by the presence of a 'soft' barrier and mediated by larval dispersal processes. This suggests that vicariance and dispersal limitation are major processes shaping β‐diversity patterns from microevolutionary to macroevolutionary scales in tropical reef fishes. [ABSTRACT FROM AUTHOR]