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  • Avian evolution

    From Pandora@21:1/5 to All on Sat May 4 12:09:00 2024
    Complexity of avian evolution revealed by family-level genomes

    Abstract

    Despite tremendous efforts in the past decades, relationships among main
    avian lineages remain heavily debated without a clear resolution.
    Discrepancies have been attributed to diversity of species sampled, phylogenetic method and the choice of genomic regions1,2,3. Here we
    address these issues by analysing the genomes of 363 bird species4 (218 taxonomic families, 92% of total). Using intergenic regions and coalescent methods, we present a well-supported tree but also a marked
    degree of discordance. The tree confirms that Neoaves experienced rapid radiation at or near the Cretaceous–Palaeogene boundary. Sufficient loci rather than extensive taxon sampling were more effective in resolving
    difficult nodes. Remaining recalcitrant nodes involve species that are a challenge to model due to either extreme DNA composition, variable
    substitution rates, incomplete lineage sorting or complex evolutionary
    events such as ancient hybridization. Assessment of the effects of
    different genomic partitions showed high heterogeneity across the
    genome. We discovered sharp increases in effective population size, substitution rates and relative brain size following the Cretaceous–Palaeogene extinction event, supporting the hypothesis that emerging ecological opportunities catalysed the diversification of
    modern birds. The resulting phylogenetic estimate offers fresh insights
    into the rapid radiation of modern birds and provides a taxon-rich
    backbone tree for future comparative studies.

    Open access:
    https://www.nature.com/articles/s41586-024-07323-1

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  • From Volney@21:1/5 to Pandora on Fri Jul 12 01:19:10 2024
    On 5/4/2024 6:09 AM, Pandora wrote:
    Complexity of avian evolution revealed by family-level genomes

    Abstract

    Despite tremendous efforts in the past decades, relationships among main avian lineages remain heavily debated without a clear resolution. Discrepancies have been attributed to diversity of species sampled, phylogenetic method and the choice of genomic regions1,2,3. Here we
    address these issues by analysing the genomes of 363 bird species4 (218  taxonomic families, 92% of total). Using intergenic regions and
    coalescent methods, we present a well-supported tree but also a marked
    degree of discordance. The tree confirms that Neoaves experienced rapid radiation at or near the Cretaceous–Palaeogene boundary. Sufficient loci rather than extensive taxon sampling were more effective in resolving difficult nodes. Remaining recalcitrant nodes involve species that are a challenge to model due to either extreme DNA composition, variable substitution rates, incomplete lineage sorting or complex evolutionary
    events such as ancient hybridization. Assessment of the effects of
    different genomic partitions showed high heterogeneity across the
    genome. We discovered sharp increases in effective population size, substitution rates and relative brain size following the Cretaceous–Palaeogene extinction event, supporting the hypothesis that emerging ecological opportunities catalysed the diversification of
    modern birds. The resulting phylogenetic estimate offers fresh insights
    into the rapid radiation of modern birds and provides a taxon-rich
    backbone tree for future comparative studies.

    Open access:
    https://www.nature.com/articles/s41586-024-07323-1

    I was thinking that since birds don't seem to have very much variation
    from the basic bird body plan, could it be possible that exactly one
    species survived the K-T event, and all modern birds are descended from
    it? When would the MRCA of all birds have lived? Older protobirds seem
    to have more variations not seen today. Some have teeth, some have claws
    on wings, long tails and/or 4 wings/feathered legs are also wings*.

    (*) I have two bantam chickens with feathers on their legs and two of
    their claws on each foot. Could this be an old "4 wing" gene becoming reactivated? Or are chickens just more prehistoric? The bantams seem to
    fly a little better than non-bantam chickens, but that's probably just
    because they are very small. I haven't seen them try to flap their legs...

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