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Birds are the most species-rich class of tetrapod vertebrates and have wide relevance across many research fields. We explored bird macroevolution using full genomes from 48 avian species representing all major extant clades. The avian genome is principally characterized by its constrained size, which predominantly arose because of lineage-specific erosion of repetitive elements, large segmental deletions, and gene loss. Avian genomes furthermore show a remarkably high degree of evolutionary stasis at the levels of nucleotide sequence, gene synteny, and chromosomal structure. Despite this pattern of conservation, we detected many non-neutral evolutionary changes in protein-coding genes and noncoding regions. These analyses reveal that pan-avian genomic diversity covaries with adaptations to different lifestyles and convergent evolution of traits.

As photosynthetic producers, phytoplankton form the foundation of aquatic food webs. Understanding the relationships among photosynthetic traits in phytoplankton is essential to revealing how diversification of these traits allows phytoplankton to harvest energy from different light environments. We investigated whether the diversification of 15 species of cryptophytes, a phylum of phytoplankton with diverse light‐capturing pigments, showed evidence of trade‐offs among photosynthetic performance traits as predicted by the gleaner–opportunist resource exploitation framework. We constructed photosynthesis versus irradiance (P–E) curves and rapid light curves (RLCs) to estimate parameters characterizing photosynthetic performance and electron transport rate. We inferred the evolutionary relationships among the 15 species with ultraconserved genomic elements and used a phylogenetically controlled approach to test for trade‐offs. Contrary to our prediction, we observed a positive correlation between maximum photosynthetic rate, Pmax, and P–E α$$ \upalpha $$, an indicator of a species' sensitivity to increases in light intensity when light is a scarce resource. This result could not be explained by electron transfer traits, which were uncorrelated with photosynthetic rate. Together, our results suggest that ecological diversification of light exploitation in cryptophytes has escaped the constraints of a gleaner–opportunist trade‐off. Photosynthetic trade‐offs may be context‐ or scale‐dependent, thereby only emerging when investigated in situations different from the one used here. [ABSTRACT FROM AUTHOR]

Abstract Background The epidermal appendages of reptiles and birds are constructed of beta (β) keratins. The molecular phylogeny of these keratins is important to understanding the evolutionary origin of these appendages, especially feathers. Knowing that the crocodilian β-keratin genes are closely related to those of birds, the published genomes of the chicken and zebra finch provide an opportunity not only to compare the genomic organization of their β-keratins, but to study their molecular evolution in archosaurians. Results The subfamilies (claw, feather, feather-like, and scale) of β-keratin genes are clustered in the same 5' to 3' order on microchromosome 25 in chicken and zebra finch, although the number of claw and feather genes differs between the species. Molecular phylogenies show that the monophyletic scale genes are the basal group within birds and that the monophyletic avian claw genes form the basal group to all feather and feather-like genes. Both species have a number of feather clades on microchromosome 27 that form monophyletic groups. An additional monophyletic cluster of feather genes exist on macrochromosome 2 for each species. Expression sequence tag analysis for the chicken demonstrates that all feather β-keratin clades are expressed. Conclusions Similarity in the overall genomic organization of β-keratins in Galliformes and Passeriformes suggests similar organization in all Neognathae birds, and perhaps in the ancestral lineages leading to modern birds, such as the paravian Anchiornis huxleyi. Phylogenetic analyses demonstrate that evolution of archosaurian epidermal appendages in the lineage leading to birds was accompanied by duplication and divergence of an ancestral β-keratin gene cluster. As morphological diversification of epidermal appendages occurred and the β-keratin multigene family expanded, novel β-keratin genes were selected for novel functions within appendages such as feathers.

Phenotypic traits associated with light capture and phylogenetic relationships were characterized in 34 strains of diversely pigmented marine and freshwater cryptophytes. Nuclear SSU and partial LSU rDNA sequence data from 33 of these strains plus an additional 66 strains produced a concatenated rooted maximum likelihood tree that classified the strains into 7 distinct clades. Molecular and phenotypic data together support: (i) the reclassification of Cryptomonas irregularis NIES 698 to the genus Rhodomonas, (ii) revision of phycobiliprotein (PBP) diversity within the genus Hemiselmis to include cryptophyte phycocyanin (Cr-PC) 569, (iii) the inclusion of previously unidentified strain CCMP 2293 into the genus Falcomonas, even though it contains cryptophyte phycoerythrin 545 (Cr-PE 545), and (iv) the inclusion of previously unidentified strain CCMP 3175, which contains Cr-PE 545, in a clade with PC-containing Chroomonas species. A discriminant analysis-based model of group membership correctly predicted 70.6% of the clades using three traits: PBP concentration · cell-1, the wavelength of PBP maximal absorption, and habitat. Non-PBP pigments (alloxanthin, chl-a, chl-c2, a-carotene) did not contribute significantly to group classification, indicating the potential plasticity of these pigments and the evolutionary conservation of the PBPs. Pigment data showed evidence of tradeoffs in investments in PBPs vs. chlorophylls (a +c2). [ABSTRACT FROM AUTHOR]

The archosauria consist of two living groups, crocodilians, and birds. Here we compare the structure, expression, and phylogeny of the beta (ß)-keratins in two crocodilian genomes and two avian genomes to gain a better understanding of the evolutionary origin of the feather ß-keratins. Unlike squamates such as the green anole with 40 ß-keratins in its genome, the chicken and zebra finch genomes have over 100 ß-keratin genes in their genomes, while the American alligator has 20 ß-keratin genes, and the saltwater crocodile has 21 ß-keratin genes. The crocodilian ß-keratins are similar to those of birds and these structural proteins have a central filament domain and N- and C-termini, which contribute to the matrix material between the twisted ß-sheets, which form the 2-3 nm filament. Overall the expression of alligator ß-keratin genes in the integument increases during development. Phylogenetic analysis demonstrates that a crocodilian ß-keratin clade forms a monophyletic group with the avian scale and feather ß-keratins, suggesting that avian scale and feather ß-keratins along with a subset of crocodilian ß-keratins evolved from a common ancestral gene/s. Overall, our analyses support the view that the epidermal appendages of basal archosaurs used a diverse array of ß-keratins, which evolved into crocodilian and avian specific clades. In birds, the scale and feather subfamilies appear to have evolved independently in the avian lineage from a subset of archosaurian claw ß-keratins. The expansion of the avian specific feather ß-keratin genes accompanied the diversification of birds and the evolution of feathers. [ABSTRACT FROM AUTHOR]

The International Crocodilian Genomes Working Group (ICGWG) will sequence and assemble the American alligator (Alligator mississippiensis), saltwater crocodile (Crocodylus porosus) and Indian gharial (Gavialis gangeticus) genomes. The status of these projects and our planned analyses are described., Organismic and Evolutionary Biology

Birds are the most species-rich class of tetrapod vertebrates and have wide relevance across many research fields. We explored bird macroevolution using full genomes from 48 avian species representing all major extant clades. The avian genome is principally characterized by its constrained size, which predominantly arose because of lineage-specific erosion of repetitive elements, large segmental deletions, and gene loss. Avian genomes furthermore show a remarkably high degree of evolutionary stasis at the levels of nucleotide sequence, gene synteny, and chromosomal structure. Despite this pattern of conservation, we detected many non-neutral evolutionary changes in protein-coding genes and noncoding regions. These analyses reveal that pan-avian genomic diversity covaries with adaptations to different lifestyles and convergent evolution of traits. [ABSTRACT FROM AUTHOR]