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A core question in evolutionary biology is whether convergent phenotypic evolution is driven by convergent molecular changes in proteins or regulatory regions. We combined phylogenomic, developmental, and epigenomic analysis of 11 new genomes of paleognathous birds, including an extinct moa, to show that convergent evolution of regulatory regions, more so than protein-coding genes, is prevalent among developmental pathways associated with independent losses of flight. A Bayesian analysis of 284,001 conserved noncoding elements, 60,665 of which are corroborated as enhancers by open chromatin states during development, identified 2355 independent accelerations along lineages of flightless paleognaths, with functional consequences for driving gene expression in the developing forelimb. Our results suggest that the genomic landscape associated with morphological convergence in ratites has a substantial shared regulatory component., (Copyright © 2019 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.)

Comparative study of character evolution in the shorebirds is presently limited because the phylogenetic placement of some enigmatic genera remains unclear. We therefore used Bayesian methods to obtain a well-supported phylogeny of 90 recognized genera using 5 kb of mitochondrial and nuclear sequences. The tree comprised three major clades: Lari (gulls, auks and allies plus buttonquails) as sister to Scolopaci (sandpipers, jacanas and allies), and in turn sister to Charadrii (plovers, oystercatchers and allies), as in previous molecular studies. Plovers and noddies were not recovered as monophyletic assemblages, and the Egyptian plover Pluvianus is apparently not a plover. Molecular dating using multiple fossil constraints suggests that the three suborders originated in the late Cretaceous between 79 and 102 Mya, and at least 14 lineages of modern shorebirds survived the mass extinction at the K/T boundary. Previous difficulties in determining the phylogenetic relationships of enigmatic taxa reflect the fact that they are well-differentiated relicts of old, genus-poor lineages. We refrain from suggesting systematic revisions for shorebirds at this time because gene trees may fail to recover the species tree when long branches are connected to deep, shorter branches, as is the case for some of the enigmatic taxa.

The tempo and mode of evolution of the extinct giant moas of New Zealand remain obscure because the number of lineages and their divergence times cannot be estimated reliably by using fossil bone characters only. We therefore extracted ancient DNA from 125 specimens and genetically typed them for a 658-bp mtDNA control region sequence. The sequences detected 14 monophyletic lineages, 9 of which correspond to currently recognized species. One of the newly detected lineages was a genetically divergent form of Megalapteryx originally described as a separate species, two more were lineages of Pachyornis in southern and northeastern New Zealand, and two were basal lineages of South Island Dinornis. When results from genetic typing and previous molecular sexing were combined, at least 33.6% of the specimens were incorrectly classified. We used longer sequences of the control region and nine other mtDNA genes totaling 2,814 base pairs to derive a strongly supported phylogeny of the 14 moa lineages. Molecular dating estimated the most recent common ancestor of moas existed after the Oligocene drowning of New Zealand. However, a cycle of lineage-splitting occurred approximately 4-10 million years ago, when the landmass was fragmented by tectonic and mountain-building events and general cooling of the climate. These events resulted in the geographic isolation of lineages and ecological specialization. The spectacular radiation of moa lineages involved significant changes in body size, shape, and mass and provides another example of the general influence of large-scale paleoenvironmental changes on vertebrate evolutionary history.

We sequenced 2800 bp of mitochondrial DNA from each of 33 species and 2 subspecies (35 taxa) of terns (Sternini), and employed Bayesian methods to derive a phylogeny with good branch support based on posterior probabilities. The resulting tree confirmed many of the generally accepted taxonomic groups, and led us to suggest a revision of the terns that recognizes 12 genera, 11 of which correspond to a distinct clade on the tree or a highly divergent species (1 genus was not represented in the phylogeny). As an example of how the molecular phylogeny reflects similarities in morphology and behavior among the terns, we used the phylogeny to examine the evolution of the breeding (alternate) head plumage patterns among the terns to test the hypothesis that this character is phylogenetically informative. The three basic types of head plumage (white crown, black cap, and black cap with a white blaze on the forehead) were highly conserved within clades, with notable exceptions in two white-crowned species that evolved independently among the black-capped terns. Based on the appearance of the close relatives of these exceptional species, their white crowns appear to be due to the retention of either winter (basic) plumage characteristics or perhaps juvenile characteristics when the birds molt into their breeding plumage. Examination of the evolutionary history of head plumage indicated that the white-crowned species such as the noddies (Anous) and the white tern (Gygis alba) are probably most representative of ancestral terns.

The evolution of avian feathers has recently been illuminated by fossils and the identification of genes involved in feather patterning and morphogenesis. However, molecular studies have focused mainly on protein-coding genes. Using comparative genomics and more than 600,000 conserved regulatory elements, we show that patterns of genome evolution in the vicinity of feather genes are consistent with a major role for regulatory innovation in the evolution of feathers. Rates of innovation at feather regulatory elements exhibit an extended period of innovation with peaks in the ancestors of amniotes and archosaurs. We estimate that 86% of such regulatory elements and 100% of the nonkeratin feather gene set were present prior to the origin of Dinosauria. On the branch leading to modern birds, we detect a strong signal of regulatory innovation near insulin-like growth factor binding protein (IGFBP) 2 and IGFBP5, which have roles in body size reduction, and may represent a genomic signature for the miniaturization of dinosaurian body size preceding the origin of flight.

Noncoding markers have a particular appeal as tools for phylogenomic analysis because, at least in vertebrates, they appear less subject to strong variation in GC content among lineages. Thus far, ultraconserved elements (UCEs) and introns have been the most widely used noncoding markers. Here we analyze and study the evolutionary properties of a new type of noncoding marker, conserved nonexonic elements (CNEEs), which consists of noncoding elements that are estimated to evolve slower than the neutral rate across a set of species. Although they often include UCEs, CNEEs are distinct from UCEs because they are not ultraconserved, and, most importantly, the core region alone is analyzed, rather than both the core and its flanking regions. Using a data set of 16 birds plus an alligator outgroup, and ∼3600-∼3800 loci per marker type, we found that although CNEEs were less variable than bioinformatically derived UCEs or introns and in some cases exhibited a slower approach to branch resolution as determined by phylogenomic subsampling, the quality of CNEE alignments was superior to those of the other markers, with fewer gaps and missing species. Phylogenetic resolution using coalescent approaches was comparable among the three marker types, with most nodes being fully and congruently resolved. Comparison of phylogenetic results across the three marker types indicated that one branch, the sister group to the passerine + falcon clade, was resolved differently and withmoderate (>70%) bootstrap support between CNEEs and UCEs or introns. Overall, CNEEs appear to be promising as phylogenomic markers, yielding phylogenetic resolution as high as for UCEs and introns but with fewer gaps, less ambiguity in alignments and with patterns of nucleotide substitution more consistent with the assumptions of commonly used methods of phylogenetic analysis. [ABSTRACT FROM AUTHOR]

Abstract: We describe whole mitochondrial genome sequences from four subspecies of the common chaffinch (Fringilla coelebs), and compare them to 31 publicly available mitochondrial genome sequences from other Passeriformes. Rates and patterns of mitochondrial gene evolution are analyzed at different taxonomic levels within this avian order, and evidence is adduced for and against the nearly neutral theory of molecular evolution and the role of positive selection in shaping genetic variation of this small but critical genome. We find evidence of mitochondrial rate heterogeneity in birds as in other vertebrates, likely due to differences in mutational pressure across the genome. Unlike in gadine fish and some of the human mitochondrial work we do not observe strong support for the nearly neutral theory of molecular evolution; instead evidence from molecular clocks, distribution of dN/dS ratios at different levels of the taxonomic hierarchy and in different lineages, McDonald–Kreitman tests within Fringillidae, and site-specific tests of selection within Passeriformes, all point to a role for positive selection, especially for the complex I NADH dehydrogenase genes. The protein-coding mitogenome phylogeny of the order Passeriformes is broadly consistent with previously-reported molecular findings, but provides support for a sister relationship between the superfamilies Muscicapoidea and Passeroidea on a short basal internode of the Passerida where relationships have been difficult to resolve. An unexpected placement of the Paridae (represented by Hume''s groundpecker) within the Muscicapoidea was observed. Consistent with other molecular studies the mtDNA phylogeny reveals paraphyly within the Muscicapoidea and a sister relationship of Fringilla with Carduelis rather than Emberiza. [Copyright &y& Elsevier]

Background: Towards lower latitudes the number of recognized species is not only higher, but also phylogeographic subdivision within species is more pronounced. Moreover, new genetically isolated populations are often described in recent phylogenies of Neotropical birds suggesting that the number of species in the region is underestimated. Previous COI barcoding of Argentinean bird species showed more complex patterns of regional divergence in the Neotropical than in the North American avifauna. Methods and Findings: Here we analyzed 1,431 samples from 561 different species to extend the Neotropical bird barcode survey to lower latitudes, and detected even higher geographic structure within species than reported previously. About 93% (520) of the species were identified correctly from their DNA barcodes. The remaining 41 species were not monophyletic in their COI sequences because they shared barcode sequences with closely related species (N = 21) or contained very divergent clusters suggestive of putative new species embedded within the gene tree (N = 20). Deep intraspecific divergences overlapping with among-species differences were detected in 48 species, often with samples from large geographic areas and several including multiple subspecies. This strong population genetic structure often coincided with breaks between different ecoregions or areas of endemism. Conclusions: The taxonomic uncertainty associated with the high incidence of non-monophyletic species and discovery of putative species obscures studies of historical patterns of species diversification in the Neotropical region. We showed that COI barcodes are a valuable tool to indicate which taxa would benefit from more extensive taxonomic revisions with multilocus approaches. Moreover, our results support hypotheses that the megadiversity of birds in the region is associated with multiple geographic processes starting well before the Quaternary and extending to more recent geological periods. [ABSTRACT FROM AUTHOR]

Background: DNA barcoding of life using a standardized COI sequence was proposed as a species identification system, and as a method for detecting putative new species. Previous tests in birds showed that individuals can be correctly assigned to species in ~94% of the cases and suggested a threshold of 10x mean intraspecific difference to detect potential new species. However, these tests were criticized because they were based on a single maternally inherited gene rather than multiple nuclear genes, did not compare phylogenetically identified sister species, and thus likely overestimated the efficacy of DNA barcodes in identifying species. Results: To test the efficacy of DNA barcodes we compared ~650 bp of COI in 60 sister-species pairs identified in multigene phylogenies from 10 orders of birds. In all pairs, individuals of each species were monophyletic in a neighbor-joining (NJ) tree, and each species possessed fixed mutational differences distinguishing them from their sister species. Consequently, individuals were correctly assigned to species using a statistical coalescent framework. A coalescent test of taxonomic distinctiveness based on chance occurrence of reciprocal monophyly in two lineages was verified in known sister species, and used to identify recently separated lineages that represent putative species. This approach avoids the use of a universal distance cutoff which is invalidated by variation in times to common ancestry of sister species and in rates of evolution. Conclusion: Closely related sister species of birds can be identified reliably by barcodes of fixed diagnostic substitutions in COI sequences, verifying coalescent-based statistical tests of reciprocal monophyly for taxonomic distinctiveness. Contrary to recent criticisms, a single DNA barcode is a rapid way to discover monophyletic lineages within a metapopulation that might represent undiscovered cryptic species, as envisaged in the unified species concept. This identifies a smaller set of lineages that can also be tested independently for species status with multiple nuclear gene approaches and other phenotypic characters. [ABSTRACT FROM AUTHOR]

We employed Bayesian coalescent modeling of samples of mitochondrial control region sequences in two species of shorebird, Red Knots (Calidris canutus) and Dunlins (Calidris alpina) to estimate evolutionary effective population size, population divergence times, and time to most recent common ancestor of genes in the samples. The gene trees for the two species contrast sharply: knot haplotypes were connected in a shallow, star phylogeny whereas Dunlin haplotypes were related in a deeper bifurcating genealogy. Divergence times of populations representing all six subspecies of knots are estimated to have occurred within the last 20 000 (95% CI: 5600-58 000) years, and evolutionary effective population sizes of females are small (Nef = 2000-14 000). We hypothesized that breeding knots were restricted to unglaciated regions of Eurasia during the last glacial maximum, and gradually expanded eastwards into Alaska, the high Canadian Arctic and Greenland as the ice melted. Population divergence times in Dunlins are much older (58 000-194 000 ybp) and effective population size has historically been higher in major lineages (Nef 12 000-44 000). We conclude that Dunlin populations were not severely reduced in size in the last 200 000 years, and major lineages have differentiated under restricted gene flow for a much longer time than knots. Knots present a snapshot of genetic evolution in the last 20 000 years, whereas Dunlins display patterns of genetic evolution over an order of magnitude longer time frame. [ABSTRACT FROM AUTHOR]

Approximately 60% of the 45 species of terns (Sternae) have an unusual form of wing molt in which a variable number of inner primaries and outer secondaries are replaced two or three times in a single year--a process that has been called "repeated molt." Although several hypotheses have been proposed for the maintenance of repeated molt, few data exist regarding potential selective forces that may have favored the evolution of this molt strategy, and there are no explanations for the high degree of interspecific variation in the extent of repeated molt. Preliminary investigations indicated that large terns tended to have less repeated molt than small terns and that the presence of repeated molt appeared to be associated with migratory behavior. We examined these initial findings by combining data from the literature, from examinations of museum specimens, and from a recent molecular phylogeny of the terns to perform phylogenetic-comparative tests. First, we used independent contrasts to verify that the association between large terns and less repeated molt was significant and not a result of shared ancestry. Second, we used tests for binary character association to evaluate the apparent link between repeated molt and migratory behavior. The results of these tests, along with reconstructions of ancestral states, led to a potential explanation for the origin of repeated molt, in which a tropical, sedentary ancestor gave rise to several lineages that spread to temperate areas and adopted a migratory life history. With this shift to a more seasonal regime came shortened breeding periods and perhaps more time for molt, which could have led to modifications of the ancestral molting strategy and the origin of repeated molt. [ABSTRACT FROM AUTHOR]