Phylogenetics, biogeography and classification of, and character evolution in, gamebirds (Aves: Galliformes): effects of character exclusion, data partitioning and missing data

Mitogenomic Insights into the Evolution, Divergence Time, and Ancestral Ranges of Coturnix Quails

The Old-World quails, Coturnix coturnix (common quail) and Coturnix japonica (Japanese quail), are morphologically similar yet occupy distinct geographic ranges. This study aimed to elucidate their evolutionary trajectory and ancestral distribution patterns through a thorough analysis of their mitochondrial genomes. Mitogenomic analysis revealed high structural conservation, identical translational mechanisms, and similar evolutionary pressures in both species. Selection analysis revealed significant evidence of positive selection across the Coturnix lineage for the nad4 gene tree owing to environmental changes and acclimatization requirements during its evolutionary history. Divergence time estimations imply that diversification among Coturnix species occurred in the mid-Miocene (13.89 Ma), and their current distributions were primarily shaped by dispersal rather than global vicariance events. Phylogenetic analysis indicates a close relationship between C. coturnix and C. japonica, with divergence estimated at 2.25 Ma during the Pleistocene epoch. Ancestral range reconstructions indicate that the ancestors of the Coturnix clade were distributed over the Oriental region. C. coturnix subsequently dispersed to Eurasia and Africa, and C. japonica to eastern Asia. We hypothesize that the current geographic distributions of C. coturnix and C. japonica result from their unique dispersal strategies, developed to evade interspecific territoriality and influenced by the Tibetan Plateau's geographic constraints. This study advances our understanding of the biogeographic and evolutionary processes leading to the diversification of C. coturnix and C. japonica, laying important groundwork for further research on this genus.

Climate Cycles, Habitat Stability, and Lineage Diversification in an African Biodiversity Hotspot

The Eastern Arc Mountains of Tanzania and Kenya, a montane archipelago of 13 uplifted fault blocks (sky islands) isolated by lowland arid savanna, are a center of exceptional biological endemism. Under the influence of humid winds from the Indian Ocean, forests and associated species may have persisted in this region since the final uplift of these blocks in the late Miocene. Today, these mountains are inhabited by a remarkable diversity of bird species. To better understand the evolutionary processes behind this diversity, we combined molecular phylogenetic studies of East African montane birds with paleoclimate modeling of its montane forests. Across its largest lowland barrier, the 125 km between the Usambara and Nguru/Nguu Mountains, 10 of the 14 bird lineages exhibited a phylogeographic break. Using Bayesian methods, we established that at least three periods of forest contraction and expansion affected the diversification of Eastern Arc birds. Habitat distribution models suggest that lower-elevation hills may have acted as stepping-stones connecting isolated highlands to allow for the dispersal of montane forest-dependent species across them. Periods of vicariance during paleoclimatic cycles extending back through the Last Glacial Maximum would have then isolated these populations within the highlands they had reached. The broad distribution of neoendemic species across the mountains of East Africa provides evidence of climate cycling as a driver of lineage diversification. The high incidence of narrow-range endemism of paleoendemic species on the Usambara, Uluguru, and Udzungwa Mountains of this region is harder to explain. Our paleoclimate models retrodicted the persistence of montane forest during climate cycles on several Eastern Arc sky islands but not on the Southern Tanzania Volcanic Highlands. Consistent with recent theoretical work, different rates of local extinction rather than increased rates of lineage diversification may explain the pattern of excessive narrow-range endemism on some sky islands over others. Thus, a regional filtering effect is generated, with paleoendemics maintaining populations through time only in areas where habitat persisted, providing a credible explanation for the dramatic variance in levels of endemism among different East African sky islands.

Historical specimens and the limits of subspecies phylogenomics in the New World quails (Odontophoridae)

As phylogenomics focuses on comprehensive taxon sampling at the species and population/subspecies levels, incorporating genomic data from historical specimens has become increasingly common. While historical samples can fill critical gaps in our understanding of the evolutionary history of diverse groups, they also introduce additional sources of phylogenomic uncertainty, making it difficult to discern novel evolutionary relationships from artifacts caused by sample quality issues. These problems highlight the need for improved strategies to disentangle artifactual patterns from true biological signal as historical specimens become more prevalent in phylogenomic datasets. Here, we tested the limits of historical specimen-driven phylogenomics to resolve subspecies-level relationships within a highly polytypic family, the New World quails (Odontophoridae), using thousands of ultraconserved elements (UCEs). We found that relationships at and above the species-level were well-resolved and highly supported across all analyses, with the exception of discordant relationships within the two most polytypic genera which included many historical specimens. We examined the causes of discordance and found that inferring phylogenies from subsets of taxa resolved the disagreements, suggesting that analyzing subclades can help remove artifactual causes of discordance in datasets that include historical samples. At the subspecies-level, we found well-resolved geographic structure within the two most polytypic genera, including the most polytypic species in this family, Northern Bobwhites (Colinus virginianus), demonstrating that variable sites within UCEs are capable of resolving phylogenetic structure below the species level. Our results highlight the importance of complete taxonomic sampling for resolving relationships among polytypic species, often through the inclusion of historical specimens, and we propose an integrative strategy for understanding and addressing the uncertainty that historical samples sometimes introduce to phylogenetic analyses.

Divergence time estimation of Galliformes based on the best gene shopping scheme of ultraconserved elements

BACKGROUND

Divergence time estimation is fundamental to understanding many aspects of the evolution of organisms, such as character evolution, diversification, and biogeography. With the development of sequence technology, improved analytical methods, and knowledge of fossils for calibration, it is possible to obtain robust molecular dating results. However, while phylogenomic datasets show great promise in phylogenetic estimation, the best ways to leverage the large amounts of data for divergence time estimation has not been well explored. A potential solution is to focus on a subset of data for divergence time estimation, which can significantly reduce the computational burdens and avoid problems with data heterogeneity that may bias results.

RESULTS

In this study, we obtained thousands of ultraconserved elements (UCEs) from 130 extant galliform taxa, including representatives of all genera, to determine the divergence times throughout galliform history. We tested the effects of different "gene shopping" schemes on divergence time estimation using a carefully, and previously validated, set of fossils. Our results found commonly used clock-like schemes may not be suitable for UCE dating (or other data types) where some loci have little information. We suggest use of partitioning (e.g., PartitionFinder) and selection of tree-like partitions may be good strategies to select a subset of data for divergence time estimation from UCEs. Our galliform time tree is largely consistent with other molecular clock studies of mitochondrial and nuclear loci. With our increased taxon sampling, a well-resolved topology, carefully vetted fossil calibrations, and suitable molecular dating methods, we obtained a high quality galliform time tree.

CONCLUSIONS

We provide a robust galliform backbone time tree that can be combined with more fossil records to further facilitate our understanding of the evolution of Galliformes and can be used as a resource for comparative and biogeographic studies in this group.

A phylogenomic supermatrix of Galliformes (Landfowl) reveals biased branch lengths

Building taxon-rich phylogenies is foundational for macroevolutionary studies. One approach to improve taxon sampling beyond individual studies is to build supermatricies of publicly available data, incorporating taxa sampled across different studies and utilizing different loci. Most existing supermatrix studies have focused on loci commonly sequenced with Sanger technology ("legacy" markers, such as mitochondrial data and small numbers of nuclear loci). However, incorporating phylogenomic studies into supermatrices allows problem nodes to be targeted and resolved with considerable amounts of data, while improving taxon sampling with legacy data. Here we estimate phylogeny from a galliform supermatrix which includes well-known model and agricultural species such as the chicken and turkey. We assembled a supermatrix comprising 4500 ultra-conserved elements (UCEs) collected as part of recent phylogenomic studies in this group and legacy mitochondrial and nuclear (intron and exon) sequences. Our resulting phylogeny included 88% of extant species and recovered well-accepted relationships with strong support. However, branch lengths, which are particularly important in down-stream macroevolutionary studies, appeared vastly skewed. Taxa represented only by rapidly evolving mitochondrial data had high proportions of missing data and exhibited long terminal branches. Conversely, taxa sampled for slowly evolving UCEs with low proportions of missing data exhibited substantially shorter terminal branches. We explored several branch length re-estimation methods with particular attention to terminal branches and conclude that re-estimation using well-sampled mitochondrial sequences may be a pragmatic approach to obtain trees suitable for macroevolutionary analysis.

The draft genome of the blood pheasant (Ithaginis cruentus): Phylogeny and high-altitude adaptation

The blood pheasant (Ithaginis cruentus), the only species in the genus Ithaginis, lives in an extremely inhospitable high-altitude environment, coping with hypoxia and ultraviolet (UV) radiation. To further investigate the phylogeny of Phasianidae species based on complete genomes and understand the molecular genetic mechanisms of the high-altitude adaptation of the blood pheasant, we de novo assembled and annotated the complete genome of the blood pheasant. The blood pheasant genome size is 1.04 Gb with scaffold N50 of 10.88 Mb. We identified 109.92 Mb (10.62%) repetitive elements, 279,037 perfect microsatellites, and 17,209 protein-coding genes. The phylogenetic tree of Phasianidae based on whole genomes revealed three highly supported major clades with the blood pheasant included in the "erectile clade." Comparative genomics analysis showed that many genes were positively selected in the blood pheasant, which was associated with response to hypoxia and/or UV radiation. More importantly, among these positively selected genes (PSGs) which were related to high-altitude adaptation, sixteen PSGs had blood pheasant-specific missense mutations. Our data and analysis lay solid foundation to the study of Phasianidae phylogeny and provided new insights into the potential adaptation mechanisms to the high altitude employed by the blood pheasant.

Molecular species delimitation in the primitively segmented spider genus Heptathela endemic to Japanese islands

Determining species boundaries forms an important foundation for biological research. However, the results of molecular species delimitation can vary with the data sets and methods that are used. Here we use a two-step approach to delimit species in the genus Heptathela, a group of primitively segmented trapdoor spiders that are endemic to Japanese islands. Morphological evidence suggests the existence of 19 species in the genus. We tested this initial species hypothesis by using six molecular species-delimitation methods to analyse 180 mitochondrial COI sequences of Heptathela sampled from across the known range of the genus. We then conducted a set of more focused analyses by sampling additional genetic markers from the subset of taxa that were inconsistently delimited by the single-locus analyses of mitochondrial DNA. Multilocus species delimitation was performed using two Bayesian approaches based on the multispecies coalescent. Our approach identified 20 putative species among the 180 sampled individuals of Heptathela. We suggest that our two-step approach provides an efficient strategy for delimiting species while minimizing costs and computational time.

Disentangling the evolutionary history and biogeography of hill partridges (Phasianidae, Arborophila) from low coverage shotgun sequences

The advent of the phylogenomic era has significantly improved our understanding of the evolutionary history and biogeography of Southeast Asia's diverse avian fauna. However, the taxonomy and phylogenetic relationships of many Southeast Asian birds remain poorly resolved, especially for those with large geographic ranges, which might have experienced both ancient and recent geological and environmental changes. In this study, we examined the evolutionary history and biogeography of the hill partridges (Galliformes: Phasianidae: Arborophila spp.), currently the second most speciose galliform genus, and thought to have colonized Southeast Asia from Africa. We present a well-resolved phylogeny of 14 Arborophila species inferred from ultra-conserved elements, exons, and mitochondrial genomes from both fresh and museum samples, which representing almost complete coverage of the genus. Our fossil-calibrated divergence time estimates and biogeographic modeling showed the ancestor of Arborophila arrived in Indochina during the early Miocene, but the initial divergence within Arborophila did not occur until ~10 Ma when global cooling intensified. Subsequent dispersal and diversification within Arborophila were driven by several tectonic and climatic events. In particular, we found evidence of rapid radiation in Indochinese Arborophila during the Pliocene global cooling and extensive dispersal and speciation of Sundaic Arborophila during the Pleistocene sea-level fluctuations. Taken together, these results suggest that the evolutionary history and biogeography of Arborophila were influenced by complex interactions among historical, geological and climatic events in Southeast Asia.

The Draft Genome of the Endangered Sichuan Partridge (Arborophila rufipectus) with Evolutionary Implications

The Sichuan partridge (Arborophila rufipectus, Phasianidae, Galliformes) is distributed in south-west China, and classified as endangered grade. To examine the evolution and genomic features of Sichuan partridge, we de novo assembled the Sichuan partridge reference genome. The final draft assembly consisted of approximately 1.09 Gb, and had a scaffold N50 of 4.57 Mb. About 1.94 million heterozygous single-nucleotide polymorphisms (SNPs) were detected, 17,519 protein-coding genes were predicted, and 9.29% of the genome was identified as repetitive elements. A total of 56 olfactory receptor (OR) genes were found in Sichuan partridge, and conserved motifs were detected. Comparisons between the Sichuan partridge genome and chicken genome revealed a conserved genome structure, and phylogenetic analysis demonstrated that Arborophila possessed a basal phylogenetic position within Phasianidae. Gene Ontology (GO) enrichment analysis of positively selected genes (PSGs) in Sichuan partridge showed over-represented GO functions related to environmental adaptation, such as energy metabolism and behavior. Pairwise sequentially Markovian coalescent analysis revealed the recent demographic trajectory for the Sichuan partridge. Our data and findings provide valuable genomic resources not only for studying the evolutionary adaptation, but also for facilitating the long-term conservation and genetic diversity for this endangered species.

Alternative ecological strategies lead to avian brain size bimodality in variable habitats

The ecological contexts that promote larger brains have received considerable attention, but those that result in smaller-than-expected brains have been largely overlooked. Here, we use a global sample of 2062 species to provide evidence that metabolic and life history tradeoffs govern the evolution of brain size in birds and play an important role in defining the ecological strategies capable of persisting in Earth's most thermally variable and unpredictable habitats. While some birds cope with extreme winter conditions by investing in large brains (e.g., greater capacity for planning, innovation, and behavioral flexibility), others have small brains and invest instead in traits that allow them to withstand or recover from potentially deadly events. Specifically, these species are restricted to large body sizes, diets consisting of difficult-to-digest but readily available foods, and high reproductive output. Overall, our findings highlight the importance of considering strategic tradeoffs when investigating potential drivers of brain size evolution.

Genome-wide analysis sheds light on the high-altitude adaptation of the buff-throated partridge (Tetraophasis szechenyii)

The buff-throated partridge (Tetraophasis szechenyii) is a hypoxia-tolerant bird living in an extremely inhospitable high-altitude environment, which has high ultraviolet (UV) radiation as well as a low oxygen supply when compared with low-altitude areas. To further understand the molecular genetic mechanisms of the high-altitude adaptation of the buff-throated partridges, we de novo assembled the complete genome of the buff-throated partridge. Comparative genomics revealed that positively selected hypoxia-related genes in the buff-throated partridge were distributed in the HIF-1 signaling pathway (map04066), response to hypoxia (GO:0001666), response to oxygen-containing compound (GO:1901700), ATP binding (GO:0005524), and angiogenesis (GO:0001525). Of these positively selected hypoxia-related genes, one positively selected gene (LONP1) had one buff-throated partridge-specific missense mutation which was classified as deleterious by PolyPhen-2. Moreover, positively selected genes in the buff-throated partridge were enriched in cellular response to DNA damage stimulus (corrected P value: 0.028006) and DNA repair (corrected P value: 0.044549), which was related to the increased exposure of the buff-throated partridge to UV radiation. Compared with other avian genomes, the buff-throated partridge showed expansion in genes associated with steroid hormone receptor activity and contractions in genes related to immune and olfactory perception. Furthermore, comparisons between the buff-throated partridge genome and red junglefowl genome revealed a conserved genome structure and provided strong evidence of the sibling relationship between Tetraophasis and Lophophorus. Our data and analysis contributed to the study of Phasianidae evolutionary history and provided new insights into the potential adaptation mechanisms to the high altitude employed by the buff-throated partridge.

Vocal specialization through tracheal elongation in an extinct Miocene pheasant from China

Modifications to the upper vocal tract involving hyper-elongated tracheae have evolved many times within crown birds, and their evolution has been linked to a ‘size exaggeration’ hypothesis in acoustic signaling and communication, whereby smaller-sized birds can produce louder sounds. A fossil skeleton of a new extinct species of wildfowl (Galliformes: Phasianidae) from the late Miocene of China, preserves an elongated, coiled trachea that represents the oldest fossil record of this vocal modification in birds and the first documentation of its evolution within pheasants. The phylogenetic position of this species within Phasianidae has not been fully resolved, but appears to document a separate independent origination of this vocal modification within Galliformes. The fossil preserves a coiled section of the trachea and other remains supporting a tracheal length longer than the bird’s body. This extinct species likely produced vocalizations with a lower fundamental frequency and reduced harmonics compared to similarly-sized pheasants. The independent evolution of this vocal feature in galliforms living in both open and closed habitats does not appear to be correlated with other factors of biology or its open savanna-like habitat. Features present in the fossil that are typically associated with sexual dimorphism suggest that sexual selection may have resulted in the evolution of both the morphology and vocalization mechanism in this extinct species.

A novel mitochondrial genome of Arborophila and new insight into Arborophila evolutionary history

The lineage of the Bar-backed Partridge (Arborophila brunneopectus) was investigated to determine the phylogenetic relationships within Arborophila as the species is centrally distributed within an area covered by the distributions of 22 South-east Asian hill partridge species. The complete mitochondrial genome (mitogenome) of A. brunneopectus was determined and compared with four other hill partridge species mitogenomes. NADH subunit genes are radical in hill partridge mitogenomes and contain the most potential positive selective sites around where variable sites are abundant. Together with 44 other mitogenomes of closely related species, we reconstructed highly resolved phylogenetic trees using maximum likelihood (ML) and Bayesian inference (BI) analyses and calculated the divergence and dispersal history of Arborophila using combined datasets composed of their 13-protein coding sequences. Arborophila is reportedly be the oldest group in Phasianidae whose ancestors probably originated in Asia. A. rufipectus shares a closer relationship with A. ardens and A. brunneopectus compared to A. gingica and A. rufogularis, and such relationships were supported and profiled by NADH dehydrogenase subunit 5 (ND5). The intragenus divergence of all five Arborophila species occurred in the Miocene (16.84~5.69 Mya) when there were periods of climate cooling. We propose that these cooling events in the Miocene forced hill partridges from higher to lower altitudes, which led to geographic isolation and speciation. We demonstrated that the apparently deleterious +1 frameshift mutation in NADH dehydrogenase subunit 3 (ND3) found in all Arborophila is an ancient trait that has been eliminated in some younger lineages, such as Passeriformes. It is unclear of the biological advantages of this elimination for the relevant taxa and this requires further investigation.

How do seemingly non-vagile clades accomplish trans-marine dispersal? Trait and dispersal evolution in the landfowl (Aves: Galliformes)

Dispersal ability is a key factor in determining insular distributions and island community composition, yet non-vagile terrestrial organisms widely occur on oceanic islands. The landfowl (pheasants, partridges, grouse, turkeys, quails and relatives) are generally poor dispersers, but the Old World quail (Coturnix) are a notable exception. These birds evolved small body sizes and high-aspect-ratio wing shapes, and hence are capable of trans-continental migrations and trans-oceanic colonization. Two monotypic partridge genera, Margaroperdix of Madagascar and Anurophasis of alpine New Guinea, may represent additional examples of trans-marine dispersal in landfowl, but their body size and wing shape are typical of poorly dispersive continental species. Here, we estimate historical relationships of quail and their relatives using phylogenomics, and infer body size and wing shape evolution in relation to trans-marine dispersal events. Our results show that Margaroperdix and Anurophasis are nested within the Coturnix quail, and are each 'island giants' that independently evolved from dispersive, Coturnix-like ancestral populations that colonized and were subsequently isolated on Madagascar and New Guinea. This evolutionary cycle of gain and loss of dispersal ability, coupled with extinction of dispersive taxa, can result in the false appearance that non-vagile taxa somehow underwent rare oceanic dispersal.

Terrestrial mountain islands and Pleistocene climate fluctuations as motors for speciation: A case study on the genus Pseudovelia (Hemiptera: Veliidae)

This study investigated the influences of geographic isolation and climate fluctuation on the genetic diversity, speciation, and biogeography of the genus Pseudovelia (Hemiptera: Veliidae) in subtropical China and tropic Indo-China Peninsula. Species nucleotide and haplotype diversities decreased with reduction in species distribution limits. The gene tree was congruent with the taxonomy of monophyly, except for four species, P. contorta, P. extensa, P. tibialis tibialis, and P. vittiformis. The conflicts between the genes and species tree could be due to long-term isolation and incomplete lineage sorting. Diversification analysis showed that the diversification rate (0.08 sp/My shifted to 0.5 sp/My) changed at 2.1 Ma, which occurred in the early Pleistocene period. Ancestral area reconstruction suggested that subtropical species possibly evolved from the tropics region (i.e., Indo-China Peninsula). Results implied that narrow endemics harbored relatively low genetic diversity because of small effective population and genetic drift. Radiation of subtropical Pseudovelia species was rapidly promoted by Pleistocene climate fluctuations and geographic isolation. The acute rising of the Hengduan Mountain with the entire uplift of the Qinghai-Tibet Plateau induced the initial differentiation of Pseudovelia species. These results highlighted the importance of geographical isolation and climate changes in promoting speciation in mountain habitat islands.

The complete mitochondrial genome and phylogenetic position of the critically endangered Trinidad Piping Guan, Pipile pipile synonym Aburria pipile (Aves: Galliformes)

The complete mitochondrial genome of the Critically Endangered Trinidad Piping Guan, Pipile pipile (Jacquin 1784) synonym Aburria pipile was sequenced for the first time in this study. The genome is 16,665 bp in length with overall base compositions of 30.1, 23.7, 32.3 and 13.9% for A, T, C, and G, respectively. Structurally, the P. pipile mitogenome is comparable to that of other Galliformes, thereby demonstrating typical avian gene organization. The mitogenome was subsequently used to produce a revised phylogenetic placement of P. pipile within the Galliforme order, positioning the Pipile genus basal within the Cracidae family. It is further envisaged that this novel genomic data will contribute to a wider understanding of genetic relationships within the genus Pipile and the analysis of the evolutionary relationships of the Galliforme order in a wider avian context.

Pairing Behavior of the Monogamous King Quail, Coturnix chinensis

Animals with socially monogamous mating systems are valuable for discovering proximate mechanisms of prosocial behavior and close social relationships. Especially powerful are comparisons between related species that differ in monogamous tendency. Birds are the most socially monogamous vertebrates. Thus far most research on mechanisms of pairing has used zebra finches, which do not have a relative with a different mating system, however. The goal of the experiments reported here was to develop a new comparative avian system by studying the pairing behavior of a reportedly strongly monogamous quail, the king quail (Coturnix chinensis), a species in the same clade as the less monogamous Japanese quail (Coturnix japonica), the subject of much prior research. In Experiment 1 male-female pairs of king quail housed together were initially avoidant or aggressive but most rapidly progressed to allopreening and huddling. A separation-reunion paradigm reliably elicited both of these behaviors in males that had cohabited for one week. In Experiment 2 the allopreening and huddling behavior of males in cohabiting pairs was highly selective, and a majority of the males were aggressive toward a familiar female that was not the cohabitation partner. In Experiment 3 males were separated from their female cohabitation partners for 9-10 weeks and then given two-choice tests. All but one male spent more time near an unfamiliar female, which may have reflected aggression and shows recognition of and memory for the past pairing experience. Thus king quail show robust, selective and easy to measure pairing behavior that can be reliably elicited with simple separation-reunion testing procedures. Copulation is rarely seen during tests. The behavior of king quail is a striking contrast to that of Japanese quail, providing a new comparative system for discovering mechanisms of behavior related to close social relationships and monogamy.

Osteology Supports a Stem-Galliform Affinity for the Giant Extinct Flightless Bird Sylviornis neocaledoniae (Sylviornithidae, Galloanseres)

The giant flightless bird Sylviornis neocaledoniae (Aves: Sylviornithidae) existed on La Grande Terre and Ile des Pins, New Caledonia, until the late Holocene when it went extinct shortly after human arrival on these islands. The species was generally considered to be a megapode (Megapodiidae) until the family Sylviornithidae was erected for it in 2005 to reflect multiple cranial autapomorphies. However, despite thousands of bones having been reported for this unique and enigmatic taxon, the postcranial anatomy has remained largely unknown. We rectify this deficiency and describe the postcranial skeleton of S. neocaledoniae based on ~600 fossils and use data from this and its cranial anatomy to make a comprehensive assessment of its phylogenetic affinities. Sylviornis neocaledoniae is found to be a stem galliform, distant from megapodiids, and the sister taxon to the extinct flightless Megavitiornis altirostris from Fiji, which we transfer to the family Sylviornithidae. These two species form the sister group to extant crown-group galliforms. Several other fossil galloanseres also included in the phylogenetic analysis reveal novel hypotheses of their relationships as follows: Dromornis planei (Dromornithidae) is recovered as a stem galliform rather than a stem anseriform; Presbyornis pervetus (Presbyornithidae) is the sister group to Anseranatidae, not to Anatidae; Vegavis iaai is a crown anseriform but remains unresolved relative to Presbyornis pervetus, Anseranatidae and Anatidae. Sylviornis neocaledoniae was reconstructed herein to be 0.8 m tall in a resting stance and weigh 27-34 kg. The postcranial anatomy of S. neocaledoniae shows no indication of the specialised adaptation to digging seen in megapodiids, with for example, its ungual morphology differing little from that of chicken Gallus gallus. These observations and its phylogenetic placement as stem galliforms makes it improbable that this species employed ectothermic incubation or was a mound-builder. Sylviornis neocaledoniae can therefore be excluded as the constructor of tumuli in New Caledonia.

Identification of CR1 retroposons in Arborophila rufipectus and their application to Phasianidae phylogeny

Chicken repeat 1 (CR1), a member of non-LTR retroposon, is an important phylogenetic marker in avian systematics. In this study, we reported several characteristics of CR1 elements in a draft genome of Arborophila rufipectus (Sichuan partridge). According to the analyses of RepeatMasker, approximately 254 966 CR1 elements were identified in A. rufipectus, covering 6.7% of the genome. Subsequently, we selected eighteen novel CR1 elements by comparing the chicken genome, turkey genome and assembled A. rufipectus scaffolds. Here, a combined data set comprising of 22 CR1 loci, mitochondrial genomes and eight unlinked introns was analysed to infer the evolutionary relationships of twelve Phasianidae species. The applicability of CR1 sequences for inferring avian phylogeny relative to mtDNA and intron sequences was investigated as well. Our results elucidated the position of A. rufipectus in Phasianidae with robust supports that it presented a sister clade to Arborophila ardens/Arborophila brunneopectus, and implied that genus Arborophila was in a basal phylogenetic position within Phasianidae and a phylogenetic affinity between Meleagris gallopavo and Pucrasia macrolopha. Therefore, this work not only resolved some of the confounding relationships among Phasianidae, but also suggested CR1 sequences could provide powerful complementary data for phylogeny reconstruction.

Avoiding Missing Data Biases in Phylogenomic Inference: An Empirical Study in the Landfowl (Aves: Galliformes)

Production of massive DNA sequence data sets is transforming phylogenetic inference, but best practices for analyzing such data sets are not well established. One uncertainty is robustness to missing data, particularly in coalescent frameworks. To understand the effects of increasing matrix size and loci at the cost of increasing missing data, we produced a 90 taxon, 2.2 megabase, 4,800 locus sequence matrix of landfowl using target capture of ultraconserved elements. We then compared phylogenies estimated with concatenated maximum likelihood, quartet-based methods executed on concatenated matrices and gene tree reconciliation methods, across five thresholds of missing data. Results of maximum likelihood and quartet analyses were similar, well resolved, and demonstrated increasing support with increasing matrix size and sparseness. Conversely, gene tree reconciliation produced unexpected relationships when we included all informative loci, with certain taxa placed toward the root compared with other approaches. Inspection of these taxa identified a prevalence of short average contigs, which potentially biased gene tree inference and caused erroneous results in gene tree reconciliation. This suggests that the more problematic missing data in gene tree-based analyses are partial sequences rather than entire missing sequences from locus alignments. Limiting gene tree reconciliation to the most informative loci solved this problem, producing well-supported topologies congruent with concatenation and quartet methods. Collectively, our analyses provide a well-resolved phylogeny of landfowl, including strong support for previously problematic relationships such as those among junglefowl (Gallus), and clarify the position of two enigmatic galliform genera (Lerwa, Melanoperdix) not sampled in previous molecular phylogenetic studies.

Comparative mitochondrial genomics and phylogenetic relationships of the Crossoptilon species (Phasianidae, Galliformes)

BACKGROUND

Phasianidae is a family of Galliformes containing 38 genera and approximately 138 species, which is grouped into two tribes based on their morphological features, the Pheasants and Partridges. Several studies have attempted to reconstruct the phylogenetic relationships of the Phasianidae, but many questions still remain unaddressed, such as the taxonomic status and phylogenetic relationships among Crossoptilon species. The mitochondrial genome (mitogenome) has been extensively used to infer avian genetic diversification with reasonable resolution. Here, we sequenced the entire mitogenomes of three Crossoptilon species (C. harmani, C. mantchuricum and C. crossoptilon) to investigate their evolutionary relationship among Crossoptilon species.

RESULTS

The complete mitogenomes of C. harmani, C. mantchuricum and C. crossoptilon are 16682 bp, 16690 bp and 16680 bp in length, respectively, encoding a standard set of 13 protein-coding genes, 2 ribosomal RNA genes, 22 transfer RNA genes, and a putative control region. C. auritum and C. mantchuricum are more closely related genetically, whereas C. harmani is more closely related to C. crossoptilon. Crossoptilon has a closer relationship with Lophura, and the following phylogenetic relationship was reconstructed: ((Crossoptilon + Lophura) + (Phasianus + Chrysolophus)). The divergence time between the clades C. harmani-C. crossoptilon and C. mantchuricum-C. auritum is consistent with the uplift of the Tibetan Plateau during the Tertiary Pliocene. The Ka/Ks analysis showed that atp8 gene in the Crossoptilon likely experienced a strong selective pressure in adaptation to the plateau environment.

CONCLUSIONS

C. auritum with C. mantchuricum and C. harmani with C. crossoptilon form two pairs of sister groups. The genetic distance between C. harmani and C. crossoptilon is far less than the interspecific distance and is close to the intraspecific distance of Crossoptilon, indicating that C. harmani is much more closely related to C. crossoptilon. Our mito-phylogenomic analysis supports the monophyly of Crossoptilon and its closer relationship with Lophura. The uplift of Tibetan Plateau is suggested to impact the divergence between C. harmani-C. crossoptilon clade and C. mantchuricum-C. auritum clade during the Tertiary Pliocene. Atp8 gene in the Crossoptilon species might have experienced a strong selective pressure for adaptation to the plateau environment.

The evolution of peafowl and other taxa with ocelli (eyespots): a phylogenomic approach

The most striking feature of peafowl (Pavo) is the males' elaborate train, which exhibits ocelli (ornamental eyespots) that are under sexual selection. Two additional genera within the Phasianidae (Polyplectron and Argusianus) exhibit ocelli, but the appearance and location of these ornamental eyespots exhibit substantial variation among these genera, raising the question of whether ocelli are homologous. Within Polyplectron, ocelli are ancestral, suggesting ocelli may have evolved even earlier, prior to the divergence among genera. However, it remains unclear whether Pavo, Polyplectron and Argusianus form a monophyletic clade in which ocelli evolved once. We estimated the phylogeny of the ocellated species using sequences from 1966 ultraconserved elements (UCEs) and three mitochondrial regions. The three ocellated genera did form a strongly supported clade, but each ocellated genus was sister to at least one genus without ocelli. Indeed, Polyplectron and Galloperdix, a genus not previously suggested to be related to any ocellated taxon, were sister genera. The close relationship between taxa with and without ocelli suggests multiple gains or losses. Independent gains, possibly reflecting a pre-existing bias for eye-like structures among females and/or the existence of a simple mutational pathway for the origin of ocelli, appears to be the most likely explanation.

Does more sequence data improve estimates of galliform phylogeny? Analyses of a rapid radiation using a complete data matrix

The resolution of rapid evolutionary radiations or "bushes" in the tree of life has been one of the most difficult and interesting problems in phylogenetics. The avian order Galliformes appears to have undergone several rapid radiations that have limited the resolution of prior studies and obscured the position of taxa important both agriculturally and as model systems (chicken, turkey, Japanese quail). Here we present analyses of a multi-locus data matrix comprising over 15,000 sites, primarily from nuclear introns but also including three mitochondrial regions, from 46 galliform taxa with all gene regions sampled for all taxa. The increased sampling of unlinked nuclear genes provided strong bootstrap support for all but a small number of relationships. Coalescent-based methods to combine individual gene trees and analyses of datasets that are independent of published data indicated that this well-supported topology is likely to reflect the galliform species tree. The inclusion or exclusion of mitochondrial data had a limited impact upon analyses upon analyses using either concatenated data or multispecies coalescent methods. Some of the key phylogenetic findings include support for a second major clade within the core phasianids that includes the chicken and Japanese quail and clarification of the phylogenetic relationships of turkey. Jackknifed datasets suggested that there is an advantage to sampling many independent regions across the genome rather than obtaining long sequences for a small number of loci, possibly reflecting the differences among gene trees that differ due to incomplete lineage sorting. Despite the novel insights we obtained using this increased sampling of gene regions, some nodes remain unresolved, likely due to periods of rapid diversification. Resolving these remaining groups will likely require sequencing a very large number of gene regions, but our analyses now appear to support a robust backbone for this order.

The updated phylogenies of the phasianidae based on combined data of nuclear and mitochondrial DNA

The phylogenetic relationships of species in the Phasianidae, Order Galliformes, are the object of intensive study. However, convergent morphological evolution and rapid species radiation result in much ambiguity in the group. Further, matrilineal (mtDNA) genealogies conflict with trees based on nuclear DNA retrotransposable elements. Herein, we analyze 39 nearly complete mitochondrial genomes (three new) and up to seven nuclear DNA segments. We combine these multiple unlinked, more informative genetic markers to infer historical relationships of the major groups of phasianids. The nuclear DNA tree is largely congruent with the tree derived from mt genomes. However, branching orders of mt/nuclear trees largely conflict with those based on retrotransposons. For example, Gallus/Bambusicola/Francolinus forms the sister-group of Coturnix/Alectoris in the nuclear/mtDNA trees, yet the tree based on retrotransposable elements roots the former at the base of the tree and not with the latter. Further, while peafowls cluster with Gallus/Coturnix in the mt tree, they root at the base of the phasianids following Gallus in the tree based on retrotransposable elements. The conflicting branch orders in nuclear/mtDNA and retrotransposons-based trees in our study reveal the complex topology of the Phasianidae.

Whole genome sequencing of the black grouse (Tetrao tetrix): reference guided assembly suggests faster-Z and MHC evolution

BACKGROUND

The different regions of a genome do not evolve at the same rate. For example, comparative genomic studies have suggested that the sex chromosomes and the regions harbouring the immune defence genes in the Major Histocompatability Complex (MHC) may evolve faster than other genomic regions. The advent of the next generation sequencing technologies has made it possible to study which genomic regions are evolutionary liable to change and which are static, as well as enabling an increasing number of genome studies of non-model species. However, de novo sequencing of the whole genome of an organism remains non-trivial. In this study, we present the draft genome of the black grouse, which was developed using a reference-guided assembly strategy.

RESULTS

We generated 133 Gbp of sequence data from one black grouse individual by the SOLiD platform and used a combination of de novo assembly and chicken reference genome mapping to assemble the reads into 4572 scaffolds with a total length of 1022 Mb. The draft genome well covers the main chicken chromosomes 1 ~ 28 and Z which have a total length of 1001 Mb. The draft genome is fragmented, but has a good coverage of the homologous chicken genes. Especially, 33.0% of the coding regions of the homologous genes have more than 90% proportion of their sequences covered. In addition, we identified ~1 M SNPs from the genome and identified 106 genomic regions which had a high nucleotide divergence between black grouse and chicken or between black grouse and turkey.

CONCLUSIONS

Our results support the hypothesis that the chromosome X (Z) evolves faster than the autosomes and our data are consistent with the MHC regions being more liable to change than the genome average. Our study demonstrates how a moderate sequencing effort can be combined with existing genome references to generate a draft genome for a non-model species.

Conservation priority of global Galliformes species based on phylogenetic diversity

In this study, based on phylogenetic diversity (PD), I develop a conservation strategy for Galliformes species around the world. A cladogram of 197 Galliformes species derived from a previous study was used for calculating PD metrics. Branch length is an important aspect of the phylogenetic information a tree can convey, but 2 traditionally-used metrics, the number of phylogenetic groups to which a taxon belongs (I) and the proportion that each taxon contributes to the total diversity of the group (W), are fully node-based and do not take branch length into account. Therefore, to measure PD more appropriately, I combined a branch-related metric, pendant edge (P), in addition to I and W. A final combined rank for Galliformes species was obtained by summing the ranks of the 3 metrics. My results showed that the 5% top priority species for conserving evolutionary potential were Galloperdix lunulata, Haematortyx sanguiniceps, Margaroperdix madagarensis, Syrmaticus soemmerringii, Coturnix pectoralis, Polyplectron napoleonis, Alectoris melanocephala, Xenoperdix udzungwensis, Afropavo congensis and Syrmaticus reevesii. The current species priority ranking based on pylogenetic diversity and the official International Union for Conservation of Nature (IUCN) ranking of Galliformes species was significantly correlated when considering the 5 categories of IUCN (critical endangered, endangered, vulnerable, near threatened and least concern). This indicated the feasibility of introducing the PD index into the network of IUCN regional Red List assessment. The 5% top priority countries selected using the complementarity principle possessing diversified Galliformes genetic resources were China, Indonesia, Mexico, India, Colombia, Australia, Brazil, Angola, Congo and Japan (in descending order). China, Indonesia, Mexico, Brazil, India and Colombia are consistently selected among the 4 top priority sets of richness, rarity, endemicity and PD. This result indicated that the priority result from PD is highly congruent with conventional measures. Along with other conventional ecological attributes, the alternative conservation scenario based on PD is reasonable and can be adopted in systematic conservation planning.

Assessing phylogenetic relationships among galliformes: a multigene phylogeny with expanded taxon sampling in Phasianidae

Galliform birds (relatives of the chicken and turkey) have attracted substantial attention due to their importance to society and value as model systems. This makes understanding the evolutionary history of Galliformes, especially the species-rich family Phasianidae, particularly interesting and important for comparative studies in this group. Previous studies have differed in their conclusions regarding galliform phylogeny. Some of these studies have suggested that specific clades within this order underwent rapid radiations, potentially leading to the observed difficulty in resolving their phylogenetic relationships. Here we presented analyses of six nuclear intron sequences and two mitochondrial regions, an amount of sequence data larger than many previous studies, and expanded taxon sampling by collecting data from 88 galliform species and four anseriform outgroups. Our results corroborated recent studies describing relationships among the major families, and provided further evidence that the traditional division of the largest family, the Phasianidae into two major groups ("pheasants" and "partridges") is not valid. Within the Phasianidae, relationships among many genera have varied among studies and there has been little consensus for the placement of many taxa. Using this large dataset, with substantial sampling within the Phasianidae, we obtained strong bootstrap support to confirm some previously hypothesized relationships and we were able to exclude others. In addition, we added the first nuclear sequence data for the partridge and quail genera Ammoperdix, Caloperdix, Excalfactoria, and Margaroperdix, placing these taxa in the galliform tree of life with confidence. Despite the novel insights obtained by combining increased sampling of taxa and loci, our results suggest that additional data collection will be necessary to solve the remaining uncertainties.

Phylogeography of Silver Pheasant (Lophura nycthemera L.) across China: aggregate effects of refugia, introgression and riverine barriers

The role of Pleistocene glacial cycles in forming the contemporary genetic structure of organisms has been well studied in China with a particular focus on the Tibetan Plateau. However, China has a complex topography and diversity of local climates, and how glacial cycles may have shaped the subtropical and tropical biota of the region remains mostly unaddressed. To investigate the factors that affected the phylogeography and population history of a widely distributed and nondeciduous forest species, we analysed morphological characters, mitochondrial DNA sequences and nuclear microsatellite loci in the Silver Pheasant (Lophura nycthemera). In a pattern generally consistent with phenotypic clusters, but not nominal subspecies, deeply divergent mitochondrial lineages restricted to different geographic regions were detected. Coalescent simulations indicated that the time of main divergence events corresponded to major glacial periods in the Pleistocene and gene flow was only partially lowered by drainage barriers between some populations. Intraspecific cytonuclear discordance was revealed in mitochondrial lineages from Hainan Island and the Sichuan Basin with evidence of nuclear gene flow from neighbouring populations into the latter. Unexpectedly, hybridization was revealed in Yingjiang between the Silver Pheasant and Kalij Pheasant (Lophura leucomelanos) with wide genetic introgression at both the mtDNA and nuclear levels. Our results highlight a novel phylogeographic pattern in a subtropical area generated from the combined effects of climate oscillation, partial drainage barriers and interspecific hybridization. Cytonuclear discordance combined with morphological differentiation implies that complex historical factors shaped the divergence process in this biodiversity hot spot area of southern China.

Parsimony and model-based analyses of indels in avian nuclear genes reveal congruent and incongruent phylogenetic signals

Insertion/deletion (indel) mutations, which are represented by gaps in multiple sequence alignments, have been used to examine phylogenetic hypotheses for some time. However, most analyses combine gap data with the nucleotide sequences in which they are embedded, probably because most phylogenetic datasets include few gap characters. Here, we report analyses of 12,030 gap characters from an alignment of avian nuclear genes using maximum parsimony (MP) and a simple maximum likelihood (ML) framework. Both trees were similar, and they exhibited almost all of the strongly supported relationships in the nucleotide tree, although neither gap tree supported many relationships that have proven difficult to recover in previous studies. Moreover, independent lines of evidence typically corroborated the nucleotide topology instead of the gap topology when they disagreed, although the number of conflicting nodes with high bootstrap support was limited. Filtering to remove short indels did not substantially reduce homoplasy or reduce conflict. Combined analyses of nucleotides and gaps resulted in the nucleotide topology, but with increased support, suggesting that gap data may prove most useful when analyzed in combination with nucleotide substitutions.

An Update of Wallace’s Zoogeographic Regions of the World

Modern attempts to produce biogeographic maps focus on the distribution of species, and the maps are typically drawn without phylogenetic considerations. Here, we generate a global map of zoogeographic regions by combining data on the distributions and phylogenetic relationships of 21,037 species of amphibians, birds, and mammals. We identify 20 distinct zoogeographic regions, which are grouped into 11 larger realms. We document the lack of support for several regions previously defined based on distributional data and show that spatial turnover in the phylogenetic composition of vertebrate assemblages is higher in the Southern than in the Northern Hemisphere. We further show that the integration of phylogenetic information provides valuable insight on historical relationships among regions, permitting the identification of evolutionarily unique regions of the world.

Sequencing of the core MHC region of black grouse (Tetrao tetrix) and comparative genomics of the galliform MHC

BACKGROUND

The MHC, which is regarded as the most polymorphic region in the genomes of jawed vertebrates, plays a central role in the immune system by encoding various proteins involved in the immune response. The chicken MHC-B genomic region has a highly streamlined gene content compared to mammalian MHCs. Its core region includes genes encoding Class I and Class IIB molecules but is only ~92Kb in length. Sequences of other galliform MHCs show varying degrees of similarity as that of chicken. The black grouse (Tetrao tetrix) is a wild galliform bird species which is an important model in conservation genetics and ecology. We sequenced the black grouse core MHC-B region and combined this with available data from related species (chicken, turkey, gold pheasant and quail) to perform a comparative genomics study of the galliform MHC. This kind of analysis has previously been severely hampered by the lack of genomic information on avian MHC regions, and the galliformes is still the only bird lineage where such a comparison is possible.

RESULTS

In this study, we present the complete genomic sequence of the MHC-B locus of black grouse, which is 88,390 bp long and contains 19 genes. It shows the same simplicity as, and almost perfect synteny with, the corresponding genomic region of chicken. We also use 454-transcriptome sequencing to verify expression in 17 of the black grouse MHC-B genes. Multiple sequence inversions of the TAPBP gene and TAP1-TAP2 gene block identify the recombination breakpoints near the BF and BLB genes. Some of the genes in the galliform MHC-B region also seem to have been affected by selective forces, as inferred from deviating phylogenetic signals and elevated rates of non-synonymous nucleotide substitutions.

CONCLUSIONS

We conclude that there is large synteny between the MHC-B region of the black grouse and that of other galliform birds, but that some duplications and rearrangements have occurred within this lineage. The MHC-B sequence reported here will provide a valuable resource for future studies on the evolution of the avian MHC genes and on links between immunogenetics and ecology of black grouse.