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Passerea
Passerea
Passerea
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Passerea
Temporal range: Early Paleocene–Holocene 62–0 Ma Possible an early origin based on molecular clock[1]
Beautiful firetail (Stagonopleura bella)
Scientific classification Edit this classification
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Infraclass: Neognathae
Clade: Neoaves
Clade: Passerea
Jarvis et al., 2014
Clades

Passerea is a taxon of neoavian birds that was proposed by Jarvis et al. (2014).[3] Their genomic analysis recovered two major clades within Neoaves, Passerea and Columbea, and concluded that both clades appear to have many ecologically driven convergent traits.

According to Jarvis (2014), these convergences include the foot-propelled diving trait of grebes in Columbea with loons and cormorants in Passerea; the wading-feeding trait of flamingos in Columbea with ibises and egrets in Passerea; and pigeons and sandgrouse in Columbea with shorebirds (killdeer) in Passerea. For Jarvis (2014), these long-known trait and morphological alliances suggest that some of the traditional nongenomic trait classifications are based on polyphyletic assemblages.

Passerea was not recovered in other studies.[4][1]

Phylogeny

[edit]

Cladogram of Passerea relationships based on Jarvis et al. (2014)[3] with some clade names after Yuri et al. (2013)[5] and Kimball et al. 2013.[6]

Passerea

The following cladogram illustrates the proposed relationships between bird clades of Passerea. This consensus phylogeny of birds is based on phylogenomic data, reflecting a recent phylogenomic supertree analysis per Stiller et al. (2024).[2]

Passerea

Failed to capture subclade with label Passerea

References

[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

Passerea

View on Grokipedia
from Grokipedia
Passerea is a proposed of neoavian birds, representing one of the two primary lineages within the diverse group , which encompasses over 90% of extant bird species. Introduced through whole-genome analyses of 48 representative species, it was defined as the sister group to Columbea and named after its most speciose component, the Passeriformes (songbirds). The includes three main subgroups: core landbirds (), which comprise perching birds like passerines, parrots, woodpeckers, and raptors such as ; core waterbirds (Aequornithia), encompassing diving and wading species including , loons, , , and pelicans; and Phaethontimorphae, featuring tropicbirds and the . This configuration suggested that the common ancestor of Passerea was likely a terrestrial predator, with vocal learning evolving independently in multiple lineages, and it accounted for nearly all modern birds, highlighting the rapid post-Cretaceous-Paleogene diversification of around 66 million years ago. Subsequent phylogenomic studies have challenged the of Passerea, attributing early branching patterns to high levels of incomplete lineage sorting and rapid radiations that complicate resolution. For example, a targeted next-generation sequencing approach across 198 and 259 nuclear loci recovered neither Passerea nor Columbea as monophyletic, instead identifying a series of successive sister clades such as nightjars and allies, cuckoos with pigeons, cranes, waterbirds, and landbirds (with basal to the latter). More recent family-level genomic analyses using coalescent-based methods on 363 further fragmented the proposed structure, resolving into four major clades— (flamingos and grebes), Columbaves (pigeons and relatives), (core landbirds), and Elementaves (aequornithians with nightjars, , and shorebirds)—without support for Passerea as a unified group. These findings underscore ongoing debates in avian , where methodological differences in data types (e.g., coding vs. non-coding regions) influence deep-level relationships, yet consistently affirm the explosive evolutionary history of birds following the end-Cretaceous .

Taxonomy

Etymology

The name Passerea derives from the Latin word passer, meaning "sparrow," which forms the root of Passeriformes, the order of perching birds (passerines) that constitutes the clade's most speciose group and exemplifies its dominant terrestrial lineages. This taxonomic term was formally proposed by Jarvis et al. in as part of their genome-scale phylogenetic analysis of modern birds, designating Passerea as one of two reciprocally monophyletic sister clades diverging early within , the other being Columbea. The authors explicitly named it after Passeriformes to underscore the clade's inclusion of diverse landbirds allied with songbirds and vocal-learning taxa. By evoking the sparrow-like perching adaptations central to Passeriformes, the name emphasizes Passerea's focus on primarily terrestrial and arboreal birds, distinguishing it from Columbea, whose highlights more aquatic and ground-dwelling forms like columbiforms.

Classification history

Prior to 2014, classifications of often informally grouped birds into landbirds and waterbirds based on ecological and morphological similarities, but these assemblages were frequently polyphyletic and lacked formal definitions. For instance, DNA-DNA hybridization studies proposed a landbird encompassing diverse orders like raptors, woodpeckers, and passerines, while morphological analyses reinforced similar divisions without resolving deeper relationships. Mitochondrial genome data sometimes failed to support landbird , highlighting inconsistencies in pre-genomic era taxonomies. The Passerea was first formally proposed in 2014 through a genome-scale phylogenetic analysis of 48 bird species representing all orders, marking the initial recognition of a group uniting core landbirds () with elements of waterbirds (Aequornithia). This study, utilizing coalescent-based methods on thousands of genes, identified Passerea as one of two primary lineages alongside Columbea, with strong bootstrap support for its . The name Passerea reflects the dominance of Passeriformes, the largest avian order, within the . Following the 2014 proposal, refinements and debates emerged regarding Passerea's exact boundaries and , particularly from a 2015 study analyzing targeted next-generation sequencing data from 198 species. This work challenged Passerea's , instead supporting a broad landbird assemblage termed Inopinaves that excluded certain waterbird elements included in the original definition, while affirming similar core groupings of raptors, parrots, and songbirds. Subsequent genomic analyses have shown mixed results, with some reinforcing Passerea-like structures in divergences—such as a 2024 study attributing support to a of suppressed recombination—though more comprehensive genome-wide analyses, including Stiller et al. (2024) resolving into four major clades (, Columbaves, , and Elementaves) without Passerea, and a 2025 morphological study of the quadrate explicitly rejecting its , indicate ongoing challenges. It has not been universally integrated into major taxonomic lists like those of the IOC World Bird List, which favor alternative higher-level arrangements based on Prum et al. (2015). These debates underscore ongoing efforts to reconcile genome-scale data with denser sampling for stable avian .

Phylogeny

Proposal and molecular evidence

The classification of , the largest clade of modern birds, had long been hampered by unresolved deep phylogenetic branches, often attributed to incomplete lineage sorting and . In 2014, a landmark study by et al. analyzed whole-genome sequences from 48 bird species, representing all orders of , to resolve these early divergences. The researchers compiled a comprising 8,251 protein-coding genes (approximately 41.8 million base pairs), including exons, introns, and 3,769 ultraconserved elements, drawn from nuclear genomes. To address challenges such as low phylogenetic signal in individual loci, they employed genome-scale phylogenomic methods, including maximum likelihood concatenation via ExaML and multispecies coalescent modeling with MP-EST*, supplemented by a statistical binning technique to group loci with similar phylogenetic signals and mitigate noise from incomplete lineage sorting. The recovered a highly supported revealing the first major divergence within extant into two reciprocally monophyletic clades: Passerea and Columbea. Passerea emerged as the larger basal Neoavian , positioned to Columbea, with 100% bootstrap support for this bipartition. According to the study, Passerea initially encompassed approximately 5,000 species, predominantly terrestrial neoavians such as core landbirds including passerines.

Support from subsequent studies

Subsequent phylogenomic studies have provided varying degrees of support for the clade proposed by Jarvis et al. in 2014, often refining its internal structure while addressing early uncertainties in neoavian relationships, though methodological differences continue to influence outcomes. Prum et al. analyzed over 390 nuclear loci from 198 species using targeted next-generation sequencing, yielding partial support for a Passerea-like grouping of perching birds, parrots, and related lineages, although the clade was not recovered as strictly due to alternative arrangements among core landbirds and waterbirds. Subsequent reanalyses of non-coding portions from this dataset have strengthened evidence for Passerea's by mitigating biases in coding regions. Kuhl et al. analyzed 3'-untranslated region (3'-UTR) sequences from 233 bird species representing nearly 90% of avian families, resolving 91% of interfamily relationships with high bootstrap support; however, this study did not recover Passerea as monophyletic, instead supporting alternative neoavian groupings. Phylogenomic investigations from 2021 to 2024 have shown mixed results for Passerea, with support in some datasets emphasizing non-coding sequences or coalescent models but challenges in others due to incomplete lineage sorting during the Cretaceous-Paleogene radiation. For instance, combined analyses incorporating retroelement insertions have identified diagnostic synapomorphies supporting Passerea's monophyly, with emergent congruence to the Jarvis arrangement in total-evidence frameworks that integrate thousands of gene trees and over 2,000 insertions. A 2024 family-level genomic analysis of 363 species by Stiller et al., using coalescent-based methods, did not recover Passerea or Columbea as monophyletic; instead, it resolved Neoaves into four major clades—Mirandornithes (flamingos and grebes), Columbaves (pigeons and relatives), Telluraves (core landbirds), and Elementaves (aequornithians with nightjars, hoatzin, and shorebirds)—attributing discrepancies to a recombination-suppressed region on chromosome 4 that misleadingly supports the Jarvis topology. These findings highlight ongoing debates in avian systematics, where data types (e.g., coding vs. non-coding regions) and genomic regions influence deep-level relationships. Areas of debate persist regarding minor boundary adjustments within Passerea-like groupings, such as the precise placement of (encompassing nightjars and swifts), which some whole-genome studies position near the base of the while others suggest closer affinity to core landbirds based on specific recombination-suppressed regions.

Cladogram and relationships

Passerea forms one of the two primary s within as proposed in 2014, positioned as the to Columbea, with this basal split supported at 100% bootstrap in the original genomic analyses. The is monophyletic in that topology, encompassing the majority of landbird lineages, and originated through a divergence approximately 66 million years ago, shortly after the Cretaceous-Paleogene (K-Pg) . A cladogram based on the Jarvis et al. (2014) whole-genome phylogenomics places as follows within : Recent phylogenomic syntheses show conflicts in relationships, including variable placement of and overall support for Passerea. One 2024 analysis using intergenic loci proposes an alternative structure with Elementaves incorporating and diverging from the Passerea-Columbea dichotomy, rendering Passerea paraphyletic, while upholding the split into Afroaves and .

Composition

Major subclades

Passerea was proposed to comprise three primary subclades reflecting its early diversification following the : core landbirds (), core waterbirds (Aequornithia), and Phaethontimorphae. These divisions were supported by the original genome-scale phylogenetic analyses of Jarvis et al. (2015), which resolved Passerea as a group within , though subsequent studies have challenged this . Telluraves forms the core landbird assemblage within the proposed Passerea, comprising predominantly diurnal, perching species adapted to terrestrial and arboreal habitats. It is subdivided into two main branches: , which includes raptorial and perching forms like seriemas (), falcons (), parrots (Psittaciformes), and passerines (Passeriformes); and Afroaves, encompassing diverse lineages such as owls (), woodpeckers (), and mousebirds (). The divergence of from the other Passerea lineages was estimated at approximately 55 Ma in the 2015 analysis. Aequornithia represents the core waterbird subclade, encompassing diving and wading species such as (Sphenisciformes), (Gaviiformes), petrels and albatrosses (), herons and egrets (Ardeidae within ), pelicans (), and cormorants (Phalacrocoracidae within ). This group is characterized by adaptations for aquatic lifestyles, with its separation from landbirds highlighting parallel radiations in marine and freshwater environments post-extinction. Phaethontimorphae is the smallest subclade, featuring tropicbirds () as to the (). These aerial and coastal specialists diverged early within Passerea, with molecular evidence placing their split around 60-70 Ma.

Included orders and families

The proposed Passerea encompasses approximately 5,000–6,000 across more than 20 orders, accounting for roughly half of all extant bird (as of 2023 estimates). This diversity is dominated by the order Passeriformes, which includes over 6,000 in about 140 families. The focuses on landbird and waterbird lineages, excluding those in the Columbea such as Columbiformes (pigeons) and Cuculiformes (cuckoos). The major orders and selected key families are outlined below, organized by representative subclades. These groupings reflect the molecular phylogenetic evidence from the 2015 proposal supporting Passerea's composition.
OrderApproximate Species CountKey Families (Examples)Subclade
Passeriformes6,000+Tyrannidae (tyrant flycatchers), Fringillidae (finches), (crows and jays)
Psittaciformes400 (true parrots), Cacatuidae (cockatoos)
450Picidae (woodpeckers), Ramphastidae (toucans)
Strigiformes250Strigidae (true owls), Tytonidae (barn owls)
260 (hawks, eagles, Old World vultures)
70 (falcons and caracaras)
120 (rollers), Alcedinidae ()
70Bucerotidae (hornbills)
Trogoniformes45Trogonidae (trogons and quetzals)
Coliiformes6Coliidae (mousebirds)
7Cariamidae (seriemas)
130 (petrels), Diomedeidae (albatrosses)Aequornithia
75Ardeidae (herons, egrets), (pelicans)Aequornithia
200Phalacrocoracidae (cormorants), (gannets, boobies)Aequornithia
Sphenisciformes20Spheniscidae ()Aequornithia
5Gaviidae (loons)Aequornithia
3Phaethontidae (tropicbirds)Phaethontimorphae
1Eurypygidae ()Phaethontimorphae
These orders represent the core proposed composition of Passerea, with Passeriformes and waterbird orders exemplifying the clade's among perching, terrestrial, and aquatic birds.

Characteristics

Shared morphological traits

Passerea, as proposed, encompasses a diverse array of bird lineages within , many of which—particularly in core landbirds ()—share morphological traits adapted to perching, climbing, and diverse feeding strategies. A key feature in is the anisodactyl foot structure, consisting of four toes with three directed forward (digits II, III, IV) and one backward (hallux), which provides strong grasping ability for perching on branches and . Vocalization capabilities are enhanced in numerous Passerea lineages through modifications to the , the avian vocal organ located at the base of the trachea. In passerines, the dominant group within Passerea, the syrinx features complex intrinsic musculature—up to six pairs of syringeal muscles in oscines—enabling precise control over sound production for learned songs and calls, though this complexity is less pronounced in other subclades like suboscines. These modifications support diverse acoustic repertoires but are not universal across all proposed Passerea members, with vocal learning evolving independently in lineages such as songbirds and parrots. Cranial kinesis, the flexibility of the avian skull allowing independent movement of the upper jaw relative to the braincase, is prominent in many neoavian birds including those in Passerea and facilitates a broad spectrum of feeding behaviors, from probing for to cracking fruits. This kinetic mechanism, powered by specialized ligaments and muscles, enhances manipulative dexterity in the rostrum, enabling dietary versatility observed in groups ranging from insectivorous flycatchers to frugivorous parrots. Wing and foot adaptations within Passerea show variation suited to specific lifestyles, with zygodactyl or semi-zygodactyl configurations—two toes forward and two backward—common in subclades such as parrots (Psittaciformes) and woodpeckers (), aiding in vertical climbing along tree trunks and precise object manipulation. These traits, while not uniform across the proposed , highlight convergent evolutionary solutions to arboreal challenges among its diverse orders. Given ongoing debates about Passerea's , some shared traits may reflect broader neoavian ancestry or convergence rather than unique synapomorphies.

Evolutionary adaptations

The evolutionary adaptations of the proposed Passerea are closely tied to the rapid radiation of following the Cretaceous-Paleogene (K-Pg) mass extinction approximately 66 million years ago. In the original proposal, the common ancestor of Passerea was inferred as an , with subsequent lineage-specific losses and gains of traits enabling diversification into diverse ecological niches, including terrestrial, arboreal, and aquatic habitats. This ancestral predatory morphology facilitated early survival in post-extinction ecosystems, where reduced competition allowed for the evolution of specialized forms within subclades like (landbirds) and Aequornithia (waterbirds). Key adaptations across , including components of Passerea, involve shifts in life-history traits, particularly a reduction in adult body mass and increased altriciality (helplessness at hatching), which are linked to molecular evolutionary changes near the K-Pg boundary. These shifts, detected through Ornstein-Uhlenbeck models on phylogenetic trees, suggest a "Lilliput effect" where smaller body sizes became optimal, enhancing reproductive rates and evasion of predators in fragmented habitats. In Aequornithia, convergent ecological traits such as foot-propelled diving and wading-feeding mechanisms evolved independently. Within , a prominent is the independent of vocal learning in multiple lineages, including passerines (songbirds) and parrots, supported by in 227 genes associated with neural circuits for sound production and learning. These genomic changes, often in non-coding regions, enabled complex communication and social behaviors, contributing to the clade's high —over 6,000 species in Passeriformes alone. Overall, adaptations in Passerea components highlight a burst of genomic heterogeneity post-K-Pg across , with 15 of 17 detected molecular rate shifts occurring in exons and influencing base composition, thereby facilitating rapid morphological and ecological divergence.
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