Abstract
BackgroundEvolutionary biologists are often misled by convergence of morphology and this has been common in the study of bird evolution. However, the use of molecular data sets have their own problems and phylogenies based on short DNA sequences have the potential to mislead us too. The relationships among clades and timing of the evolution of modern birds (Neoaves) has not yet been well resolved. Evidence of convergence of morphology remain controversial. With six new bird mitochondrial genomes (hummingbird, swift, kagu, rail, flamingo and grebe) we test the proposed Metaves/Coronaves division within Neoaves and the parallel radiations in this primary avian clade.ResultsOur mitochondrial trees did not return the Metaves clade that had been proposed based on one nuclear intron sequence. We suggest that the high number of indels within the seventh intron of the β-fibrinogen gene at this phylogenetic level, which left a dataset with not a single site across the alignment shared by all taxa, resulted in artifacts during analysis. With respect to the overall avian tree, we find the flamingo and grebe are sister taxa and basal to the shorebirds (Charadriiformes). Using a novel site-stripping technique for noise-reduction we found this relationship to be stable. The hummingbird/swift clade is outside the large and very diverse group of raptors, shore and sea birds. Unexpectedly the kagu is not closely related to the rail in our analysis, but because neither the kagu nor the rail have close affinity to any taxa within this dataset of 41 birds, their placement is not yet resolved.ConclusionOur phylogenetic hypothesis based on 41 avian mitochondrial genomes (13,229 bp) rejects monophyly of seven Metaves species and we therefore conclude that the members of Metaves do not share a common evolutionary history within the Neoaves.
Highlights
Evolutionary biologists are often misled by convergence of morphology and this has been common in the study of bird evolution
Fain and Houde [3] liken the division of Neoaves into two major clades to the well known convergence of marsupial and placental mammals and list eleven examples of ecological and/or morphological convergence among Metaves and Coronaves
Complete mitochondrial genomes The six new mitochondrial genome sequences have been deposited in GenBank under the following accession numbers: ruby-throated hummingbird (Archilocus colubris: EF532935, > 16,356 bp [incomplete due to repeats in the control region]), common swift (Apus apus: AM237310 EMBL, 17,037 bp), Australian little grebe (Tachybaptus novaehollandiae: EF532936, 18,002 bp), kagu (Rhynochetos jubatus: EF532933, 16,937 bp)) and greater flamingo (Phoenicoptera ruber roseus: EF532932, 17,446 bp); a New Zealand rail
Summary
Evolutionary biologists are often misled by convergence of morphology and this has been common in the study of bird evolution. Fain and Houde [3] proposed a major new division of Neoaves (that is, all extant birds except paleognaths [ratites and tinamous] and Galloanserae [ducks, chicken and relatives], see Figure 1) Their division of Neoaves into Metaves and Coronaves was based on data from the seventh intron of the β-fibrinogen gene (FGB-int7), including insertions and deletions. Fain and Houde [3] liken the division of Neoaves into two major clades to the well known convergence of marsupial and placental mammals and list eleven examples of ecological and/or morphological convergence among Metaves and Coronaves Their examples of convergence are in most cases, widely accepted and include for example the convergence of form and feeding of swallows and swifts as aerial insectivores. In contrast to the placental/marsupial division that is supported by at least 50 anatomical and physiological synapomorphies [4,5,6] the Metaves clade does not have a single published morphological character to support it, and there is no clear geographic separation from Coronaves
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