Abstract
Many phylogenetic questions in the Ciconiiformes remain unresolved and complete mitogenome data are urgently needed for further molecular investigation. In this work, we determined the complete mitogenome sequence of the little egret (Egretta garzetta). The genome was 17,361 bp in length and the gene organization was typical of other avian mtDNA. In protein-coding genes (PCGs), a C insertion was found in ND3, and COIII and ND4 terminated with incomplete stop codons (T). tRNA-Val and tRNA-Ser (AGY) were unable to fold into canonical cloverleaf secondary structures because they had lost the DHU arms. Long repetitive sequences consisting of five types of tandem repeats were found at the 3′ end of Domain III in the control region. A phylogenetic analysis of 11 species of Ciconiiformes was done using complete mitogenome data and 12 PCGs. The tree topologies obtained with these two strategies were identical, which strongly confirmed the monophyly of Ardeidae, Threskiorothidae and Ciconiidae. The phylogenetic analysis also revealed that Egretta was more closely related to Ardea than to Nycticorax in the Ardeidae, and Platalea was more closely related to Threskiornis than to Nipponia in the Threskiornithidae. These findings contribute to our understanding of the phylogenetic relationships of Ciconiiformes based on complete mitogenome data.
Highlights
With more than 9,000 living species, Aves is the most diverse class of vertebrates
In protein-coding genes (PCGs), a C insertion was found in ND3, and CO III and ND4 terminated with incomplete stop codons (T). tRNA-Val and tRNA-Ser (AGY) were unable to fold into canonical cloverleaf secondary structures because they had lost the DHU arms
There have been various uncertainties regarding the evolutionary relationships of different taxa in this order: (1) The phylogenetic relationships among the five families have been questioned in morphological studies (Kahl, 1972; Cracraft, 1981), (2) the Family Ardeidae was divided into two subfamilies (Ardeinae and Botaurinae) by Bock (1956) and Zheng (1997), but into four subfamilies (Ardeinae, Nycticoracinae, Botaurinae and Tigrisomatinae) by Payne and Risley (1976), and (3) the phylogenetic status of several species in the traditional
Summary
With more than 9,000 living species, Aves is the most diverse class of vertebrates. The huge number of species, complex morphological characters and wide range of ecological behaviors make it difficult to solve the phylogenetic relationship of birds in traditional taxonomy (Bock, 1956; Howard and Moore, 1980; Monroe and Sibley, 1993).The order Ciconiiformes, consisting of more than 110 species of large or medium size waders, has traditionally be classified into five families (Ciconiidae, Threskiornithidae, Ardeidae, Balaenicipitidae and Scopidae) (Howard and Moore, 1980; Austin, 1985; Gill, 1990; Clements, 2000; Zheng, 2002). A phylogenetic analysis of species of Ciconiiformes was done using complete mitogenome data and PCGs. The tree topologies obtained with these two strategies were identical, which strongly confirmed the monophyly of Ardeidae, Threskiorothidae and Ciconiidae.
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