Tetrapod phylogeny inferred from 18S and 28S ribosomal RNA sequences and a review of the evidence for amniote relationships [published erratum appears in Mol Biol Evol 1991 May;8(3):398]

The 18S ribosomal RNAs of 21 tetrapods were sequenced and aligned with five published tetrapod sequences. When the coelacanth was used as an outgroup, Lissamphibia (living amphibians) and Amniota (amniotes) were found to be statistically significant monophyletic groups. Although little resolution was obtained among the lissamphibian taxa, the amniote sequences support a sister-group relationship between birds and mammals. Portions of the 28S ribosomal RNA (rRNA) molecule in 11 tetrapods also were sequenced, although the phylogenetic results were inconclusive. In contrast to previous studies, deletion or down- weighting of base-paired sites were found to have little effect on phylogenetic relationships. Molecular evidence for amniote relationships is reviewed, showing that three genes (beta-hemoglobin, myoglobin, and 18S rRNA) unambiguously support a bird-mammal relationship, compared with one gene (histone H2B) that favors a bird- crocodilian clade. Separate analyses of four other genes (alpha- crystallin A, alpha-hemoglobin, insulin, and 28S rRNA) and a combined analysis of all sequence data are inconclusive, in that different groups are defined in different analyses and none are strongly supported. It is suggested that until sequences become available from a broader array of taxa, the molecular evidence is best evaluated at the level of individual genes, with emphasis placed on those studies with the greatest number of taxa and sites. When this is done, a bird-mammal relationship is most strongly supported. When regarded in combination with the morphological evidence for this association, it must be considered at least as plausible as a bird-crocodilian relationship.      

大黄鱼16SrRNA和18SrRNA基因的测定与序列分析

利用多对引物,扩增并测定出大黄鱼16SrRNA基因和18SrRNA基因的部分序列,其长度分别为1202bp和1275bp,16SrRNA基因序列的GC含量为46．12％,18SrRNA基因的Gc含量为53．oo％。将大黄鱼16SrRNA基因序列与GenBank中15种硬骨鱼类的同源序列结合,同时将其18SrRNA基因序列与GenBank中9种脊索动物的同源序列相结合,运用软件获得各自序列间差异百分比,转换和颠换数值等信息。基于这两种基因序列,利用NJ法和BI法,分别构建16种硬骨鱼类和10种脊索动物的分子系统树。18SrRNA构建的系统树包括三大支,一支为哺乳类、鸟类和爬行类共6个物种,一支为两栖类的1个物种,另一支为2种硬骨鱼类。16SrRNA构建的系统树显示大黄鱼所在的石首鱼科与鲈科和盖刺鱼科亲缘关系较近。此外还讨论了这两个基因的序列特征。     

Genetic differentiation of the endemic Baikalian mollusk <Emphasis Type="Italic">Baicalia carinata</Emphasis> (Mollusca: Caenogastropoda)

In gastropod mollusk Baicalia carinata Dybowski, 1875, sampled in different sites of the Lake Baikal, comparison of 81 sequences of internal transcribed spacer 1 (ITS1) located between the genes for 18S rRNA and 5.8S rRNA, and of 100 sequences of the fragment of mitochondrial DNA cytochrome-c-oxidase subunit 1 gene (CO1) was performed. Molecular phylogenetic analysis showed that the endemic mollusk species studied formed at least two distinct populations, Southwestern and Eastern. Statistical significance of the species subdivision into two populations was evaluated using the Mann-Whitney rank test.     

Discordant 16S and 23S rRNA gene phylogenies for the genus Helicobacter: implications for phylogenetic inference and systematics

Analysis of 16S rRNA gene sequences has become the primary method for determining prokaryotic phylogeny. Phylogeny is currently the basis for prokaryotic systematics. Therefore, the validity of 16S rRNA gene-based phylogenetic analyses is of fundamental importance for prokaryotic systematics. Discrepancies between 16S rRNA gene analyses and DNA-DNA hybridization and phenotypic analyses have been noted in the genus Helicobacter. To clarify these discrepancies, we sequenced the 23S rRNA genes for 55 helicobacter strains representing 41 taxa (>2,700 bases per sequence). Phylogenetic-tree construction using neighbor-joining, parsimony, and maximum likelihood methods for 23S rRNA gene sequence data yielded stable trees which were consistent with other phenotypic and genotypic methods. The 16S rRNA gene sequence-derived trees were discordant with the 23S rRNA gene trees and other data. Discrepant 16S rRNA gene sequence data for the helicobacters are consistent with the horizontal transfer of 16S rRNA gene fragments and the creation of mosaic molecules with loss of phylogenetic information. These results suggest that taxonomic decisions must be supported by other phylogenetically informative macromolecules, such as the 23S rRNA gene, when 16S rRNA gene-derived phylogeny is discordant with other credible phenotypic and genotypic methods. This study found Wolinella succinogenes to branch with the unsheathed-flagellum cluster of helicobacters by 23S rRNA gene analyses and whole-genome comparisons. This study also found intervening sequences (IVSs) in the 23S rRNA genes of strains of 12 Helicobacter species. IVSs were found in helices 10, 25, and 45, as well as between helices 31' and 27'. Simultaneous insertion of IVSs at three sites was found in H. mesocricetorum.     

Genetic differentiation of the endemic Baikalian mollusk Baicalia carinata (Mollusca: Caenogastropoda)

In gastropod mollusk Baicalia carinata Dybowski, 1875, sampled in different sites of the Lake Baikal, comparison of 81 sequences of internal transcribed spacer 1 (ITS1) located between the genes for 18S rRNA and 5.8S rRNA, and of 100 sequences of the fragment of mitochondrial cytochrome-c-oxidase subunit 1 gene (CO1) was performed. Molecular phylogenetic analysis showed that the endemic mollusk species studied formed at least two distinct populations, Southwestern and Eastern. Statistical significance of the species subdivision into two populations was evaluated using the Mann-Whitney rank test.     

青海湖裸鲤舌状绦虫裂头蚴的分子鉴定及系统发育研究

通过PCR方法扩增了青海湖裸鲤体腔寄生舌状绦虫18S rRNA、COⅠ和COB基因部分序列, 并进行分子鉴定, 分析了3种基因的同源性, 利用这3种基因进行分子进化和系统发育研究。结果显示, 经过分子鉴定, “面条样”绦虫为肠舌状绦虫, 克隆的18S rRNA、COⅠ和COB基因序列分别与AF254121(中国)、AF153910(中国)和JQ279109(阿尔及利亚)的核苷酸序列同源性为100.00%、99.49%和93.32%。同时, 利用GenBank中其他种属绦虫的18S rRNA、COⅠ和COB基因序列构建系统发育树, 均与已鉴定的肠舌状绦虫聚在同一支上, 且与肠舌状绦虫中国广州分离株种属亲缘关系较近, 与其他绦虫所属分支相距较远。初步阐明了鉴定的肠舌状绦虫分离株与其他种属之间的系统发育关系。     

Detection and characterization of fungal infections of Ammophila arenaria (marram grass) roots by denaturing gradient gel electrophoresis of specifically amplified 18s rDNA.

Marram grass (Ammophila arenaria L.), a sand-stabilizing plant species in coastal dune areas, is affected by a specific pathosystem thought to include both plant-pathogenic fungi and nematodes. To study the fungal component of this pathosystem, we developed a method for the cultivation-independent detection and characterization of fungi infecting plant roots based on denaturing gradient gel electrophoresis (DGGE) of specifically amplified DNA fragments coding for 18S rRNA (rDNA). A nested PCR strategy was employed to amplify a 569-bp region of the 18S rRNA gene, with the addition of a 36-bp GC clamp, from fungal isolates, from roots of test plants infected in the laboratory, and from field samples of marram grass roots from both healthy and degenerating stands from coastal dunes in The Netherlands. PCR products from fungal isolates were subjected to DGGE to examine the variation seen both between different fungal taxa and within a single species. DGGE of the 18S rDNA fragments could resolve species differences from fungi used in this study yet was unable to discriminate between strains of a single species. The 18S rRNA genes from 20 isolates of fungal species previously recovered from A. arenaria roots were cloned and partially sequenced to aid in the interpretation of DGGE data. DGGE patterns recovered from laboratory plants showed that this technique could reliably identify known plant-infecting fungi. Amplification products from field A. arenaria roots also were analyzed by DGGE, and the major bands were excised, reamplified, sequenced, and subjected to phylogenetic analysis. Some recovered 18S rDNA sequences allowed for phylogenetic placement to the genus level, whereas other sequences were not closely related to known fungal 18S rDNA sequences. The molecular data presented here reveal fungal diversity not detected in previous culture-based surveys.     

干酪乳杆菌的近缘种及亚种部分看家基因的系统发育分析

【背景】16S rRNA基因序列分析已广泛应用于细菌的分类鉴定,但是存在一定局限性,而使用看家基因作为分子标记在近缘种及亚种间的系统发育分析中具有其独特的优势。【目的】研究16S rRNA、uvr C (核酸外切酶ABC,C亚基)和mur E (UDP-N-乙酰胞壁酰三肽合酶)基因序列对干酪乳杆菌的近缘种及亚种的区分能力。【方法】采用分离自传统发酵乳中的6株干酪乳杆菌为研究对象,选取uvr C和mur E基因片段,通过PCR扩增、测序,结合已公布的干酪乳杆菌的近缘种或亚种的相应序列计算遗传距离、构建系统发育树,并与16S rRNA基因序列分析技术进行比较。【结果】研究发现Lactobacilluscasei及相近种间的uvr C、mur E和联合基因(uvr C-mur E)构建的系统发育树拓扑结构与16S rRNA基因结果基本一致,区别在于相似性的不同,其分别为79.00%-99.16%、89.08%-99.20%、76.56%-99.69%和99.58%-100%。基于16S rRNA基因不能区分干酪乳杆菌的近缘种及亚种,而看家基因uvr C和mur E基因序列能够很好地区分干酪乳杆菌的近缘种及亚种,并且将uvr C和mur E基因串联使用后,试验菌株与参考菌株的分类关系更加清晰。【结论】联合基因(uvr C-mur E)可作为16SrRNA基因的辅助工具用于干酪乳杆菌的近缘种及亚种的快速准确鉴定。     

Evolution and phylogeny of the heterogeneous cytosolic SSU rRNA genes in the genus Plasmodium

Unlike other eukaryotes, malaria parasites in the genus Plasmodium have structurally and functionally different paralogous copies of the cytosolic (cyto-) SSU rRNA (18S rRNA) gene that are expressed at different developmental stages. In P. falciparum, P. vivax, and P. berghei, A-type cyto-SSU rRNA is expressed in asexual stage, while S-type in sporozoite stage. A third type (O-type) has been described in P. vivax. It is expressed only in oocyst stage in the mosquito. Recently, it has been shown that the maintenance of heterogeneous cyto-SSU rRNAs in Plasmodium can be modeled as a birth-and-death process under strong purifying selection [Rooney, A.P., 2004. Mechanisms underlying the evolution and maintenance of functionally heterogeneous 18S rRNA genes in Apicomplexans. Mol. Biol. Evol. 21, 1704-1711]. In this study, we performed detailed phylogenetic analyses of Plasmodium cyto-SSU rRNAs with special emphasis on the evolution of multi-copy genes in simian Plasmodium species. We sequenced paralogous copies of the cyto-SSU rRNA genes from an African simian Plasmodium species, P. gonderi, and Asian simian Plasmodium species, P. fragile, P. coatneyi, P. inui, P. hylobati, P. fieldi, P. simiovale, and P. cynomolgi. Interestingly, all Asian simian Plasmodium species have a single S-type-like gene and several A-type-like genes. Alignment analysis demonstrated for the first time that an approximately 50-residue insertion in the V7 variable region near the stem 43 is shared exclusively by the S-type-like sequences of the Asian simian Plasmodium species and the S- and O-type sequences of P. vivax. We comprehensively analyzed all cyto-SSU rRNA sequences of the genus Plasmodium currently available in the database. Phylogenetic analyses of all publicly available cyto-SSU rRNA sequences for the genus Plasmodium clearly demonstrated that gene duplication events giving rise to A- and S-type-like sequences took place independently at least three times in the Plasmodium evolution, supporting the hypothesis that these genes evolve according to a birth-and-death model.     

Phylogeny of protostome moulting animals (Ecdysozoa) inferred from 18 and 28S rRNA gene sequences

Reliability of reconstruction of phylogenetic relationships within a group of protostome moulting animals was evaluated by means of comparison of 18 and 28S rRNA gene sequences sets both taken separately and combined. Reliability of reconstructions was evaluated by values of the bootstrap support of major phylogenetic tree nodes and by degree of congruence of phylogenetic trees inferred by various methods. By both criteria, phylogenetic trees reconstructed from the combined 18 and 28S rRNA gene sequences were better than those inferred from 18 and 28S sequences taken separately. Results obtained are consistent with phylogenetic hypothesis separating protostome animals into two major clades, moulting Ecdysozoa (Priapulida + Kinorhyncha, Nematoda + Nematomorpha, Onychophora + Tardigrada, Myriapoda + Chelicerata, Crustacea + Hexapoda) and unmoulting Lophotrochozoa (Plathelminthes, Nemertini, Annelida, Mollusca, Echiura, Sipuncula). Clade Cephalorhyncha does not include nematomorphs (Nematomorpha). Conclusion was taken that it is necessary to use combined 18 and 28S data in phylogenetic studies.     

Taxonomic Resolutions Based on 18S rRNA Genes: A Case Study of Subclass Copepoda

Biodiversity studies are commonly conducted using 18S rRNA genes. In this study, we compared the inter-species divergence of variable regions (V1–9) within the copepod 18S rRNA gene, and tested their taxonomic resolutions at different taxonomic levels. Our results indicate that the 18S rRNA gene is a good molecular marker for the study of copepod biodiversity, and our conclusions are as follows: 1) 18S rRNA genes are highly conserved intra-species (intra-species similarities are close to 100%); and could aid in species-level analyses, but with some limitations; 2) nearly-whole-length sequences and some partial regions (around V2, V4, and V9) of the 18S rRNA gene can be used to discriminate between samples at both the family and order levels (with a success rate of about 80%); 3) compared with other regions, V9 has a higher resolution at the genus level (with an identification success rate of about 80%); and 4) V7 is most divergent in length, and would be a good candidate marker for the phylogenetic study of Acartia species. This study also evaluated the correlation between similarity thresholds and the accuracy of using nuclear 18S rRNA genes for the classification of organisms in the subclass Copepoda. We suggest that sample identification accuracy should be considered when a molecular sequence divergence threshold is used for taxonomic identification, and that the lowest similarity threshold should be determined based on a pre-designated level of acceptable accuracy.     

Large expansion segments in 18S rDNA support a new sponge clade (Class Demospongiae, Order Haplosclerida)

Newly emerging molecular phylogenetic hypotheses involving the sponge Order Haplosclerida (Class Demospongiae) are far removed from traditional views on their classification using morphology. In the new grouping of marine haplosclerid taxa by molecular data all members of one highly supported clade were found to have three large indels in the 18S rRNA gene. These indels were not found in this gene in other marine haplosclerids or in any other demosponges analysed. These indels were found in the variable V4 and V7 region of the gene, had high GC contents and formed stable double stranded helices in the 18S rRNA secondary structure. These indels are very important synapomorphies, provide high support for an alternative taxonomic scheme and could help resolve the phylogeny of this order in conjunction with other phylogenetically informative characters.     

Molecular phylogenetics of Trypanosomatidae: contrasting results from 18S rRNA and protein phylogenies

Phylogenetic analyses of the family Trypanosomatidae have been conducted using both 18S rRNA gene sequences and a variety of protein sequences. Using a variety of phylogenetic methods, 18S rRNA phylogenies indicate that the genus Trypanosoma is not monophyletic. Rather, they suggest that the American and African trypanosomes constitute distinct clades. By contrast, phylogenetic analyses of available sequences in 42 protein families gene generally supported monophyly of the genus Trypanosoma. One possible explanation for these conflicting results is poor taxon sampling in the case of protein coding genes, most of which have been sequenced for only a few species of Trypanosomatidae.     

Multiple cophylogenetic analyses reveal frequent cospeciation between pelecaniform birds and Pectinopygus lice

Lice in the genus Pectinopygus parasitize a single order of birds (Pelecaniformes). To examine the degree of congruence between the phylogenies of 17 Pectinopygus species and their pelecaniform hosts, sequences from mitochondrial 12S rRNA, 16S rRNA, COI, and nuclear wingless and EF1-alpha genes (2290 nucleotides) and from mitochondrial 12S rRNA, COI, and ATPases 8 and 6 genes (1755 nucleotides) were obtained for the lice and the birds, respectively. Louse data partitions were analyzed for evidence of incongruence and evidence of long-branch attraction prior to cophylogenetic analyses. Host-parasite coevolution was studied by different methods: TreeFitter, TreeMap, ParaFit, likelihood-ratio test, data-based parsimony method, and correlation of coalescence times. All methods agree that there has been extensive cospeciation in this host-parasite system, but the results are sensitive to the selection of different phylogenetic hypotheses and analytical methods for evaluating cospeciation. Perfect congruence between phylogenies is not found in this association, probably as a result of occasional host switching by the lice. Errors due to phylogenetic reconstruction methods, incorrect or incomplete taxon sampling, or to different loci undergoing different evolutionary histories cannot be rejected, thus emphasizing the need for improved cophylogenetic methodologies.     

Phylogenetic analysis of gamma-proteobacteria inferred from nucleotide sequence comparisons of the house-keeping genes adk, aroE and gdh: comparisons with phylogeny inferred from 16S rRNA gene sequences

Nucleotide sequence comparisons of three house-keeping genes, adenylate kinase (adk), shikimate dehydrogenase (aroE), and glucose-6-phosphate dehydrogenase (gdh), were used to infer the phylogeny of 33 gamma-proteobacteria. Phylogenetic trees inferred from each gene, and from the concatenated sequences of all three genes, are, in general, similar to a 16S rRNA gene-inferred tree. Similar grouping of bacteria are revealed at the family, genus, species and strain levels in all five trees. The house-keeping genes, however, show a higher rate of nucleotide sequence substitutions. Consequently, they can possibly probe deeper branches of a phylogenetic tree than the 16S rRNA gene. However, because their nucleotide sequences are not as highly conserved among gamma-proteobacteria, family- or genus-specific primers would need to be designed for the amplification of any of these three house-keeping genes. Since these genes are used in multilocus sequence typing, it is expected that the number of sequences publicly available for many taxa will increase over time proving them very useful either at complementing 16S rRNA-inferred phylogenies or for specific, targeted, phylogenetic analysis.     

Among-site rate variation and phylogenetic analysis of 12S rRNA in sigmodontine rodents

We analyze sequences from two mitochondrial genes, cytochrome b (cyt b) and 12S rRNA (12S), for a group of sigmodontine rodents among which phylogenetic relationships are well understood based on concordance of morphological, chromosomal, allozyme, and other DNA data sets. Because these two genes are physically linked on the nonrecombining mitochondrial genome, they necessarily share the same history. Phylogenetic analysis of the cyt b gene recovers the well-corroborated relationships, generally with strong support. None of the methods that we employed, including variously weighted parsimony, neighbor joining on both single-rate and gamma-corrected distances, and maximum likelihood, were able to recover these relationships for the 12S gene. Parsimony analyses of the 12S data resulted in a relatively strongly supported placement of Peromyscus eremicus that conflicts with that suggested by cyt b and all other data. There is extreme among-site rate variation in the 12S sequences and moderate levels in the cyt b sequences. This highly skewed distribution of rates in the 12S gene makes phylogenetic analyses of these sequences particularly susceptible to the misleading effects of nonindependence and other nonrandom noise, suggesting that phylogenetic analyses of data sets that contain a great deal of among-site rate variation be interpreted with caution.      

16S rRNA-based analysis of microbiota from the cecum of broiler chickens.

The microbiota of the intestinal tract of chickens plays an important role in inhibiting the establishment of intestinal pathogens. Earlier culturing and microscopic examinations indicated that only a fraction of the bacteria in the cecum of chickens could be grown in the laboratory. Therefore, a survey of cecal bacteria was done by retrieval of 16S rRNA gene sequences from DNA isolated from the cecal content and the cecal mucosa. The ribosomal gene sequences were amplified with universal primers and cloned or subjected to temporal temperature gradient gel electrophoresis (TTGE). Partial 16S rRNA gene sequences were determined from the clones and from the major bands in TTGE gels. A total of 1,656 partial 16S rRNA gene sequences were obtained and compared to sequences in the GenBank. The comparison indicated that 243 different sequences were present in the samples. Overall, sequences representing 50 phylogenetic groups or subgroups of bacteria were found, but approximately 89% of the sequences represented just four phylogenetic groups (Clostridium leptum, Sporomusa sp., Clostridium coccoides, and enterics). Sequences of members of the Bacteroides group, the Bifidobacterium infantis subgroup, and of Pseudomonas sp. each accounted for less than 2% of the total. Sequences related to those from the Escherichia sp. subgroup and from Lactobacillus, Pseudomonas, and Bifidobacterium spp. were generally between 98 and 100% identical to sequences already deposited in the GenBank. Sequences most closely related to those of the other bacteria were generally 97% or less identical to those in the databases and therefore might be from currently unknown species. TTGE and random cloning indicated that certain phylogenetic subgroups were common to all birds analyzed, but sequence data from random cloning also provided evidence for qualitative and quantitative differences among the cecal microbiota of individual birds reared under very similar conditions.     

Phylogenetic relationships of the Santalales and relatives

Summary Determining relationships among parasitic angiosperms has often been difficult owing to frequent morphological reductions in floral and vegetative features. We report 18S (small-subunit) rRNA sequences for representative genera of three families within the Santalales (Olacaceae, Santalaceae, and Viscaceae) and six outgroup dicot families (Celastraceae, Cornaceae, Nyssaceae, Buxaceae, Apiaceae, and Araliaceae). Using Wagner parsimony analysis, one most parsimonius tree resulted that shows the Santalales to be a holophyletic taxon most closely related toEuronymus (Celastraceae). The santalalean taxa showed approximately 13% more transitional mutations than the group of seven other dicot species. This suggests a higher fixation rate for mutations in these organisms, possibly owing to a relaxation of selection pressures at the molecular level in parasitic vs nonparasitic plants. Outgroup relationships are generally in accord with current taxonomic classifications, such as the grouping of Nyssaceae and Cornaceae together (Cornales) and the grouping of Araliaceae with Apiaceae (Apiales). These data provide the first nucleotide sequences for any parasitic flowering plant and support the contention that rRNA sequence analysis can result in robust phylogenetic comparisons at the family level and above.     

The phylogenetic significance of peptidoglycan types: Molecular analysis of the genera Microbacterium and Aureobacterium based upon sequence comparison of gyrB, rpoB, recA and ppk and 16SrRNA genes

The type strains of 27 species of the genus Microbacterium, family Microbacteriaceae, were analyzed with respect to the phylogeny of the housekeeping genes coding for DNA gyrase subunit B (gyrB), RNA-polymerase subunit B (rpoB), recombinase A (recA) and polyphosphate kinase (ppk). The resulting gene trees were compared to the 16S rRNA gene phylogeny of the same species. The topology of neighbour-joining and maximum parsimony phylogenetic trees based upon nucleic acid sequences and protein sequences of housekeeping genes differed among each other and no gene tree was identical to that of the 16S rRNA gene tree. Only some species showed consistent clustering by all genes analyzed, but the majority of species branched with different neighbours in most gene trees. The failure to phylogenetically cluster type strains into two groups based upon differences in the amino acid composition of peptidoglycan on the basis of 16S rRNA gene sequence similarity, once leading to the union of the genera Microbacterium and Aureobacterium, was also seen in the analysis of recA, rpoB and gyrB gene and protein phylogenies. Analysis of the pkk gene and protein as well as of a concatenate tree, combining sequences of all five genes (total of 3.700 nucleotides), sees members of the former genus Aureobacterium and other type strains with lysine as diagnostic diamino acid to form a coherent cluster that branches within the radiation of Microbacterium species with ornithine in the peptidoglycan.     

鹳形目12种鸟类核c-mos 基因和线粒体12S rRNA基因序列分析及其系统发生研究

鹳形目鸟类的传统分类一直存在分歧,而近期的分子系统学研究大多只用单个基因,其结论的可信度需要进一步验证.本文通过核c-mos基因和线粒体12S rRNA基因序列分别和合并分析,采用分子系统学方法探讨了鹳形目6科12种鸟类的系统发生关系.文中测出鹳形目鸟类6种核c-mos基因的片断序列,结合来自Genebank的其他种类的c-mos和12S rRNA基因序列,分别经Clustal W软件对位排列后,以原鸡为外类群用最大似然法、邻接法和最大简约法建立系统树.系统树分析表明, 鹳形目6科之间的系统发生关系总结为：（鹭科,（（鹮科,美洲鹫科）,（鹳科,（鲸头鹳科,锤头鹳科））））.鹭科7个属之间的系统发生关系总结为：（麻（开鸟）属（夜鹭属（池鹭属（苍鹭属（中白鹭属（白鹭属,大白鹭属））））））.分别基于两个单基因的系统树有一定差异,而基于合并数据的系统树支持率和分辨率都高于基于单基因的系统树,表明使用在遗传上相对独立的分子数据合并建立系统树有较高的可信度和分辨率,是一种更好的研究方法.