自引率: 9.5%
被引量: 16501
通过率: 暂无数据
审稿周期: 6
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国人发稿量: 3
期刊描述简介:
Systematic Biology is the bimonthly journal of the Society of Systematic Biologists. Papers for the journal are original contributions to the theory, principles, and methods of systematics as well as phylogeny, evolution, morphology, biogeography, paleontology, genetics, and the classification of all living things. A Points of View section offers a forum for discussion, while book reviews and announcements of general interest are also featured.
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Host-symbiont stability and fast evolutionary rates in an ant-bacterium association: cospeciation of camponotus species and their endosymbionts, candidatus blochmannia.
Bacterial endosymbionts are widespread across several insect orders and are involved in interactions ranging from obligate mutualism to reproductive parasitism. Candidatus Blochmannia gen. nov. (Blochmannia) is an obligate bacterial associate of Camponotus and related ant genera (Hymenoptera: Formicidae). The occurrence of Blochmannia in all Camponotus species sampled from field populations and its maternal transmission to host offspring suggest that this bacterium is engaged in a long-term, stable association with its ant hosts. However, evidence for cospeciation in this system is equivocal because previous phylogenetic studies were based on limited gene sampling, lacked statistical analysis of congruence, and have even suggested host switching. We compared phylogenies of host genes (the nuclear EF-1alphaF2 and mitochondrial COI/II) and Blochmannia genes (16S ribosomal DNA [rDNA], groEL, gidA, and rpsB), totaling more than 7 kilobases for each of 16 Camponotus species. Each data set was analyzed using maximum likelihood and Bayesian phylogenetic reconstruction methods. We found minimal conflict among host and symbiont phylogenies, and the few areas of discordance occurred at deep nodes that were poorly supported by individual data sets. Concatenated protein-coding genes produced a very well-resolved tree that, based on the Shimodaira-Hasegawa test, did not conflict with any host or symbiont data set. Correlated rates of synonymous substitution (d(S)) along corresponding branches of host and symbiont phylogenies further supported the hypothesis of cospeciation. These findings indicate that Blochmannia-Camponotus symbiosis has been evolutionarily stable throughout tens of millions of years. Based on inferred divergence times among the ant hosts, we estimated rates of sequence evolution of Blochmannia to be approximately 0.0024 substitutions per site per million years (s/s/MY) for the 16S rDNA gene and approximately 0.1094 s/s/MY at synonymous positions of the genes sampled. These rates are several-fold higher than those for related bacteria Buchnera aphidicola and Escherichia coli. Phylogenetic congruence among Blochmannia genes indicates genome stability that typifies primary endosymbionts of insects.
被引量：59 发表：2004
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Hidden morphological support for the phylogenetic placement of Pseudoryx nghetinhensis with bovine bovids: a combined analysis of gross anatomical evidence and DNA sequences from five genes.
The saola, Pseudoryx nghetinhensis, was unknown to science until its formal description in 1993. This endangered species is a member of the ruminant artiodactyl family Bovidae (cattle, sheep, goats, and antelopes). However, given its puzzling combination of morphological traits, the specific affinities of Pseudoryx within Bovidae are controversial. A preliminary genetic investigation suggested that Pseudoryx should be placed in the subfamily Bovinae (cattle, buffaloes, spiral-horned antelopes, and nilgai), but a recent cladistic analysis of skeletal and dental characters allied Pseudoryx with caprine bovids (sheep, goats, musk oxen, goat antelopes, and Pantholops). The morphological and molecular hypotheses differ in assigning the saola to either of the two most divergent clades of Bovidae. In this report, phylogenetic analyses of DNA sequences from five genes are used to test these alternatives. Protein coding regions, introns, and ribosomal DNAs from the nuclear and mitochondrial genomes discount the hypothesis that Pseudoryx is a close relative of Caprinae. Instead, combined analyses of the DNA data and published morphological evidence place Pseudoryx with Bovini (cattle and buffaloes), a subclade of Bovinae. In a separate analysis, the matrix of morphological characters links Pseudoryx with caprine bovids, but in the context of the molecular data, the gross anatomical evidence strongly supports a grouping of Pseudoryx with Bovinae. Surprisingly, the morphological partition provides the most character support in the combined analysis. This striking result is obscured by separate analyses of the individual data sets and the taxonomic congruence approach.
被引量：8 发表：2000
