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The evolutionary position of nematodes.

Blair JE, Ikeo K, Gojobori T, Hedges SB - BMC Evol. Biol. (2002)

Bottom Line: Instead, we found significant support for the traditional hypothesis, Coelomata.Our result is robust to different rates of sequence change among genes and lineages, different numbers of taxa, and different species of nematodes.We conclude that insects (arthropods) are genetically and evolutionarily closer to humans than to nematode worms.

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Affiliation: Astrobiology Research Center and Department of Biology, The Pennsylvania State University, University Park, PA 16802, USA. jeb322@psu.edu

ABSTRACT

Background: The complete genomes of three animals have been sequenced by global research efforts: a nematode worm (Caenorhabditis elegans), an insect (Drosophila melanogaster), and a vertebrate (Homo sapiens). Remarkably, their relationships have yet to be clarified. The confusion concerns the enigmatic position of nematodes. Traditionally, nematodes have occupied a basal position, in part because they lack a true body cavity. However, the leading hypothesis now joins nematodes with arthropods in a molting clade, Ecdysozoa, based on data from several genes.

Results: We tested the Ecdysozoa hypothesis with analyses of more than 100 nuclear protein alignments, under conditions that would expose biases, and found that it was not supported. Instead, we found significant support for the traditional hypothesis, Coelomata. Our result is robust to different rates of sequence change among genes and lineages, different numbers of taxa, and different species of nematodes.

Conclusion: We conclude that insects (arthropods) are genetically and evolutionarily closer to humans than to nematode worms.

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The three possible relationships of vertebrates, arthropods, and nematodes.
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Figure 1: The three possible relationships of vertebrates, arthropods, and nematodes.

Mentions: The three possible relationships of these animal phyla are: (I) arthropods + vertebrates, (II) arthropods + nematodes, and (III) nematodes + vertebrates. The first hypothesis corresponds to the traditional grouping Coelomata and the second corresponds to Ecdysozoa [3]. For convenience, we will use these names in reference to the two hypotheses while recognizing that this study, by necessity, involves only a subset of all animal phyla. The third hypothesis will be referred to as "hypothesis III" (Fig. 1). To test each hypothesis, sequence alignments of more than 100 nuclear proteins were assembled and subjected to a series of analyses designed to reveal biases that could result in an incorrect phylogeny.


The evolutionary position of nematodes.

Blair JE, Ikeo K, Gojobori T, Hedges SB - BMC Evol. Biol. (2002)

The three possible relationships of vertebrates, arthropods, and nematodes.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC102755&req=5

Figure 1: The three possible relationships of vertebrates, arthropods, and nematodes.
Mentions: The three possible relationships of these animal phyla are: (I) arthropods + vertebrates, (II) arthropods + nematodes, and (III) nematodes + vertebrates. The first hypothesis corresponds to the traditional grouping Coelomata and the second corresponds to Ecdysozoa [3]. For convenience, we will use these names in reference to the two hypotheses while recognizing that this study, by necessity, involves only a subset of all animal phyla. The third hypothesis will be referred to as "hypothesis III" (Fig. 1). To test each hypothesis, sequence alignments of more than 100 nuclear proteins were assembled and subjected to a series of analyses designed to reveal biases that could result in an incorrect phylogeny.

Bottom Line: Instead, we found significant support for the traditional hypothesis, Coelomata.Our result is robust to different rates of sequence change among genes and lineages, different numbers of taxa, and different species of nematodes.We conclude that insects (arthropods) are genetically and evolutionarily closer to humans than to nematode worms.

View Article: PubMed Central - HTML - PubMed

Affiliation: Astrobiology Research Center and Department of Biology, The Pennsylvania State University, University Park, PA 16802, USA. jeb322@psu.edu

ABSTRACT

Background: The complete genomes of three animals have been sequenced by global research efforts: a nematode worm (Caenorhabditis elegans), an insect (Drosophila melanogaster), and a vertebrate (Homo sapiens). Remarkably, their relationships have yet to be clarified. The confusion concerns the enigmatic position of nematodes. Traditionally, nematodes have occupied a basal position, in part because they lack a true body cavity. However, the leading hypothesis now joins nematodes with arthropods in a molting clade, Ecdysozoa, based on data from several genes.

Results: We tested the Ecdysozoa hypothesis with analyses of more than 100 nuclear protein alignments, under conditions that would expose biases, and found that it was not supported. Instead, we found significant support for the traditional hypothesis, Coelomata. Our result is robust to different rates of sequence change among genes and lineages, different numbers of taxa, and different species of nematodes.

Conclusion: We conclude that insects (arthropods) are genetically and evolutionarily closer to humans than to nematode worms.

Show MeSH
Related in: MedlinePlus