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Evolutionary changes in the complexity of the tectum of nontetrapods: a cladistic approach.

Maximino C - PLoS ONE (2008)

Bottom Line: Both traits presented a considerably large phylogenetic signal and were positively associated.However, no difference was found between two clades classified as per the general developmental pathways of their brains.Those findings shed new light on the evolution of an functionally important structure in nontetrapods, the most basal radiations of vertebrates.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Psychobiology and Experimental Psychopatology, Department of Psychology, Universidade Estadual Paulista, Bauru, Brazil. caio.maximino@gmail.com

ABSTRACT

Background: The tectum is a structure localized in the roof of the midbrain in vertebrates, and is taken to be highly conserved in evolution. The present article assessed three hypotheses concerning the evolution of lamination and citoarchitecture of the tectum of nontetrapod animals: 1) There is a significant degree of phylogenetic inertia in both traits studied (number of cellular layers and number of cell classes in tectum); 2) Both traits are positively correlated accross evolution after correction for phylogeny; and 3) Different developmental pathways should generate different patterns of lamination and cytoarchitecture.

Methodology/principal findings: The hypotheses were tested using analytical-computational tools for phylogenetic hypothesis testing. Both traits presented a considerably large phylogenetic signal and were positively associated. However, no difference was found between two clades classified as per the general developmental pathways of their brains.

Conclusions/significance: The evidence amassed points to more variation in the tectum than would be expected by phylogeny in three species from the taxa analysed; this variation is not better explained by differences in the main course of development, as would be predicted by the developmental clade hypothesis. Those findings shed new light on the evolution of an functionally important structure in nontetrapods, the most basal radiations of vertebrates.

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Phylogenetic relationships between species, as assessed by Neighborhood Joining of aligned cytochrome B sequences.Branch annotations refer to branch lengths.
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pone-0003582-g001: Phylogenetic relationships between species, as assessed by Neighborhood Joining of aligned cytochrome B sequences.Branch annotations refer to branch lengths.

Mentions: The estimated phylogenetic relations between species is presented in figure 1. Both traits presented a significant phylogenetic signal (table 1), and are positively associated (Felsenstein's correlation, r2 = 0.654, P = 0.005, df = 6). Phylogenetic IC-based regressions yielded prediction and confidence intervals presented in figure 2. All species fell into the prediction intervals for the regression of number of cell classes into number of layers; the bowfin Amia calva, the lamprey Petromyzon marinus and the bichir Polypterus palmas fell outside of the 95% confidence interval for the regression. As such, those species present a higher (A. calva and P. palmas) or lower (P. marinus) number of cell classes in their tecta than would be expected by their pattern of lamination, as predicted to the taxa analysed.


Evolutionary changes in the complexity of the tectum of nontetrapods: a cladistic approach.

Maximino C - PLoS ONE (2008)

Phylogenetic relationships between species, as assessed by Neighborhood Joining of aligned cytochrome B sequences.Branch annotations refer to branch lengths.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2571994&req=5

pone-0003582-g001: Phylogenetic relationships between species, as assessed by Neighborhood Joining of aligned cytochrome B sequences.Branch annotations refer to branch lengths.
Mentions: The estimated phylogenetic relations between species is presented in figure 1. Both traits presented a significant phylogenetic signal (table 1), and are positively associated (Felsenstein's correlation, r2 = 0.654, P = 0.005, df = 6). Phylogenetic IC-based regressions yielded prediction and confidence intervals presented in figure 2. All species fell into the prediction intervals for the regression of number of cell classes into number of layers; the bowfin Amia calva, the lamprey Petromyzon marinus and the bichir Polypterus palmas fell outside of the 95% confidence interval for the regression. As such, those species present a higher (A. calva and P. palmas) or lower (P. marinus) number of cell classes in their tecta than would be expected by their pattern of lamination, as predicted to the taxa analysed.

Bottom Line: Both traits presented a considerably large phylogenetic signal and were positively associated.However, no difference was found between two clades classified as per the general developmental pathways of their brains.Those findings shed new light on the evolution of an functionally important structure in nontetrapods, the most basal radiations of vertebrates.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Psychobiology and Experimental Psychopatology, Department of Psychology, Universidade Estadual Paulista, Bauru, Brazil. caio.maximino@gmail.com

ABSTRACT

Background: The tectum is a structure localized in the roof of the midbrain in vertebrates, and is taken to be highly conserved in evolution. The present article assessed three hypotheses concerning the evolution of lamination and citoarchitecture of the tectum of nontetrapod animals: 1) There is a significant degree of phylogenetic inertia in both traits studied (number of cellular layers and number of cell classes in tectum); 2) Both traits are positively correlated accross evolution after correction for phylogeny; and 3) Different developmental pathways should generate different patterns of lamination and cytoarchitecture.

Methodology/principal findings: The hypotheses were tested using analytical-computational tools for phylogenetic hypothesis testing. Both traits presented a considerably large phylogenetic signal and were positively associated. However, no difference was found between two clades classified as per the general developmental pathways of their brains.

Conclusions/significance: The evidence amassed points to more variation in the tectum than would be expected by phylogeny in three species from the taxa analysed; this variation is not better explained by differences in the main course of development, as would be predicted by the developmental clade hypothesis. Those findings shed new light on the evolution of an functionally important structure in nontetrapods, the most basal radiations of vertebrates.

Show MeSH