Limits...
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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Root node reconstruction mapped back in the scatterplot for the relation between number of cell classes and number of layers in the tectum.Green lines represent 95% confidence intervals for the estimates of root node values.
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pone-0003582-g003: Root node reconstruction mapped back in the scatterplot for the relation between number of cell classes and number of layers in the tectum.Green lines represent 95% confidence intervals for the estimates of root node values.

Mentions: Figure 3 presents the replotting of estimated ancestral states of both traits into the plot relating the observed values of terminal taxa, along with 95% confidence intervals for the estimates. Most species fall within the confidence intervals; the exceptions were A. calva (number of cell classes above upper CI for root node), P. marinus and L. fluviatilis (number of cell classes below lower CI for root node), E. burgeri (number of layers below lower CI for root node) and P. dolloi (both number of layers and number of cell classes below lower CI for root node). Since there was an association between the number of cell classes and the number of layers, those species which fall outside the 95% confidence intervals can be interpreted as having significantly departed from the common ancestor of the species studied in terms of the rules that should have governed this relationship.


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

Maximino C - PLoS ONE (2008)

Root node reconstruction mapped back in the scatterplot for the relation between number of cell classes and number of layers in the tectum.Green lines represent 95% confidence intervals for the estimates of root node values.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0003582-g003: Root node reconstruction mapped back in the scatterplot for the relation between number of cell classes and number of layers in the tectum.Green lines represent 95% confidence intervals for the estimates of root node values.
Mentions: Figure 3 presents the replotting of estimated ancestral states of both traits into the plot relating the observed values of terminal taxa, along with 95% confidence intervals for the estimates. Most species fall within the confidence intervals; the exceptions were A. calva (number of cell classes above upper CI for root node), P. marinus and L. fluviatilis (number of cell classes below lower CI for root node), E. burgeri (number of layers below lower CI for root node) and P. dolloi (both number of layers and number of cell classes below lower CI for root node). Since there was an association between the number of cell classes and the number of layers, those species which fall outside the 95% confidence intervals can be interpreted as having significantly departed from the common ancestor of the species studied in terms of the rules that should have governed this relationship.

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