A new approach to the study of genetic variability of complex characters

Ефимов, В. М.; Kovaleva, V. Yu.; Markel, A. L.

doi:10.1038/sj.hdy.6800580

“…If selection is treated as approximately constant, the left dominant eigenvector of GP Ϫ1 describes the direction in the phenotype space that will yield the maximal response to selection (Klingenberg and Leamy 2001). The dominant eigenvalue associated with this direction describes the maximum additive heritability (Efimov et al 2005) of a set of phenotypic traits (…”

Section: Statistical Analysesmentioning

confidence: 99%

QUANTITATIVE GENETICS OF PLASTRON SHAPE IN SLIDER TURTLES ( TRACHEMYS SCRIPTA )

Myers

¹

,

Janzen

²

,

Adams

³

et al. 2006

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Shape variation is widespread in nature and embodies both a response to and a source for evolution and natural selection. To detect patterns of shape evolution, one must assess the quantitative genetic underpinnings of shape variation as well as the selective environment that the organisms have experienced. Here we used geometric morphometrics to assess variation in plastron shell shape in 1314 neonatal slider turtles (Trachemys scripta) from 162 clutches of laboratory-incubated eggs from two nesting areas. Multivariate analysis of variance indicated that nesting area has a limited role in describing plastron shape variation among clutches, whereas differences between individual clutches were highly significant, suggesting a prominent clutch effect. The covariation between plastron shape and several possible maternal effect variables (yolk hormone levels and egg dimensions) was assessed for a subset of clutches and found to be negligible. We subsequently employed several recently proposed methods for estimating heritability from shape variables, and generalized a univariate approach to accommodate unequal sample sizes. Univariate estimates of shape heritability based on Procrustes distances yielded large values for both nesting populations (h2 approximately 0.86), and multivariate estimates of maximal additive heritability were also large for both nesting populations (h2max approximately 0.57). We also estimated the dominant trend in heritable shape change for each nesting population and found that the direction of shape evolution was not the same for the two sites. Therefore, although the magnitude of shape evolution was similar between nesting populations, the manner in which plastron shape is evolving is not. We conclude that the univariate approach for assessing quantitative genetic parameters from geometric morphometric data has limited utility, because it is unable to accurately describe how shape is evolving.

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“…If selection is treated as approximately constant, the left dominant eigenvector of GP Ϫ1 describes the direction in the phenotype space that will yield the maximal response to selection (Klingenberg and Leamy 2001). The dominant eigenvalue associated with this direction describes the maximum additive heritability (Efimov et al 2005) of a set of phenotypic traits (…”

Section: Statistical Analysesmentioning

confidence: 99%

Quantitative Genetics of Plastron Shape in Slider Turtles (Trachemys Scripta)

Myers

¹

,

Janzen

²

,

Adams

³

et al. 2006

Evol

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Shape variation is widespread in nature and embodies both a response to and a source for evolution and natural selection. To detect patterns of shape evolution, one must assess the quantitative genetic underpinnings of shape variation as well as the selective environment that the organisms have experienced. Here we used geometric morphometrics to assess variation in plastron shell shape in 1314 neonatal slider turtles (Trachemys scripta) from 162 clutches of laboratory-incubated eggs from two nesting areas. Multivariate analysis of variance indicated that nesting area has a limited role in describing plastron shape variation among clutches, whereas differences between individual clutches were highly significant, suggesting a prominent clutch effect. The covariation between plastron shape and several possible maternal effect variables (yolk hormone levels and egg dimensions) was assessed for a subset of clutches and found to be negligible. We subsequently employed several recently proposed methods for estimating heritability from shape variables, and generalized a univariate approach to accommodate unequal sample sizes. Univariate estimates of shape heritability based on Procrustes distances yielded large values for both nesting populations (h2 approximately 0.86), and multivariate estimates of maximal additive heritability were also large for both nesting populations (h2max approximately 0.57). We also estimated the dominant trend in heritable shape change for each nesting population and found that the direction of shape evolution was not the same for the two sites. Therefore, although the magnitude of shape evolution was similar between nesting populations, the manner in which plastron shape is evolving is not. We conclude that the univariate approach for assessing quantitative genetic parameters from geometric morphometric data has limited utility, because it is unable to accurately describe how shape is evolving.

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“…The theory of multivariate phenotypic evolu tion has been extrapolated from the theory for allele frequencies and uses generally the same equations (Fisher, 1930;Wright, 1968;Lande, 1976;Roff, 1997;Polly, 2008). The heritability of some craniometric characters varying in a range of 0.4-0.6 (Atchley et al, 1981) and of their linear combinations, which exceeds 0.9 in some cases (Efimov et al, 2005, Kovaleva et al, 2006, indicates that these characters are determined by gene complexes.…”

Section: Resultsmentioning

confidence: 99%

Shrews (Soricidae, Eulipotyphla) from the Russian Far East and Siberia: Combination and search for congruence of molecular genetic and morphological data

Kovaleva

¹

,

Litvinov

²

,

Ефимов

³

2014

Biol Bull Russ Acad Sci

2

0

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The distance joining (DJ) method has been used to combine morphological and molecular genetic (cytb) data on 19 species of Siberian and Far Eastern shrews. It has been found that morphological distances between the species do not correspond to molecular genetic distances (Mantel's test, r = 0.336) due to the size component of morphological variation. Data on the relationships between taxa of generic and spe cies levels according to the molecular marker (cytb) are incongruent to those based on morphometric char acters of the Soricidae, since the cytb gene is a recorder of neutral mutations, whereas the size of morpholog ical characters is a reflection of adaptive evolution. The correlation between the two types of data has notice ably increased (r = 0.799) after the size component was excluded from the morphological distance matrix. The combination of morphological and molecular distance matrices with subsequent nonmetric two dimen sional scaling and dendrogram construction has provided a basis for conclusions about the generic and sub generic structure of the family Soricidae, which basically correspond to current views on the taxonomy of this group, and for hypotheses concerning the taxonomic status of S. mirabilis and S. minutissimus.

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A new approach to the study of genetic variability of complex characters

Cited by 10 publications

References 15 publications

QUANTITATIVE GENETICS OF PLASTRON SHAPE IN SLIDER TURTLES ( TRACHEMYS SCRIPTA )

QUANTITATIVE GENETICS OF PLASTRON SHAPE IN SLIDER TURTLES ( TRACHEMYS SCRIPTA )

Quantitative Genetics of Plastron Shape in Slider Turtles (Trachemys Scripta)

Shrews (Soricidae, Eulipotyphla) from the Russian Far East and Siberia: Combination and search for congruence of molecular genetic and morphological data

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