A New Fluctuating Asymmetry Index, or the Solution for the Scaling Effect?
Two principal methods are commonly employed for the estimation of developmental instability at the population level. Some studies use variances of morphological traits (σ2p), while others use fluctuating asymmetry (FA). In both cases, differences in the degree of developmental instability can be tes...
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| Format: | Article |
| Language: | English |
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MDPI AG
2015-04-01
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| Series: | Symmetry |
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| Online Access: | http://www.mdpi.com/2073-8994/7/2/327 |
| _version_ | 1811187339922243584 |
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| author | Cino Pertoldi Torsten Nygaard Kristensen |
| author_facet | Cino Pertoldi Torsten Nygaard Kristensen |
| author_sort | Cino Pertoldi |
| collection | DOAJ |
| description | Two principal methods are commonly employed for the estimation of developmental instability at the population level. Some studies use variances of morphological traits (σ2p), while others use fluctuating asymmetry (FA). In both cases, differences in the degree of developmental instability can be tested with an F-test, which is the most common way to compare variances. However, the variance is expected to scale proportionally to the square of the mean as there is a tendency in biological data for σ2p to scale proportionally to the square of the mean ( ): σ2p = Z ξ, where ξ is the scaling exponent, which is expected to be two for pure statistical reasons, is the mean of the trait and Z is a measure of individual-level variability. Because of this scaling effect, the fluctuating asymmetry will be affected, FA is estimated as the variance between the right and the left sides of a trait (σ2r − l = σ2r + σ2l − 2rσrσl), where σ2r and σ2l are the variances of the right and the left trait values, respectively. In this paper, we propose a novel method that allows an exact correction of the scaling effect, which will enable a proper comparison of the degree of fluctuating asymmetry for a trait. The problem of the scaling of the FA with the trait size is quite crucial if FA is to be considered an indicator of fitness or an indicator of environmental or genetic stress, as different stresses or fitness levels are typically accompanied by a change of the traits’ . |
| first_indexed | 2024-04-11T14:01:35Z |
| format | Article |
| id | doaj.art-7fb3321cc58a4a8890b275c1e178d599 |
| institution | Directory Open Access Journal |
| issn | 2073-8994 |
| language | English |
| last_indexed | 2024-04-11T14:01:35Z |
| publishDate | 2015-04-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Symmetry |
| spelling | doaj.art-7fb3321cc58a4a8890b275c1e178d5992022-12-22T04:20:07ZengMDPI AGSymmetry2073-89942015-04-017232733510.3390/sym7020327sym7020327A New Fluctuating Asymmetry Index, or the Solution for the Scaling Effect?Cino Pertoldi0Torsten Nygaard Kristensen1Department of Chemistry and Bioscience, Aalborg University, Fredrik Bajers Vej 7H, 9220 Aalborg, DenmarkDepartment of Chemistry and Bioscience, Aalborg University, Fredrik Bajers Vej 7H, 9220 Aalborg, DenmarkTwo principal methods are commonly employed for the estimation of developmental instability at the population level. Some studies use variances of morphological traits (σ2p), while others use fluctuating asymmetry (FA). In both cases, differences in the degree of developmental instability can be tested with an F-test, which is the most common way to compare variances. However, the variance is expected to scale proportionally to the square of the mean as there is a tendency in biological data for σ2p to scale proportionally to the square of the mean ( ): σ2p = Z ξ, where ξ is the scaling exponent, which is expected to be two for pure statistical reasons, is the mean of the trait and Z is a measure of individual-level variability. Because of this scaling effect, the fluctuating asymmetry will be affected, FA is estimated as the variance between the right and the left sides of a trait (σ2r − l = σ2r + σ2l − 2rσrσl), where σ2r and σ2l are the variances of the right and the left trait values, respectively. In this paper, we propose a novel method that allows an exact correction of the scaling effect, which will enable a proper comparison of the degree of fluctuating asymmetry for a trait. The problem of the scaling of the FA with the trait size is quite crucial if FA is to be considered an indicator of fitness or an indicator of environmental or genetic stress, as different stresses or fitness levels are typically accompanied by a change of the traits’ .http://www.mdpi.com/2073-8994/7/2/327Taylor’s power lawdevelopmental instabilityF-test |
| spellingShingle | Cino Pertoldi Torsten Nygaard Kristensen A New Fluctuating Asymmetry Index, or the Solution for the Scaling Effect? Symmetry Taylor’s power law developmental instability F-test |
| title | A New Fluctuating Asymmetry Index, or the Solution for the Scaling Effect? |
| title_full | A New Fluctuating Asymmetry Index, or the Solution for the Scaling Effect? |
| title_fullStr | A New Fluctuating Asymmetry Index, or the Solution for the Scaling Effect? |
| title_full_unstemmed | A New Fluctuating Asymmetry Index, or the Solution for the Scaling Effect? |
| title_short | A New Fluctuating Asymmetry Index, or the Solution for the Scaling Effect? |
| title_sort | new fluctuating asymmetry index or the solution for the scaling effect |
| topic | Taylor’s power law developmental instability F-test |
| url | http://www.mdpi.com/2073-8994/7/2/327 |
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