Fluctuating Asymmetry and Measurement Error

1995 ◽  
Vol 44 (1) ◽  
pp. 97-101 ◽  
Author(s):  
Juha Merilä ◽  
Mats Björklund
Keyword(s):  
Measurement Error ◽  
Fluctuating Asymmetry

scholarly journals Fluctuating Asymmetry and Developmental Instability, a Guide to Best Practice

Symmetry ◽  
2020 ◽  
Vol 13 (1) ◽  
pp. 9
Author(s):  
John H. Graham
Keyword(s):  
Measurement Error ◽  
Best Practices ◽  
Environmental Stress ◽  
Fluctuating Asymmetry ◽  
Best Practice ◽  
Developmental Instability ◽  
The Past ◽  
Size Scaling ◽  
Research Designs

Best practices in studies of developmental instability, as measured by fluctuating asymmetry, have developed over the past 60 years. Unfortunately, they are haphazardly applied in many of the papers submitted for review. Most often, research designs suffer from lack of randomization, inadequate replication, poor attention to size scaling, lack of attention to measurement error, and unrecognized mixtures of additive and multiplicative errors. Here, I summarize a set of best practices, especially in studies that examine the effects of environmental stress on fluctuating asymmetry.

scholarly journals Asimetría cráneo-mandibular de Artibeus lituratus (Chiroptera, Phyllostomidae) en Colombia

2014 ◽  
Vol 20 (1) ◽  
pp. 141 ◽  
Author(s):  
Camilo López-Aguirre ◽  
Jairo Pérez-Torres
Keyword(s):  
Measurement Error ◽  
Fluctuating Asymmetry ◽  
Morphological Plasticity ◽  
Wide Distribution ◽  
Functional Similarity ◽  
High Abundance ◽  
Directional Asymmetry ◽  
Functional Importance ◽  
Mandibular Asymmetry ◽  
Artibeus Lituratus

Analyzing asymmetry in species associated with disturbed environments enables the evaluation of the morphological plasticity of generalistic species and the different evolutionary responses of sexes or populations to environmental or genetic stress. This report is a study of the cranial and mandibular asymmetry of Colombian Artibeus lituratus. This species has a wide distribution and high abundance, but its morphological plasticity remains uncertain. We characterized its presence, fluctuating asymmetry, directional asymmetry and antisymmetry by measuring 11 craneometric traits in 146 adults from different localities. Fluctuating asymmetry was present in all traits; directional asymmetry and antisymmetry in three; and no measurement error in any trait. Females showed more fluctuating asymmetry in the splachnocranium and males in the neurocranium. Traits with functional importance while biting had lower levels of asymmetry and higher similarity. Traits with antisymmetry did not show association while traits with directional asymmetry showed mandibular association. We discuss the relation between the presence of cranial and mandibular asymmetry, with the functional similarity of different traits.

Directional and fluctuating asymmetry in the black-winged damselfly Calopteryx maculata (Beauvois) (Odonata: Calopterygidae)

2000 ◽  
Vol 78 (10) ◽  
pp. 1740-1748 ◽  
Author(s):  
Jason Pither ◽  
Philip D Taylor
Keyword(s):  
Measurement Error ◽  
Fluctuating Asymmetry ◽  
Directional Asymmetry ◽  
Sample Group ◽  
Literature Evidence ◽  
Calopteryx Maculata

Directional asymmetry (DA) has received considerably less attention than fluctuating asymmetry (FA) in the literature. Evidence for DA, however, is building among insect taxa. We examined asymmetries in two wing traits within both sexes of the damselfly Calopteryx maculata (Beauvois) (Odonata: Calopterygidae) sampled from three sites in southeastern Ontario. After accounting for measurement error, we show that proximal segments within right fore and hind wings are consistently longer than those in the left in all but one sample group. Full wing lengths, however, exhibited FA rather than DA. Mean asymmetry values for both traits (segment and length) occurred in the direction of right-wingedness significantly more often than expected by chance. Patterns of asymmetry were generally consistent among the sexes and sites, although males tended to exhibit more pronounced DA. We suggest that the wings of C. maculata may undergo compensatory development, so that full lengths are more bilaterally symmetrical than their component parts.

Fluctuating asymmetry in an ornamental trait in the cave weta, Pleioplectron simplex Hutton (Orthoptera: Rhaphidophoridae): no role for parasites

1998 ◽  
Vol 76 (5) ◽  
pp. 931-935 ◽  
Author(s):  
F Thomas ◽  
D F Ward ◽  
R Poulin
Keyword(s):  
Measurement Error ◽  
Fluctuating Asymmetry ◽  
Expression Intensity ◽  
Stabilising Selection ◽  
Significant Difference ◽  
Cuticular Ornamentation

Using digitised pictures of the pronotum, we investigated the influence of nematomorph and mermithid parasites on the expression (intensity and fluctuating asymmetry) of cuticular ornamentation in the cave weta, Pleioplectron simplex. Because P. simplex is nocturnal, this ornamentation is probably not subject to strong directional or stabilising selection. Based on measurements of brightness, we found no significant difference in the amount of pigmented area between unparasitised and parasitised males or females. Parasitised individuals were not significantly more asymmetrical than unparasitised ones. This result was not due to measurement error. Among parasitised wetas, brightness and the fluctuating asymmetry were not related to the length of the parasite, even when the size of the host was taken into account. These results are discussed in relation to current ideas concerning the influence of parasites on fluctuating asymmetry of traits in the host.

Fluctuating Asymmetry and Measurement Error

1995 ◽  
Vol 44 (1) ◽  
pp. 97 ◽  
Author(s):  
Juha Merila ◽  
Mats Biorklund
Keyword(s):  
Measurement Error ◽  
Fluctuating Asymmetry

scholarly journals Fluctuating Asymmetry in Metric Traits; a Practical Example of Calculating Asymmetry, Measurement Error, and Repeatability

2008 ◽  
Vol 45 (1) ◽  
pp. 32-38 ◽  
Author(s):  
Thea Ø. Bechshøft ◽  
Frank F. Rigét ◽  
Øystein Wiig ◽  
Christian Sonne
Keyword(s):  
Measurement Error ◽  
Fluctuating Asymmetry ◽  
Asymmetry Measurement ◽  
Metric Traits

Benefits from Computerized Adaptive Testing as Seen in Simulation Studies

1999 ◽  
Vol 15 (2) ◽  
pp. 91-98 ◽  
Author(s):  
Lutz F. Hornke
Keyword(s):  
Measurement Error ◽  
Computerized Adaptive Testing ◽  
Test Procedure ◽  
Adaptive Testing ◽  
Parameter Estimates ◽  
Simulation Studies ◽  
Computerized Adaptive Test ◽  
Item Banks ◽  
Item Parameters ◽  
General Reliability

Summary: Item parameters for several hundreds of items were estimated based on empirical data from several thousands of subjects. The logistic one-parameter (1PL) and two-parameter (2PL) model estimates were evaluated. However, model fit showed that only a subset of items complied sufficiently, so that the remaining ones were assembled in well-fitting item banks. In several simulation studies 5000 simulated responses were generated in accordance with a computerized adaptive test procedure along with person parameters. A general reliability of .80 or a standard error of measurement of .44 was used as a stopping rule to end CAT testing. We also recorded how often each item was used by all simulees. Person-parameter estimates based on CAT correlated higher than .90 with true values simulated. For all 1PL fitting item banks most simulees used more than 20 items but less than 30 items to reach the pre-set level of measurement error. However, testing based on item banks that complied to the 2PL revealed that, on average, only 10 items were sufficient to end testing at the same measurement error level. Both clearly demonstrate the precision and economy of computerized adaptive testing. Empirical evaluations from everyday uses will show whether these trends will hold up in practice. If so, CAT will become possible and reasonable with some 150 well-calibrated 2PL items.

Measurement error and person-specific reliability in multilevel autoregressive modeling.

2019 ◽  
Vol 24 (1) ◽  
pp. 70-91 ◽  
Author(s):  
Noémi K. Schuurman ◽  
Ellen L. Hamaker
Keyword(s):  
Measurement Error ◽  
Autoregressive Modeling
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