Digit Ratio, Color Polymorphism and Egg Testosterone in the Australian Painted Dragon

Tobler, Michael; Healey, Mo; Olsson, Mats

doi:10.1371/journal.pone.0016225

Cited by 25 publications

(40 citation statements)

References 56 publications

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“…In all studies on lizards and frogs (Chang et al, 2008Gomes and Kohlsdorf, 2011;Penuela, 2011;Tobler et al, 2011;Direnzo and Stynoski, 2012) measurement was done from the basal crease to the tip of the digit. However, on forelimbs and rear limbs of newts there is no visible basal crease.…”

Section: Digit Measurementmentioning

confidence: 99%

“…According to the latest research, 2D:4D is independent of body size in humans and non-human animals such as zebra finches, iguanas, and strawberry poison dart frogs (Burley and Foster, 2003;Rahman et al, 2005;McIntyre et al, 2006;Chang, 2006;Manning, 2010;Almasry et al, 2011;Gomes and Kohlsdorf, 2011). However, the research of Tobler et al (2011) on the Australian painted dragon showed that 3D:4D was negatively related to body size. The effects of size on sexual differences in digit ratios have also been observed in other studies Direnzo and Stynoski, 2012).…”

Section: Introductionmentioning

confidence: 99%

“…The articles conclude that this is probably an ancestral state, and that the mechanisms underlying this relationship seem to have been largely conserved (Burley and Foster, 2003;Tobler et al, 2011). The establishment of general phylogenetic patterns is fundamental to testing the 2D:4D hypothesis and to understanding the broad evolutionary significance of the phenomenon.…”

Section: Introductionmentioning

confidence: 99%

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Females Have Larger Ratio of Second‐to‐Fourth Digits Than Males in Four Species of Salamandridae, Caudata

Kaczmarski

Kubicka

Tryjanowski

et al. 2015

The Anatomical Record

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Digit ratio (2D:4D) denotes the relative length of the second and fourth digits. It is considered to be a suitable biomarker of the in utero balance of fetal sex hormones, which affect early development of individua ls behavioral and morphological characteristics. In recent decades, digit ratio attracted a great attention in biology and psychology. However, for unmasking the biological basis of the phenomenon, extensive studies on nonhuman animals are necessary. Despite it was hypothesized that digit ratio is well conserved in all Tetrapoda, and there exist studies on mammals, birds, and reptiles, there are only two such study on anuran amphibians. Therefore, the aim of this study is to investigate the 2D:4D in the most basal salamanders, Caudata. We have studied digit ratio in four species of newts: Triturus cristatus, Mesotriton alpestris, Lissotriton montandoni, and Lissotriton vulgaris, using museum collection. We used computerized measuring of each limbs photos. We have found out that, in M. alpestris, females 2D:4D of all four limbs were significantly larger than in males. In L. montandoni and L. vulgaris, only 2D:4D of rear limbs significantly differed, in females being larger. In T. cristatus, digit ratios of males and females did not statistically differ. Thus, the results confirmed our hypothesis that at least in M. alpestris, L. montandoni, and L. vulgaris, females seem to have larger 2D:4D comparing to males, the pattern known from most mammals and opposite to birds, reptiles and anuran amphibians.

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Section: Digit Measurementmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Females Have Larger Ratio of Second‐to‐Fourth Digits Than Males in Four Species of Salamandridae, Caudata

Kaczmarski

Kubicka

Tryjanowski

et al. 2015

The Anatomical Record

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“…Orange males have relatively larger heads and therefore bite harder than both yellow and white males (Huyghe et al 2007). In Australian painted dragons (Ctenophorus pictus), adult colour morphs have been shown to exhibit differences in digit ratios, suggesting that prenatal androgen exposure may be modulating the polymorphism (Tobler et al 2011). Levels of early sex hormone exposure are also believed to mediate morphspecific adult behaviour in American tree lizards (Urosaurus ornata) (Hews et al 1994;Moore et al 1998).…”

Section: Introductionmentioning

confidence: 99%

Digit ratios in two lacertid lizards: sexual dimorphism and morphological and physiological correlates

et al. 2015

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Digit length ratio (primarily 2D:4D) has become increasingly popular as a possible biomarker of intrauterine steroid exposure in the human medical, social and psychological literature. Human males tend to have lower digit ratios than females, and individuals with low ratios tend to excel in physical performance, especially in endurance-related sports. Because early limb development is evolutionarily conservative, it has been speculated that these trends should also be visible in other tetrapod vertebrates. However, studies on non-human vertebrates are scant, and their results suggest that sexual dimorphism in digit ratios and the associations with physical performance are much more intricate and taxon-specific than presumed. In this study, we compared digit ratios of two Podarcis lizards among sexes, colour morphs and species. We also tested for associations with three performance characteristics that are of ecological relevance. Both species examined exhibit male-larger sexual dimorphism in digit ratio. 2D:4D, 3D:4D and 2D:3D ratios are tightly correlated within the manus and the pes, but less so between manus and pes. In the colour polymorphic species P. melisellensis, the yellow morph exhibits higher dimorphism than the orange and white morphs. Digit ratios did not correlate with individual performance for sprint speed or endurance, but within males of P. melisellensis, individuals with higher digit ratios correlated positively with head size and bite force. We conclude that digit ratios in lizards deserve attention, because they exhibit sexual dimorphism and correlate with ecologically relevant morphological and performance variables. As lizard species differ widely in mating systems, reproductive mode, habitat use and locomotor behaviour, they seem excellent model animals for studying patterns in digit length ratios.

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“…It is easy to imagine that most researchers would agree with their conclusion. Moreover, three follow-up studies have discussed and examined the propositions of the Kratochvíl and Flegr (2009) study in great detail (Höne-kopp and Watson, 2010;Manning, 2010;Tobler et al, 2011). Although all of them, by various means, reach the conclusion that digit ratio remains sexually dimorphic even when accounting for allometry, none of the studies questions the validity of using OLS regression.…”

Section: Example 2: Making Negative Size Dimorphism Disappearmentioning

confidence: 99%

Women have Relatively Larger Brains than Men: A Comment on the Misuse of General Linear Models in the Study of Sexual Dimorphism

Forstmeier

2011

The Anatomical Record

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General linear models (GLM) have become such universal tools of statistical inference, that their applicability to a particular data set is rarely questioned. These models are designed to minimize residuals along the yaxis, while assuming that the predictor (x-axis) is free of statistical noise (ordinary least square regression, OLS). However, in practice, this assumption is often violated, which can lead to erroneous conclusions, particularly when two predictors are correlated with each other. This is best illustrated by two examples from the study of allometry, which have received great interest: (1) the question of whether men or women have relatively larger brains after accounting for body size differences, and (2) whether men indeed have shorter index fingers relative to ring fingers (digit ratio) than women. In depth analysis of these examples clearly shows that GLMs produce spurious sexual dimorphism in body shape where there is none (e.g. relative brain size). Likewise, they may fail to detect existing sexual dimorphisms in which the larger sex has the lower trait values (e.g. digit ratio) and, conversely, tend to exaggerate sexual dimorphism in which the larger sex has the relatively larger trait value (e.g. most sexually selected traits). These artifacts can be avoided with reduced major axis regression (RMA), which simultaneously minimizes residuals along both the x and the y-axis. Alternatively, in cases where isometry can be established there are no objections against and good reasons for the continued use of ratios as a simple means of correcting for size differences.

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Digit Ratio, Color Polymorphism and Egg Testosterone in the Australian Painted Dragon

Cited by 25 publications

References 56 publications

Females Have Larger Ratio of Second‐to‐Fourth Digits Than Males in Four Species of Salamandridae, Caudata

Females Have Larger Ratio of Second‐to‐Fourth Digits Than Males in Four Species of Salamandridae, Caudata

Digit ratios in two lacertid lizards: sexual dimorphism and morphological and physiological correlates

Women have Relatively Larger Brains than Men: A Comment on the Misuse of General Linear Models in the Study of Sexual Dimorphism

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