A Comparative Study of Population Density and Sexual Size Dimorphism in Lizards

Stamps, Judy A.; Losos, Jonathan B.; Andrews, Robin M.

doi:10.1086/285979

Cited by 131 publications

(108 citation statements)

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“…As indicated by Purvis and Garland (1993:569), topological errors could affect performance of independent contrasts (or any other method), to an unknown and potentially serious degree. If competing phylogenetic hypotheses differ substantially, then results should be compared with the different trees (e.g., Bauwens and Dṍ az-Uriarte, 1997), or the approach of Losos (1994) could be used (e.g., Stamps et al, 1997).…”

Section: Discussionmentioning

confidence: 99%

“…Use of the lower bound on the degrees of freedom should protect against in ated Type I error rates, while at the same time improving estimation by using a full set of N -1 contrasts (see Purvis and Garland, 1993:573). However, the performance of Purvis and Garland's approach has never been examined by computer simulations (Stamps et al [1997] presented an empirical example comparing this method with that of Losos [1994].) So far, only Grafen (1989) and Purvis et al (1994) have examined the effects of polytomies on the performance of independent contrasts.…”

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confidence: 99%

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Polytomies and Phylogenetically Independent Contrasts: Examination of the Bounded Degrees of Freedom Approach

Garland¹,

1999

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Abstract.-We examined the effect of soft polytomies on the performance (Type I error rate and bias) of Felsenstein's (1985; Am. Nat. 125:1-15) method of phylogenetically independent contrasts for estimating a bivariate correlation. We speci cally tested the adequacy of bounding degrees of freedom, as suggested by Purvis and Garland (1993; Syst. Biol. 42:569-575). We simulated bivariate character evolution under Brownian motion (assumed by independent contrasts) and eight other models on ve phylogenetic trees. For non-Brownian motion simulations, the adequacy of branchlength standardization was checked with a simple diagnostic (Garland et al., 1992; Syst. Biol. 41: 18-32), and transformations were applied as indicated. Surprisingly, soft polytomies tended to have negligible effects on Type I error rates when models other than Brownian motion were used. Overall, and irrespective of evolutionary model, degrees of freedom were appropriately bounded for hypothesis testing, and unbiased estimates of the correlation coef cient were obtained. Our results, along with those of previous simulation studies, suggest that independent contrasts can reliably be applied to real data, even with phylogenetic uncertainty.

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Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

Polytomies and Phylogenetically Independent Contrasts: Examination of the Bounded Degrees of Freedom Approach

Garland¹,

1999

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“…For example, fecundity selection has been invoked to explain large abdomen size in females (Preziozi et al, 1996;Olsson et al, 2002;Nespolo and Bacigulupe, 2009), whereas male-male competition has been suggested to drive the evolution of exaggerated weapons in males (Darwin, 1871;Andersson, M., 1994;Berglund et al, 1996). The most obvious and widely studied sexually dimorphic trait is the phenotypic divergence in overall body size or sexual size dimorphism (SSD) (Fairbairn and Preziosi, 1994;Fairbairn, 1997;Stamps et al, 1997;Blanckenhorn, 2005;Starostova et al, 2010).…”

Section: Sexual Selection and Size Dimorphismmentioning

confidence: 99%

“…As males and females frequently differ in their use of microhabitats (Butler et al, 2000;Asbury and Adolph, 2004), behaviour and overall activity (Stamps et al, 1997;Lailvaux et al, 2003;Asbury and Adolph, 2007;Yu et al, 2011), sex-specific variation in their use of the environment could be an important driver of divergence in wholeorganism performance. Each sex may benefit from different thermal dependence and sensitivities of performance that allow them to maximise fitness across the environments to which they are actually exposed; especially for traits closely related with either male or female reproductive success (Huey and Pianka, 2007).…”

Section: Sex Differences In Thermal Sensitivitymentioning

confidence: 99%

“…From the few studies investigating sex-specific performance capacities, we know that males and females can differ in whole-organism performance, although little is known about the evolutionary drivers of these differences (Cullum, 1998;Lailvaux et al, 2003;Krasnov et al, 2004). As males and females frequently differ in their use of microhabitats (Butler et al, 2000;Asbury and Adolph, 2004), behaviour and overall activity (Stamps et al, 1997;Lailvaux et al, 2003;Asbury and Adolph, 2007;Yu et al, 2011), sex-specific variation in their use of the environment could be an important driver of divergence in whole-organism performance. For ectotherms, any differences in habitat use and activity could profoundly affect their thermal activity profiles (Bakken, 1992;Miles, 1994) leading to divergence in thermal optimum environments between the sexes.…”

Section: Introductionmentioning

confidence: 99%

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Sex-specific variation in morphology and performance in the Asian house gecko

Cameron¹

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Ever since Darwin's theory of sexual selection was first published, understanding the evolutionary mechanisms that lead to sex-specific traits and quantifying patterns therein has been a large focus of evolutionary ecologists. Sexual variation in phenotypes in form and function is ubiquitous in nature, and its extent varies widely, within closely related groups and even species. Understanding patterns and the circumstances under which sexually divergent phenotypes evolve requires an understanding of both the proximate and evolutionary mechanisms involved. While studies have primarily focused on sex-specific morphological traits such as size and secondary trait dimorphism, less attention has been given to the functional differences between the sexes. From an evolutionary perspective, sexspecific traits result from many factors that act differentially on each sex, modifying phenotypic and behavioural components that influence the capacity of fulfilling reproductive roles. Therefore, sexual selection alone does not define the magnitude of phenotypic divergence between the sexes, but it is rather the interplay between sexual and natural selection and their interactions with the environment. Intraspecific studies investigating associations between form and function of sexspecific traits provide a useful tool to understand the fundamental mechanisms that lead to the evolution of complex traits in males and females. The overall aim of this thesis was to gain a better understanding of the evolutionary mechanisms that drive patterns in sex-specific phenotypes, using a territorial gecko species (Hemidactylus frenatus) distributed over a large latitudinal cline.The first aim of this thesis was to examine the potential trade-offs between performance functions associated with reproductive success and to test whether compensatory mechanisms may obscure the detection of such costs (Chapter 2). Fighting capacity and escape performance of male H. frenatus are likely to pose conflicting demands on the optimum phenotype for each task. Highly territorial and aggressive males may require greater investment in head size/strength but such an enhancement may reduce overall escape performance. To test this idea, the second aim (also in Chapter 2) was to determine the role of morphological and functional traits in determining the outcome of male-male combat (reproductive success) and prey-capture ability (survivorship).Among male geckos, I found that larger head size resulted in greater biting capacity, but at a cost of reduced spring performance. Females, however, showed no evidence of this trade-off. The sex specificity of this trade-off suggests that the sexes differ in their optimal strategies for dealing with the conflicting requirements of bite force and sprint speed. Unlike males, female H. frenatus had a positive association between hind-limb length and head size, suggesting that they have utilised a compensatory mechanism to alleviate the possible locomotor costs of larger head sizes. It appears that there is greater sel...

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Development of sexual dimorphism in two sympatric skinks with different growth rates

Yang

Jiang

Díaz

et al. 2019

Ecology and Evolution

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Sexual size dimorphism (SSD) is widespread in animals, especially in lizards (Reptilia: Squamata), and is driven by fecundity selection, male–male competition, or other adaptive hypotheses. However, these selective pressures may vary through different life history periods; thus, it is essential to assess the relationship between growth and SSD. In this study, we tracked SSD dynamics between a “fading‐tail color skink” (blue tail skink whose tail is only blue during its juvenile stage: Plestiodon elegans ) and a “nonfade color” tail skink (retains a blue tail throughout life: Plestiodon quadrilineatus ) under a controlled experimental environment. We fitted growth curves of morphological traits (body mass, SVL, and TL) using three growth models (Logistic, Gompertz, and von Bertalanffy). We found that both skinks have male‐biased SSD as adults. Body mass has a higher goodness of fit (as represented by very high R 2 values) using the von Bertalanffy model than the other two models. In contrast, SVL and TL for both skinks had higher goodness of fit when using the Gompertz model. Two lizards displayed divergent life history tactics: P. elegans grows faster, matures earlier (at 65 weeks), and presents an allometric growth rate, whereas P. quadrilineatus grows slower, matures later (at 106 weeks), and presents an isometric growth rate. Our findings imply that species‐ and sex‐specific trade‐offs in the allocation of energy to growth and reproduction may cause the growth patterns to diverge, ultimately resulting in the dissimilar patterns of SSD.

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A Comparative Study of Population Density and Sexual Size Dimorphism in Lizards

Cited by 131 publications

References 108 publications

Polytomies and Phylogenetically Independent Contrasts: Examination of the Bounded Degrees of Freedom Approach

Polytomies and Phylogenetically Independent Contrasts: Examination of the Bounded Degrees of Freedom Approach

Sex-specific variation in morphology and performance in the Asian house gecko

Development of sexual dimorphism in two sympatric skinks with different growth rates

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