Integrative and Comparative Biology Advance Access originally published online on June 6, 2007
Integrative and Comparative Biology 2007 47(2):172-188; doi:10.1093/icb/icm019
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Functional and ecological correlates of ecologically-based dimorphisms in squamate reptiles
*Department of Anatomical Sciences, Health Sciences Center T8 (069), Stony Brook University, Stony Brook, NY 11794-8081, USA; Functional Morphology Laboratory, University of Antwerp, Universiteitsplein 1, B-2610 Antwerp, Belgium
Correspondence: 1E-mail: sevince1{at}hotmail.com
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 Synopsis IntroductionIntersexual dietary divergence...Empirical examples from snakesIntersexual dietary divergence...Empirical examples from lizardsAcknowledgmentsReferences |
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Sexual dimorphism in phenotypic traits associated with the use of resources is a widespread phenomenon throughout the animal kingdom. While ecological dimorphisms are often initially generated by sexual selection operating on an animal's size, natural selection is believed to maintain, or even amplify, these dimorphisms in certain ecological settings. The trophic apparatus of snakes has proven to be a model system for testing the adaptive nature of ecological dimorphisms because head size is rarely under sexual selection and it limits the maximum ingestible size of prey in these gape-limited predators. Significantly less attention has been paid to the evolution of ecological dimorphisms in lizards, however, which may be due to the fact that lizards’ feeding apparatus can be under both sexual and natural selection simultaneously, making it difficult to formulate clear-cut hypotheses to distinguish between the influences of natural and sexual selection. In order to tease apart the respective influences of natural selection and sexual selection on the feeding apparatus of squamates, we take an integrative approach to formulate two hypotheses for snakes and lizards, respectively: (1) For gape-limited snakes, we predict that natural selection will act to generate differences in maximum gape, which will translate into differences in maximum ingestible prey size between the sexes. (2) For lizards which mechanically reduce their prey, we predict that the degree of dimorphism in head size should be positively correlated to the degree of dimorphism in bite force which, in turn, should be correlated to dimorphism in aspects of size or hardness of prey. Finally, we predict that functional differences in the feeding apparatus of these animals will also be linked with differences in sex-based feeding behavior and with selection of prey.
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Introduction |
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SynopsisIntroductionIntersexual dietary divergence...Empirical examples from snakesIntersexual dietary divergence...Empirical examples from lizardsAcknowledgmentsReferences |
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Sexual dimorphism in phenotypic traits associated with the use of resources is a widespread phenomenon throughout the animal kingdom (Darwin 1871
; Selander 1972; Ralls 1976; Slatkin 1984; Shine 1989, 1991; Cullum 1998; Myersterud 2000; Temeles et al. 2000; Lailvaux et al. 2003; Heatwole et al. 2005; Vincent 2006). As discussed in the introduction to this symposium (Lailvaux and Vincent in review), ecological dimorphisms are often generated initially by sexual selection acting on an animal's body size (either male–male combat or selection for increased fecundity leading to larger body sizes), but are typically amplified or maintained by natural selection (Slatkin 1984; Myersterud 2000). Even so, the potential role(s) of natural selection in this process is not always clear-cut. For example, Slatkin (1984) showed by taking a quantitative genetic modeling approach that sex-based divergence in phenotype and in ecological traits can evolve in a manner similar to competitive character displacement (i.e., one or both sexes diverge in ways that reduce intersexual competition for resources) (Fig. 1). In contrast, empirical work has shown that in species exhibiting size dimorphism in size (SSD; body size in females differs from that in males), intersexual ecological divergence is more likely to evolve purely as the result of adaptation to divergent niches (i.e., the sexes have different adaptive peaks due to differences in body size) (Selander 1972; Ralls 1976; Shine 1991; Myerstud 2000; Vincent 2006). Although previous authors have formulated several sub-hypotheses (e.g., predation risk, differential energetic requirements) under the "dimorphic niche hypothesis" (reviewed by Myersterud 2000; Shine and Wall 2004), here we will largely restrict our attention to the broad implications of the hypothesis. Understanding the evolutionary origins and adaptive significance of ecological dimorphisms is still further complicated by the fact that hormones can play a pivotal role in the evolution of SSD in many animal species (Lerner and Mason 2001; Cox and John-Alder 2005 and references therein; but see Taylor and DeNardo 2005 for a counterexample), which may in turn influence the ecology of the sexes.
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The feeding apparatus of gape-limited snakes (that do not reduce the size of their prey before ingestion) has proven to be a model system for testing the adaptive nature of ecological dimorphisms for two reasons: (1) head size is believed to rarely be under sexual selection in snakes (e.g., Shine 1991
), and (2) because head size limits the maximum size of prey that can be consumed; the sex with the larger head should thus consume larger prey (Shine 1991; Houston and Shine, 1993; Pearson et al. 2002; Shetty and Shine 2002; Shine et al. 2002; Shine and Wall 2004; Vincent et al. 2004a). In contrast, significantly less attention has been paid to the evolution of dietary dimorphisms in other types of squamates such as lizards. This lack of research is likely due to the fact that the feeding apparatus of lizards can be under both sexual and natural selection simultaneously, and these animals extensively chew their prey prior to ingestion (see Herrel et al. 1996, 1999, 2001a, 2001b for an overview; Reilly et al. 2001). Consequently, it is significantly more difficult to generate clear-cut hypotheses to test for the presence of adaptive ecological dimorphisms in lizards compared to snakes.
Furthermore, a potentially serious confounding factor in the analysis of adaptive sex-based morphological divergence is the pervasive influence of hormones on animal growth and development. This issue is particularly relevant for both lizards and snakes because steroid hormones such as testosterone have been shown to directly influence the degree of SSD, as well as the shape of the feeding apparatus (Crews et al. 1985; Shine and Crews 1988; Lerner and Mason 2001; Cox et al. 2006), due to its inhibitory effect on male growth in some species (reviewed by Cox and John-Alder 2005). For example, red-sided garter snakes (Thamnophis sirtalis parietalis) exhibit significant sexual dimorphism in both body size and relative jaw length (corrected for body size), with females being larger in both aspects. The proximate cause of this dimorphism, however, was shown to be higher levels of circulating testosterone in males than in females, thus causing males to grow more slowly than females (Crews et al. 1985; Lerner and Mason 2001), and not sex-based ecological divergence (but see Krause et al. 2003; Krause and Burghardt in press for recent counterevidence). Further supporting this claim, Shine and Crews (1988) showed that the marked dimorphism in relative jaw length did not always translate into differences between the sexes in maximum size of prey consumed in natural populations. As a result, sex-based divergence in head shape—in the absence of quantitative dietary data—should not be viewed as compelling evidence for adaptive ecological divergence between the sexes.
In order to tease apart the respective influences of natural and sexual selection on the one hand, and developmental effects on the feeding apparatus of male and female squamates on the other, we formulate two straightforward testable hypotheses for snakes and lizards, respectively. Our overarching goal is to provide a quantitative framework that will enable future researchers to clearly distinguish between adaptive and nonadaptive influences on the feeding apparatus of male and female animals, and to point out areas that still need to be addressed with empirical data. We subsequently test these hypotheses by both reviewing the scientific literature on intersexual dietary divergence in lizards and snakes, and by providing empirical data to fill in critical gaps for some species.
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Intersexual dietary divergence in snakes |
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SynopsisIntroductionIntersexual dietary divergence...Empirical examples from snakesIntersexual dietary divergence...Empirical examples from lizardsAcknowledgmentsReferences |
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Theoretically, there are two nonmutually exclusive mechanisms by which the sexes in gape-limited snakes may exploit different types, shapes, and/or maximum sizes of prey. (1) The sexes can differ in absolute size of head and body because larger-bodied snakes can consume larger maximum sizes of prey (Arnold 1993
; Forsman and Lindell 1993), and/or (2) the sexes can differ in relative head dimensions (head shape) when they overlap in body size, enabling males and females of similar body sizes to consume different diets (Houston and Shine 1993; Vincent et al. 2004a). To invoke adaptive scenarios for the evolution of sex-based ecological divergence, however, we suggest that morphological divergence in either body size or head shape should be coupled with divergence in feeding behavior (foraging mode, prey handling method/time, sensory modalities used for prey detection), realized diet, and subsequently differential prey selection between the sexes. We suggest that multiple lines of evidence are needed to support the hypothesis of adaptation in this case because sexual selection and/or developmental effects alone can cause sex-based morphological divergence, which in turn could result in spurious correlations arising between intersexual morphology and diet in these animals. For example, Shine (1991) showed that most macrostomatan (enlarged gape) snakes exhibit female-biased dimorphism in body size, which is likely the result of selection on fecundity and offspring size in these animals (Shine 1991; Rivas and Burghardt, 2001). At the same time, however, this larger body size could result in females taking larger maximum sizes of prey than do males simply because of females’ increased functional capacity to do so, not as a result of natural selection acting to reduce intersexual competition for resources or driving adaptation to divergent niches. By contrast, if natural selection is either maintaining or driving the sex-based morphological divergence, one would expect clear functional links amongst intersexual morphology, feeding behavior, realized diet, and selection of prey, given that sexual selection and developmental effects should not influence either feeding behavior or dietary selection in snakes. We thus reviewed the literature on sexual dietary dimorphisms in snakes and supplemented that review with our own unpublished data to fill in gaps whenever possible (Table 1). It should be noted that we only included species for which dietary data for both sexes had been reported (but see Shine 1991 for a large data set on intersexual morphology in snakes).
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Empirical examples from snakes |
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SynopsisIntroductionIntersexual dietary divergence...Empirical examples from snakesIntersexual dietary divergence...Empirical examples from lizardsAcknowledgmentsReferences |
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Our nonexhaustive literature search resulted in data on the intersexual dietary habits of 38 species of snake, among 25 genera, and five families (Table 1), with all species belonging to a single monophyletic clade, Macrostomata (literally meaning, "large-mouthed" snakes) (Cundall and Greene 2000
). Our review revealed that at least some aspects of intersexual phenotype (i.e., morphology and/or behavior) was clearly associated with sex-based dietary divergence in 73.6% of the snake species studied to date, suggesting that ecological dimorphisms are widespread amongst macrostomatans. Moreover, the gender with the relatively larger feeding structures—independent of body size—always consumed the larger prey, with some species even lacking SSD altogether but still exhibiting significant differences in head shape and diet (e.g., Colubridae: Coronella austriaca) (Luiselli et al. 1996). Sexual dimorphism in body size is thus not a prerequisite for the evolution of ecological dimorphisms in snakes, whereas dimorphisms in shape of the head are almost always present when the sexes differ in diet.
Interestingly, the majority of species that did not exhibit a clear link between intersexual phenotype and diet belonged to a single monophyletic clade (i.e., terrestrial elapids). Specifically, Shine et al. (in press) showed that most venomous terrestrial elapids exhibit significant SSD, with adult females having larger maximum body sizes than those of conspecific adult males, but males in this case tended to have longer heads relative to body size than did females (Table 1). Nonetheless, the relatively larger heads of males in this clade were generally not associated with males taking larger maximum prey sizes than do females (i.e., both sexes tended to consume relatively small [compared to the size of the predator] ectothermic vertebrates, except perhaps in one species, Aspidelaps scutatus [Shine et al. 1996c]. Given that terrestrial elapid males are known to vigorously bite each other during male–male combat in a manner similar to that of lizards (Lailvaux et al. 2004; Huyghe et al. 2005). Shine et al. (2006) suggested that this relatively longer head in males is, therefore, the result of sexual selection (i.e., male–male combat favoring males with relatively larger heads), and not adaptation to divergent niches.
Nonecological factors driving sex-based divergence in head shape, however, were not limited to venomous terrestrial elapids. Two colubrid species (Elaphe quadrivirgata and Symphimus mayae) were also reported to exhibit significant dimorphisms in shape of the head (i.e., females had relatively larger heads in both cases) without a corresponding shift in intersexual diet (Table 1). Previous authors have suggested that the evolution of larger heads in female snakes, in the absence of a dietary dimorphism, may be the result of either hormonal effects (i.e., male growth is inhibited by higher levels of circulating testosterone) (Cox and John-Alder 2005) or possibly sexual selection (i.e., males selecting females with relatively larger heads) (Rivas and Burghardt 2001; Luiselli et al. 2002). We suggest that hormones are not likely to play a major role in producing the relatively larger heads of females in these two colubrids because the males of one species (E. quadrivirgata) were both larger than conspecific females and grew faster (Mori and Hasegawa 2002), and the sexes of the other species (S. mayae) did not differ in maximum body size. By the simple process of elimination, then, it would appear that the males of these two colubrids may actually be choosing to breed with females with relatively larger heads, although any empirical data that would test this hypothesis are currently lacking [but see Rivas and Burghardt (2001) for a theoretical argument]. Even so, previous authors have cast serious doubt on the possibility that male snakes may choose to breed with females with relatively larger heads on the grounds that most snakes employ chemical and not visual cues during mate recognition (Shine 1991). Hence, the female-biased dimorphisms in head shape in these two colubrids clearly warrants further investigation to resolve this apparent paradox.
Despite the fact that numerous studies have now tested the ecological hypothesis in relation to dimorphism in snakes, we were only able to find eight taxa that met all five of our criteria for rigorously testing it (Table 1). Surprisingly, six of these eight species were either highly aquatic or semi-aquatic, with most species being only distantly related to one another (i.e., acrochordid filesnakes, natricine colubrids, and laticaudid sea kraits). Furthermore, all of these aquatic species show clear functional links amongst divergence in body size, head shape, feeding behavior, realized diet, and prey selection. Within these taxa, females tend to be substantially larger in body size, have relatively longer and wider heads, consume and prefer larger prey, and forage in deeper water than do conspecific males (Table 1). For example, females of the highly aquatic Arafurae filesnake (Acrochordus arafurae) are nearly twice as large as conspecific males in body size (max female SVL = 170 cm; max male SVL = 105) (Camilleri and Shine 1990) and have significantly longer jaws and quadrates relative to skull length (Camilleri and Shine 1990). Coupled with this morphological divergence, females ambush large fishes in deep water, whereas males actively search for smaller fishes in shallow water (Shine and Lambeck 1985; Houston and Shine 1993). Laboratory-based studies further showed that this sex-based divergence in foraging mode of filesnakes is directly linked to the sensory modalities used in the detection of prey (Vincent et al. 2005). Specifically, actively foraging males respond most intensely to long-lasting chemical cues (fish scent, regardless of movement) whereas ambush females see ambush and respond most strongly to movement (Table 1). The highly similar patterns reported for other distantly related taxa strongly suggest that adaptive ecological dimorphisms have evolved in a convergent manner amongst aquatic snakes in general (Shetty and Shine 2002; Shine et al. 2002; Shine and Wall 2004).
By contrast, we only found two terrestrial snake species that met all five of our criteria, even though several terrestrial taxa do show clear functional links among divergence in head shape, feeding behavior, and realized diet (Table 1). Further, these two taxa present a mixed picture for the adaptive nature of intersexual divergence in terrestrial snakes. Specifically, Pearson et al. (2002, 2003) showed that terrestrial carpet pythons (Morelia spilota imbricata) from tropical Australia exhibit marked geographic variation in intersexual divergence in body size, head shape, and realized diet, depending on local availability of prey. Overall, females tended to have larger body sizes, wider and longer heads, and consumed much larger mammalian prey whereas the smaller males primarily consumed lizards. Presumably in compensation for taking smaller prey, males in most populations subsequently spent significantly more time foraging than did females. The only other terrestrial snake species meeting all our criteria (E. quadrivirgata) did not support the ecological hypothesis (see earlier text). Hence, unlike aquatic snakes in which adaptive ecological dimorphisms have clearly evolved several times independently, the evidence for terrestrial snakes is less clear-cut.
In summary, our review led to three general conclusions for snakes. (1) Intersexual dietary divergence only evolves within snakes when one sex forages on a relatively large prey item (e.g., birds, mammals, large fish) compared with the size of the predator and never within species that consume relatively small prey (invertebrates, small frogs, lizards), even when SSD is already present within a species (e.g., terrestrial elapids) (Table 1). Maximum ingestible size of prey, therefore, appears to be the main axis of ecological differentiation between the sexes in snakes, and this general pattern holds across all five families examined here. (2) Dimorphisms in shape of the head are commonly linked to intersexual dietary divergence across macrostomatans, with the remaining cases being attributable primarily to sexual selection. Moreover, we did not find any clear-cut cases supporting the hypothesis that hormones alone can drive dimorphisms in head shape in snakes as was previously believed (also see Krause et al. 2003; Krause and Burghardt, in press). (3) Although numerous studies have reported dimorphisms in diet and head shape in snakes (Table 1), only a few studies have examined either sex-based foraging behavior or sex-based selection of prey in these animals. Finally, the overwhelming majority of studies that have addressed these two issues have been performed on aquatic snake taxa, making it difficult to compare patterns of sex-based ecological divergence between aquatic and terrestrial species in a robust manner.
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Intersexual dietary divergence in lizards |
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SynopsisIntroductionIntersexual dietary divergence...Empirical examples from snakesIntersexual dietary divergence...Empirical examples from lizardsAcknowledgmentsReferences |
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For lizards that mechanically reduce their prey (Reilly et al. 2001
), the selective drive causing dimorphisms in diet is often more difficult to determine than it is for snakes. Not only can head size, performance and dietary dimorphisms be the result of a dimorphism in body size, which in turn is likely under both natural and sexual selection, but even in the absence of dimorphism in body size the dietary dimorphism could still be an epiphenomenon of sexual selection on bite force in males. Although differences in bite force have been shown to be correlated with differences in handling times and size and hardness of prey (Verwaijen et al. 2002; Herrel et al. 2006), bite force has also been shown to be important in male dominance (e.g., Lailvaux et al. 2004; Huyghe et al. 2005). Thus, even if one of the sexes has a bigger head, shows higher bite forces and eats larger prey this does not imply per se that natural selection is the driving agent for the observed dimorphism. Sexual selection leading to differences in head size and bite force between the sexes because of its importance in male combat, for example, could secondarily result in differences in diet between the sexes. Thus, for lizards that mechanically reduce their prey, we predict that the degree of dilmorphism in head size should be positively correlated with the degree of dimorphism in bite force, which should in turn be correlated with the dimorphism in aspects of size or hardness of prey if natural selection for resource partitioning is to be a likely candidate for the observed dimorphism. In essence, in species with large differences in head size between the sexes males and females should differ greatly in bite force and should take greatly different sizes of prey. If sexual selection is driving the dimorphism in head size, we would also expect a correlation between the degree of dimorphism in head size and the degree of dimorphism in bite force, but not necessarily with degree of dimorphism in prey size. In essence, species with large differences in head size should also have differences in bite force and although not necessarily showing great differences in prey size between the sexes, such may occur.
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Empirical examples from lizards |
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SynopsisIntroductionIntersexual dietary divergence...Empirical examples from snakesIntersexual dietary divergence...Empirical examples from lizardsAcknowledgmentsReferences |
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A nonexhaustive literature search resulted in data on size of the body and/or head for 140 species of lizards belonging to 13 families and 49 genera (Table 2). Of these, only 24 were not dimorphic in body size suggesting that body size dimorphism is a common phenomenon in lizards. Of these remaining species, only 21 showed female-biased dimorphism in body size. Data on head size were available for 99 species, only six of which were not dimorphic in head size. Interestingly, only in three species (Gambelia wisizenii, G. copei and Draco melanopogon) (Lappin and Swinney 1999
; Shine et al. 1998c) was a female-biased dimorphism in head size observed. Thus, not only is dimorphism in size of the head common in lizards, it is generally male-biased. Interestingly, for those species for which data were available, the dimorphism in bite-force mimicked that of head size in all cases. This is not entirely surprising as head size has been demonstrated to be a good predictor of bite force in lizards (e.g., Herrel et al. 1999, 2001a, 2001b) and other vertebrates (Herrel et al. 2005; Herrel and Gibb, 2006). Given that dimorphism in size of the head in lizards is typically male-biased and that it appears to result in a dimorphism in bite force which is important during male–male interactions (Lailvaux et al. 2004; Huyghe et al. 2005), sexual selection is likely the main selective force driving dimorphism in head size in most cases.
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Information on prey size for the two sexes was available for only 33 species. In 21 of these, males consumed larger prey than did females; in seven species both sexes consumed prey of similar size; and only in five species did females eat larger prey than did males. Although this data set is rather limited, it does suggest that head size dimorphisms are translated into differences in prey size between the sexes in lizards. Even so, the role of natural selection in maintaining or driving these prey-size dimorphisms is presently unclear due to the prominent role of sexual selection in driving the dimorphisms of head size in the first place.
In conclusion, this brief review suggests that in lizards dimorphism in head size is common and associated with dimorphism in bite force, with the larger-headed gender biting harder. Although the larger-headed gender also consumes larger prey in most cases, these data cannot address whether niche divergence drives the observed dimorphisms in head size and bite force. The most likely scenario at present is one in which sexual selection leading to larger heads in one sex resulted in a dimorphism in bite force. Secondarily, this may have resulted in differences in the size of prey eaten by both sexes in many species of lizards. Clearly, more quantitative data on head size, bite force, and dimorphism in diet are needed to test these hypotheses in a rigorous manner. Moreover, the causal relationship between bite force and diet needs to be examined in more detail for both sexes by investigating its effect on handling time and the cost of capture and transport of prey. A single study in which handling times were examined for two species of lacertid lizards suggested that the dimorphism in bite force resulted in faster processing of prey in the sex with the larger bite force (Verwaijen et al. 2002), suggesting this approach to be a fruitful avenue for further research.
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Acknowledgments |
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SynopsisIntroductionIntersexual dietary divergence...Empirical examples from snakesIntersexual dietary divergence...Empirical examples from lizardsAcknowledgmentsReferences |
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This manuscript was generously supported by the Divisions of Animal Behavior, Ecology and Evolution, and Vertebrate Morphology. AH is a postdoctoral fellow of the Fund for Scientific Research Flanders, Belgium (FWO-Vl).
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Footnotes |
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From the symposium "Ecological Dimorphisms in Vertebrates: Proximate and Ultimate Causes" presented at the annual meeting of the Society for Integration and Comparative Biology, January 3–7, 2007, at Phoenix, Arizona.
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References |
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|---|
Abell AJ. Phenotypic correlates of male survivorship and reproductive success in the striped plateau lizard, Sceloporus virgatus. Herpetol J (1998) 8::173–80.
Agrimi U, Luiselli L. Feeding strategies of the viper Vipera ursinii ursinii (Reptilia: Viperidae) in the appennines. Herpetol J (1992) 2::37–42.
Anderson R, Vitt L. Sexual selection versus alternative causes of sexual dimorphism in teiid lizards. Oecologia (1990) 84::145–57.[Web of Science]
Andrews RM. Structural habitat and time budget of a tropical Anolis lizard. Ecology (1971) 52::262–70.[CrossRef][Web of Science]
Andrews RM. Evolution of life histories: a comparison of Anolis lizards from matched island and mainland habitats. Breviora (1979) 454::1–51.
Arnold SJ. Foraging theory and prey-size-predator-size relations in snakes. In: Snakes: ecology and behavior—Seigel RA, Collins JT, eds. (1993) New York: McGraw-Hill. 87–115.
Baird TA, Vitt LJ, Baird TD, Cooper Jr WE, Caldwell JP, Pérez-Mellado V. Social behavior and sexual dimorphism in the Bonaire whiptail, Cnemidophorus murinus (Squamata: Teiidae): the role of sexual selection. Can J Zool (2003) 81::1781–90.
Brana F. Sexual dimorphism in lacertid lizards: male head increase vs. female abdomen increase? Oikos (1996) 66::216–22.[CrossRef]
Butler MA, Losos JB. Multivariate sexual dimorphism, sexual selection, and adaptation in Greater Antillean Anolis lizards. Ecol Mono (2002) 72::541–59.[CrossRef][Web of Science]
Camilleri C, Shine R. Sexual dimorphism and dietary divergence: differences in trophic morphology between male and female snakes. Copeia (1990) 3::649–58.
Carothers JH. Sexual selection and sexual dimorphism in some herbivorous lizards. Am Nat (1984) 124::244–54.[CrossRef][Web of Science]
Censky EJ. The evolution of sexual size dimorphism in the teiid lizard Ameiva plei: a test of alternative hypotheses. In: Powell R, Henderson RW, editors. In: Contributions to West Indian Herpetology: a tribute to Albert Schwartz (1996) New York: Ithaca. SSAR Contr. Herpetol. 12:277–89.
Clemann N, Chapple DG, Wainer J. Sexual dimorphism, diet and reproduction in the swamp skink, Egernia coventryi. J Herp (2004) 38::461–7.[CrossRef]
Cooper Jr WE, Vitt LJ. Sexual dimorphism of head and body size in the iguanid lizard Sceloporus undulatus: paradoxical results. Am Nat (1989) 133::729–35.[CrossRef][Web of Science]
Cordes IG, Mouton P, Le FN, van Wyk JH. Sexual dimorphism in two girdled lizard species, Cordylus niger and Cordylus cordylus. S Afr J Zool (1995) 30::187–96.
Cox RM, John-Alder HB. Testosterone has opposite effects on male growth in lizards (Sceloporus spp.) with opposite patterns of sexual size dimorphism. J Exp Biol (2005) 208::4679–87.
Cox RM, Zilberman V, John-Alder HB. Environmental sensitivity of sexual size dimorphism: laboratory common garden removes effects of sex and castration on lizard growth. Funct Ecol (2006) 20::880–8.[CrossRef]
Crews D, Diamond M, Whittier MJ, Mason R. Small male body size in garter snakes depends on testes. Am J Physiol (1985) 249::R62–6.[Web of Science][Medline]
Cullum AJ. Sexual dimorphism in physiological performance of whiptail lizards (genus Cnemidophorus). Physiol Zool (1998) 71::541–52.[Medline]
Cundall D, Greene HW. Feeding in snakes. In: Schwenk K, editor. In: Feeding: form, function and evolution in Tetrapod vertebrates (2000) London: Academic Press. 293–333.
Darwin C. The descent of man and selection in relation to sex (1871) London: J. Murray.
Dearing MD, Schall JJ. Atypical reproduction and sexual dimorphism of the Bonaire island whiptail lizard, Cnemidophorus murinus. Copeia (1994) 3::760–6.
Filippi E, Rugiero L, Capula M, Capizzi D, Luiselli L. Comparative food habits and body size of five populations of Elaphe quatuorlineata: the effects of habitat variation, and the consequences of intersexual body size dimorphism on diet divergence. Copeia (2005) 2005::517–25.[CrossRef]
Fitch HS. Resources of a snake community in prairie -woodland habitat of northeastern Kansas. In: Scott NJ, editor. In: Herpetological communities (1982) Wildl Res Rep 13:83–98. Washington, D.C.: U.S. Department of the Interior Fish and Wildlife Service.
Fleming TH, Hooker RS. Anolis cupreus: the reponse of a lizard to tropical seasonality. Ecology (1975) 56::1243–61.[CrossRef][Web of Science]
Forsman A, Lindell LE. The advantage of a big head: swallowing performance in adders, Vipera berus. Funct Ecol (1993) 7::183–9.[CrossRef]
Gregory PT. Sexual dimorphism and allometric size variation in a population of grass snakes (Natrix natrix) in Southern England. J Herp (2004) 38::231–40.[CrossRef]
Griffith H. Heterochrony and evolution of sexual dimorphism in the fasciatus group of the Scincid genus. Eumeces. J Herp (1991) 25::24–30.[CrossRef]
Gvozdik L, Boukal M. Sexual dimorphism and intersexual food niche overlap in the sand lizard, Lacerta agilis (1998) 47::189–95. Folia Zoologica.
Gvozdik L, Van Damme R. Evolutionary maintenance of sexual dimorphism in head size in the lizard Zootoca vivipara: a test of two hypotheses. J Zool Lond (2003) 259::7–13.
Heatwole H, Busack S, Cogger H. Geographic variation in sea kraits of the Laticauda colubrina complex (Serpentes:Elapidae: Hydrophiinae: Laticaudini.). Herpetological Monographs (2005) 19::1–136.[CrossRef]
Herrel A, Van Damme R, De Vree F. Sexual dimorphism of head size in Podarcis hispanica atrata: testing the dietary divergence hypothesis by bite force analysis. Neth J Zool (1996) 46::253–62.
Herrel A, Spithoven L, Van Damme R, De Vree F. Sexual dimorphism of head size in Gallotia galloti; testing the niche divergence hypothesis by functional analyses. Funct Ecol (1999) 13::289–97.[CrossRef]
Herrel A, De Grauw E, Lemos-Espinal JA. Head shape and bite performance in xenosaurid lizards. J Exp Zool (2001a) 290::101–7.[CrossRef][Web of Science][Medline]
Herrel A, Van Damme R, Vanhooydonck B, De Vree F. The implications of bite performance for diet in two species of lacertid lizards. Can J Zool (2001b) 79::662–70.
Herrel A, Vanhooydonck B, Joachim R, Irschick DJ. Frugivory in polychrotid lizards: effects of body size. Oecologia (2004a) 140::160–8.[CrossRef][Web of Science][Medline]
Herrel A, Vanhooydonck B, Van Damme R. Omnivory in lacertid lizards: adaptive evolution or constraint? J Evol Biol (2004b) 17::974–84.[CrossRef][Web of Science][Medline]
Herrel A, Van Wassenbergh S, Wouters S, Aerts P, Adriaens D. A functional morphological approach to the scaling of the feeding system in the African catfish, Clarias gariepinus. J Exp Biol (2005) 208::2091–102.
Herrel A, Gibb AC. Ontogeny of performance in vertebrates. Physiol Biochem Zool (2006) 79::1–6.[CrossRef][Web of Science][Medline]
Herrel A, Joachim R, Vanhooydonck B, Irschick DJ. Ecological consequences of ontogenetic changes in head shape and bite performance in the Jamaican lizard Anolis lineatopus. Biol J Linn Soc (2006) 89::443–54.[CrossRef][Web of Science]
Hews DK. Size and allometry of sexually-selected traits in the lizard Uta palmeri. J Zool Lond (1996) 238::743–57.
Hibbitts TJ, Pianka ER, Huey RB, Whiting MJ. Ecology of the common barking gecko (Ptenopus garrulus) in southern Africa. J Herp (2005) 39::509–15.[CrossRef]
Houston D, Shine R. Sexual dimorphism and niche divergence: feeding habits of the Arafura file snake. J Anim Ecol (1993) 62::737–48.
Huang WS. Sexual size dimorphism in the five-striped blue-tailed skink, Eumeces elegans, with notes on the life history in Taiwan. Zool Stud (1996) 35::188–164.
Huyghe K, Vanhooydonck B, Scheers H, Molina-Borja M, Van Damme R. Morphology, performance and fighting capacity in male lizards, Gallotia galloti. Funct Ecol (2005) 19::800–7.[CrossRef]
Johnson BJ, McBrayer LD, Saenz D. Allometry, sexual size dimorphism, and niche partitioning in the Mediterranean gecko (Hemidactylus turcicus). Southwest Nat (2005) 50::435–9.[CrossRef]
King RB. Population ecology of the Lake Erie water snake, Nerodia sipedon insularium. Copeia (1986) 1986::757–72.[CrossRef]
King RB. Microgeographic, historical, and size-correlated variation in water snake diet composition. J Herp (1993) 27::90–4.[CrossRef]
Krause MA, Burghardt GM. Sexual dimorphism of body and relative head sizes in neonatal common garter snakes (Thamnophis sirtalis). J Zool. in press.
Krause MA, Burghardt GM, Gillingham JC. in press. Body size plasticity and local variation of relative sexual size dimorphism in garter snakes (Thamnophis sirtalis). J Zool (2003) 261::399–407.[CrossRef][Web of Science]
Lailvaux SP, Vincent SE. Ecological dimorphism: an introduction to the symposium. Int Comp Biol (2007) doi: 10.1093/icb/icm003.
Lailvaux SP, Alexander GJ, Whiting MJ. Sex-based differences and similarities in locomotor performance, thermal preferences and escape behaviour in the lizard Platysaurus intermedius wilhelmi. Physiol Biochem Zool (2003) 76::511–21.[CrossRef][Web of Science][Medline]
Lailvaux SP, Herrel A, Vanhooydonck B, Meyers JJ, Irschick DJ. Performance capacity, fighting tactics, and the evolution of life-stage male morphs in the green anole lizard (Anolis carolinensis). Proc Roy Soc Lond B: Biol Sci (2004) 271::2501–8.[Medline]
Lappin AK, Swinney EJ. Sexual dimorphism as it relates to the natural history of leopard lizards (Crotaphytidae: Gambelia). Copeia (1999) 1999::649–60.[CrossRef]
Lappin AK, Hamilton PS, Sullivan BK. Bite-force performance and head shape in a sexually dimorphic crevice-dwelling lizard, the common chuckwalla [Sauromalus ater (= obesus)]. Biol J Linn Soc (2006) 88::215–22.[CrossRef][Web of Science]
Lemos-Espinal JA, Smith GR, Ballinger RE. Natural history of the Mexican knob-scaled lizard, Xenosaurus rectocollaris. Herpetol. Nat Hist (1996) 4::151–4.
Lemos-Espinal JA, Smith GR, Ballinger RE. Sexual dimorphism and body temperatures of Sceloporus siniferus from Guerrero, Mexico. Western North Am Nat (2001) 61::498–500.
Lemos-Espinal JA, Smith GR, Ballinger RE. Body temperature and sexual dimorphism of Sceloporus aeneus and Sceloporus palaciosi from Mexico. Amphibia-Reptilia (2002) 23::114–9.
Lerner DT, Mason RT. The influence of sex steroids in the sexual size dimorphism in the red-spotted garter snake, Thamnophis sirtalis concinnus. Gen Comp Endocr (2001) 124::218–25.[CrossRef][Medline]
Luiselli L, Angelici FM. Sexual size dimorphism and natural history traits are correlated with intersexual dietary divergence in royal pythons (Python regius) from the rainforests of southeastern Nigeria. Ital J Zool (1998) 65::183–5.
Luiselli L, Capula M, Shine R. Reproductive output, costs of reproduction, and ecology of the smooth snake, Coronella austriaca, in the eastern Italian Alps. Oecologia (1996) 106::100–10.[Web of Science]
Luiselli L, Akani GC, Corti C, Angelici FM. Is sexual size dimorphism in relative head size correlated with intersexual dietary divergence in West African forest cobras, Naja melanoleuca? Contrib Zool (2002) 71::141–5.
Marques OAV, Sawaya RJ, Stender-Oliveira F, Franca FGR. Ecology of the colubrid snake Pseudablabes agassizii in south-eastern South America. Herpetol J (2006) 16::37–45.
McCoy JK, Fox SF, Baird TA. Geographic variation in sexual dimorphism of Crotaphytus collaris. Southwest. Nat (1994) 39::328–35.
Mesquita DO, Colli GR, Costa GC, França FGR, Garda AA, e Péres Jr AK. At the water's edge: the ecology of semi-aquatic teiids in Brazilian Amazon. J Herp (2006) 40::221–9.[CrossRef]
Mori A, Hasegawa M. Early growth of Elaphe quadrivirgata from an insular gigantic population. Curr Herpetol (2002) 21::43–50.
Mouton P, Le FN, van Wyk JH. Sexual dimorphism in cordylid lizards: a case study of the Drakensberg crag lizard, Pseudocordylus melanotus. Can J Zool (1993) 71::1715–23.
Mouton P, Le FN, Flemming AF, Kanga EM. Grouping behaviour, tail-biting behaviour and sexual dimorphism in the armadillo lizard (Cordylus cataphractus) from South Africa. J Zool Lond (1999) 249::1–10.
Mushinsky HR, Hebrard JJ, Vodopich DS. Ontogeny of water snake foraging ecology. Ecology (1982) 63::1624–9.[CrossRef][Web of Science]
Myersterud A. The relationship between ecological segregation and sexual body size dimorphism in large herbivores. Oecologia (2000) 124::40–54.[CrossRef][Web of Science]
Olsson M. Nuptial coloration in the sand lizard (Lacerta agilis): an intrasexually selected cue to fighting ability. Anim Behav (1994) 48::607–13.[CrossRef][Web of Science]
Olsson M, Shine R, Wapstra E, Ujvari B, Madsen T. Sexual dimorphism in lizard body shape: the roles of sexual selection and fecundity selection. Evolution (2002) 56::1538–42.[Web of Science][Medline]
Pearson D, Shine R, How R. Sex-specific niche partitioning and sexual size dimorphism in Australian pythons (Morelia spilota imbricata). Biol J Linn Soc (2002) 77::113–25.[CrossRef][Web of Science]
Pearson D, Shine R, Williams A. Thermal biology of large snakes in cool climates: a radiotelemetric study of carpet pythons (Morelia spilota imbricata) in south-western Australia. J Therm Biol (2003) 28::117–31.[CrossRef][Web of Science]
Perez-Mellado V, de la Riva I. Sexual size dimorphism and ecology: the case of a tropical lizard, Tropidurus melanopleurus (Sauria: Tropiduridae). Copeia (1993) 1993::969–76.[CrossRef]
Pinto ACS, Wiederhecker HC, Colli GR. Sexual dimorphism in the Neotropical lizard, Tropidurus torquatus (Squamata, Torpiduridae). Amphibia-Retilia (2005) 26::127–38.
Plummer MV. Habitat utilization, diet, and movements of a temperate arboreal snake (Opheodrys aestivus). J Herp (1981) 15::425–32.[CrossRef]
Powell GL, Russell AP. The diet of the eastern short-horned lizard (Phrynosoma douglassi brevirostre) in Alberta and its relationship to sexual size dimorphism. Can J Zool (1984) 62::428–40.
Preest MR. Sexual size dimorphism and feeding energetics in the lizard Anolis carolinensis. J Herp (1994) 28::292–8.[CrossRef]
Radcliffe CW, Chiszar DA. A descriptive analysis of predatory behaviour in the yellow lipped sea krait (Laticauda colubrina). J Herpetol (1980) 14::422–4.[CrossRef]
Radder RS, Shangbhag BA, Saidapur SK. Ontogeny of sexual dimorphism in the tropical garden lizard, Calotes versicolor (Daud.). J Herpetol (2001) 35::156–60.[CrossRef]
Ralls K. Mammals in which females are larger than males. Quart Rev Biol (1976) 51::245–76.[CrossRef][Medline]
Reaney LT, Whiting MJ. Life on a limb: ecology of the tree agama (Acanthocercus a. atricollis) in southern Africa. J Zool (2002) 257::439–48.[CrossRef][Web of Science]
Reilly SM, McBrayer LD, White TD. Prey processing in amniotes: biomechanical and behavioral patterns of food reduction. Comp Biochem Physiol A. (2001) 128::397–415.[CrossRef][Medline]
Rivas JA, Burghardt GM. Sexual size dimorphism in snakes: wearing the snake's shoes. Anim Behav (2001) 62::F1–6.[CrossRef]
Rocha CFD. Sexual dimorphism in the sand lizard Liolaemus lutzae of southeastern Brazil. In: Pefaur JE, editor. In: Herpetologia neotropical (1996) 2:. Mérida: Universidad de los Andes: Conselho de Publicaciones. 131–140.
Rocha CFD. Home range of the tropidurid lizard Liolaemus lutzae: sexual and body size differences. Revista Brasileira de Biologia (1999) 59::125–30.
Saenz D, Conner RN. Sexual Dimorphism in head size of the Mediterranean gecko Hemidactylus turcicus (Sauria: Gekkonidae). Texas J Sci (1996) 48::207–12.
Santos X, Llorente GA. Sexual and size-related differences in the diet of the snake Natrix maura from the Ebro Delta, Spain. Herpetol J (1998) 8::161–5.
Santos X, Gonzalez-Solis J, Llorente GA. Variation in the diet of the viperine snake Natrix maura in relation to prey availability. Ecography (2000) 23::185–92.
Savidge JA. Food habits of Boiga irregularis, an introduced predator on Guam. J Herp (1988) 22::275–82.[CrossRef]
Schoener TW. The ecological significance of sexual dimorphism in size in the lizard Anolis conspersus. Science (1967) 155::474–7.
Schoener TW. The Anolis lizards of Bimini: resource partitioning in a complex fauna. Ecology (1968) 49::704–26.[CrossRef][Web of Science]
Schoener TW, Gorman GC. Some niche differences in three lesser Antillean lizards of the genus Anolis. Ecology (1968) 49::819–30.[CrossRef][Web of Science]
Schoener TW, Slade JB, Stinson CH. Diet and sexual dimorphism in the very catholic lizard genus Leiocephalus of the Bahamas. Oecologia (1982) 53::160–9.[CrossRef][Web of Science]
Seib RL. Size and shape in a neotropical burrowing colubrid snake, Geophis nasalis, and its prey. Am Zool (1981) 21::933.
Selander A. Sexual selection and dimorphism in birds. In: Campbell B, editor. In: Sexual selection and the descent of man (1972) Chicago: Aldine Publishing Company. 1871–971.
Shetty S, Shine R. Sexual divergence in diets and morphology in Fijian sea snakes, Laticauda colubrina (Laticaudidae). Aust Ecol (2002) 27::77–84.[CrossRef]
Shewchuk CH, Austin JD. Food habits of the racer (Coluber constrictor mormon) in the northern part of its range. Herp J (2001) 11::151–5.
Shine R. Activity patterns in Australian elapid snakes. (Squamata: Serpentes: Elapidae). Herpetologica (1979) 35::1–11.[Web of Science]
Shine R. Ecological causes for the evolution of sexual dimorphism: a review of the evidence. Quart Rev Biol (1989) 64::419–61.[CrossRef][Medline]
Shine R. Intersexual dietary divergence and the evolution of sexual dimorphism in snakes. Am Nat (1991) 138::103–22.[CrossRef][Web of Science]
Shine R, Lambeck R. A radiotelemetric study of movements, thermoregulation and habitat utilization of Arafura filesnakes (Serpentes, Acrochordidae). Herpetologica (1985) 41::351–61.[Web of Science]
Shine R, Crews D. Why male garter snakes have small heads: the evolution and endocrine control of sexual dimorphism. Evolution (1988) 42::1105–10.[CrossRef][Web of Science]
Shine R, Wall M. Ecological divergence between the sexes in reptiles. In: Sexual segregation in vertebrates—Neuhaus P, Ruckstuhl KE, eds. (2004) Cambridge: Cambridge University Press. 221–53.
Shine R, Branch WR, Harlow PS, Webb JK. Sexual dimorphism, reproductive biology and food habits of two species of African filesnakes (Mehelya, Colubridae). J Zool Lond (1996a) 240::327–40.
Shine R, Harlow PS, Branch WR, Webb JK. Life on the lowest branch: sexual dimorphism, diet and reproductive biology of an African twig snake, Thelotornis capensis (Serpentes, Colubridae). Copeia (1996b) 1996::290–9.[CrossRef]
Shine R, Haagner GV, Branch WR, Harlow PS, Webb JK. Natural history of the African shieldnose snake Aspidelaps scutatus (Serpentes, Elapidae). J Herp (1996c) 30::361–6.[CrossRef]
Shine R, Branch WR, Harlow PS, Webb JK. Reproductive biology and food habits of horned adders, Bitis caudalis (Viperidae) from southern Africa. Copeia (1998a) 1998::391–401.[CrossRef]
Shine R, Harlow PS, Keogh JS, Boeadi. The influence of sex and body size on food habits of a tropical snake, Python reticulatus. 12::248–58. Funct Ecol.
Shine R, Mumpuni Ambariyanto. Ecological traits of commercially harvested water monitors, Varanus salvator (1998c) 25::437–47. in northern Sumatra. Wildl Res.
Shine R, Keogh JS, Doughty P, Giragossyan H. Costs of reproduction and the evolution of sexual dimorphism in a "flying lizard" (Draco melanopogon, Agamidae). J Zool Lond (1998d) 246::203–13.
Shine R, Reed RN, Shetty S, Cogger HG. Relationships between sexual dimorphism and niche partitioning within a clade of sea snakes (Laticaudinae). Oecologia (2002) 133::45–53.[CrossRef][Web of Science]
Shine R, Branch WR, Webb JK, Harlow PS, Shine T, Keogh JS. in press. Ecology of cobras from Southern Africa. J Zool Lond.
Slatkin M. Ecological causes of sexual dimorphism. Evolution (1984) 38::622–30.[CrossRef][Web of Science]
Smith GR, Lemos-Espinal JA, Ballinger RE. Sexual dimorphism in two species of knob-scaled lizards (genus Xenosaurus) from Mexico. Herpetologica (1997) 53::200–5.[Web of Science]
Snell HL, Jennings RD, Snell HM, Harcourt S. Intrapopulation variation in predator-avoidance performance of Galápagos lava lizards: the interaction of sexual and natural selection. Evol Ecol (1988) 2::353–69.[CrossRef]
Spencer NJ, Thomas BW, Mason RF, Dugdale JS. Diet and life history variation in the sympatric lizards Oligosoma nigriplantare polychroma and Oligosoma lineoocellatum. New Zeal J Zool (1998) 25::457–64.
Stafford PJ. Diet and reproductive ecology of the Yucatan cricket-eating snake Symphimus mayae (Colubridae). J Zool Lond (2005) 265::301–10.
Stamps JA. Relationships between female density and sexual size dimorphism in samples of Anolis sagrei. Copeia (1999) 1999::760–5.[CrossRef]
Stamps JA, Losos JB, Andrews RM. A comparative study of population density and sexual size dimorphism in lizards. Am Nat (1997) 149::64–90.[CrossRef][Web of Science]
Sugg DW, Fitzgerald LA, Snell HL. Growth rate, timing of reproduction, and size dimorphism in the Southwestern earless lizard (Cophosaurus texanus scitulus). Southwest. Nat (1995) 40::193–202.
Tanaka K, Mori A, Hasegawa M. Apparent decoupling of prey recognition ability with prey availability in an insular snake population. J Ethol (2001) 19::27–32.[CrossRef]
Taylor EN, DeNardo DF. Sexual size dimorphism and growth plasticity: an experiment on the western diamondbacked rattlesnake (Crotalus atrox). J Exp Zool (2005) 303A::598–607.
Teixeira-Filho PF, Rocha CFD, Ribas SC. Feeding specialization may depress ontogenetic, seasonal and sexual variations in diet: the endemic lizard Cnemidophorus littoralis (Teiidae). Brazil J Biol (2003) 63::321–8.
Temeles EJ, Pan IL, Brennan JL, Horwitt JN. Evidence for ecological causation of sexual dimorphism in a hummingbird. Science (2000) 289::441–3.
Tollestrup K. Growth and reproduction in two closely related species of leopard lizards, Gambelia silus and Gambelia wislizenii. Am Midl Nat (1983) 108::1–20.[CrossRef]
Vanhooydonck B, Herrel A, Meyers JJ, Van Damme R, Irschick DJ. The relationship between dewlap size and performance changes with age and sex in an A. carolinensis lizard population. Behav Ecol Sociobiol (2005) 59::157–65.[CrossRef][Web of Science]
Van-Sluys M. Food habits of the lizard Tropidurus itambere (Tropiduridae) in Southeastern Brazil. J Herp (1993) 27::347–351.[CrossRef]
Verrastro L. Sexual dimorphism in Liolaemus occipitalis (Iguania, Tropiduridae). Iheringia, Porto Alegre (2004) 94::45–48.
Verwaijen D, Van Damme R, Herrel A. Relationships between head size, bite force, prey handling efficiency and diet in two sympatric lacertid lizards. Funct Ecol (2002) 16::842–50.[CrossRef]
Vidal M, Ortiz JC, Labra A. Sexual and age differences in ecological variables of the lizard Microlophus atacamensis (Tropiduridae) from northern Chile. Revista Chilena de Historia Naturall SI (2002) 75::283–92.
Vincent SE. Sex-based divergence in head shape and diet in the Eastern Lubber grasshopper (Romalea microptera). Zoology (2006) 109::331–8.[CrossRef][Web of Science][Medline]
Vincent SE, Herrel A, Irschick DJ. Sexual dimorphism in head shape and diet in the cottonmouth snake (Agkistrodon piscivorus). J Zool Lond (2004a) 264::53–9.
Vincent SE, Herrel A, Irschick DJ. Ontogeny of intersexual head shape and prey selection in the pitviper Agkistrodon piscivorus. Biol J Linn Soc (2004b) 81::151–9.[CrossRef][Web of Science]
Vincent SE, Shine R, Brown GP. Does foraging mode influence sensory modalites for prey detection? A comparison between males and female filesnakes (Acrochordus arafurae, Acrochordidae). Anim Behav (2005) 70::715–21.[CrossRef][Web of Science]
Vitt LJ, Lacher Jr TE. Behavior, habitat, diet, and reproduction of the iguanid lizard Polychrus acutirostris in the caatinga of northeastern Brazil. Herpetologica (1981) 37::53–63.
Vogrin M. Sexual dimorphism in Podarcis sicula campestris. Turk J Zool (2005) 29::189–91.
Watkins GG. Proximate causes of sexual size dimorphism in the iguanian lizard Microlophus occipitalis. Ecology (1996) 77::1473–82.[CrossRef][Web of Science]
Wikelski M, Trillmich F. Body size and sexual size dimorphism in marine iguanas fluctuate as a result of opposing natural and sexual selection: an island comparison. Evolution (1997) 51::922–36.[CrossRef][Web of Science]
van Wyk JH. Life history and physiological ecology of the lizard. In: Cordylus giganteus (1992) Unpubl. Ph.D. diss. Univ. Cape Town, South Africa.
Zamudio KR. The evolution of female-biased sexual size dimorphism: a population-level comparative study in horned lizards (Phrynosoma). Evolution (1998) 52::1821–33.[CrossRef][Web of Science]
Zinner H. On behavioral and sexual dimorphism of Telescopus dhara Forscal 1776 (Reptilia: Serpentes, Colubridae). J Herpetol. Assoc Africa (1985) 31::5–6.
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