Sexual dimorphism in cordylid lizards: a case study of the Drakensberg crag lizard, Pseudocordylus melanotus

Abstract

1993. Sexual dimorphism in cordylid lizards: a case study of the Drakensberg crag lizard, Pseudocordylus melanotus. Can. J . Zool. 71: 17 15 -1723. In a high-altitude population of the Drakensberg crag lizard, Pseudocordylus melanotus, most adult males, unlike adult females, are brightly coloured, and they are larger in body size and have relatively larger heads than females. Three basic colour phases can be distinguished among the brightly coloured adult males. No apparent differences in reproductive activity, number and differentiation state of the generation glands and femoral pores, or scar frequency were noted among the three colour phases. In males the development of bright colours and the differentiation of the epidermal glands coincide with the onset of sexual maturity. Sexual dimorphism in head size of adults is due to a decrease in female head size relative to juvenile head size as well as an increase in relative head size of males. Preliminary data indicate a social structure of territorial polygyny in P. melanotus and suggest that the dimorphism can partly be ascribed to sexual selection. There are also, however, indications of altitudinal variation in the expression of sexual dimorphism, which may be explained in terms of differential energy allocation by females at different altitudes. MOUTON, P. LE EN., et VAN WYK, J.H. 1993. Sexual dimorphism in cordylid lizards: a case study of the Drakensberg crag lizard, Pseudocordylus melanotus. Can. J . Zool. 71 : 17 15 -1723. Chez une population de haute altitude du lezard Pseudocordylus melanotus, la plupart des miles adultes, contrairement aux femelles, sont trks colores et ils sont aussi plus gros et ont la ttte relativement plus grosse. I1 existe trois types de coloration chez les miles adultes trks colores, mais il ne semble pas y avoir de differences entre ces trois types quant B l'activite reproductrice, quant au nombre ou au stade de differenciation des glandes genitales ou des pores femoraux, ou quant B la frkquence des cicatrices. Chez les mQles, l'apparition des couleurs vives et la differenciation des glandes Cpidermiques coincide avec l'avknement de la maturite sexuelle. Le dimorphisme sexuel de la taille de la tCte chez les adultes est attribuable B la fois B une reduction de la taille de la tCte chez les femelles comparativement B celle des juveniles et B une augmentation de la taille relative de la tCte chez les miles. D'aprks des donnees preliminaires, il semble que la structure sociale de P. melanotus soit basee sur la polygynie territoriale et que le dimorphisme soit attribuable en partie B la selection sexuelle. Cependant, il existe aussi des indices d'un gradient altitudinal dans l'expression du dimorphisme sexuel qui peut peut-etre s'expliquer par une variation dans la repartition de la depense Cnergetique chez les femelles B differentes altitudes.[Traduit par la redaction]

Multivariate and geometric morphometrics in the analysis of sexual dimorphism variation in Podarcis lizards

“…The increase of males' head size in sympatry could be explained if interspecific male-male combats take place or if access to females is restrained because of the presence of a closely related species. Although no behavioral studies are available for the populations in question, a bigger head is known to be advantageous in fights between male lizards (Fitch, 1981;Anderson and Vitt, 1990;Mouton and van Wyk, 1993;Perry et al, 2004) and the pattern observed could be the result of the presence of both conspecific and interspecific rivals when both species coexist. The absence of such morphological modifications in females does not contradict such a hypothesis, because there is no evidence for combats between female lizards, at least in these species (Carretero and Kaliontzopoulou, personal observation).…”

“…Sexual dimorphism (SD) is a common trait in animals, most species being dimorphic rather than monomorphic (Schoener, 1977;Mouton and van Wyk, 1993;Andersson, 1994). Different evolutionary mechanisms have been proposed for the development of sexual dimorphism in various animal taxa.…”

“…In many lacertid lizards, as in other lizard families, males present larger body size and head dimensions (Cooper and Vitt, 1989;Anderson and Vitt, 1990;Mouton and van Wyk, 1993;Andersson, 1994;Brañ a, 1996;Herrel et al, 1996Herrel et al, , 1999Herrel et al, , 2001aKratochvil et al, 2003;Molina-Borja, 2003;Uller and Olsson, 2003), while females have a longer trunk (Andersson, 1994;Brañ a, 1996;Butler and Losos, 2002;Olsson et al, 2002;Schwarzkopf, 2005). Moreover, both head dimensions and trunk length have been shown to present a positive allometric relationship with total size in males and females, respectively, offering indirect support of sex-specific selection for these traits (Carothers, 1984;Brañ a, 1996;Hews, 1996;Olsson et al, 2002;Kratochvil et al, 2003).…”

Body size, male combat and the evolution of sexual dimorphism in eublepharid geckos (Squamata: Eublepharidae)

“…In lizards, heads are typically used as weapons in combats. Taxonomically widespread male-biased head size dimorphism (HSD) therefore probably reflects that head size apparently determines the outcome of direct physical aggressive encounters (Carothers, 1984;Vitt & Cooper, 1985;Vial & Stewart, 1989;Anderson & Vitt, 1990;Hews, 1990;Mouton & Wyk, 1993). Lizards also engage in a number of threat displays without physical combat or risk of injury, such as push-up displays or chemical signals (Martins, 1994).…”

The cryptic significance of melanism in cordylid lizards: A case study ofCordylus nigerandC. polyzonus

“…Sexual dichromatism, where males normally are the more brightly coloured sex, for example, illustrates the selective advantage that bright coloration may confer upon males possessing it in male-male interactions or in mate selection by females (Stamps 1983;Mouton & Van Wyk 1993).…”