Sexual dimorphism of tail length in lacertid lizards: test of a morphological constraint hypothesis

Abstract

With 2 figures in the text)Males of many lizard species have longer tails than similarly-sized females. We hypothesized that this dimorphism is induced by a longer non-autotomous tail part in males, which is associated with the presence of the copulatory organs at the tail base, and presumably reduces the males' ability to escape predation by tail shedding. A compensatory mechanism would be an increase of total tail length in males, to achieve equal lengths of the autotomous tail part in both sexes. A critical prediction of this 'morphological constraint' hypothesis is that the extent of dimorphism in total tail length increases with the magnitude of sexual differences in length of the non-autotomous tail base. We tested this prediction through a comparative study in a small clade of lacertid lizards. Within each of nine species, sexual differences in length of the non-autotomoos tail base and in total tail length do not change with body size. All species, except one, exhibit a clear male-biased dimorphism in length of the non-breakable tail base. In all species studied, males have longer tails than females. We used the method of phylogenetically independent contrasts to explore the interspecific relation between dimorphism in length of the tail base and sexual differences in total tail length. Contrary to our prediction, we found no evidence for a positive correlation between the extent of dimorphism in both traits. Thus, constraints imposed by the male copulatory organs on tail autotomy do not seem to be a significant factor in the evolution of dimorphism in tail length in this clade of lacertid lizards.

The movement dynamics of autotomized lizards and their tails reveal functional costs of caudal autotomy

“…Two-way ANCOVA was done for distance moved by the tail, with time of tail movement as the covariate and tail condition and sex as the factors. Due to the presence of the hemipenes at the base of the tail, males have greater robustness and some morphological specializations in that region; for example, the first complete fracture plane occurs in the 6th-7th vertebra in males, while in females occurs in the 5th-6th vertebra (Barbadillo et al 1995;Barbadillo & Bauwens 1997). For these reasons, we tested for possible differences between males and females in the performance of the detached tails, including sex as factor in the previous two-way ANOVAs and ANCOVAs.…”

Head shape allometry and proximate causes of head sexual dimorphism in Podarcis lizards: joining linear and geometric morphometrics

“…Another important aspect to consider is sexual dimorphism of different body parts. Although total size has attracted more attention in sexual dimorphism studies, the relative size and shape of different body parts can be much more informative of the selective pressures posed on each sex (Cooper & Vitt, 1989; Braña, 1996; Hews, 1996; Barbadillo & Bawens, 1997; Butler & Losos, 2002; Olsson et al ., 2002; Kratochvil et al ., 2003). Sexual size and shape dimorphism are not necessarily interdependent and different species may exhibit different combinations of the two, being dimorphic in both size and shape (Butler & Losos, 2002; Baird et al ., 2003; Kaliontzopoulou, Carretero & Llorente, 2007), only shape (Carretero & Llorente, 1993; Herrel et al ., 2001b; Schwarzkopf, 2005), or only size (Kratochvil et al ., 2003).…”

Hormonal control of seasonal color change in female spiny-footed lizards: an observational and experimental approach

“…Males tend to be larger than females (Castilla et al. 1992; Carretero and Llorente 1993), particularly in tail length (Barbadillo and Bauwens 1997). This species reaches sexual maturity during their second spring at approximately 57–65 mm SVL (Busack and Jaksić 1982; Bauwens and Díaz-Uriarte 1997).…”