Sex-specific evolution of bite performance in Liolaemus lizards (Iguania: Liolaemidae): the battle of the sexes

Abstract

Although differential selective pressures on males and females of the same species may result in sex-specific evolutionary trajectories, comparative studies of adaptive radiations have largely neglected within-species variation. In this study, we explore the potential effects of natural selection, sexual selection, or a combination of both, on bite performance in males and females of 19 species of Liolaemus lizards. More specifically, we study the evolution of bite performance, and compare evolutionary relationships between the variation in head morphology, bite performance, ecological variation and sexual dimorphism between males and females. Our results suggest that in male Liolaemus, the variation in bite force is at least partly explained by the variation in the degree of sexual dimorphism in head width (i.e. our estimate of the intensity of sexual selection), and neither bite force nor the morphological variables were correlated with diet (i.e. our proxy for natural selection). On the contrary, in females, the variation in bite force and head size can, to a certain extent, be explained by variation in diet. These results suggest that whereas in males, sexual selection seems to be operating on bite performance, in the case of females, natural selection seems to be the most likely and most important selective pressure driving the variation in head size.

Sex-specific trade-offs and compensatory mechanisms: bite force and sprint speed pose conflicting demands on the design of geckos (Hemidactylus frenatus)

“…In these animals, sexual selection on the underlying functional trait (bite force) could indirectly cause selection for larger head sizes, compromising locomotor function (Anderson and Vitt, 1990;Lopez and Martin, 2002;Huyghe et al, 2005;Husak et al, 2006a;Vanhooydonck et al, 2010). For example, fighting capacity and escape performance are likely to rely upon different suites of morphological traits, potentially placing conflicting demands on an individual's phenotypic design, which may lead to evolutionary or functional trade-offs (Lewontin, 1978;Garland and Carter, 1994;.…”

Variation in Display Behavior, Ornament Morphology, Sexual Size Dimorphism, and Habitat Structure in the Fan-Throated Lizard (Sitana, Agamidae)

“…Male-male competition often is suggested as the mechanism of sexual selection in lizards, and both increased body size and increased ornamentation are expected under stronger malemale competition (Stamps, 1977;Tokarz, 1995). Larger individuals frequently win agonistic interactions against smaller individuals (Stamps, 1977(Stamps, , 1983Cox et al, 2007), and ornamentation is thought to signal fighting ability to potential competitors (Ord et al, 2001;Vanhooydonck et al, 2005;Whiting et al, 2006;Irschick et al, 2007). The co-elaboration of both male body size and ornamentation is therefore interpreted as evidence for sexual selection via male-male competition ( tions between reproductive success and male body size and ornamentation within populations will be necessary, however, to confirm whether and how sexual selection acts in this system.…”

“…The co-elaboration of both male body size and ornamentation is therefore interpreted as evidence for sexual selection via male-male competition ( tions between reproductive success and male body size and ornamentation within populations will be necessary, however, to confirm whether and how sexual selection acts in this system. Also, the correlation between signal components and performance metrics such as bite force (Vanhooydonck et al, 2005;Irschick et al, 2007) will need to be examined in different environmental and social conditions to understand their role in signaling during male-male competition (Bro-Jørgenson, 2009;Lailvaux and Kasumovic, 2011) and other social interactions. More fundamentally, the mating systems of these lizards remain unknown, so we cannot know the precise mechanisms by which sexual selection acts upon them.…”

Reliable quantification of bite-force performance requires use of appropriate biting substrate and standardization of bite out-lever

“…Many studies have focused on ontogenetic scaling (Erickson et al, 2003), sexual dimorphism (Herrel et al, 1999;Lappin et al, 2006b), display and signaling (Lappin et al, 2006a), reproductive output and fitness (Lappin and Husak, 2005;Husak et al, 2009), skull biomechanics and model testing (Curtis et al, 2010a;Becerra et al, 2013) and feeding behavior and diet (Binder and Van Valkenburgh, 2000;Measey et al, 2011) within a single species. In several studies multiple species have been compared, including some analyses of over 15 species Aguirre et al, 2002;van der Meij and Bout, 2004;Santana and Dumont, 2009;Vanhooydonck et al, 2010;Santana et al, 2010;Freeman and Lemen, 2010). The majority of research has been conducted on lepidosaurs (lizards and tuatara) (Herrel et al, 1999;Lappin and Husak, 2005;Anderson et al, 2008;Jones and Lappin, 2009;D'Amore et al, 2011;Cameron et al, 2013), in part because of their diversity of feeding and reproductive biology, as well as their experimental tractability.…”