Sexual Selection and Dynamics of Jaw Muscle in Tupinambis Lizards

Abstract

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It takes two: Seasonal variation in sexually dimorphic weaponry results from divergent changes in males and females

“…For example, crayfish show sexual dimorphism in claw size only during the reproductive season; for males, the molt following the reproductive season results in increases in body (carapace) length that are much greater than increases in claw size, resulting in a reduction in claw/body size ratios (Stein, ). Greater dimorphism during the reproductive season in traits used in male–male competition has been documented in hermit crabs (claw size; Yasuda, Otoda, Nakano, Takiya, & Koga, ) and Tupinambis lizards (jaw muscles; Naretto, Gardozo, Blengini, & Chiaraviglio, ). In contrast, weaponry used in competition for nonreproductive resources would be predicted to show no seasonal variation (as seen in female crayfish, Stein, ), as the benefits of nonreproductive competition are likely to accrue year‐round.…”

Relationship between pre- and post-copulatory traits inSalvator rufescens(Squamata: Teiidae)

“…However, we did not find a relationship between pterygoideus muscle mass and sperm velocity. Pterygoideus muscle mass was proposed as an honest signal of reproductive condition in Salvator lizards (Naretto et al ., ); however, it is not clear his role as indicator of sperm quality. Even though, there are evidences about the relationship between sperm traits and fertilization success in other taxa (Gomendio & Roldan, ; Pitnick, Hosken & Birkhead, ; Pitnick et al ., ), this has not been studied in lizards.…”

“…Salvator rufescens is a Teiidae lizard that occurs in the southernmost area of genus distribution in South America (Lanfri et al ., ). At adulthood, it can exceed 50 cm in snout‐to‐vent length, or SVL (130 cm total length) and weigh up to 4.7 kg (Naretto et al ., ). This species is included in the appendix II of the Convention on International Trade of Endangered Species of Wild Fauna and Flora (Cites, Convention on International Trade in Endangered Species, ) and is under legal commercial harvesting in Argentina (Porini, ).…”

“…Forty‐three Salvator rufescens individuals were caught by local authorized hunters from wild populations in central Argentina (29°35′W, 64°10′S to 31°10′W, 63°15′S) throughout the reproductive season (Naretto et al ., ). We were authorized by the government environmental agencies for scientific capture, and we selected and accompanied local hunters to standardize the sampling procedure with the aim of avoiding size bias in capture rates.…”

“…Sexual dimorphism in the pterygoideus muscle is produced by an increase in muscle mass during the reproductive period. Moreover, the relative jaw muscle mass is related to relative testis mass and to the presence of sperm, suggesting that the relative size of the jaw muscle acts as an honest signal of the reproductive condition of males (Naretto et al ., ). However, the relationship between jaw muscle mass and sperm quality has not been studied in this and in other lizard species.…”