Sexual size dimorphism in the Cuban treefrog Osteopilus septentrionalis

Abstract

To find out the main cause of the sexual size dimorphism (SSD) in the Cuban treefrog Osteopilus septentrionalis, I studied between April 2002 and April 2004 the breeding behavior and survival of individuals in a population localized in north-western Puerto Rico, West Indies. This species is an explosive breeder whose breeding events lasted one night. Mature females were larger in body size (snout vent-length, SVL) (range 57-107 mm) than mature males (range 41.5-67 mm), and exhibited higher levels of survival (males: 0.72, 95% confidence interval 0.66-0.78; females 0.91, 95% confidence interval 0.88-0.93). Females can increase their reproductive success if they breed with large SVL because large females can lay more eggs than small females. In contrast, the reproductive success of males was not enhanced by large SVL because the mating pattern was random and non-assortative by SVL. Thus, for males it could be better to start to breed with small SVL, and participate in all possible breeding events, which implies high mortality risk. As a consequence, the SSD in O. septentrionalis may be due to fecundity advantages in females, and because males tend to die before reaching larger SVL.

Demography and Movement in a Relocated Population of Oregon Spotted Frogs (Rana pretiosa): Influence of Season and Gender

“…between sexes in Columbia Spotted Frogs (R. luteiventris), the other recognized species of spotted frog, though femalebiased survival has been reported for R. pretiosa (Licht, 1974). Higher survival of female than male anurans has been reported in other studies (Howard, 1981;Woolbright, 1989;Wood et al, 1998;Vargas-Salinas, 2006). We show that seasonal patterns of mortality differed between sexes.…”

“…We also hypothesized that density effects associated with a growing frog population should lead to decreased survival with increasing pond age. As in many other amphibians, we hypothesized that survival should be higher for larger frogs (Berven, 1990;Altwegg and Reyer, 2003;Chelgren et al, 2006), and should be higher for females than males (Licht, 1974;Howard, 1981;Woolbright, 1989;Wood et al, 1998;Vargas-Salinas, 2006). In addition to hypotheses about survival, we examined two hypotheses regarding movement and growth to determine the value of specific ponds for growth versus reproduction.…”

Geographic trend in sexual size dimorphism and body size of Osteopilus septentrionalis (Cuban treefrog): implications for invasion of the southeastern United States

“…Female O. septentrionalis are highly fecund, producing large clutches of eggs that increase in number with increasing female SVL (Meshaka 2001;Owen 2005;Vargas-Salinas 2006b). In contrast, mean clutch size of native hylids generally falls well below even the minimum clutch size of O. septentrionalis (Meshaka 2001).…”

“…We rounded these published SVL values to the nearest 0.1 mm. Site-specific SSD data for O. septentrionalis collected at our field sites, along with published SSD data across the range of the species (Meshaka 2001;Vargas-Salinas 2006b), are shown in Table 2. We used correlation analyses to evaluate the potential significance of trends by testing the relationship between female to male SVL ratio and mean female and male SVL and approximate degrees north latitude, expressed in decimal degree notation rounded to the nearest 0.1°.…”

Sexual dimorphism, reproduction and diet of the casque-headed treefrogItapotihyla langsdorffii(Hylidae: Lophiohylini)

“…This characteristic may be plesiomorphic for anurans, with the derived condition (males larger than females) occurring mainly in taxa that have male-male combat (Shine 1979). Nevertheless, the observation of fights among male I. langsdorffii and other large-bodied lophiohylines such as Osteopilus septentrionalis (Vargas-Salinas 2006) indicates that the presence of male-male combat is not necessarily indicative of large male size in anurans (see Halliday and Verrell 1986).…”