WE. The evolution of sexual dimorphism in the skink Eumeces laticeps: an example of sexual selection

Adults of the skink Eumeces laticeps are sexually dimorphic in coloration, body size, head size, and relative head size. Males have larger heads at a given body size than females and the divergence in relative head size is coincident with the size at which sexual maturity is reached. Although there were no differences between sexes in tail loss frequencies, there were substantial differences in frequencies of body and head scars, a consequence of aggressive male–male interactions. Prey size was correlated with body and head size and males tended to eat larger prey items than females. However, both sexes are capable of eating prey much larger than the mean or maximum size of prey found in stomachs, suggesting that resource partitioning is a consequence of sexual size differences rather than a cause. The heads of males at a given body size increase during the breeding season, and a combination of head and body size apparently determines the outcome of intrasexual aggressive encounters. Moreover, small males were never observed with females during the breeding season, and those males observed "guarding" females were significantly larger than males observed in the absence of females. We conclude that sexual selection accounts for many of the differences in morphological traits between sexes of E. laticeps.

Desert lizard reproduction: seasonal and annual variation in Urosaurus ornatus (Iguanidae)

The reproductive cycle and cycles in fat body and liver masses were examined in Urosaurus ornatus from central Arizona. Adult males underwent spermiogenesis from mid-April until late August. The cycle in testes mass was paralleled by cyclical activity in structure of the seminiferous tubules and epididymides. Mass of fat bodies and livers also fluctuated seasonally, showing a distinct increase with declining reproductivity. Yolk deposition in females occurred from May until late August with ovulation occurring from early June until early September. Breeding females comprised two groups: young females in their first breeding season and older females that were in at least their second breeding season. The younger (smaller) group had a mean clutch size of 6.0 and produced only one clutch, whereas the older (larger) group had a mean clutch size of 7.7 and at least a portion of these females produced more than one clutch. For the most part, older females began breeding earlier in the reproductive season than younger females. Females cycled fat body and liver masses with a distinct increase in organ size associated with declining reproductivity. Reproductive intensity varied during a given season but not annually, even though rainfall varied annually.

Conspecific odor detection by the male broad-headed skink, Eumeces laticeps: effects of sex and site of odor source and of male reproductive condition

Olfactory stimuli are sufficient for detection and discrimination of sex of conspecific lizards by the male broad-headed skink, Eumeces laticeps, a member of a large group of lizards with pronounced chemosensory abilities, the Autarchoglossa. The capacity of male broad-headed skinks to detect conspecific odors was assessed by measuring tongue extrusion rates in response to odor stimuli presented on moist cotton applicators. Tongue-flick rates of postreproductive males were significantly higher for cloacal odors of postreproductive conspecifics of both sexes than to distilled water and higher to female than male odors over the initial 20- and 60-sec intervals. In a second experiment using testosterone-treated males and estrogen-injected females, testosterone-treated males emitted significantly more tongue flicks to female cloacal odors than to the other stimuli, and two males bit applicators bearing male odors. Testosterone did not affect reaction to male cloacal odors, but markedly increased tongue-flick rates in response to cloacal odors of estrogen-treated females. Postreproductive males also responded to female, but not male, skin odors at a significantly higher rate than to water. Possible sources and presumed adaptive significance of conspecific odors are discussed.

Reproduction in the lizard Mabuya heathi (Scincidae): a commentary on viviparity in new world Mabuya

The tropical Brazilian skink Mabuya heathi is viviparous, producing ova which increase in wet mass by 53 800% and in dry mass by 38 400% during gestation. Ovulation occurs during October–January, rapid growth in embryos takes place during June–October, and parturition occurs in September–November, between 9 and 12 months after ovulation. Female and male reproduction is cyclic and is synchronous between the sexes. Brood size is 2–9 [Formula: see text] and is significantly correlated to female size. Fat bodies of females are largest when embryos are small, and decrease in mass as embryos increase in size. Testes in males are largest during September–February, associated with a decrease in fat body size. Mabuya heathi is the second species of lizard in the caatinga herpetofauna shown to be strongly cyclical in reproduction and to reproduce only once per year.

Ecology of a Snake Community in Northeastern Brazil

Abstract

Nineteen species of snakes representing four families were simultaneously studied in a caatinga habitat of northeastern Brazil. Of these, 10 are terrestrial, 3 are terrestrial-aquatic, 1 is arboreal-terrestrial, 4 are arboreal, and 1 is terrestrial-fossorial. Four species are nocturnal, 5 species are nocturnal and diurnal, and 10 are strictly diurnal. Diets include mammals, birds, bird eggs, lizards, snakes, frogs, toads, and reptile eggs, with some snake species being food specialists and others being food generalists. Surprisingly, none of the species of snakes at the study site feed on invertebrates. A diversity of reproductive tactics is evident among the species in this snake community. There are oviparous and viviparous species, and clutch/brood size may be large or small depending upon the species. Both clutch/brood size and neonate (or egg) size were correlated with body size of female snakes. A principal components analysis (PCA) of morphological data revealed that two axes, one representing variation in body size and one representing variation in tail length and head size, explained 95% ofthe variation in the data. Portions of the morphological results corresponded well with ecological data. However, in some instances the morphological results were discordant with ecological results. Certain patterns, for example appear to have a phylogenetic basis. It is concluded that morphological analyses of snake communities cannot be adequately interpreted in the absence of ecological data.

Reproductive tactics of Ameiva ameiva (Lacertilia: Teiidae) in a seasonally fluctuating tropical habitat

The reproductive ecology of Ameiva ameiva was studied for 12 months in a caatinga habitat of northeast Brazil. Even though rainfall was seasonal, the female reproductive cycle was not associated with this seasonality. Females reproduced year-round, with peak reproductive periods during August–October and January–February. Clutch size ranged from one to nine and was correlated to female size but egg size was constant. Males showed evidence of reproductive activity throughout the year. Fat body mass of males and females varied greatly among individuals. There was no association between fat storage and wet–dry seasonality. In females, fat body mass tended to decrease during peak reproductive periods. Most striking was the observation that 97.8% of all adult Ameiva possessed enlarged fat bodies, suggesting that resource periods low enough to affect reproduction did not exist during 1977–1978. The reproductive tactics of Ameiva were similar to those of other tropical macroteiids, regardless of their distribution, but very different than reproductive tactics of sympatric iguanid lizards. Compared with iguanid lizards, resources may be less limiting for macroteiids because their widely foraging behavior for prey acquisition may allow them to find rich patches of resources which would be unavailable to habitat specific sit-and-wait foragers, like most iguanid lizards.

The adaptive significance of a complex caudal adaptation in the tropical gekkonid lizard Lygodactylus klugei

The tail of the Brazilian gekkonid lizard, Lygodactylus klugei, exhibits a suite of characteristics associated with both tail retention and tail loss adaptations. Tails are specialized for locomotion, possess specialized cutaneous glands, and are high in lipid and energy content. Tail loss in a natural population, however, is high and presumably associated with escape from predation via tail autotomy. The importance of the presence of a complete tail both functionally and for future predator escape is reflected by rapid regeneration of a tail complete with specialized functionally important structures.