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Abstract

We present information on the reproduction of Gymnodactylus darwinii based on macroscopic analysis of its gonads. We found no sexual dimorphism in body size (SVL) between adult males and females, but males had, on average, wider heads and longer forearms. Both sexes had very similar sizes at sexual maturity and maximum body sizes, suggesting male–male competition for resources does not occur, and/or there are no sexual differences in survival rates. The smallest specimen had 24 mm SVL, and juvenile/immature specimens of similar or slightly bigger sizes were collected throughout the year suggesting a continuous turnover of individuals in the population. Adult males showed a continuous reproductive cycle, contrasting with a seasonal cycle of females, where maximum gonadal volume was observed from September to December. This is not uncommon and may be related to differential response to local environmental conditions, or because distinct investment in reproduction. Females have a small and fixed clutch size (two eggs per clutch), a pattern also observed in its congener G. amarali and in many geckonids, which is likely due to phylogenetic inertia. To compensate for a fixed clutch size, females may be able to lay more than one clutch per reproductive season.

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Aim Clutch size is a key life‐history trait. In lizards, it ranges over two orders of magnitude. The global drivers of spatial and phylogenetic variation in clutch have been extensively studied in birds, but such tests in other organisms are lacking. To test the generality of latitudinal gradients in clutch size, and their putative drivers, we present the first global‐scale analysis of clutch sizes across lizard taxa. Location Global. Time period Recent. Major taxa studied Lizards (Reptilia, Squamata, Sauria). Methods We analysed clutch‐size data for over 3,900 lizard species, using phylogenetic generalized least‐square regression to study the relationships between clutch sizes and environmental (temperature, precipitation, seasonality, primary productivity, insularity) and ecological factors (body mass, insularity, activity times, and microhabitat use). Results Larger clutches are laid at higher latitudes and in more productive and seasonal environments. Insular taxa lay smaller clutches on average. Temperature and precipitation per se are unrelated to clutch sizes. In Africa, patterns differ from those on other continents. Lineages laying small fixed clutches are restricted to low latitudes. Main conclusions We suggest that the constraint imposed by a short activity season, coupled with abundant resources, is the main driver of large‐clutch evolution at high latitudes and in highly seasonal regions. We hypothesize that such conditions – which are unsuitable for species constrained to laying multiple small clutches – may limit the distribution of fixed‐clutch taxa.
Article
Tarentola annularis is a climbing gecko with a wide distribution in Africa north of the equator. In the present paper, we describe the development of the osteocranium of this lizard, from the first appearance of the cranial elements up to the point of hatching. This is based on a combination of histology and cleared and stained specimens. This is the first comprehensive account of gekkotan pre‐hatching skull development based on a comprehensive series of embryos, rather than a few selected stages. Given that Gekkota is now widely regarded as representing the sister group to other squamates, this account helps to fill a significant gap in the literature. Moreover, as many authors have considered features of the gekkotan skull and skeleton to be indicative of paedomorphosis, it is important to know whether this hypothesis is supported by delays in the onset of cranial ossification. In fact, we found the sequence of cranial bone ossification to be broadly comparable to that of other squamates studied to date, with no significant lags in development.
Article
The evolution of reproductive strategies depends on local environmental conditions. When environments are seasonal, selection favors individuals that align changes in key reproductive traits with seasonal shifts in habitat quality. Offspring habitat quality can decline through the season, and increased maternal provisioning to late-produced offspring may compensate. This shift, however, may depend on environmental factors that influence reproduction and are, themselves, subject to temporal changes (e.g., food abundance). We studied the brown anole lizard (Anolis sagrei) to demonstrate how prey abundance modifies seasonal changes in key reproductive traits. We bred lizards in controlled laboratory conditions across the reproductive season and manipulated the availability of food by providing some breeding pairs high prey availability and some low. Halfway through the season, we switched half of the breeding pairs to the opposite treatment. We measured growth of male and female lizards as well as latency to oviposit, fecundity, egg size, egg content (yolk, water, shell mass), and egg quality (steroid hormones, yolk caloric content) over this period. Higher prey availability enhanced lizard growth and some key reproductive traits (egg size, fecundity) but not others (egg content and quality). Moreover, we found that seasonal patterns of reproduction were modified by prey treatment in ways that have consequences for offspring survival. Our results demonstrate that seasonal changes in reproduction are dependent on fluctuations in local environmental conditions. Moreover, researchers must account for seasonal shifts in environmental factors and reproductive traits (and their interactions) when designing experiments and drawing conclusions about how the environment influences reproduction.
Article
Four sympatric species of gekkonid lizards were studied simultaneously in northeastern Brazil for 12 months. Lygodactylus klugei was the smallest species and Phyllopezus pollicaris was the largest with Gymnodactylus geckoides and Hemidactylus mabouia intermediate in size. Lygodactylus is diurnal whereas Hemidactylus and Phyllopezus are primarily nocturnal. Gymnodactylus may be partially nocturnal and partially diurnal but is usually active in dark microhabitats. Females are larger than males in two species and sexes were similar in the other two. In L. klugei, the only diurnal species, male head size increased with SVL more rapidly than in females. This sexual dimorphism is most likely a consequence of sexual selection. Sexually dimorphic characters may differ in visually-oriented lizards compared to auditory-oriented species. Reproduction is continuous in all four species and egg size among species is correlated with female size. Egg size is not correlated with female size within a species. A summary of data on offspring size of additional gekkonids reveals a tight correlation between female size and offspring size. It is suggested that selection for optimal offspring size may be a partial determinant of female body size in species with invariable clutch size. A comparison with sympatric species studied during the same time period adds to the diversity of reproductive strategies exhibited by lizards occurring at the same place. Nearly every known lizard reproductive strategy is represented by at least one species occurring in the semi-arid caatinga of northeast Brazil.
Article
The reproductive cycle of the lizard Tropidurus itambere was studied in an open area near Campinas, São Paulo State, southeastern Brazil. Females had vitellogenic follicles or oviductal eggs only during the wet season, whereas males had large testes with spermatozoa throughout the year. Hatchlings were found from the height of the rainy season to its end (January to May). Mean growth rate was inversely related to snout-vent length. Juveniles from eggs laid at the beginning of the rainy season could potentially have reproduced in the first wet season after they hatched.
Article
An eight-year survey of a population of the sleepy lizard, Tiliqua rugosa, near Mt. Mary in South Australia, resulted in 10,771 random encounters of active adult lizards. Among this sample there was a significant change from a male bias in spring samples to a female bias in summer samples. This change coincided with the end of the period when males were paired with females. It appeared that the change resulted from a relatively larger decline in male than in female activity after mating. A similar trend was found in direct observations of the time active and distance moved per day of lizards in pairs at Mt. Mary, and of male and female lizards at another site near Tickera (also in South Australia). Males were more active than females in the spring before mating occurred. Females became more active than males in the summer, after mating. This asymmetry in seasonal activity patterns may be a component of the asymmetrical distribution of reproductive costs.
Article
Gerrhonotus coeruleus is a viviparous lizard that ranges into high latitudes and altitudes in western North America. Females in a population on the N coast of California (Mendocino Co.) reach sexual maturity in 32 months and produce a single litter each season. Relatively low clutch sizes (X̄ = 3.8 ± 0.2) contribute to low fecundity. Annual survivorship was approximately 73% for adults and 54% for juvenile lizards. Female survivorship exceeded male survivorship during 1974 and mean female size (87.7 ± 1.0 mm) was significantly larger than mean male size (83.6 ± 1.2 mm) the following year. Growth of females in a second coastal population (Monterey Co.) was more rapid and these lizards were larger at sexual maturity than Mendocino County females. Females in a montane population (El Dorado Co., Calif.) reached reproductive maturity when larger and older (44 months) than females in either coastal population although they attain a size in 32 months equal to Mendocino County females at the same age. Litter size, newborn size and relative clutch mass were significantly higher in the El Dorado County population. The evolution of delayed maturity and larger adult size in this species may result from selection for both larger litters and larger young.
Article
Animal species differ in the variability of their clutch sizes, as well as in mean clutch sizes. This phenomenon is particularly obvious in lizards, where virtually invariant clutch sizes have evolved independently in at least 23 lineages in seven families. Reduced variance in clutch size may arise either as an adaptation (because females with less variable clutch sizes have higher fitness) or as an indirect by-product of selection on other life-history characteristics. Comparative data on Australian scincid lizards indicate that variance in clutch sizes is lowest among species with low mean clutch sizes, small body sizes and a low variance in body sizes of adult females. Phylogenetic analysis shows that evolutionary decreases in the variance of clutch size have accompanied decreases in mean clutch sizes and decreases in the variance of adult female body sizes. Tropical lizards may also exhibit lower variance in clutch size. Most of these characteristics are correlated in occurrence, and may be allometrically tied to small body size. Hence, low variance in clutch size may be a consequence of allometric effects on a correlated suite of life-history characteristics. Exceptions to the general patterns noted above-especially, lizard species with invariant clutch sizes but large body sizes-may be due to loss of genetic variance for clutch sizes in lineages that have passed through a "bottleneck" of small body sizes and hence, low variance in clutch sizes.
Article
This study analyzes the circumstances under which certain lizards shift and fail to shift their habitats. At each of 20 localities, I measured the structural habitats utilized by all the diurnal arboreal lizard species as well as the availability of those habitats. I selected localities so as to include for four widespread species (Anolis grahami, A. sagrei, A. carolinensis, A. distichus) nearly all of the species-combinations in which they occur. Data were fitted to equations that (1) adjust for locality-specific differences in vegetation, and (2) estimate the direction and intensity of apparent interaction between sympatric forms. Shift was valuated both for species and separately for age and sex classes within species. Female-sized individuals shift more frequently than do adult @M @M. Linear equations that evaluate sympatric forms one at a time showed the strongest apparent competitors for a widespread from to be (1) adult @M @M rather than female-sized individuals, especially when adult @M @M represent the widespread species; (2) species of similar climatic habitat; (3) classes of similar size (especially against female-sized individuals of widespread species; and (4) classes of large size (especially against adult @M @M). The most abundant classes are the strongest apparent competitors for A. distichus but not for the other widespread species. These results are unchanged or strengthened when different habitat categories or nonlinear equations are used. Combining all sympatric forms into locality-specific linear equations supports Results 1 and 2 but is inconclusive for Results 3 and 4. The parameter proportional to the size of a refugium from interference is estimated for some cases to be significantly greater for female-size individuals than for adult @M @M. In general, results imply that animals similar to widespread forms in some niche dimension other than structural habitat are those most likely to cause shift in structural habitat. In addition, they suggest existence of a competition function with respect to size: in such a function intensity of competition is uniquely determined by the direction and amount of size difference, regardless of the competitors' absolute sizes. Competition intensity appears to (1) decrease overall with increasing difference in size, (2) be greater for a given size difference if the competitor is larger than if it is smaller, and (3) decrease at nonconstant rates, such that near complete size similarity there is a more rapid decline in intensity for smaller than larger competitors. Morphological differences between populations and short-term field observations suggest that both evolutionary and behavioral mechanisms regulate habitat shift.
Article
Specimens were collected monthly from January 1959 through September 1962, primarily at Dale Dry Lake, San Bernardino County, California, and were autopsied to determine the breeding cycle of both sexes. Most individuals reach reproductive maturity during the second summer following hatching. Adult testis volumes change markedly during the year, generally reaching maximum size in May. Males were found as potential breeders from mid-April to late July. Females contained eggs in the oviducts from mid-May to mid-July, and probably lay more than one clutch per year. Reproductive activity varies from year to year due, at least in part, to the amount of rainfall that occurs in the preceding winter. Uma scoparia testes (and presumably ovaries) apparently do not become as reproductively active if the lizards do not obtain adequate food. Insects that live in low-growing plants (predominantly annuals) normally are used for food by these lizards. However, insects that develop on these plants can do so only if sufficient rainfall occurs in winter to produce annuals. Following dry winters, reduced testis size, fewer eggs in ovaries, decreased numbers of potentially breeding males and females, and lack of juveniles at the end of the breeding season were observed.
Article
Sceloporus f. formosus exhibits a fall reproductive cycle. Females breed asynchronously within a distinct breeding season in which ovulation and fertilization occur during the fall months and parturition the following spring. In males, testicular volume begins to increase in February, peaks in April, and declines in June. Lipids stored in fat bodies appear to be used by both sexes for gonadal development. This energy reserve is used by females for vitellogenesis and possibly for nutrition during the winter months. Males utilize the majority of their fat body stores during the reproductive period, with little remaining for winter nutrition. Fat body and reproductive cycles of females are positively correlated with precipitation, whereas the male testicular cycle is positively correlated with mean ambient temperature.
Article
Costs of feeding were investigated in Anolis carolinensis to determine whether differences in feeding energetics related to sexual dimorphism in head size could explain differences in average prey size taken by male and female lizards in the field. The amount of time required to subdue and swallow prey, as well as the oxygen consumed and lactate produced during feeling, were measured for lizards feeding on a range of prey sizes. There was no difference between the sexes in the amount of lactate produced during feeding. There were however, differences in the amount of time required to subdue and swallow prey and in the amount of oxygen consumed during feeding. Female lizards required more time and more oxygen to consume prey than did males. Energetic considerations, however, are probably not responsible for prey size differentiation as net energy gains are likely to be high and similar for the sexes. While females do spend more time swallowing prey than males, the total amount of time to consume prey is a trivial part of a day. It is probable that the amount of time available to females for activities other than feeding is a less important determinant of fitness than it is for males. However, the longer prey handling times may deter females from selecting large prey because of a probable increase in the risk of predation.
Article
Lizards with invariant clutch sizes offer an ideal opportunity to examine the effects of "fixed" clutch size on other reproductive traits. Because females with invariant clutch sizes are unable to increase offspring number even when sufficient space and energy are available, females may compensate by laying larger eggs or increasing reproductive frequency. I studied the reproductive biology of Oedura lesueurii, a diplodactyline gekkonid lizard that lays two parchment-shelled eggs per clutch once per year. Eggs of gravid O. lesueurii females occupied most of the available space in the lower abdomen, and relative clutch masses were moderately large and similar to those of other diplodactyline geckos for which data are available. Measures of female body size (snout-vent length, mass) were correlated with several measures of egg and hatchling size, but not with energetic content on a per-gram basis. Pelvic constraints on maximum egg size and body volume constraints on reproductive output (females can only increase egg size) may account for positive female-offspring size correlations in O. lesueurii and some other species of lizards with invariant clutch sizes, but more experimental and comparative work on such species is needed. It is possible that more realistic and predictive life-history models of the evolution of propagule size can be achieved by explicitly incorporating specific life-history features of organisms, such as the positive correlations between female size and propagule size in O. lesueurii and other species of lizards with invariant clutch sizes.
Article
Eggshell structure is related to fundamental aspects of embryonic development (via water and gas exchange), adult ecology and behavior (via nest site selection), and demography (via effects on survival). We compared life-history characteristics between gekkotans that lay rigid- versus parchment- shelled eggs to determine if evolutionary shifts in eggshell structure are associated with life-history evolution. Ancestral gekkotans laid parchment-shelled eggs, with rigid-shelled eggs evolving later. Clutch size in oviparous gekkotans is fixed at one or two eggs, and this characteristic eliminates an egg size versus clutch size tradeoff as a life-history strategy. We found that species laying rigid-shelled eggs exhibit (1) smaller eggs relative to adult body size, (2) smaller hatchlings relative to the size of the egg, (3) earlier embryonic stage at oviposition, (4) longer incubation periods, and (5) smaller adult body sizes than species laying parchment-shelled eggs. These patterns hold when accounting for phylogenetic relatedness, and are not explained by geographic distributions of climate and habitat. In general, our data support the hypothesis that the spherical shapes of rigid-shelled eggs limit their size (volume), which in turn has restricted hatchling size and adult body size. In contrast, while parchment-shelled eggs are similarly constrained in width, elongate shapes allow egg sizes, and hence hatchling sizes, to increase relative to adult body sizes. Finally, the evolution of rigid-shelled eggs may have allowed gekkotans to become so successful; over 1,000 species lay rigid-shelled eggs, as compared to about 200 species that lay eggs exhibiting the ancestral parchment-shelled condition.
Article
Eighty-nine species of lizards, six of which polytypic (forming a total of 97 taxa), are presently known from Brazilian Amazonia. This number includes six species and one subspecies described as new to science in this paper: Stenocercus fimbriatus, Lepidoblepharis hoogmoedi, Leposoma osvaldoi, L. snethlageae, Tretioscincus oriximinensis, Tupinambis longilineus, and Anolis nitens tandai. Stenocercus dumerilii is resurrected from the synonymy of S. tricristatus. Bachia cophias is considered a junior synonym of B. flavescens. B. peruana is a new record from Brazil. Anolis nitens has priority over A. chrysolepis. The Amazonian Tupinambis is shown to be T. teguixin (of which T. nigropunctatus is a junior synonym). The name T. merianae should be used for T. teguixin sensu Boulenger (1885b). Mabuya ficta is a junior synonym of M. bistriata, while the name M. nigropunctata should be used for M. bistriata sensu Vanzolini & Williams (1980). Of all species extensive descriptions and ecological data, if available, are presented. A zoogeographical analysis based on the combined distribution maps of the various species shows a main division in Amazonia of a western and an eastern fauna. A southwestern group is also recognised and, although defined by a smaller number of species, a Guianan group. The lizard fauna from Rondônia shows multiple affinities. The distribution of lizards in enclaves of open formations in Amazonia does not support the idea of continuous areas of savannas throughout Amazonia in relatively recent times.
Article
The female rock lizard, Psammophilus dorsalis (Agamidae), lays multiple clutches of eggs over a period of 6 months (June–December). The later clutches of eggs are presumably fertilized by sperm stored from earlier matings, since testes and epididymides are regressed after August. Sperm storage is seen in pockets of the anterior vaginal region of the oviduct. Sperm recovered from the uterovaginal region are intact and motile. Discrete granules resembling the secretory granules present in the vas deferens also occur along with sperm in the vaginal sperm storage structures. The PAS-positive granules and acid phosphatase form important components of the secretions present along with sperm in the vaginal sperm storage pockets. The epithelium of the vaginal sperm storage pockets is PAS-positive and contains lipid. Several enzymes, including hydroxysteroid dehydrogenases and hydrolases, are localized histochemically in the epithelium of the vaginal sperm storage pockets. A possible role is suggested for the secretions from the male reproductive tract during sperm storage in the oviduct, in which physiological “dormancy” of the sperm during their storage may be maintained by the metabolic “milieu” in the vaginal sperm storage pockets by a mechanism similar to that effecting dormancy of the epididymal sperm in the male. © 1995 Wiley-Liss, Inc.