Mating pattern, female reproduction and sexual size dimorphism in a narrow-mouthed frog (Microhyla fissipes)

To determine the age structure of a Hynobius leechii breeding population and analyze relationships between the order of entrance to breeding ponds and physical parameters and age, we studied a wild population of the species in the Research Forests of Kangwon National University in Chuncheon, Kangwon, South Korea from March 16 to April 13, 2005. The age of breeding males ranged one to nine years old and that of females ranged from three to nine years old. The asymptotic sizes of males and females were 6.36 and 6.51 cm, respectively, and the growth coefficients of males and females were 0.71 and 0.81, respectively. The snout-vent length (SVL), head length, and body mass of males were all positively correlated with their age, but female age did not show a significant relationship with any physical parameter. The tail depth, body mass, and condition factors (SVL/body mass <TEX>$\times$</TEX> 100) of both males and females were negatively related with the order of entrance to the breeding pond. The head width and SVL of males were also negatively correlated with the order of entrance, but the SVL of females was positively related with the order of entrance. These results suggest that physical parameters are more important determinants of breeding migration patterns than age. We discuss which of two hypotheses, the mate opportunity hypothesis and the susceptibility hypothesis, is better able to explain the order of entrance to breeding ponds for male and female H. leechii.

Simple SummaryWe review the results of studies performed during the last four decades on the morphology, behaviour and evolution of lizards of the genus Gallotia, from the Canary Islands. We show that there is sexual dimorphism in all species of that genus, with males having larger snout-vent length (SVL), head width (HW) and hind limb lengths (HLLs) than females. The changes in SVL of males and females have been correlated throughout the evolution of these lizards in the islands. In two species, longer HLLs were found in populations from open (less vegetation) rather than closed habitats. In most species, males have a more conspicuous coloration, with blue or green large lateral spots. Blue spots in some species also have their peak reflectance in the ultraviolet part of the spectrum (300–400 nm wavelength). Detailed analysis of Gallotia galloti shows a large repertoire of behaviour patterns, and results of intramale competition trials show that the outcome of fights depends on several morphological patterns and especially on bite frequency. Detailed behavioural analyses of individuals of two endangered lizard species proved to be a useful tool for keeping them while in breeding centres, as well as to train them to recognize local predators before they were reintroduced into natural habitats.We summarize, here, the results from several studies conducted over many years on several endemic species of lizards (genus Gallotia) from the Canary Islands. Quantitative analyses show clear differences both among the species of every island and populations within each species. Sexual dimorphism exists in all analysed species, and a phylogenetic analysis shows that the degree of dimorphism did not change along the evolutionary history of the Canary Islands: species with large and small body sizes have a similar degree of sexual dimorphism, with male body size changes closely following those undergone by females. In G. caesaris (from El Hierro and La Gomera islands) and in G. stehlini (from Gran Canaria), longer hind limb length was correlated with more open habitats. Within most species, males are more conspicuous than females, mainly in terms of body size, behaviour and coloration pattern. Lateral colour spots are blue in most species and green in others. In G. galloti from Tenerife, male lateral spots have larger spot areas and percentage of reflectance in the ultraviolet/blue part of the spectrum than females. This trait shows a monthly variation along April to July, both in males and females, its magnitude being larger in May–June. Behaviour analysis, especially in the last species, shows a great diversity in behaviour patterns, and analysis of intrasexual male competition revealed that contest outcome depends on several morphological and colouration characteristics but mainly on the individual’s behaviour. Detailed behavioural analyses were useful for managing a few captive individuals of the highly endangered G. bravoana from La Gomera island. Experimental analyses of some behaviours in the endemic Hierro island lizard (G. simonyi, in danger of extinction) show that individuals may learn to recognize predator models and increase their running speeds with training.

We studied the reproduction, sexual dimorphism, and diet of Oxyrhopus trigeminus from two sites in southeastern Brazil. Oxyrhopus trigeminus from Irapé Power Plant (IPP) contained vitellogenic follicles and eggs in both rainy and dry seasons and clutch size was not correlated with female snout–vent length (SVL). Sexual dimorphism was evident. Females attain larger SVL but males have longer tails. We found three females from Santa Clara Power Plant (SPP) with vitellogenic follicles, all of them collected in the dry season. Mean SVLs of adult females from IPP and SPP were 717.7 mm and 786 mm, respectively. Mean SVL of adult males from IPP was 553.4 mm and the single adult male from SPP was 507 mm. The diet of O. trigeminus from IPP included rodents (46.7%), lizards (33.3%), and birds (20%). The volume of individual prey items was not correlated with snake SVL. The diet of O. trigeminus from SPP included rodents (37.5%), lizards (37.5%), birds (12.5%), and marsupials (12.5%). It seemed that an ontogenetic shift may occur in individuals of this snake species from IPP.

We studied ontogenetic shifts in sexual dimorphism and female reproduction in the Reeves's Butterfly Lizard, Leiolepis reevesii (Agamidae), from Hainan, southern China. The smallest reproductive female was 84 mm snout–vent length (SVL). The largest female and male were 136 mm and 166 mm SVL, respectively. Sexual dimorphism in head size and tail size was evident in adults, with adult males having larger heads and longer tails than did adult females of the same SVL. Head size relative to SVL was greatest in hatchlings and smallest in adults, with juveniles in between. Tail length relative to SVL was shorter in hatchlings than in juveniles and adults but did not differ between juveniles and adults. Females produced a single clutch of 2–8 eggs per breeding season stretching from mid-April to mid-July. Clutch size, egg mass, and clutch mass were all positively related to female SVL. Egg mass was negatively correlated with clutch size when holding female SVL constant, and egg length was negatively correlated with egg width when holding egg mass constant. Larger females increased reproductive output primarily through production of more and larger eggs (and hence heavier clutches). Males are the larger sex in L. reevesii presumably because (1) the selective pressure toward increased male size is strong; (2) the selective pressure toward increased female size is comparatively low; and (3) somatic growth is more likely to be constrained by reproduction in smaller females because of a negative correlation between relative clutch mass and SVL.

Sexual dimorphism (SD) is a widespread phenomenon in most vertebrate species and is exhibited in a myriad of ways. In amphibians, sexual size dimorphism, in which females are larger than males, is the most common type, and sexual shape dimorphism varies among species. Different selection forces (sexual selection, fecundity selection, and ecological selection) that act differently upon the sexes form the consequence of SD. Thus, studies of SD provide information about the general intersexual divergence of the same species and allow insights into the impact of selective forces on the sexes. In this study, we analyzed morphometric data of the Shangcheng stout salamander, Pachyhynobius shangchengensis, an endemic and poorly known Chinese salamander, to examine sexual dimorphism in size and shape. The morphometric data included 15 characteristics of 68 females and 55 males which were analyzed using univariate and multivariate methods. A significant difference was found between the sexes in terms of both body size (snout-vent length) and some body shapes (e.g., head length and width, tail length and width, distance between limbs, and limb length and width) in this salamander. The longer snout-vent length in males may be attributed to sexual selection, longer and wider head in males may contribute to male-male competition, longer and wider tail in males may be attributed to energy storage and reproductive success, the larger distance between limbs in females is likely due to a fecundity advantage, and longer and more robust limbs in males may be related to reproductive or competitive behaviors. These results demonstrated that sexual dimorphism of different morphological traits is the consequence of different selection forces that act differently upon the sexes.

In animals with asymptotic growth after maturity, a variety of factors can lead to inter- and intraspecific variation in sexual size dimorphism (SSD). Growth-based models tailored for a particular taxon provide a useful framework for analyzing questions about the proximate bases, adaptive significance, and evolution of SSD. This paper shows how growth-based models designed for Anolis lizards have been used to study the effects of male territorial and competitive behavior on SSD and adult size distributions. In a comparative study of different species of anoles, indices of SSD based on male and female asymptotic snout-vent length (SVL) have been used to confirm a prediction from territorial theory that SSD should be related to inter-female distance. Within populations of Anolis sagrei and Anolis limifrons, adult size distributions were sometimes skewed in favor of larger males than predicted by null growth-based models, as a result of the underrepresentation of small, young males in samples containing females of the same age. A relative shortage of newly mature males in adult size distributions is consistent with behavioral studies suggesting that young, small males may bear the brunt of aggression from larger territorial males. Hence, growth-based models can be used to suggest and test behavioral and other hypotheses about the factors affecting SSD.

Males and females of the oriental garden lizard (Calotes versicolor) from a population in Hainan, southern China, differed in head size at hatching: males had larger heads than females. This dimorphism was slightly more pronounced in adults than in hatchlings. Hatchlings had larger heads but shorter tails relative to snout–vent length (SVL) than subadults and adults. When SVL was held constant, tail length of subadults and adults of the same sex was similar. Adult lizards were not sexually dimorphic in body size (SVL), but males possessed longer tails than females at the same SVL throughout their size range. The smallest and largest reproductive females in our sample were 78.9 and 103.8 mm SVL, respectively. Females in our laboratory (Hangzhou, eastern China) laid multiple clutches from April to June. Clutch size, clutch mass, and egg mass varied from 3 to 14 (mean = 9.0) eggs, 1.58 to 6.47 (mean = 4.65) g, and 0.45 to 0.61 (mean = 0.52) g, respectively. Clutch size and clutch mass were both positively correlated with female SVL. Egg mass was not correlated with female SVL even when clutch size was held constant using a partial correlation analysis. Clutch size was not correlated with female condition when female SVL was held constant. Egg length, egg width, and clutch size were not correlated with each other when the remaining variable was held constant. Egg mass was not correlated with clutch size when female SVL was kept constant. Larger-sized C. versicolor females increased reproductive output primarily through production of more eggs (and hence heavier clutches).

Atypical assortative mating based on body size in an explosive-breeding toad from a tropical island of southern China

Age determination and some growth parameters were studied in a population of Rana ridibunda from Yildizli Stream, Trabzon, Turkey by skeletochronology. Age was determined for individual frogs by counting the number of resting lines (RL) in cross-sections taken from phalanges. The maximum longevity of females and males was 6 and 7 years, respectively. The minimum age at maturity was 2, at 55 mm snout-vent length (SVL), for females, and 2, at 46 mm, for males. Males were sexually mature after the third or fourth winter although some fe- males mature after the fifth winter. SVL was ranged from 55 to 99 mm (74.64±13.37) in fe- males and 38 to 83 mm (64.58±11.09) in males. Male SVL was significantly correlated with age, but no significant correlation was obtained between female SVL and age. Gonad weights show highly significant correlation with SVL in both sexes but no significant correlation with age.

We studied sexual dimorphism and female reproduction in Many-Lined Sun Skinks (Mabuya multifasciata) from a population in Hainan (southern China). The smallest reproductive female was 90 mm snout–vent length (SVL). The largest male was 117 mm SVL and the largest female was 116 mm SVL. To measure the potential influence of gestation temperature on female reproduction, pregnant females were maintained under five thermal conditions until they gave birth. Parturition began in early May, and females produced up to two litters per breeding season. Litter size, litter mass, and offspring size (mass) were all positively correlated with female SVL. Litter size ranged from 2–7, and it was independent of relative fecundity (litter size relative female SVL). We did not detect a trade-off between body size and offspring number. Gestation temperature affected parturition date but not litter size, litter mass, neonate mass, or relative litter mass. Females at higher (average) gestation temperatures gave birth t...

We examined sexual size dimorphism (SSD), mating pattern, fertilization efficiency and female reproductive traits in two bufonid toads (Bufo gargarizans and Duttaphrynus melanostictus) to test the idea that importance of male body size for egg fertilization success depends on the mating pattern. Female-biased SSD was evident only in D. melanostictus. Female B. gar-garizans laid fewer larger eggs nearly three months earlier than did female D. melanostictus. Fertilization efficiencies on average were higher in B. gargarizans (95%) than in D. melanostictus (91%). Though differing in the degree of SSD, body size, breeding season, clutch size, egg size and fertilization efficiency, the two toads were similar in four aspects: (1) both showed size-assortative mating; (2) females did not tradeoff egg size against egg number; (3) male size, clutch size and clutch dry mass were greater in male-larger than in female-larger pairs after accounting for female snout-vent length (SVL); and (4) the ratio of male to female SVL did not affect fertilization efficiency. Our data show that: (1) a female preference for large males is likely not important in terms of egg fertilization success; (2) a male preference for large females is likely important because larger females are more fecund; and (3) size-assortative mating arises from a male preference for large females. Our study demonstrates that male size is not always important for egg fertilization success in anurans that show size-assortative mating.

Sexual dimorphism, female reproduction and egg incubation in the oriental leaf-toed gecko ( Hemidactylus bowringii) from southern China

-Sex, family, and microgeographic variation in body size, head dimensions, tail length, and scalation were assessed from 273 wild-caught brown snakes (Storeria dekayi) from seven island and mainland sites near Lake Erie and from 145 neonates born to 25 wild-caught females. Significant differences between males and females were present both in wild-caught snakes and in neonates, with females exceeding males in snout-vent length and number of ventral scales and males exceeding females in tail length, head dimensions, and number of subcaudal scales. Previous analyses have typically focused on the effect that sex differences might have on adult snakes, e.g, in foraging or reproduction. The presence of sex differences among neonates raises the possibility that these differences may be of ecological and evolutionary significance in younger snakes as well. Significant differences among families were found in neonates for all characters except number of labial scales, and significant heritability (estimated from offspring-dam regression) was found for tail length, head length, and numbers of ventral, subcaudal, and temporal scales. Heritable variation in scalation is well known, but this is the first study to document heritable variation in snake morphology. This result is important because heritable variation is an implicit assumption of hypotheses for the evolution of sex, population, and species differences in morphology. Significant differences among sites were found for adult snout-vent length, head dimensions, number of subcaudal scales, and number of temporal scales. In addition, significant phenotypic correlations (e.g, among head dimensions, between tail length and number of subcaudal scales, between snout-vent length and number of ventral scales) and genetic correlations (e.g, between tail length and number of subcaudal scales, between head length and number of ventral scales) were found between pairs of traits. The presence of these correlations suggests that groups of traits may be influenced by the same genetic or ontogenetic processes and may exhibit patterns of correlated evolution. rnal of Herpetol gy, Vol. 31, No. 3, pp. 335-346, 1997 right 19 7 Society for the Study of Amphibians and Reptiles iation in Brown Snake (Storeria dekayi) Morph logy and Scalation: , Family, and Microgeographic Differences Differences in morphology, behavior, or physiology between sexes, among age classes, or among localities may influence ecological relationships and reflect evolutionary trends. In snakes, sex differences in body size and relative head size may result in reduced diet overlap between males and females (Shine, 1991a; Houston and Shine, 1993) and geographic differences in body size and relative head size may reflect adaptation to local prey characteristics (Forsman and Lindell, 1993). Such hypotheses can be strengthened by an understanding of the genetic and ontogenetic processes giving rise to observed patterns of variation. For example, natural selection will result in sex or geographic differences only if traits show heritable variation. In addition, if multiple traits are genetically or ontogenetically correlated (e.g., if they are influenced by the same genes or by the same ontogenetic processes), then ecological or evolution335 This content downloaded from 157.55.39.4 on Fri, 09 Sep 2016 04:13:43 UTC All use subject to http://about.jstor.org/terms

Sexual size dimorphism is widespread among snakes and has also been observed in lengths of body appendages such as in tails. Males typically possess longer tails than females and this dimorphism in tail length has generally been attributed to the importance of the tail in mating and reproduction. We used body size measurements, snout-vent length (SVL) and tail length (TL) as well as a body condition index (BCI) as a measure of quality in Caspian Whip Snakes from Hungary, in order to shed light on sexual dimorphism patterns. The SVL of males (1061 ± 133 mm, n = 25) were significantly longer than that of females (887 ± 208 mm, n = 41). However, the proportion of TL to total length was lower in males than in females (0.257 ± 0.018 and 0.274 ± 0.017, respectively). The BCI of females (386 ± 10) was significantly higher than that of males (343 ± 15). Females having proportionally longer tails compared to males seems to be the reverse of the usual trend. Selective pressures on the tails of female snakes are less obvious, as tail length may be linked to more than one function, and hence be simultaneously subjected to more than one type of selective force.

In a model group of giant reptiles, we explored the allometric relationships between male and female body size and compared the effects of sexual and fecundity selection, as well as some proximate causes, on macroevolutionary patterns of sexual size dimorphism (SSD). Monitor lizards are a morphologically homogeneous group that has been affected by extreme changes in body size during their evolutionary history, resulting in 14-fold differences among the body sizes of recent species. Here, we analysed data concerning the maximum and/or mean male and female snout–vent lengths in 42 species of monitor lizard from literary sources and supplemented these data with measurements made in zoos. There was a wide scale of SSD from nearly monomorphic species belonging mostly to the subgenus Odatria and Prasinus group of the Euprepriosaurus to apparently male-larger taxa. The variable best explaining SSD was the body size itself; the larger the species, the higher the SSD. This pattern agrees with the currently discussed Rensch’s rule, claiming that the relationship between male and female body size is hyperallometric, i.e. the allometric exponent of this relationship exceeds unity and thus SSD increases with body size in the case of male-larger taxa. All our estimates of the reduced major axis regression slopes of this relationship ranged from 1.132 to 1.155. These estimates are significantly higher than unity, and thus unequivocally corroborate the validity of Rensch’s rule in this reptilian group. In spite of our expectation that the variation in SSD can be alternatively explained by variables reflecting the strength of sexual selection (presence of male combat), fecundity selection (e.g. clutch size and mass) and/or proximate ecological factors (habitat type), none of these variables had consistent effects on SSD, especially when the data were adjusted to phylogenetic dependence and/or body size. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100, 293–306. ADDITIONAL KEYWORDS: allometry – body size – evolution of SSD – fecundity selection – monitor lizards – sexual selection – Varanidae.