池塘中斑索蟾的种群结构、个体生长与存活率

在澳大利亚新南威尔士南部沿海,作者搜集了一个池塘繁殖的斑索蟾(Crinia signifera)的种群统计资料。通过捕捉进出池塘的1 612只个体,获得种群大小、结构、生长率、性成熟时的大小和年龄、死亡率及寿命资料。迁移高峰从6月持续到11月,蛙的最高、最低遇见数量分别出现在春季和秋季。但第2年,该池塘蛙的数量明显减少,可能是由于补充到种群中的幼体数量很少的缘故。6个月后个体的重捕率很低;但距第一次捕获18个月以后,仍有个别个体再次被捕获。性成熟时,雌性比雄性的身体大一些。生长曲线显示,雌性比雄性的生长更快,所以更早地达到性成熟。研究种群的数量、结构和死亡率趋势等与已知的其它Crinia signifera种群基本一致。但研究种群迁移活动的高峰出现较晚,并且夏季的活动水平明显很高。这种长的活动时间可能会导致存活率的下降,同时有利于选择迅速性成熟的雌性[动物学报51 (3) : 393 -400 , 2005]。     

Age and growth of threaded sculpin <Emphasis Type="Italic">Gymnocanthus pistilliger</Emphasis> (Cottidae) in the southern Primorye (Sea of Japan)

The features are discussed of the growth of threaded sculpin Gymnocanthus pistilliger in the southern part of its range, in the Sea of Japan. Several methods were tested to determine the age of this species. The improved approach is suggested for determinating the age of threaded sculpin by annual increments on sagitta using thin cross-sections, characteristics of optical density in different zones of otolith growth, and their positions relative to otolith center. It was demonstrated that the growth rate of threaded sculpin in the waters of southern Primorye was significantly higher than in the northern part of its range: the males reached a length of about 20 cm and the females about 22 cm at the age 5+. The maximum length of individuals, 26 cm in the males and 31 cm in the females, significantly exceed those known from literature. The longevity of threaded sculpin calculated for maximum size is 12–13 yr for the waters of Primorye.     

Growth, maturation and survival of frogs Rana temporaria L.

A total of 1560 breeding frogs were collected in three consecutive years at sites in the west of Ireland. Alt were weighed and measured and the ages of 702 individuals were determined by skeletochronology. The length-weight relationship differed between gravid females, spent females and males, with the gravid females showing the largest weight gain for any increase in length. The majority of males bred for the first time at two years, but most females delayed maturity until they were a year older. While the two-year olds were of similar size, the females subsequently grew at a faster rate and achieved larger maximal sizes than the males. However, both sexes exhibited a decelerating growth rate with age. There was no apparent difference between the sexes in post-maturation survival, which was estimated to be about 50% annually. The oldest frogs were seven years old.     

Altitudinal variation in age and body size in Yunnan pond frog (Pelophylax pleuraden)

Large-scale systematic patterns of body size are a basic concern of evolutionary biology. Identifying body size variation along altitudinal gradients may help us to understand the evolution of life history of animals. In this study, we investigated altitudinal variation in body size, age and growth rate in Chinese endemic frog, Pelophylax pleuraden. Data sampled from five populations covering an altitudinal span of 1413 to 1935 m in Sichuan province revealed that body size from five populations did not co-vary with altitudes, not following Bergmann's rule. Average adult SVL differed significantly among populations in males, but not in females. For both sexes, average adult age differed significantly among populations. Post-metamorphic growth rate did not co-vary with altitude, and females grew faster than males in all populations. When controlling the effect of age, body size did not differ among populations in both sexes, suggesting that age did not affect variation in body size among populations. For females, there may be other factors, such as the allocation of energy between growth and reproduction, that eliminated the effect of age on body size. To our minds, the major reason of body size variation among populations in male frogs may be related to individual longevity. Our findings also suggest that factors other than age and growth rate may contribute to size differences among populations.     

Sex ratios, size distributions, and sexual dimorphism in the dioecious tree Ilex aquifolium (Aquifoliaceae)

Sex ratio and sexual dimorphism in physiology and growth were studied in the dioecious tree Ilex aquifolium at two localities in northern Spain. Genet sex ratio was significantly male biased in one locality but not in the other. However, ramet and flowering ramet sex ratios were male biased at both study sites. Males had significantly thicker main trunks than females in one locality and produced more ramets in the other. Growth rate, estimated from mean width of annual rings, did not differ between localities, but males produced wider rings than females at both sites. Mean annual growth rates over the last 10, 20, and 30 yr were significantly higher for males. Measurements of chlorophyll fluorescence indicated that the efficiency of photosynthesis of leaves on nonfruiting branches of females was higher than for leaves on branches of male plants under low-light conditions, though not under saturating-light conditions. Efficiency of photosynthesis was significantly lower on fruiting branches of female plants than on nonfruiting branches. We discuss whether the observed between-sex differences are attributable to the higher cost of reproduction in females and/or to pollen competition.     

Geographic variation of genetic and behavioral traits in northern and southern tüngara frogs

We use a combination of microsatellite marker analysis and mate-choice behavior experiments to assess patterns of reproductive isolation of the túngara frog Physalaemus pustulosus along a 550-km transect of 25 populations in Costa Rica and Panama. Earlier studies using allozymes and mitochondrial DNA defined two genetic groups of túngara frogs, one ranging from Mexico to northern Costa Rica (northern group), the second ranging from Panama to northern South America (southern group). Our more fine-scale survey also shows that the northern and southern túngara frogs are genetically different and geographically separated by a gap in the distribution in central Pacific Costa Rica. Genetic differences among populations are highly correlated with geographic distances. Temporal call parameters differed among populations as well as between genetic groups. Differences in calls were explained better by geographic distance than by genetic distance. Phonotaxis experiments showed that females preferred calls of males from their own populations over calls of males from other populations in about two-thirds to three-fourths of the contrasts tested. In mating experiments, females and males from the same group and females from the north with males from the south produced nests and tadpoles. In contrast, females from the south did not produce nests or tadpoles with males from the north. Thus, northern and southern túngara frogs have diverged both genetically and bioacoustically. There is evidence for some prezygotic isolation due to differences in mate recognition and fertilization success, but such isolation is hardly complete. Our results support the general observation that significant differences in sexual signals are often not correlated with strong genetic differentiation.     

Seasonality determines patterns of growth and age structure over a geographic gradient in an ectothermic vertebrate

Environmental variation connected with seasonality is likely to affect the evolution of life-history strategies in ectotherms, but there is no consensus as to how important life-history traits like body size are influenced by environmental variation along seasonal gradients. We compared adult body size, skeletal growth, mean age, age at first reproduction and longevity among 11 common frog (Rana temporaria) populations sampled along a 1,600-km-long latitudinal gradient across Scandinavia. Mean age, age at first reproduction and longevity increased linearly with decreasing growth season length. Lifetime activity (i.e. the estimated number of active days during life-time) was highest at mid-latitudes and females had on average more active days throughout their lives than males. Variation in body size was due to differences in lifetime activity among populations??individuals (especially females) were largest where they had the longest cumulative activity period??as well as to differences between populations in skeletal growth rate as determined by skeletochronological analyses. Especially, males grew faster at intermediate latitudes. While life-history trait variation was strongly associated with latitude, the direction and shape of these relationships were sex- and trait-specific. These context-dependent relationships may be the result of life-history trade-offs enforced by differences in future reproductive opportunities and time constraints among the populations. Thus, seasonality appears to be an important environmental factor shaping life-history trait variation in common frogs.     

Activity and home range in a recently widespread European mink population in Western Europe

The European mink is a critically endangered mustelid species of conservation concern throughout Europe. Several conservation interventions have been implemented in recent years, supported by both national and European governments. However, knowledge about the natural history of the European mink is scarce and localized to a few specific areas. From 2007 to 2009, we studied mink activity patterns, home range sizes, and macrohabitats of mink home ranges based on 28 radio-tracked European mink (10 adult females, 11 adult males, 3 young females, and 4 young males) in the Foral Community of Navarre (northern Spain), in the Arga and Aragón rivers. We also provide insights on the spatial organization of the species. European mink presented a stable, mainly nocturnal and crepuscular activity pattern and required between 15 and 75 ha of fluvial habitats to establish their home ranges, which were also quite stable throughout the year. There were great differences between adult females and adult males, the latter having home ranges five times larger. In addition, whereas adult females mainly settled in lagoons and small tributaries, males also used to a large extent the main river sections. European mink presented a polygynous mating system, where males were territorial and encompassed several female home ranges within their home ranges. Lagoons and similar structures should be preserved and favored in management strategies, and tributaries maintained in good condition, as female requirements should be prioritized in plans to improve the general habitat quality for the species. Any conservation plan aimed at the improvement or recovery of European mink populations through habitat management should consider management blocks of at least 15 ha per each potential breeding female.     

Age structure and body size of the Chuanxi Tree Frog Hyla annectans chuanxiensis from two different elevations in Sichuan (China)

Age, body size, and growth patterns in the subtropical anuran Hyla annectans chuanxiensis from high (Dengchigou Protection Station) and low (Lingguan Town) elevations in Baoxing County of Sichuan province (China) were described using skeletochronology. Females were significantly older than males at the low-elevation site, but there was no significant difference between the sexes at the high-elevation site. Age at sexual maturity of both males and females was 2 years at the high-elevation site, whereas males matured at 1 year and females at 2 years at the low-elevation site. Males and females from the low-elevation population reached a maximum age of 3 and 4 years, respectively, whereas males and females from the high-elevation population reached a maximum age of 4 and 5 years, respectively. At both sites, females were significantly larger than males. Females and males from the high-elevation population were larger than individuals from the low-elevation population. When the effect of age was controlled, the differences in body size of the two populations were significant only for females. Von Bertalanffy growth curves indicated that the growth rates in males was greater than in females in both populations. They also showed that the growth of both sexes slowed at an earlier age in the low-elevation population than in the high-elevation population. The findings suggest that age is a major factor underlying body size patterns for both sexes, but that the elevation of the locality affects the body size of females.     

Population biology of three-spined sticklebacks, Gasterosteus aculeatus, in Scotland

The age of maturation, longevity and aspects of anti-predator morphology were studied for seven Gasterosteus aculeatus L. populations in Scotland during 1978 and 1979. All seven populations are annual with less than 1% of adults surviving a second year. At the four mainland study sites, breeding adult sticklebacks were larger than at any of the three Hebridean sites. Adult females were larger than adult males at all sites, except Lennox Castle where parasitism may account for the lack of sexual dimorphism. Two of the Hebridean sites, Loch Fada and Loch a Bharpa have spine-deficient G. aculeatus populations which are morphologically unprotected from predation. In the five normally spined populations, some aspects of defensive morphology (index of increase in critical dimension, ventral spine size) are associated with predation risk, while others (lateral plate number) are not. These data are discussed in relation to the current stickleback literature.     

Age structure and body size of the Chuanxi Tree Frog Hyla annectans chuanxiensis from two different elevations in Sichuan (China)

Age, body size, and growth patterns in the subtropical anuran Hyla annectans chuanxiensis from high (Dengchigou Protection Station) and low (Lingguan Town) elevations in Baoxing County of Sichuan province (China) were described using skeletochronology. Females were significantly older than males at the low-elevation site, but there was no significant difference between the sexes at the high-elevation site. Age at sexual maturity of both males and females was 2 years at the high-elevation site, whereas males matured at 1 year and females at 2 years at the low-elevation site. Males and females from the low-elevation population reached a maximum age of 3 and 4 years, respectively, whereas males and females from the high-elevation population reached a maximum age of 4 and 5 years, respectively. At both sites, females were significantly larger than males. Females and males from the high-elevation population were larger than individuals from the low-elevation population. When the effect of age was controlled, the differences in body size of the two populations were significant only for females. Von Bertalanffy growth curves indicated that the growth rates in males was greater than in females in both populations. They also showed that the growth of both sexes slowed at an earlier age in the low-elevation population than in the high-elevation population. The findings suggest that age is a major factor underlying body size patterns for both sexes, but that the elevation of the locality affects the body size of females.     

Does intraspecific niche partitioning in a native predator influence its response to an invasion by a toxic prey species?

Abstract The introduced and highly toxic cane toad (Bufo marinus) is rapidly spreading across northern Australia where it may affect populations of large terrestrial vertebrate predators. The ecological impact of cane toads will depend upon the diets, foraging modes and habitat use of native predators, and their feeding responses to cane toads. However, intraspecific niche partitioning may influence the degree of vulnerability of predators to toxic prey, as well as the time course of the impact of alien invaders on native species. We studied the diet of the northern death adder Acanthophis praelongus and their feeding responses to cane toads. In the laboratory, death adders from all size classes and sexes readily consumed frogs and cane toads. Diets of free ranging A. praelongus from the Adelaide River floodplain were more heterogeneous. Juvenile snakes ate mainly frogs (39% of prey items) and small scincid lizards (43%). Both sexes displayed an ontogenetic dietary shift from lizards to mammals, but adult males fed on frogs (49%) and mammals (39%) whereas adult females (which grew larger than males) fed mainly on mammals (91%) and occasionally, frogs (9%). Feeding rates and body condition of adult snakes varied temporally and tracked fluctuations in prey availability. These results suggest that cane toads may negatively affect populations of northern death adders in the Darwin region. However, we predict that different size and sex classes of A. praelongus will experience differential mortality rates over different timescales. The initial invasion of large toads may affect adult males, but juveniles may be unaffected until juvenile toads appear the following year, and major affects on adult female death adders may be delayed until annual rainfall fluctuations reduce the availability of alternative (rodent) prey.     

Patterns of growth and sexual size dimorphism in two species of box turtles with environmental sex determination

An adaptive explanation for environmental sex determination is that it promotes sexual size dimorphism when larger size benefits one sex more than the other. That is, if growth rates are determined by environment during development, then it is beneficial to match developmental environment to the sex that benefits more from larger size. However, larger size may also be a consequence of larger size at hatching or growing for a longer time, i.e., delayed age at first reproduction. Therefore, the adaptive significance of sexual size dimorphism and environmental sex determination can only be interpreted within the context of both growth and maturation. In addition, in those animals that continue to grow after maturation, sexual size dimorphism at age of first reproduction could differ from sexual size dimorphism at later ages as growth competes for energy with reproduction and maintenance. I compared growth using annuli on carapace scales in two species of box turtles (Terrapene carolina and T. ornata) that have similar patterns of environmental sex determination but, reportedly, have different patterns of sexual size dimorphism. In the populations I studied, sexual size dimorphism was in the same direction in both species; adult females were, on average, larger than adult males. This was due in part to males maturing earlier and therefore at smaller sizes than females. In spite of similar patterns of environmental sex determination, patterns of growth differed between the species. In T. carolina, males grew faster than females as juveniles but females had the larger asymptotic size. In T. ornata, males and females grew at similar rates and had similar asymptotic sizes. Sexual size dimorphism was greatest at maturation because, although males matured younger and smaller, they grew more as adults. There was, therefore, no consistent pattern of faster growth for females that may be ascribed to developmental temperature. Received: 20 March 1996 / Accepted: 10 March 1998     

A skeletochronological study on a subtropical, riparian ranid (Rana swinhoana) from different elevations in Taiwan

We estimated the age, longevity, and growth patterns of a subtropical ranid, Rana swinhoana from high (Lishing) and low (Wulai) elevations using skeletochronology. In addition, we also measured body mass and length of frogs from five other localities. Results showed that both snout-vent length and body mass of frogs were significantly correlated with altitudes for both sexes. Frogs of Lishing were significantly larger and older than that of Wulai. We used LAGs to estimate the age and growth of frogs and found that the growth of Wulai frog of both sexes slowed down at an earlier age than that of Lishing frogs. Male and female frogs from Wulai did not exceed 6 and 7 years, respectively, while the maximum age of males and females of Lishing was 7 and 11 years, respectively. Results suggest that the LAGs observed in R. swinhoana correspond to low temperature and/or decreased food availability instead of desiccation during the harsh annual period (November to February). Skeletochronological data suggest that the variations of body size of R. swinhoana among elevations are likely associated with the growth, age at sexual maturity, and longevity.     

Determination of growth and maturation in the common frog, Rana temporaria, by skeletochronology

Growth and maturation in a Swiss population of Rana temporaria were studied in 1983 and 1984 by means of skeletochronology. Resting line (growth ring) diameters were used to back-calculate individual body sizes in previous years; these permitted establishment of an average growth curve and determination of individual ages and sizes at first reproduction. Growth was rapid up to maturation, but continued thereafter at a decreased rate. Males were larger than females at age two but females grew faster thereafter, causing sexual dimorphism in adult body sizes. Body size distributions for both years and for frogs recaptured and first captured in 1984 were established. Growth in immatures was positively, but in adults negatively correlated with body size, with considerable variation at all sizes. Individual adult sizes were positively correlated with body sizes at the end of the first year. Average individual age at first reproduction was 2.8 years in males and 3.1 years in females (range in both sexes two to four years). There is no evidence for a two-year-cycle of reproduction.     

Macrogeographic clines in fecundity, reproductive allocation, and offspring size of the forest tent caterpillar Malacosoma disstria

1. The fecundity of the forest tent caterpillar varies considerably across its geographic range. Field data indicate that populations in the southern United States (Gulf States) produce nearly twice as many eggs as females from Canada or the Lake States, with little or no difference in the size of adult females. 2. In controlled rearing experiments, female forest tent caterpillar from the southern United States (Louisiana) had much larger clutch sizes than same sized females from northern populations in Michigan or Manitoba, Canada. Increased fecundity in Louisiana females was achieved through a significant reduction in egg size and a concomitant increase in the allocation of resources to egg production. 3. Comparison of 10 forest tent caterpillar populations spanning a 27° latitudinal gradient, validated the results of detailed comparisons among the three populations above by confirming the strong negative correlation between latitude and clutch size. 4. Neonate forest tent caterpillars from Manitoba were significantly larger than larvae from either Michigan or Louisiana. Michigan larvae were intermediate in size. It is postulated that large neonates are advantageous in thermally limiting environments. More than three times as many degree‐days are available to Louisiana neonates during the first 2 weeks after hatching. A consistently favourable climate during the vulnerable post‐hatching period may have allowed the evolution of larger clutches at the expense of neonate size in southern populations.     

PROXIMATE MECHANISMS OF SEXUAL SELECTION IN WOOD FROGS

Observations and several types of field experiments on the mating behavior of wood frogs have revealed the proximate mechanisms for a size-related reproductive advantage in both males and females. For females, larger individuals produce larger clutches; for males, larger individuals can better remain clasped to females when contested by rival males and can better depose males clasped to other females. No results obtained support of the existence of mate choice in either males or females. Males were estimated to be 4.74 times as variable as females in the number of zygotes produced per individual per season; however, much of the variation in male RS resulted from a male-biased sex ratio at the breeding site rather than from sexual selection. After taking sex ratio effects into consideration, males were estimated to be only 1.63 times as variable as females. Patterns of variation in RS in males and females are associated with numerous sex-specific differences in life history and morphology. Life history differences include differential growth rates, ages at sexual maturity, and rates of mortality. Interpretation of how the body size dimorphism (females larger than males) in this species relates to sexual selection is consistent with information on how similar variations in body size influence RS for each sex, and how males and females differ in the functional relationship between body size and RS. Average RS increases more with body size in females than in males. Although body size directly influences RS for females, the possibility exists that, for males, other anatomical features correlated with body size more directly affect RS. Preliminary evidence suggests that sexual selection influences male arm length and that the male body size : RS relationship results as an incidental correlation.     

GEOGRAPHIC VARIATION IN LIFE-HISTORY TRAITS OF THE ANT LION,MYRMELEON IMMACULATUS: EVOLUTIONARY IMPLICATIONS OF BERGMANN'S RULE

In eastern North America, body size of the larval ant lion Myrmeleon immaculatus increases from south to north, following Bergmann's rule. We used a common-garden experiment and a reciprocal-transplant experiment to evaluate the effects of food and temperature on ant lion growth, body size, and survivorship. In the laboratory common-garden experiment, first-instar larvae from two southern (Georgia, South Carolina) and two northern (Connecticut, Rhode Island) populations were reared in incubators under high- and low-food and high- and low-temperature regimes. For all populations, high food increased final body mass and growth rate and decreased development time. Growth rates were higher at low temperatures, but temperature did not affect larval or adult body mass. Survivorship was highest in high-food and low-temperature treatments. Across all food and temperature treatments, northern populations exhibited a larger final body mass, shorter development time, faster growth rate, and greater survivorship than did southern populations. Results were similar for a field reciprocal-transplant experiment of third-instar larvae between populations in Connecticut and Oklahoma: Connecticut larvae grew faster than Oklahoma larvae, regardless of transplant site. Conversely, larvae transplanted to Oklahoma grew faster than larvae transplanted to Connecticut, regardless of population source. These results suggest that variation in food availability, not temperature, may account for differences in growth and body size of northern and southern ant lions. Although northern larvae grew faster and reached a larger body size in both experiments, northern environments should suppress growth because of reduced food availability and a limited growing season. This study provides the first example of countergradient selection causing Bergmann's rule in an ectotherm.     

Geographic variation as a result of evolution of the traits with broad and narrow norms of reaction in the moor frog (Rana arvalis)

Females reproductive, size, and age characteristics were studied in isolated local populations of Rana arvalis in the southern and northern parts of its range. The yearlings of the southern populations used to get larger by their first overwintering due to earlier beginning of the breeding season, as compared with the yearlings of the northern population. As a result, "southern" females become sexually mature at the age of two years while the "northern" ones become mature at the age of three years. This causes geographic differences in age composition among two populations, the "southern" reproductive females being younger on average than the "northern" ones. The earlier female maturation in the first case is not compensated by respective rise of the growth rate; to the contrary, the "southern" females grow more slowly during the first two years of their life and appear to be smaller than the "norhern" ones. These reproduction and growth patterns arise supposedly due to paedomorphosis, which causes specific reproductive characteristics, namely decrease in the egg size, increase in the reproductive effort and more strong correlation between female fertility and body size. Local and geographic differences are expressed not in the extent but in the structure of reproductive pattern, as no negative correlation was revealed between female reproductive age and body size in the southern populations. Southern habitats cannot be considered as "unfavourable with respect to body size", so the geographic differences under consideration cannot be explained by optimization of the reproductive strategies at population level. Paedomorphosis appears as a result of the female maturation rate possessing a wider norm of reaction than the growth rate. At the same time, fixation of the specific growth rate narrows norm of reaction of some other characters important for the phenotype reproductive fitness thus predetermining their subsequent evolution.     

Altitudinal and environmental variation in lifespan in the Copper butterfly Lycaena tityrus

1.  Variation in longevity within and between natural populations is widespread, and understanding the relative importance of environmental and genetic factors as well as their interactions in mediating such variation is crucial in longevity research.
2.  In this study lifespan of adult copper butterflies was examined in relation to altitude, temperature (20 and 27 °C), sex and adult feeding.
3.  As expected, longevity increased with decreasing temperature, and sucrose-fed butterflies had longer lifespans compared to water-fed and finally non-fed individuals. The impact of feeding, especially of having access to water or not, was larger at the higher compared to the lower temperature.
4.  Regarding altitudinal patterns, increased lifespan in high-altitude populations was largely restricted to beneficial feeding conditions, while under carbohydrate deprivation low-altitude animals lived longer, suggesting that low-altitude butterflies do better under food stress.
5.  Differences in longevity between sexes were small at 20 °C, while females lived substantially longer than males at the higher temperature. Consequently, females may be less susceptible to high temperature stress than males. Further, males suffered more from food stress than females, suggesting that females are generally more stress resistant than males.
6.  Using a full factorial design, this study demonstrates that variation in longevity is caused by several factors, and additionally by substantial interactive effects. Consequently, patterns of variation in longevity are complex, and one needs to be cautious when neglecting this source of variation, by focussing on individual factors only.