繁殖盛期雄性普通东方小蛙的个体大小不影响交配成功率

通过比较抱对和非抱对普通东方小蛙(Crinia signifera) 的吻尾干骨长(体长) 和检测个体较大或状态较好的雄体是否为成功繁殖个体, 检测雌蛙体长与交配成功的雄蛙的体长和相对状态(体重/体长) 之间是否存在线形关系, 评估交配与个体大小之间的关系。在实验室内, 令未交配雌体选择随机选出的雄体, 观测雌体是否与最大的雄体交配; 将抱对的蛙暴露于其它雄蛙, 观测其它较大或较小的雄蛙是否取代已抱对的雄蛙。结果表明: 抱对雄蛙和雌蛙的个体大小无显著的关系, 成功交配的雄蛙并不比未交配的雄蛙大, 其它雄蛙不能取代已抱对的雄蛙。在这一C. signifera种群中, 繁殖盛期雄性个体的大小似乎不影响交配成功率, 在此期间即便存在配偶选择, 亦决定于与雄性个体大小无关的其它因素。在更长的繁殖期内, 雄性个体大小则与交配成功率有关, 这是该种的典型特征。     

瑞士西部农田周围生态保留带中小型兽类种群结构特征及数量动态的初步研究

为了评价生态保留带对小型兽类种群的影响,2003年7月至2004年6月在瑞士西部Salavaux,chevmux和Montbrelloz 3个地区采用标志重捕方法对小型兽类种群进行了研究。在3个生态保留带中,共发现6种1206只小型兽类,其中普通田鼠、小林姬鼠、中麝晌捕获数量多。普通田鼠为优势种。普通田鼠的种群数量在生态保留带间有差异,但具有相同的季节性波动趋势,一般种群数量随着植被覆盖度和食物丰富度的增加,春季末开始出现增加,仲夏达到最高水平。种群中雌雄个体年龄结构之间有明显的差异,成体和亚成体的数量比幼体多,雄性亚成体的数量比雌性多,雌性成体数量比雄性多（X^2=44．09,df=10,P〈0．001,N=203）。普通田鼠种群中雌雄个体体重之间有明显的差异,雄性的体重比雌性大（t一检验：t=5．011,df=162,P〈0．05,N=213）。种群性比之间有明显的月间变化,雌性的捕获次数比雄性大。普通田鼠只在短距离范围内活动,在生态保留带中的巢区为350～400m^2,雌雄个体的巢区大小之间没有显著性差异。     

泽陆蛙(Fejervarya limnocharis)两性异形的个体发育和雌体繁殖

2010年3月下旬-7月上旬于浙江富阳市农田采集680只泽陆蛙(Fejervarya limnocharis),研究了泽陆蛙成体和幼体的个体大小和局部形态特征的两性异形;通过解剖雌体获得窝卵数、测量抱对个体获得形态数据,研究了雌体大小与生育力关系以及抱对两性个体体形大小的相关性.结果表明:捕获个体中,雌性和雄性成体的最小体长分别为33mm和30 mm;雄性成体个体数显著超过雌性成体,两性幼体个体数无显著差异;两性成体头部大小、四肢长随体长呈同速增长,眼径和体重随体长呈异速增长,两性幼体所有被检形态特征均随体长呈同速增长;雌性成体平均体长显著大干雄性成体,去除体长差异的影响后发现,除眼径无显著的两性差异外,其余被检形态特征均为雌性大于雄性;幼体除雌性体重大于雄性外,其余被检形态特征均无两性差异;窝卵数与雌体大小(体长和体重)呈显著的正相关;两性抱对个体的体长无显著相关性;泽陆蛙雄性成体体形小于雌性成体的个体大小两性异形模式可能决定于驱使雄性向较大体形发展的进化驱动力相对较弱,雌性增大体形可增加繁殖输出,故向较大体形发展的进化驱动力相对较强;除体重外,其余被检形态特征的两性异形均形成于性成熟之后.     

贺兰山岩羊的生命表和春夏季节社群结构的研究

利用６２架自然死亡的雄性岩羊角,初步探讨了贺兰山岩羊种群的生命表、年龄结构和存活曲线：贺兰山岩羊５．５龄和９．５龄死亡率明显增大,为两个死亡高峰;有一半以上的雄性个体年龄超过８岁;存活曲线基本接近Ａ型．此外,将春季调查的１３９群８０８只岩羊和夏季调查的６７群４４８只岩羊的社群结构进行比较,发现春季与夏季的雌幼比相似,雌雄比都是雄性大于雌性;春、夏季社群大小变化不显（Ｐ＞０．０５）,并且贺兰山岩羊     

海南坡鹿种群生活史特征及种群动态趋势预测

本文应用生命表和Leslie矩阵等生活史常规研究方法,分析了生存于海南邦溪自然保护区的国家I级珍稀濒危哺乳动物海南坡鹿种群的年龄结构、特定年龄存活率、特定年龄繁殖率、初次产仔年龄、产仔季节、性比、寿命等重要生活史特征,并预测其种群动态趋势.邦溪海南坡鹿种群平均寿命4.6岁,雌性平均寿命略高于雄性,分别为4.7岁,4.4岁;雌性平均初次产仔年龄为24月龄;雌性平均性成熟年龄为16月龄;雌性最长繁殖寿命为8.5岁,雄性最长繁殖寿命约为4岁;成年雌性平均一年一胎,胎仔数为1;新生幼仔数量雄性大于雌性,性比为1.33∶1;种群动态生命表的分析结果表明,各年龄段雄性存活率高于雌性.幼体(0～2岁)死亡数雌性高于雄性,壮年成体(3～8岁)死亡数雄性高于雌性,老体(9岁～)死亡数两性几乎相等.雌性幼体受到较强的自然选择作用,体弱个体被淘汰;壮年雄体为繁殖付出较高的代价,死亡个体数量较高.Leslie矩阵预测结果表明,如果影响出生率和死亡率的因子不变,种群数量将逐年增长,周限增长率为λ≈1.011; 种群内禀增长率r≈0.012;种群世代增长率R0 ≈1.06;世代长度T≈5.12年.产仔时间为秋季与冬季,春、夏季节不产仔,此为适应海南岛独特的热带环境选择压力的结果.     

不同放牧强度下矮嵩草（Kobresia humilis）无性系分株种群的动调

以矮嵩草无性系分株和分蘖分别作为其种群的基本单元,对不同放牧强度下种群的动态与调节进行了研究。结果表明：随着放牧强度的增加,每分株的分蘖数、叶片数及分株个体地上生物量均增加．分蘖死亡率和叶片死亡率在各处理间差异不显著。分蘖死亡率的高峰出现在生长季末,叶片死亡率在生长初期和末期较高,而且都不属于密度制约性的死亡。矮嵩草多重种群结构水平的数量调节是由最外层次（叶片层次）的数量变化引起的,进而影响到较内层次上结构单元的大小和数量。     

社鼠种群生态研究

1983—1987年在北京西山研究了社鼠的种群生态学,共捕获标本870只,用胴体重方法划分5个年龄组。种群年龄组成,随季节而有变化。年龄锥体有季节和年度差异。雌雄性比亦有年度变化。在多数年份中,幼体和亚成体的雌性比例高于雄性。社鼠一般在3—4月开始繁殖,9月基本结束,10月见到个别孕鼠。雄性个体性成熟时的睾丸重量在0.8克以上,雌性产仔数平均为5.20。多数雌体一年繁殖2次,个别可繁殖3次。生态寿命约一年半或更长一些。有些雌体参加两年的繁殖活动。社鼠的种群数量,有明显的季节和年度变化。     

金沙江攀枝花江段白缘(鱼央)的繁殖生物学

为丰富白缘(鱼央)Liobagrus marginatus(Günther)的基础生物学资料,于金沙江攀枝花江段收集到729尾性腺可辨的样本,分析其年龄结构、性别比、初次性成熟个体大小以及繁殖力等繁殖生物学特征。结果表明:繁殖群体由1~4龄4个年龄组组成,其中2龄个体在数量上占绝对优势(63.83%),其对种群繁殖力的贡献为62.07%。在性成熟个体中,雌性和雄性分别为64尾和77尾,雌雄比=1∶1.20;符合1∶1理论比值(χ~2=1.199,P0.05);雌、雄最小性成熟个体体长分别为66.80 mm、67.32 mm,体质量分别为5.7 g、6.7 g。攀枝花江段白缘(鱼央)的繁殖季节为3—6月,绝对繁殖力平均值为161.2粒±55.1粒。Ⅳ期卵巢中卵子发育不完全同步,卵径变幅为0.29~3.86 mm。金沙江攀枝花江段白缘性成熟快,但繁殖力低,繁殖群体主要由低龄个体组成,种群资源亟需保护。     

气温对出蛰期泽陆蛙(Fejervarya limnocharis)日间活动的影响

以泽陆蛙(Fejervarya limnocharis)为模型动物, 在浙江省温州市瑞安碧山镇涂厂村农田生境, 通过近1个月时间的野外活动数量调查, 检测出蛰期时间尺度和气温变化对白天泽陆蛙野外活动数量及活动个体大小的影响。结果显示:(1)月周期调查中泽陆蛙个体大小在不同采集时间上差异不显著, 气温与个体大小相关亦不显著, 气温与白天活动个体的数量呈显著正相关;(2)持续4天的泽陆蛙的活动数量的调查显示, 上下午间差异显著, 上午的活动数量显著少于下午, 个体大小在上下午间差异不显著, 气温与个体大小相关不显著, 与白天活动个体的数量呈显著的正相关;(3)3月份时间推移的温度和数量的数据和4月初上午和下午数据的单因子协方差分析显示, 两者回归关系具有平行性, 但截距差异显著。据此我们推断气温是影响野外出蛰期泽陆蛙活动数量的重要的生态因子。     

洞庭湖区社鼠的繁殖生态

在洞庭湖区域,社鼠（Niviventer confucianus）种群主要栖息在山区和丘陵地带的林地内.总体而言,其种群雌性比基本维持在50%左右,但在季节间和年龄组间有一定的差别,雌性比在冬、春季较低,夏、秋季的雌性比都超过50%.年龄组间,雌性比最高的为幼年组66.7%,亚成年和成年组的雌性比接近50%,而老年组的雌性比为最低,为33.3%.所有雌鼠全年的怀孕率为31.1%,平均胎仔数为3.7只,繁殖指数为0.58.春、夏季怀孕率较高,冬季没有捕获到怀孕的雌鼠,仅捕获到有怀孕经历（有宫斑）的雌鼠.繁殖指数在夏、秋季维持高峰水平.雌性社鼠总的参产率为53.3%,各季间呈现从春、夏到秋逐渐增加的趋势,冬季停止怀孕.可见夏、秋季为雌鼠的繁殖高峰期.随着年龄组增长,平均胎仔数有明显增加的趋势,老年组胎仔数最高,而繁殖指数以成年组最高,说明成年组是种群中繁殖的主体.雄性社鼠的睾丸下位率全年总计为75.6%,分四季平均为86.0%,夏、秋季维持在较高水平,冬、春季稍低,低谷在春季.下位睾丸的重量与大小有明显的季节变化,呈现春、夏、秋、冬逐渐下降的规律,春季与冬季相比,有显著性差异,说明开春后,雄性社鼠在生殖潜能上已有明显变化.这些特征与雌鼠的繁殖高峰基本吻合.说明社鼠主要在春、夏、秋季繁殖,繁殖盛期在夏秋季.从不同年龄组看,幼年组个体不参与繁殖,亚成年组个体开始参与繁殖,繁殖主体是成年组个体.     

Sexual size dimorphism and sex-specific survival in adults of the damselfly Lestes disjunctus

1. A population of adult Lestes disjunctus (Odonata: Lestidae) was studied in eastern Ontario, Canada. Mass at sexual maturity and activity rates of individuals were measured. Population density was estimated on transects, while survival rates and population size were estimated using mark−recapture methods.
2. There was no difference in mass of mated and unmated males. Females were more than 50% heavier than males, and were also more active than males.
3. Males were almost eight times more abundant on transects than females, but Manly−Parr estimates of male population size were only a maximum of 2.5 times larger than estimates for females.
4. Males were 2.5 times more likely to be resighted after marking than were females. This accounts for much of the discrepancy between transect estimates and mark−recapture estimates of relative population size.
5. Daily survival rates of sexually mature females were not significantly less than those of males, and therefore cannot account for a change in sex-ratio from 1 : 1 at emergence to more males than females in sexually mature adults.
6. Differences in mortality must occur prior to sexual maturity, coincident with the time during which differences in mass gain are also taking place.     

Spatial distribution and population composition of the brown mouse lemur (Microcebus rufus) in Ranomafana National Park, Madagascar, and its implications for social organization

Through a 16-mo mark-recapture trap study, I examined aspects of spatial distribution and population composition in the brown mouse lemur, Microcebus rufus, a 42 g nocturnal strepsirhine. The study took place in the rainforest of Ranomafana National Park in southeastern Madagascar. Sherman live traps were set monthly for a variable number of nights in a quasi-grid 50 m apart. Captured individuals were marked for future identification and released at site of capture. More males than females were captured overall (102 versus 72) and at 83% of trap sites. Trap sex ratio fluctuated significantly over the course of the study. It was particularly male-biased between June and August (3.9:1), when more previously uncaptured males than females (14 versus 6) entered the trap population. Some of these males remained in the trap population. Although the average number of individuals captured was not significantly different between the first four and last four months of the study, the composition of the population changed. The female population, however, changed less: 28.9% of all females captured in the first four months of the study were recaptured in the last four months, compared to 9.7% of males. It is suggested that the pattern of appearance of new individuals and disappearance of others, both predominantly male, may indicate migratory activity. Furthermore, an average of eight individuals were captured at each trap site (approximately 70% of traps captured more than five), suggesting a high degree of spatial overlap. The average number of male and female individuals captured in each trap (5.5 males versus 2.5 females), the average number of trap sites at which males and females were captured (3.6 versus 2.4), and the average number of captures for males and females (9.8 versus 5.7) all differed significantly between the sexes.     

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.     

Reproductive cycle,sexual maturity and longevity of Odontophrynus americanus (Anura: Odontophrynidae) in South Brazil

Studies on the reproductive biology and age of amphibians provide primary information about the life history and population demographic parameters of species. Here, we describe the reproductive cycle, size–fecundity relationships, reproductive effort, sexual dimorphism and sexual maturity of Odontophrynus americanus, the flood frog, from South Brazil. A total of 96 individuals were analysed. The reproductive cycles of males and females were described through morphoanatomical analysis of testis and ovary. Age at onset of sexual maturity and estimated longevity were determined by skeletochronology. Individuals of O. americanus presented a potentially continuous reproductive cycle with a peak of reproductive activity in the warmer months. Females presented a higher reproductive investment than males. Sexual maturity was reached at around one year of age for both sexes while longevity differed between the sexes, with females living up to six years and males up to ten years. No evidence of sexual size dimorphism was found. This study is among the few that have assessed age at sexual maturity and longevity in a Neotropical anuran. Basic aspects of life history are of paramount importance because they allow comparisons and test of hypotheses to be made, which can help to build generalizations about the evolutionary meaning of ecological strategies.     

Life-history characteristics of a wild population of vervets (Cercopithecus aethiops sabaeus) in Barbados,West Indies

Life history data are presented for a population of vervets, Cercopithecusaethiops sabaeus, in Barbados, West Indies. The data were obtained from two habituated troops and from vervets captured during a large-scale trapping program. Individuals of known age from one troop were weighed periodically, and separate growth curves generated for males and females. The mean weight of captured adult females was 3.3 kg; that of adult males, 5.3 kg. The average age at sexual maturity is estimated at 34 months for females and 60 months for males. Vervets give birth throughout the year, but most infants are born between April and July. The average interbirth interval following a surviving infant is 11.8 months. The mortality of juveniles is heaviest between birth and 2 years of age and decreases thereafter. Males emigrate from their natal troops at sexual maturity and one incident of a juvenile female emigrating is reported.     

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.     

MEASURING SELECTION ON A POPULATION OF DAMSELFLIES WITH A MANIPULATED PHENOTYPE

The estimation of the relationship between phenotype and fitness in natural populations is constrained by the distribution of phenotypes available for selection to act on. Because selection is blind to the underlying genotype, a more variable phenotypic distribution created by using environmental effects can be used to enhance the power of a selection study. I measured selection on a population of adult damselflies (Enallagma boreale) whose phenotype had been modified by raising the larvae under various levels of food availability and density. Selection on body size (combination of skeletal and mass at emergence) and date of emergence was estimated in two consecutive episodes. The first episode was survival from emergence to sexual maturity and the second was reproductive success after attaining sexual maturity. Female survival to sexual maturity was lower, and therefore opportunity for selection greater, than males in both years. Opportunity for selection due to reproductive success was greater for males. The total opportunity for selection was greater for males one year and for females the other. Survival to sexual maturity was related to mass gain between emergence and sexual maturity. Females gained more mass and survived less well than males in both years but there was no linear relationship between size at emergence and survival for females in either year. However, females in the tails of the phenotype distribution were less likely to survive than those near the mean. In contrast, small males consistently gained more mass than large males and survived less well in one year. There was significant selection on timing of emergence in both years, but the direction of selection changed due to differences in weather; early emerging females were more successful one year and late emerging males and females the other. The number of clutches laid by females was independent of body size. Because the resources used to produce eggs are acquired after emergence and this was independent of size at emergence, female fitness did not increase with size. Small males may have had lower survival to sexual maturity but they had higher mating success than large males. Resources acquired prior to sexual maturity are essential for reproductive success and may in some species alter their success in inter- and intrasexual competition. Therefore, ignoring the mortality associated with resource acquisition will give an incomplete and potentially misleading picture of selection on the phenotype.     

Sexual size dimorphism,growth, and maturity of the fluvial eight-barbel loach in the Kako River,Japan

The maturation and growth pattern of the fluvial eight-barbel loach Lefua sp. (Japanese name: nagare-hotoke-dojo), an endangered species, was investigated using an individual identification-recapture method from 1995 to 1998 in an upper reach of a headwater tributary of the Kako River, Hyogo Prefecture, Japan. Based on observations of the gonads through the abdominal skin, the loach was estimated to breed mostly from May to July. All the males matured by age 1⁺, and all the females matured by age 2⁺. Gamete release in all individuals of both males and females was predicted from recaptured loaches during each breeding season. The standard length of mature females was significantly larger than that of males, showing sexual size dimorphism (SSD). The maximum sizes recorded were 75.4 mm SL for females and 61.2 mm SL for males. Both males and females of immature specimens grew mainly from May to November, including the breeding season, with no significant differences in growth rates between them. After sexual maturity, both males and females grew mainly from July to October (or November), after the breeding season, and the females exhibited higher growth rates than males. Therefore, SSD of the species seems to be attributable to the different growth rates after maturity. The longevity of the loach was estimated to exceed ten years based on individual growth patterns of various sizes during the survey period. It is likely that the loach has an iteroparous life history, breeding every year, and moderate growth rates after maturity.     

Reproductive success, mortality and sexual size dimorphism in the adder, Vipera berus

From 1981 to 1986 an isolated adder population was studied in the extreme south of Sweden. During this period 48 adult males and 44 adult females were marked. Male adders did not grow as large as the females. Large males had a significantly higher annual mating success and were engaged in more combats than smaller males. The mean length of recaptured males was significantly lower than that of those not recaptured, indicating a higher motality of larger males. Females brood size was positively correlated with body size. In females there was no difference in mean length of recaptured vs not recaptured individuals. The adder is one of the few snake species with male combat where males are smaller than females. I suggest that this is due to stronger selective advantages for large body size in females than in males.     

OBSERVATIONS ON NOCTULE BATS (NYCTALUS NOCTULA) CAPTURED WHILE FEEDING

In the summer and early autumn of 1960, 1961 and 1962, noctule bats flying low, taking house crickets as these flew from a municipal rubbish tip, were captured in mist nets, ringed, released and in many cases recaptured a number of times. The flying bats showed no fear of human beings or predatory birds and did not learn to avoid the net. In June and July of each year the majority of bats caught were adult females, the flying young of the year first appearing in August though some did not fly until September and October. Young males did not reach sexual maturity in the year of their birth, though five out of fourteen females recaptured at a year old did. There was a considerable movement of adult males in the late summer, adult bats being captured in approximately equal numbers of both sexes during August and September. In October the females seemed to disappear, the majority of the bats caught during that month being males: by November the crickets had ceased to fly and no more bats could be captured though a few wero still flying on warm nights. There was a marked difference in feeding behaviour over these three years, the bats concentrating more on crickets in 1960 than in 1961 and 1962. Though the differences are not statistically significant there were indications of an increase in body weight between July and October in the years when less cricket feeding was occurring. About 50 per cent of the females captured in each of the years 1960 and 1961 were recaptured feeding on the same site in the following year: the recovery rate of males was about 30 per cent in 1961, 60 per cent in 1962.