Female-biased Dispersal of the Emei Moustache Toad (Leptobrachium boringii) under Local Resource Competition

Dispersal is an important area of ecological and evolutionary research.Although many studies have been conducted in mammals and birds,dispersal pattern in amphibians is still unclear.To verify dispersal patterns of amphibians,an endangered species the Emei Moustache Toad(Leptobrachium boringii)was selected.In this study,we analyzed six genetic parameters:inbreeding coefficient(F_(IS)),gene diversity(H_S),the mean of corrected assignment index(mAI_C),the variance of corrected assignment index(vAI_C),relatedness(r)for all three years together and each year separately based on eight highly polymorphic microsatellite loci.Data in totaled across years and each year for 581 individuals captured during 2013–2015 revealed a significant female-biased dispersal pattern.Significantly higher F_(IS) and H_S in females,and lower mAI_C and r for each year separately in females support that L.boringii displays femalebiased dispersal,although r for the total dataset and vAI_C tests did not show significant differences between the sexes.Female-biased dispersal patterns may be explained by the local resource competition hypothesis.     

Significant Male Biased Sexual Size Dimorphism in Leptobrachium leishanensis

Sexual size dimorphism(SSD) is a widespread phenomenon among animals, and whose evolution and maintenance has been a central topic in evolutionary biology since Darwin's time. SSD varies in direction among the major taxonomic groups of animals and even within the same groups. In anurans, female biased SSD is the rule in many lineages, whereas male biased SSD is a rare phenomenon. In this paper, we analyze whether SSD exists inLeptobrachium leishanensis by comparing morphological characteristics between the sexes. Our results show that all six morphological characteristics measured are significantly different between the sexes. Males are significantly larger than females, indicating that the male biased SSD of this species is apparent. The size of the nuptial spines, a special secondary sex trait of males, is significantly and positively correlated with body size. We suggest that the resource defense polygyny mating system and parental care behavior may be explanations for the evolution of male biased SSD and nuptial spine development in this species.     

Sexual Size Dimorphism,Canine Dimorphism,and Male-Male Competition in Primates

Sexual size dimorphism is generally associated with sexual selection via agonistic male competition in nonhuman primates. These primate models play an important role in understanding the origins and evolution of human behavior. Human size dimorphism is often hypothesized to be associated with high rates of male violence and polygyny. This raises the question of whether human dimorphism and patterns of male violence are inherited from a common ancestor with chimpanzees or are uniquely derived. Here I review patterns of, and causal models for, dimorphism in humans and other primates. While dimorphism in primates is associated with agonistic male mate competition, a variety of factors can affect male and female size, and thereby dimorphism. The causes of human sexual size dimorphism are uncertain, and could involve several non-mutually-exclusive mechanisms, such as mate competition, resource competition, intergroup violence, and female choice. A phylogenetic reconstruction of the evolution of dimorphism, including fossil hominins, indicates that the modern human condition is derived. This suggests that at least some behavioral similarities with Pan associated with dimorphism may have arisen independently, and not directly from a common ancestor.     

Lack of Evolution of Sexual Size Dimorphism in Heteromyidae (Rodentia): The Influence of Resource Defense and the Trade-Off between Pre- and Post-Copulatory Trait Investment

One paradoxical finding in some mammals is the presence of male–male intrasexual competition in the absence of sexual size dimorphism. It has been a major goal of evolutionary biologists for over a century to understand why some species in which large males can monopolize multiple mates while excluding smaller competitors, exhibit little or no sexual dimorphism. In this paper I examine three of the main hypotheses that have been proposed to explain this conundrum using as study case the Heteromyidae, a rodent family with subtle sexual size dimorphism. Using a phylogenetic comparative approach, I address the potential influence of (1) fecundity selection, (2) covariation between pre- and post-copulatory traits, and (3) environmental constraints (resource shortage) in explaining patterns of body size and sexual size dimorphism (SSD) across 62 heteromyid species. Baculum size, a proxy of the strength of post-copulatory sexual selection, and SSD were negatively correlated suggesting that heteromyid rodents balance their reproductive investment between pre- and post-copulatory traits, which may prevent the evolution of extensive SSD. Results also support a role for resource competition in moderating SSD. The amount of SSD correlated negatively with latitude. This can be explained if high productivity relaxes the level of intrasexual competition among females, leading to more male-biased dimorphism since forces acting on both sexes are not cancelled. In line with this argument, territorial species exhibited a higher dimorphism in comparison with social species. No support was found for the fecundity selection hypothesis. Overall, this study provides insight into the factors driving observed patterns of sexual dimorphism in this iconic group and highlights the need to consider a broader framework beyond sexual selection for better understanding the evolution of dimorphism in this family.     

雄性峨眉髭蟾“胡子”的组织结构特征

采用石蜡切片与苏木精-伊红染色及扫描电镜,对雄性峨眉髭蟾Leptobrachium boringii的角质刺及其周边皮肤进行了显微结构和亚显微结构的观察。显微结构观察发现,峨眉髭蟾的角质刺属于皮肤衍生物,突起呈倒"V"形。角质刺由表皮和真皮构成,表皮为复层扁平上皮,可分成4层;最外层细胞角质化,细胞轮廓不清,被染成深红色。真皮由疏松结缔组织构成,分辨不出致密层与疏松层,其内未见皮肤腺,但有少量色素细胞与毛细血管分布。表皮嵴伸入到真皮层,在以往的无尾两栖类研究中未见报道。角质刺基部可见皮肤褶翻起将其包裹在内,皮肤褶向上延伸形成角质刺。扫描电镜观察表明,角质刺顶端呈锥形的"小山丘"状,表面可分辨出表皮细胞轮廓,细胞为呈覆瓦状排列的角质化细胞。角质刺与皮肤交界处为多边形的角质化细胞。角质化上皮细胞的上表面与下表面均具有凹凸不平的花纹结构,细胞之间以镶嵌的方式连接。     

根田鼠身体大小的性二型

在雌雄异体的有性生物中 ,反映身体结构和功能特征的某些变量在两性之间常常出现固有的和明显的差别 ,使得人们能够以此为根据判断一个个体的性别 ,这种现象被称为性二型 (ｓｅｘｕａｌｄｉｍｏｒ ｐｈｉｓｍ)。国外大量研究表明 ,哺乳动物性二型现象十分普遍 ,并且 ,在大多数情况下 ,雄性个体大于雌性个体[1] ;国内同类研究还不多 ,仅见周立等[2 ] 、盛和林[3] 、陈国芳[4 ] 、杜铭章[5] 分别对高原鼠兔(Ｏｃｈｏｔｏｎａｃｕｒｚｏｎｉａｅ)、黄鼬 (Ｍｕｓｔｅｌａｓｉｂｉｒｉｃａ)、摇蚊和海蛇的性二型现象作过报道 ,但均未分析其产生原…     

Geographical Variation in Body Size and Sexual Size Dimorphism in an Australian Lizard,Boulenger's Skink (Morethia boulengeri)

Ecogeographical rules help explain spatial and temporal patterns in intraspecific body size. However, many of these rules, when applied to ectothermic organisms such as reptiles, are controversial and require further investigation. To explore factors that influence body size in reptiles, we performed a heuristic study to examine body size variation in an Australian lizard, Boulenger''s Skink Morethia boulengeri from agricultural landscapes in southern New South Wales, south-eastern Australia. We collected tissue and morphological data on 337 adult lizards across a broad elevation and climate gradient. We used a model-selection procedure to determine if environmental or ecological variables best explained body size variation. We explored the relationship between morphology and phylogenetic structure before modeling candidate variables from four broad domains: (1) geography (latitude, longitude and elevation), (2) climate (temperature and rainfall), (3) habitat (vegetation type, number of logs and ground cover attributes), and (4) management (land use and grazing history). Broad phylogenetic structure was evident, but on a scale larger than our study area. Lizards were sexually dimorphic, whereby females had longer snout-vent length than males, providing support for the fecundity selection hypothesis. Body size variation in M. boulengeri was correlated with temperature and rainfall, a pattern consistent with larger individuals occupying cooler and more productive parts of the landscape. Climate change forecasts, which predict warmer temperature and increased aridity, may result in reduced lizard biomass and decoupling of trophic interactions with potential implications for community organization and ecosystem function.     

Sexual Size Dimorphism and Body Condition in the Australasian Gannet

Sexual size dimorphism is widespread throughout seabird taxa and several drivers leading to its evolution have been hypothesised. While the Australasian Gannet (Morus serrator) has previously been considered nominally monomorphic, recent studies have documented sexual segregation in diet and foraging areas, traits often associated with size dimorphism. The present study investigated the sex differences in body mass and structural size of this species at two colonies (Pope’s Eye, PE; Point Danger, PD) in northern Bass Strait, south-eastern Australia. Females were found to be 3.1% and 7.3% heavier (2.74 ± 0.03, n = 92; 2.67 ± 0.03 kg, n = 43) than males (2.66 ± 0.03, n = 92; 2.48 ± 0.03 kg, n = 43) at PE and PD, respectively. Females were also larger in wing ulna length (0.8% both colonies) but smaller in bill depth (PE: 2.2%; PD: 1.7%) than males. Despite this dimorphism, a discriminant function provided only mild accuracy in determining sex. A similar degree of dimorphism was also found within breeding pairs, however assortative mating was not apparent at either colony (R² < 0.04). Using hydrogen isotope dilution, a body condition index was developed from morphometrics to estimate total body fat (TBF) stores, where TBF(%) = 24.43+1.94*(body mass/wing ulna length) – 0.58*tarsus length (r² = 0.84, n = 15). This index was used to estimate body composition in all sampled individuals. There was no significant difference in TBF(%) between the sexes for any stage of breeding or in any year of the study at either colony suggesting that, despite a greater body mass, females were not in a better condition than males. While the driving mechanism for sexual dimorphism in this species is currently unknown, studies of other Sulids indicate segregation in foraging behaviour, habitat and diet may be a contributing factor.     

Sexual Dimorphism in the Hindlimb Muscles of the Asiatic Toad(Bufo gargarizans)in Relation to Male Reproductive Success

In many anurans, the forelimb muscles of males are used to grasp females and are often heavier than those of females despite the larger female body size. Such sexual dimorphism in forelimb musculature is thought to result from sexual selection. In addition, the hindlimbs of frogs and toads play an important role in the reproductive process as amplectant males can expel rivals with robust hindlimbs through kicking. In this study, the sexual dimorphism in dry mass for six hindlimb muscles of the Asiatic toad(Bufo gargarizans) was investigated. The results showed that, when controlled for body size, the hindlimb muscle mass of males significantly exceeded that of females for every muscle. The hindlimb muscle mass of amplectant males was also significantly larger than that of non-amplectant males. These results suggested that if strong hindlimb muscles could improve mating success of males, sexual selection would promote the evolution of dimorphism in this character.     

雷山髭蟾生态初步观察

雷山髭蟾(Vibrissphora leishanensis)主要栖息在植被类型保存较好、水源充足,海拔在800~2 100 m的山间小溪附近。每年大部分时间栖息在溪流附近陆地上比较阴暗潮湿的环境。雌雄抱对产卵从11月初开始,到月底基本结束。雌雄抱对产卵一般在午后和晚上,有集群产卵和雄蟾守窝护卵的现象。雷山髭蟾可能没有"冬眠"和"夏蛰"习性,即便有也可能很短暂。雷山髭蟾蝌蚪可能需要3年时间才发育成幼蛙。     

Sex Ratio and Sexual Size Dimorphism in a Toad-headed Lizard,Phrynocephalus guinanensis

Phrynocephalus guinanensis has sexual dimorphism in abdominal coloration, but its ontogenetic development of sexual size dimorphism(SSD) is unknown. Using mark-recapture data during four days each year from August from 2014 to 2016, we investigated the development of sex ratios, SSD, sex-specific survivorship and growth rates in a population of P. guinanensis. Our results indicated that the sex ratio of males to females was 1:2.8. Males had a lower survival rate(6%) than females(14%) across the age range from hatchling to adult, which supported the discovered female-biased sex ratio potentially associated with the low survival rate of males between hatchlings and juveniles. Male-biased SSD in tail length and head width existed in adults rather than in hatchling or juvenile lizards. The growth rates in body dimensions were undistinguishable between the sexes during the age from hatchling to juvenile, but the growth rate in head length from juvenile to adult was significantly larger in males than females. Average growth rate of all morphological measurements from hatchling to juvenile were larger compared with corresponding measurements from juvenile to adult, but only being significant in tail length, head width, abdomen length in females and snout-vent length in males. We provided a case study to strengthen our understanding of the important life history traits on how a viviparous lizard population can survive and develop their morphology in cold climates.     

The Dilemma of Choosing a Reference Character for Measuring Sexual Size Dimorphism,Sexual Body Component Dimorphism,and Character Scaling: Cryptic Dimorphism and Allometry in the Scorpion Hadrurus arizonensis

Sexual differences in morphology, ranging from subtle to extravagant, occur commonly in many animal species. These differences can encompass overall body size (sexual size dimorphism, SSD) or the size and/or shape of specific body parts (sexual body component dimorphism, SBCD). Interacting forces of natural and sexual selection shape much of the expression of dimorphism we see, though non-adaptive processes may be involved. Differential scaling of individual features can result when selection favors either exaggerated (positive allometry) or reduced (negative allometry) size during growth. Studies of sexual dimorphism and character scaling rely on multivariate models that ideally use an unbiased reference character as an overall measure of body size. We explored several candidate reference characters in a cryptically dimorphic taxon, Hadrurus arizonensis. In this scorpion, essentially every body component among the 16 we examined could be interpreted as dimorphic, but identification of SSD and SBCD depended on which character was used as the reference (prosoma length, prosoma area, total length, principal component 1, or metasoma segment 1 width). Of these characters, discriminant function analysis suggested that metasoma segment 1 width was the most appropriate. The pattern of dimorphism in H. arizonensis mirrored that seen in other more obviously dimorphic scorpions, with static allometry trending towards isometry in most characters. Our findings are consistent with the conclusions of others that fecundity selection likely favors a larger prosoma in female scorpions, whereas sexual selection may favor other body parts being larger in males, especially the metasoma, pectines, and possibly the chela. For this scorpion and probably most other organisms, the choice of reference character profoundly affects interpretations of SSD, SBCD, and allometry. Thus, researchers need to broaden their consideration of an appropriate reference and exercise caution in interpreting findings. We highly recommend use of discriminant function analysis to identify the least-biased reference character.     

Tooth Size Variation in Assemblages of Tremacyllus (Hegetotheriidae,Notoungulata): Insights into Geographical Gradients,Systematics, and Sexual Dimorphism

Tooth size variation within fossil assemblages can be associated with intra- or interspecific variation, functional, developmental, and geographical factors, and/or sexual dimorphism. Understanding these sources of variation is necessary to develop diagnoses for fossil mammals, where teeth are usually the most frequent remains. Tremacyllus (Ameghino, 1891) (Hegetotheriidae, Notoungulata) is a genus of small-sized herbivorous mammals abundant in late Miocene to Pliocene outcrops of southern South America. Its simplified, euhypsodont dentition and size variability have hampered systematics studies and led, for instance, to an overestimation of the number of species. I analyzed tooth size variations within assemblages of Tremacyllus in a quantitative framework to test three hypotheses: (1) magnitudes of size variation are different among tooth loci and assemblages; (2) tooth size follows a geographical pattern within the analyzed sample (Bergmann’s rule), but is also associated with taxonomy; and (3) there is a correlation between size variation and sexual dimorphism reflected in distinguishable subgroups. Results indicate that patterns of variation might be associated with eruption time and/or functional position. Northwestern forms are larger than southwestern-Pampean ones, not conforming to Bergmann’s rule but revealing a strong influence of latitude. Size differences between assemblages agree with dental features that distinguish T. incipiens and T. impressus, allowing expanded species diagnoses. Two size subgroups might reflect sexual dimorphism in the absence of biostratigraphic or morphological differences between them. This interpretation indicates that northwestern specimens referred to T. diminutus should be referred to T. incipiens.

     

大山雀身体大小的性二态及其季节变化

动物中普遍存在雌雄个体身体大小的性二态现象。了解近缘种之间身体大小性二态现象的差异,可为深入探讨身体大小性二态现象的潜在驱动机制提供证据。国外对欧亚大山雀(Parus major)的研究发现,其喙长、跗跖长、翅长等6项身体大小指标存在着明显的性二态,且喙长的性二态存在季节间差异。大山雀(P.cinereus)曾被作为欧亚大山雀的一个亚种,其形态和行为与欧亚大山雀存在着诸多相似之处。为探讨大山雀是否也存在身体大小性二态及季节性差异,本研究分析了2018至2020年间在河南董寨国家级自然保护区捕捉的226只(雌性96只和雄性130只)大山雀的喙长、头喙长、跗跖长、翅长、尾长和体长这6项体征指标的两性差异及其季节变化。结果显示,大山雀上述6项身体大小指标均存在不同程度的性二态现象,且雄性个体仅喙长与雌性的差异不显著,其余5项指标均显著大于雌性。此外,身体大小指标的两性差异不随季节显著变化,但两性的跗跖长在秋季均显著短于冬季和繁殖季,尾长在繁殖季均显著长于秋季和冬季。上述结果表明,大山雀身体大小的性二态及其季节性差异与欧亚大山雀并不完全相似。无论其身体大小存在性二态和季节变化的原因,还是其与欧亚大山雀在身体大小性二态模式上的差别,都有待今后进一步研究。     

四眼斑水龟个体大小和体形的两性异形

研究龟鳖的两性异形对理解形态适应具有重要意义。通过测量41只(21♀,20♂)成体四眼斑水龟(Sacalia quadriocellata)的20个形态特征指标,研究四眼斑水龟个体大小和体形的两性异形。结果表明:除头长、头宽、尾长和尾长肛前段长外,四眼斑水龟其他的形态特征均与背甲长呈正相关。雌性的背甲长、腹甲长、腹甲中线长、腹甲曲线长显著大于雄性;雄性的头长、头宽、后肢长、尾长和尾长肛前段长显著大于雌性;雌雄两性的体重、体周长、前肢长、腹甲宽、肛盾切口长、肛盾切口宽以及除背甲长外的所有背甲形态特征指标均无显著差异。研究结果表明,四眼斑水龟存在个体大小和体形两性异形。     

Sexual Strategy and Size Dimorphism in Rattlesnakes: Integrating Proximate and Ultimate Causation

SYNOPSIS. Integrating proximate and ultimate causes and effectssimultaneously in the study of behavior is challenging and complex,but useful. This is equivalent to asking both "How?" (in thesense of proximate mechanisms) and "Why?" (in the sense of ultimateevolutionary payoffs) an organism operates in one way and notanother. Sex differences in rattlesnake (i) size and growthand (ii) mating and reproductive strategies and tactics, providea good theoretical and empirical context in which to attemptsuch integration. We employ interdisciplinary and multidisciplinaryapproaches in our behavioral and physiological work, but wemean something different by "integrative," that amounts to thesimultaneous study of both proximate and ultimate levels ofcausation and explanation. Though not always feasible, thisapproach represents an important goal to work towards becauseit attempts to represent faithfully the complexity inherentin living systems. To this end, we also employ a variety ofmodeling approaches, which entrain intuition, generate new hypotheses,and sharpen inference. Individual-based simulations, for example,offer promise for broad, integrative programs of biologicalresearch.     

宁波滑蜥两性异形和雌性繁殖

蜥蜴的雌性繁殖特征对理解两性异形的进化原因起着重要作用。于2011年4月在安徽滁州采集宁波滑蜥(Scincella modesta),定量研究该种形态特征的两性异形和雌性繁殖特征,检验成体形态特征两性异形与雌性繁殖的相关性。研究共采集43条(17♀♀,26♂♂)宁波滑蜥,雄性和雌性个体的最大体长分别为47.4 mm和46.6 mm。雌雄两性在体长和头宽上没有差异,而在腹长和头长上差异显著,雄性有较大的头长,雌性有较大的腹长。宁波滑蜥年产单窝卵。窝卵数和窝卵重与雌体体长及腹长呈正相关,卵重与雌体体长无相关性。窝卵数及卵重的变异系数分别为0.20和0.12。卵长径与窝卵数呈负相关,而卵短径与窝卵数无关。雌体主要通过增加窝卵数来增加繁殖输出。这些结果表明,宁波滑蜥是雌雄个体大小同形的两性异形模式,性选择使得雄性有着较大的头长,以具有较高的交配成功率,生育力选择使得雌性有着较大的腹长,以具有较大的生育力和繁殖输出。     

丽纹攀蜥头体大小的两性异形和繁殖期的生长

测定了丽纹攀蜥的体长、头长、头宽、头高、尾长和体重等形态指标,以及通过44天的生长后体长、头长、头宽和头高的增长。表明成年两性个体体长无显著的两性异形,局部形态特征皆与体长呈正相关。协方差分析表明,雄性的头长、头宽、头高和尾长显著大于雌性个体,繁殖期雌性个体的体重显著大于雄性个体。丽纹攀蜥繁殖期雄性体长的增长显著大于雌性体长的增长,雌雄两性头长、头宽和头高的增长无显著的差异。     

Sexual Interference and Sexual Defense in the Smooth Newt,Triturus vulgaris (Amphibia,Urodela, Salamandridae)

• 1 When a male smooth newt encounters a ♀ who is already engaged in courtship, he may mimic her behaviour during the spermatophore deposition and transfer stages of the courtship. He thereby usurps the courting ♂ and may inseminate the ♀ himself. Such sexual interference depresses the short-term, and perhaps long-term, mating success of the courting ♂.
• 2 In the presence of a potential rival, the courting ♂ alters certain aspects of his sexual behaviour. He displays more intensely to the ♀ and attempts to draw her away from the rival by increasing the duration of his display. He may also “check” that it is the ♀, and not the rival, who will elicit the deposition of a spermatophore from him. These changes in the behaviour of the courting ♂ are interpreted as defense against sexual interference.
• 3 Female smooth newts may be multiply inseminated as a consequence of sexual interference; this may result in sperm competition. However, ♀♀ seem to find competitive interactions between ♂ ♂ “aversive”.
• 4 Sexual interference by ♀-mimicry and associated defensive behaviour patterns are common in the urodele amphibians. Interference can be thought of as a “side-payment” conditional mating strategy.