黑眶蟾蜍的两性异形与选型配对模式

本研究以黑眶蟾蜍(Duttaphrynus melanostictus)为研究对象,通过对比黑眶蟾蜍抱对个体的体长、头长、头宽、眼间距、鼓膜径、耳后腺长、眼径、前臂及手长、前肢长以及后肢长等形态特征,分析雌性黑眶蟾蜍繁殖输出与其体型的关系,探究黑眶蟾蜍两性异形模式及其与雌性生育力的关系;同时通过对配对个体形态学特征的相关性分析探究了黑眶蟾蜍的配对模式。结果表明,黑眶蟾蜍雌性体长和体重显著大于雄体;两性的所有局部形态特征均与体长成正相关;去除体长因素影响后,雄性头长以及后肢长均明显大于雌性,其余局部形态特征两性间则皆无显著差异。雌体的窝卵重、窝卵数均与其体长和体重成正相关关系。雌性成体的前肢长与抱对雄性成体的前肢长之间呈显著正相关,其余形态特征两性间均无相关性。研究表明,生育力选择是导致黑眶蟾蜍两性异形的重要驱动力;黑眶蟾蜍的选型配对模式未表现在个体大小上,而是体现在局部特征(前肢长),这不仅为揭示两栖类配对模式的普遍性提供了参考,还表明对两栖类选型配对的研究应以多个性状为对象。     

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.     

红瘰疣螈玉龙雪山种群的两性异形

分别测量于2018年6—8月采自云南丽江玉龙雪山的32只(17♂,15♀)红瘰疣螈Tylototriton shanjing成体的全长、头体长、头长等13项形态特征指标,并检验该物种的两性异形。结果表明:雌性平均全长为160.72 mm±3.02 mm(n=15),雄性平均全长为138.58 mm±2.57 mm(n=17),雌性与雄性平均全长比为1.160,两性异形指数为0.138,属雌性大于雄性的两栖类;全长在两性间的差异有统计学意义;除了雌性的头宽、尾宽、尾高和腋至胯距外,其他形态特征与全长均有显著或极显著相关性;以全长为协变量的协方差分析结果显示,红瘰疣螈的头体长、头长、吻长、尾长和前肢长在两性间的差异有统计学意义;雌性的尾长和前肢长随全长的生长速率大于雄性,而头体长、头长和吻长随全长的生长速率小于雄性。生育力选择假说能解释红瘰疣螈玉龙雪山种群的两性异形现象。     

新疆沙虎的两性异形

通过测量和比较采自新疆且末县的新疆沙虎Teratoscincus przewalskii成体的体型和口宽等6个形态特征,研究了新疆沙虎的两性异形。研究共采集64只新疆沙虎(雌性26只,雄性38只),雌雄成体最小体长(SVL)分别为63.6 mm和59.7 mm。口宽、头宽、头高、眼间距和尾长5个局部形态特征均与体长呈显著正相关。新疆沙虎体长雌雄间无差异,其它身体形态特征仅口宽具有显著的两性差异,且口宽相对于体长呈异速生长,雌性增长速率大于雄性。新疆沙虎口宽的两性异形可能与两性间食性的差异有关,而体长和其它身体形态特征无显著两性差异则可能与性选择和自然选择的综合作用有关。     

旱地沙蜥的两性异形和雌性繁殖投入

为研究旱地沙蜥的两性异形和繁殖投入,于2013年5月和2014年5月在新疆北屯捕捉了166号活体进行9项形态学指标测量,受孕雌性室内暂养用于收集繁殖数据。t检验结果表明:旱地沙蜥亚成体的两性异形体现在雄性头体长显著大于雌性(P0.05);成体中,雌性的头体长显著大于雄性(P0.05)。协方差分析(ANCOVA)表明,成体雄性的头长(P0.01)、头高(P0.01)、尾长(P0.01)、后肢长(P0.01)极显著大于雌性。旱地沙蜥的局部形态指标量度与头体长呈正相关,且雄性个体的尾长(P0.05)、后肢长(P0.05)和头高(P0.05)的增长速率显著较雌性快。雌性繁殖窝卵数、窝卵重和卵重与雌性头体长相关性不显著。本研究结果拒绝繁殖力优势假说而支持性选择假说是旱地沙蜥两性异形形成的内在机制。     

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。     

海陆蛙的两性异形和雌性繁殖特征

用采自海南东寨港红树林保护区的58只(35 ♀♀,23 ♂♂)成体海陆蛙(Fejervarya cancrivora),通过测量头体长、体重、头长、头宽、吻长等11个形态特征指标和雌体卵巢质量(窝卵重),研究该种形态特征的两性异形和雌性繁殖特征,并检验雌性成体大小(头体长和体重)与其繁殖的相关性.雌雄两性个体的最小头体长分别为44.9 mm和45.2 mm.除吻长和眼间距外,其余局部形态特征与头体长皆呈正相关性.头体长在雌雄两性之间差异显著,雌性显著大于雄性;而体重、头长、头宽等局部形态均无两性差异.海陆蛙雌体的窝卵重与头体长和体重之间皆成正相关关系,表明雌性可能是通过增大体型从而增加繁殖输出,而向较大体型发展.     

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。     

康县隆肛蛙的两性异形

测量和比较了采自甘肃省康县的康县隆肛蛙Feirana kangxianensis标本共计90只(雌性48只,雄性42只)。结果表明,康县隆肛蛙成体的头体长、头长、头宽、吻长、鼻间距、眼间距、眼径、鼓膜长、前臂及手长、后肢全长、手长、足长的形态特征在两性间的差异有统计学意义。以头体长为协变量的协方差分析显示,康县隆肛蛙两性的差异均有统计学意义,异形指数达到0.08,雌性与雄性的平均头体长比值为1.091。对所有测量的形态特征与头体长进行一元线性回归分析表明,雌性康县隆肛蛙局部形态特征的生长速度明显大于雄性,其中,吻长、眼间距、眼径、鼓膜长、前臂及手长、手长的两性差异最明显。生育力选择假设能解释康县隆肛蛙的两性异形现象。     

饰纹姬蛙的两性异形及雌性繁殖能力

用采自云南省西双版纳傣族自治州勐腊县的53只(28♂♂,25♀♀)成体饰纹姬蛙(Microhyla fissipes),测量全部个体的体长、头长、头宽、体重等16项形态特征和雌体怀卵量数据,通过独立样本t检验和协方差检验该物种所有形态特征的两性差异,进而采用线性回归方法分析雌雄成体局部形态特征与体长的相关性,以及雌性成体怀卵量与局部形态特征的相关性。结果表明,饰纹姬蛙平均体长雌性为(25.08±0.40)mm,雄性为(24.78±0.31)mm,体长和体重在雌雄两性间差异不显著(P> 0.05),两性个体大小基本同形。该蛙的所有局部形态特征与体长均存在极显著正相关性(P <0.01);雌雄两性间只在头宽和前臂及手长这两个形态特征上存在显著差异(P <0.05),且随体长的增大其生长速率也存在显著差异。雌性成体的怀卵量与体长、体重、眼间距、前臂宽、胫宽和跗足长均存在显著正相关性(P <0.05),且与体重存在极显著正相关性(P <0.01)。分析认为,饰纹姬蛙成体两性异形主要表现在头宽和前臂及手长,与生存竞争中对食物的获取能力及雄性争夺交配权的成功率有关;而...     

浙江丽水虎纹蛙形态特征的两性异形和食性

用数显游标卡尺测量了407只2001—2003年9月下旬至10月上旬浙江丽水罚没的死亡虎纹蛙的体长等10个形态指标,结果表明:雌性成体体长(SUL)大于雄性成体,幼体形态无显著两性差异;ANCOVA去除SUL差异的影响后,雌性成体的头长和后肢长大于雄性成体,前肢长、眼径和耳径则小于雄性成体。前肢两侧对称性的偏移度成体大于幼体,雌性大于雄性;后肢两侧对称性成幼体和两性无显著差异。10个形态指标主成分分析的前三个主成分共解释64·6%的变异:第一主成分中头宽、眼径和耳径,第二主成分中后肢长,第三主成分中眼间距和鼻间距分别有较高的正负载系数。用NikonSMZ-1000解剖镜鉴别277只个体胃内容物中的食物种类,发现其秋季食物以节肢动物为主;成幼体和两性食物生态位宽度为3·42~5·25,食物生态位重叠度较高为0·93~0·98。分析表明,虎纹蛙局部形态特征的两性差异微弱,而体长两性异形差异显著;雌体具有较大的体形与食性无关,而可能与生育力选择的作用有关。     

鳄蜥的两性异形

通过比较鳄蜥的体型与头部大小等特征的差异,研究了鳄蜥的两性异形情况.结果表明:性成熟鳄蜥个体体色差异显著,成年雄性头胸部腹面呈鲜红色或浅蓝色,而雌性为浅黄色或淡红色;成年雄性头部显著大于成年雌性(头长(HL),P＜0.001;头宽(HW),P＜0.001),成年雌性腹部长(AL)显著大干成年雄性(P=0.018);而成...     

Tail Length and Mutual Mate Choice in Bearded Tits (Panurus biarmicus)

Direct sexual selection via mutual mate choice can result in both sexes showing conspicuous traits. We experimentally tested whether this hypothesis can explain tail length in the bearded tit (Panurus biarmicus). In this species, both sexes have a long, graduated tail. Males have, however, a longer tail than females, suggesting perhaps that females are choosier than males in selecting mates. We used two choice set‐ups for each sex: shortened vs. control tail individuals and elongated vs. control tail individuals. We found that direct sexual selection seems to operate differently in the two sexes. In both set‐ups, females spent more time with the male with the longest tail, and they also showed sexual display behaviour only towards these males. Males spent more time with control than with short‐tailed females, but they did not discriminate between control and long‐tailed females. Moreover, males displayed preference towards both short‐ and long‐tailed females. Thus, females preferred long‐tailed males, whereas males did not always prefer long‐tailed females. Our study suggests that mutual mate choice has played a role in the evolution of long tails in bearded tits. It also suggests that the sexual dimorphism in tail length has evolved because mate choice exerts a stronger sexual selection pressure on males than on females.     

Females prefer males producing a high-rate song with shorter timbal–stridulatory sound intervals in a cicada species

Uncovering mate choice and factors that lead to the choice are very important to understanding sexual selection in evolutionary change. Cicadas are known for their loud sounds produced by males using the timbals. However, males in certain cicada species emit 2 kinds of sounds using respectively timbals and stridulatory organs, and females may produce their own sounds to respond to males. What has never been considered is the mate choice in such cicada species. Here, we investigate the sexual selection and potential impact of predation pressure on mate choice in the cicada Subpsaltria yangi Chen. It possesses stridulatory sound-producing organs in both sexes in addition to the timbals in males. Results show that males producing calling songs with shorter timbal–stridulatory sound intervals and a higher call rate achieved greater mating success. No morphological traits were found to be correlated with mating success in both sexes, suggesting neither males nor females display mate preference for the opposite sex based on morphological traits. Males do not discriminate among responding females during mate searching, which may be due to the high energy costs associated with their unusual mate-seeking activity and the male-biased predation pressure. Females generally mate once but a minority of them re-mated after oviposition which, combined with the desirable acoustic traits of males, suggest females may maximize their reproductive success by choosing a high-quality male in the first place. This study contributes to our understanding mechanisms of sexual selection in cicadas and other insects suffering selective pressure from predators.     

Size and scaling of sexually-selected traits in the lizard, Uta palmeri

Differences between the sexes in overall body size and in the size of other morphological traits, relative to overall body size, are common in many animals. In this study, patterns of growth and scaling of sexually dimorphic tratis are assessedin a lilzard and then used to sugest general developmental mechanisms responsible for sexual size dimorphism (SSD). Adult make Uta palmeri lizards are larger than adult females inoverall body size (snout-vent length, SVL), body mass, jaw length head width, and head depth. Two general growth processes produce this adult SSD. First, juvenile males have greater annual SVL growth rates than do juvenile females, contributing to adult SSD because males will be larger than females in any trait positively correlated with SVL. Secondly, males and females differ in age-related changes in growth of the three head size traits, relative to growth in SVL. Comparing slopes from reduced major axis regressions of each trait on SVL reveals that the sexes do not differ in the scaling of these traits as juveniles, but as adults males have greater slopes than adult females, indicating ontogenetic differences in scaling of these traits in males. Two other topics in SSD are addressed with these data. First, comparing these data on scaling to those of an earlier analysis that used ordinary least squares regression reveals that conclusions about underlying mechanisms in an analysis of scaling can be altered by the choice of a regression model. Secondly, these data indicate that postmaturational differences in scaling contribute to adult sexual size differences, contrary to an earlier study. Shine (1990) found that for many ectotherms, which continue to grow after sexual maturation, post-maturational events contribute little to sexual differences in overall body size. Results for U. palmeri suggest that these findings may only hold for measures of overall body size (e.g. SVL) and may not generalize to traits that exhibit sex difference in scaling.     

Sex,androgens, and whole‐organism performance in an Australian lizard

Understanding underlying physiological differences between the sexes in circulating androgens and how hormonal variation affects morphology–performance relationships may help clarify the evolution of sexual dimorphism in diverse taxa. Using a widely distributed Australian lizard (Eulamprus quoyii) with weak sexual dimorphism and no dichromatism, we tested whether circulating androgens differed between the sexes and whether they covaried with morphological and performance traits (bite force, sprint speed, endurance). Males had larger head dimensions, stronger bite force, faster sprint speed, and longer endurance compared to females. We found that the sexes did not differ in androgen concentrations and that androgens were weakly associated with both morphological and performance traits. Interestingly, high circulating androgens showed a nonlinear relationship with bite force in males and not females, with this relationship possibly being related to alternative male reproductive tactics. Our results suggest that androgens are not strongly correlated with most performance and morphological traits, although they may play an important organizational role during the development of morphological traits, which could explain the differences in morphology and thus performance between the sexes. Differences in performance between the sexes suggest differential selection on these functional traits between males and females. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 111, 834–849.     

Morphological Correlates of a Combat Performance Trait in the Forked Fungus Beetle, Bolitotherus cornutus

Combat traits are thought to have arisen due to intense male-male competition for access to females. While large and elaborate weapons used in attacking other males have often been the focus of sexual selection studies, defensive traits (both morphological and performance) have received less attention. However, if defensive traits help males restrict access to females, their role in the process of sexual selection could also be important. Here we examine the morphological correlates of grip strength, a defensive combat trait involved in mate guarding, in the tenebrionid beetle Bolitotherus cornutus. We found that grip strength was repeatable and differed between the sexes. However, these differences in performance were largely explained by body size and a non-additive interaction between size and leg length that differed between males and females. Our results suggest that leg size and body size interact as part of an integrated suite of defensive combat traits.     

Sexual size and shape dimorphism and allometric scaling patterns in head traits in the New Zealand common gecko Woodworthia maculatus

Sexual dimorphism in shape and size is widespread across animal taxa and arises when natural or sexual selection operates differently on the sexes. Male and female common geckos (Woodworthia maculatus; formerly Hoplodactylus maculatus) in New Zealand do not appear to experience different viability selection pressure, nor do males appear to be under intense pre-copulatory sexual selection. It was therefore predicted that this species would be sexually monomorphic with regard to body size and the size and shape of the head. In line with the prediction, there was no sexual difference in head width, depth, or length or in lateral head shape. However, contrary to prediction, males had a larger body and lateral head size than females. This study suggests that males, at least on Maud Island, NZ, might be under stronger pre-copulatory sexual selection than previously recognized and thus have evolved larger heads (i.e. lateral head size) for use in male combat for females. Allometric scaling patterns do not differ between the sexes and suggest that head width and depth are under directional selection whereas lateral head size is under stabilizing selection. Diet ecology – an agent of natural selection common to both sexes – is likely largely responsible for the observed patterns of head size and shape and the lack of sexual dimorphism in them.     

The evolution of sexual size dimorphism in the house finch. III. Developmental basis

Sexual size dimorphism of adults proximately results from a combination of sexually dimorphic growth patterns and selection on growing individuals. Yet, most studies of the evolution of dimorphism have focused on correlates of only adult morphologies. Here we examined the ontogeny of sexual size dimorphism in an isolated population of the house finch (Carpodacus mexicanus). Sexes differed in growth rates and growth duration; in most traits, females grew faster than males, but males grew for a longer period. Sexual dimorphism in bill traits (bill length, width, depth) and in body traits (wing, tarsus, and tail length; mass) developed during different periods of ontogeny. Growth of bill traits was most different between sexes during the juvenile period (after leaving the nest), whereas growth of body traits was most sexually dimorphic during the first few days after hatching. Postgrowth selection on juveniles strongly influenced sexual dimorphism in all traits; in some traits, this selection canceled or reversed dimorphism patterns produced by growth differences between sexes. The net result was that adult sexual dimorphism, to a large degree, was an outcome of selection for survival during juvenile stages. We suggest that previously documented fast and extensive divergence of house finch populations in sexual size dimorphism may be partially produced by distinct environmental conditions during growth in these populations.