菲菊头蝠回声定位声波频率的性二态有利于性别识别

许多动物的叫声频率呈现性二态现象。蝙蝠夜间活动,主要利用声音信号导航空间、追踪猎物、传递交流信息。本研究选择成体菲菊头蝠作为研究对象,检验回声定位声波频率性二态是否有利于性别识别。研究发现,菲菊头蝠回声定位声波频率参数具有显著性别差异。播放白噪音、雄性回声定位声波及雌性回声定位声波期间,实验个体的反应叫声数量依次递减。播放白噪音、雌性回声定位声波及雄性回声定位声波后,实验个体的反应叫声数量依次递增。白噪音诱导反应叫声强度高于回声定位声波诱导反应叫声强度。研究结果表明,菲菊头蝠回声定位声波的频率参数编码发声者性别信息,有利于种群内部的性别识别。本研究暗示,回声定位声波可能在蝙蝠配偶选择中扮演一定作用。     

太行山猕猴髋臼性别二态性研究

本文使用几何形态测量法探讨42例成年太行山猕猴Macaca mulatta tcheliensis髋臼的性别二态性。结果显示,太行山猕猴雌雄个体的髋臼形态具有明显的性别二态性,利用髋臼可以正确判别92.3%的雌性和87.5%的雄性个体。髋臼的形态差异主要分布于月状面的后上部,即与髋臼切迹相对的月状面区域的宽度表现为雄性大于雌性,另外雄性髋臼大小的波动范围也比雌性更广。造成髋臼性别二态性的生物学原因可能与其功能有关,髋臼作为髋关节的组成部分,起着支撑身体和协同运动的功能,能够优化关节接触面的压力分布。推测雄性髋臼受到的体质量压力更大可能是雄性进化出比雌性更宽大的月状面的主要原因。     

成虫体型大小驱动六斑月瓢虫性间相互选择(英文)

【目的】配偶选择是性选择的中心过程,当繁殖成本发生波动和配偶质量存在差异时,传统的性别作用也随之不同。为了验证在某些条件下雄性也可以像雌性一样进行选择,我们研究了雄性和雌性六斑月瓢虫Menochilus sexmaculatus(Fabricius)的交配成功率与作为适合度指标的成虫体型大小之间的关系。【方法】从初始种群中随机选择体型小和体型大的两性成虫,进行雄性和雌性配偶选择试验。并对成功交配的各个配对组的后代也进行配偶选择试验,测试其交配成功率。【结果】配偶选择试验结果表明,在雄性和雌性交配试验中交配的成功取决于体型大小。雄性根据其品质即体型大小这一繁殖力指标对雌性进行区分。同样,在雌性交配试验中体型大的雄虫比体型小的雄虫交配成功率高。无论亲本体型如何,体型大的雌虫都比体型小的雌虫产卵量高;不过,体型大小不影响卵的存活力。体型大的亲本的后代比体型小的亲本的后代发育更快,寿命更长,但是将其与来自初始种群的后代进行配偶选择时,它们在性合意(sexual desirability)或竞争力方面没有表现任何优势。【结论】六斑月瓢虫中存在以体型大小为目的性状的相互配偶选择。     

雌性偏好促进象型类的性别异时进化（英文）

性双型的特征通常被认为产生于种内争夺交配优先权的斗争。例如,现生和化石的雄性长鼻类动物具有较大的体型和较粗壮的上门齿。本研究阐释了如下现象:化石象型类动物(Elephantiformes,长鼻类的主要类群)一些性双型特征与其进化历史具有相关性,而与性别竞争并非直接相关。在中新世的葛氏铲齿象(Platybelodon grangeri)和狭齿嵌齿象(Gomphotherium angustidens)中,雄性比雌性倾向于具有进化中更进步的特征,如同雄性在进化中领先雌性一步。这种现象可能与雌性偏好的机制相耦合。在象型类动物进化的早期(繁荣期),性别选择压促使雄性比雌性产生更加显著的进步特征;然而,在它们进化的晚期(衰退期),性别选择压似乎减弱,性别的异时进化也减少。这种新的发现或许在大型有蹄类的演化过程中有一定的普遍意义,因为那些繁荣的类群中通常性双型显著,如鹿科和牛科;而衰落的类群中通常性双型不显著。     

毛翼管鼻蝠性二型特征及其在湖北和浙江的分布新纪录

哺乳动物的性别二态性（Sexual dimorphism）是动物中的一种普遍现象,常表现为雄性个体大于雌性个体,而在蝙蝠中则表现出雌性个体体型大于雄性的偏雌性二型现象,其具体的驱动机制仍未明确。本文对采集于广东、广西、江西、湖南、海南、湖北和浙江的32只毛翼管鼻蝠（Harpiocephalus harpia）进行头骨与翼型在两性特征上的多元统计分析,尝试探讨其性二型驱动机制。结果表明：毛翼管鼻蝠雌雄在头骨中与牙齿及咀嚼力相关的区域存在明显分化,而翼型（含翼指标和翼面积）在整体和局部特征上均无显著性差异,该结果提示雌雄可能存在食性上的分化,更倾向于“资源竞争假说”而非“大母蝠优势假说”。本研究于2017年7~10月分别在湖北（3雄,2雌）和浙江（2雄,5雌）采集的12只毛翼管鼻蝠,为二省翼手目分布新纪录,该发现丰富和完善了我国翼手目分布信息。上述标本保存于广州大学华南生物多样性保护与利用重点实验室。     

日本梅花鹿与大丰麇鹿发情期反刍行为的差异

家养有蹄类动物的反刍行为已有大量研究,而受限于野外条件,野生有蹄类动物反刍行为的研究有限。以往研究认为,体型可能是影响动物反刍行为的重要因素。本研究以日本奈良公园日本梅花鹿Cervus nippon nippon和中国江苏大丰麋鹿Elaphurus davidianus为研究对象,观察记录并比较分析了发情期的日本梅花鹿与发情期的麋鹿在卧息时反刍行为的种内及种间差异。按照年龄性别差异,分5种类型(成年雄性、成年雌性、亚成雄性、亚成雌性和幼鹿)研究两物种食团咀嚼时间、咀嚼频率和咀嚼速率的差异。结果表明,1)日本梅花鹿的咀嚼速率和食团咀嚼时间受性别-年龄的显著影响:咀嚼速率为幼体>亚成雌性>亚成雄性>成年雌性>成年雄性,而食团咀嚼时间为成年雄性>亚成雄性>成年雌性>亚成雌性>幼体;2)性别-年龄对麋鹿咀嚼频率有显著的影响,成年雄性<成年雌性<亚成雄性<亚成雌性<幼体;3)两物种在咀嚼频率、食团咀嚼时间和咀嚼速率上的差异均有统计学意义,体型更大的麋鹿咀嚼速率更慢,食团咀嚼时间更长。与体型相关的性别及年龄显著影响了日本梅花鹿和麋鹿的反刍行为。     

亚洲玉米螟的一个生活史特征——体重与温度呈正相关

【目的】温度是变温动物最重要的环境因子,影响了所有的生活史特性。本研究旨在探明亚洲玉米螟Ostrinia furnacalis生活史特性随温度变异的特点。【方法】在恒温20,22,24,26,28,30和32℃,光周期16L∶8D室内条件下,测定了亚洲玉米螟南昌种群从卵孵化到化蛹和化蛹到成虫羽化的时间,以及蛹和成虫的体重。【结果】亚洲玉米螟幼虫和蛹的历期及总发育历期随温度的升高显著缩短。雄性幼虫历期和总发育历期显著短于雌性,显示了雄性先熟现象。生长速率与温度呈正相关。雌性生长速率在较低温度下显著低于雄性,但在高温下显著高于雄性。体重和温度之间的相关性没有遵循温度-体型大小法则,雌雄个体在高温下体重更重,雌性个体显著大于雄性,显示了雌性偏向的性体型二型性(sex size dimorphism,SSD)。与任希法则相反,亚洲玉米螟的SSD指数和体重随温度升高趋于增大。雄蛹在变态中比雌蛹丢失了更多的重量,导致成虫期的SSD指数大于蛹期。【结论】高温不仅显著缩短了亚洲玉米螟发育历期,而且导致了其在成熟时体重更大。亚洲玉米螟雌雄间的生活史特性存在较大差异。     

旱地沙蜥三个地理种群形态变异与两性异形——Bergmann法则、Allen法则和Rensch法则的检验

环境对动物体型和暴露附器大小的影响已有大量研究,但对两性异形的影响研究尚不多见,本文研究了旱地沙蜥Phrynocephalus helioscopus 3个地理种群形态的两性异形和地理变异,综合了Bergmann法则、Allen法则和Rensch法则分析其体型、四肢和尾部大小的变化规律。结果表明,伊宁和塔城种群的雌、雄亚成体体型差异无统计学意义(P0.05),北屯市雄性体型显著大于雌性(P0.05);伊宁和北屯种群的雌性成体体型均显著大于雄性(P0.05),但塔城地区两性体型差异无统计学意义(P0.05)。协方差分析结果表明,亚成体两性间只有塔城地区的雄性前肢长显著大于雌性(P0.05);3个地区雄性成体均具有较大的后肢和尾部(P0.01),伊宁市雌性具有较长的前肢(P0.05),塔城和北屯市两性前肢长差异均无统计学意义(P0.05),3个地区旱地沙蜥的体型呈反Bergmann法则的现象;四肢和尾部的大小遵循Allen法则;体型、前肢长、后肢长和尾长不遵循Rensch法则。旱地沙蜥3个地理种群受弥散性的自然选择压力比定向性的繁殖力选择和性选择的作用更强。     

条纹短攀鲈的雄性个体大小、雌性偏好以及雄性之间的竞争

本研究考察了条纹短攀鲈(Trichopsis vittata)雄性个体的身体大小对雌性个体性偏好的影响以及对雄性之间竞争的影响。本研究设立了两种处理来研究雌性个体的性偏好以及雄性之间的竞争。在一种处理中,放入同样大小的雄性个体,而在另一种处理中,放入大小不同的雄性个体。结果表明,雄性个体的大小不影响雌性条纹短攀鲈的性偏好。在对雄性之间竞争的研究中,发现个体较大的个体获胜的次数比较多。在个体大小相同的处理中,雄性之间打斗的持续时间比另一种处理中的打斗持续时间长。对这两种处理中不同对抗行为的比较表明,个体大小相同处理组中的发声、咬、以及总体对抗行为发生得更为频繁。对个体大小不同处理组中的大、小个体的进一步观察也揭示出体型大的个体比体型小的个体有更多的追逐行为和更少的逃脱行为。这些结果表明,在雄性个体比雌性个体大的物种中,体型的性两型可能与雄性之间的竞争有关,而不是与雌性偏好有关。     

灰椋鸟身体大小和内脏器官形态的两性差异

鸟类性二态现象广泛存在,比如身体大小、羽色等,性二态很可能是自然选择和性选择共同作用的结果。为了探索和更好地了解雀形目鸟类身体大小性二态的进化,在2019年繁殖季节早期研究了灰椋鸟(Sturnus cineraceus)野外种群身体大小和内脏器官形态的两性差异。结果表明,除嘴宽外,其他身体特征参数均雄性显著大于雌性,表现出雄性偏向的身体大小二态性。内脏器官大小两性间无显著差异。灰椋鸟是聚群生活的鸟类,雌雄鸟常一起觅食,食性相似,雌雄鸟内脏器官和消化道形态差异不显著,暗示食性分化在灰椋鸟身体大小性二态进化中的作用并不明显;雄鸟体型较大的原因可能是其在巢址竞争、配偶保护中适应进化的结果。本研究明确了灰椋鸟身体大小的两性差异,对于该物种身体大小性二态进化的确切原因,尚需更多研究。     

A Test of Rensch’s Rule in Greater Horseshoe Bat (Rhinolophus ferrumequinum) with Female-Biased Sexual Size Dimorphism

Sexual size dimorphism (SSD) is widespread within the animal kingdom. Rensch’s rule describes a relationship between SSD and body size: SSD increases with body size when males are the larger sex, and decreases with body size when females are the larger sex. Rensch’s rule is well supported for taxa that exhibit male-biased SSD but patterns of allometry among taxa with female-biased size dimorphism are mixed, there is evidence both for and against the rule. Furthermore, most studies have investigated Rensch’s rule across a variety of taxa; but among-population studies supporting Rensch’s rule are lacking, especially in taxa that display only slight SSD. Here, we tested whether patterns of intraspecific variation in SSD in greater horseshoe bats conform to Rensch’s rule, and evaluated the contribution of latitude to Rensch’s rule. Our results showed SSD was consistently female-biased in greater horseshoe bats, although female body size was only slightly larger than male body size. The slope of major axis regression of log₁₀ (male) on log₁₀ (female) was significantly different from 1. Forearm length for both sexes of greater horseshoe bats was significantly negatively correlated with latitude, and males displayed a slightly but nonsignificant steeper latitudinal cline in body size than females. We suggest that variation in patterns of SSD among greater horseshoe bat populations is consistent with Rensch’s rule indicating that males were the more variable sex. Males did not have a steeper body size–latitude relationship than females suggesting that sex-specific latitudinal variation in body size may not be an important contributing factor to Rensch’s rule. Future research on greater horseshoe bats might best focus on more comprehensive mechanisms driving the pattern of female-biased SSD variation.     

Intraspecific variation in body size and sexual size dimorphism,and a test of Rensch's rule in bats

The magnitude and direction of sexual size dimorphism (SSD) may vary considerably within and among taxa, and the primary causes of such variation have not been thoroughly elucidated. For example, the effect of abiotic factors is frequently attributed to explain intra‐ and interspecific variation in SSD. Rensch's rule, which states that males vary more in size than females when body size increases, has rarely been tested in bats. Therefore, whether bats follow Rensch's rule remains unclear, particularly when females are larger than males. We investigated whether four bat species presented SSD, as well as whether their body sizes varied within each sex across localities, testing the hypothesis that intraspecific SSD varies substantially depending of sampling localities. We finally examined whether bats followed Rensch's rule by simultaneously using intraspecific and interspecific approaches. Although SSD was not observed for most bat species within each locality, the females of three of the four captured species exhibited differences in body size between particular localities. Usually the females varied more in size than did males across localities, mostly exhibiting a female‐biased SSD. Significant differences in SSD were observed (i.e. mean values of the sexual dimorphism index), even though Rensch's rule was not followed.     

Evolution of Sexual Size Dimorphism in a Frog Obeys the Inverse of Rensch’s Rule

Rensch’s rule refers to a pattern in sexual size dimorphism (SSD) in which SSD increases with body size when males are the larger sex and decreases with body size when females are the larger sex. Using data on body size from 40 populations and age from 31 populations of the rice frog Rana limnochari with female-biased size dimorphism, I tested the consistency of allometric relationships between males and females with Rensch’s rule and evaluated the hypothesis that SSD was largely a function of age differences between the sexes. Statistical comparisons of body sizes between the sexes showed the evidence for the inverse of Rensch’s rule, indicating the level of SSD increased with increasing mean body size. One of the explanations for the occurrence of the inverse of Rensch’s rule may be the fecundity selection hypothesis assuming increased reproductive output in large females. However, differences in age between males and females among populations could explain mildly the variation in SSD.     

A test of Rensch’s rule in dwarf chameleons (Bradypodion spp.), a group with female-biased sexual size dimorphism

Rensch’s rule describes a pattern of allometry in sexual size dimorphism (SSD): when males are the larger sex (male-biased SSD), SSD increases with increasing body size, and when females are the larger sex (female-biased SSD), SSD decreases with increasing body size. While this expectation generally holds for taxa with male-biased or mixed SSD, examples of allometry for SSD consistent with Rensch’s rule in groups with primarily female-biased SSD are remarkably rare. Here, I show that the majority of dwarf chameleons (Bradypodion spp.) have female-biased SSD. In accordance with Rensch’s rule, the group exhibits an allometric slope of log(female size) on log(male size) less than one, although statistical significance is dependent on the phylogenetic comparative method used. In this system, this pattern is likely due to natural selection on both male and female body size, combined with fecundity selection on female body size. In addition to quantifying SSD and testing Rensch’s rule in dwarf chameleons, I discuss reasons why Rensch’s rule may only rarely apply to taxa with female-biased SSD.     

Sexual selection explains sex-specific growth plasticity and positive allometry for sexual size dimorphism in a reef fish

In 1950, Rensch noted that in clades where males are the larger sex, sexual size dimorphism (SSD) tends to be more pronounced in larger species. This fundamental allometric relationship is now known as ‘Rensch''s rule’. While most researchers attribute Rensch''s rule to sexual selection for male size, experimental evidence is lacking. Here, we suggest that ultimate hypotheses for Rensch''s rule should also apply to groups of individuals and that individual trait plasticity can be used to test those hypotheses experimentally. Specifically, we show that in the sex-changing fish Parapercis cylindrica, larger males have larger harems with larger females, and that SSD increases with harem size. Thus, sexual selection for male body size is the ultimate cause of sexual size allometry. In addition, we experimentally illustrate a positive relationship between polygyny potential and individual growth rate during sex change from female to male. Thus, sexual selection is the ultimate cause of variation in growth rate, and variation in growth rate is the proximate cause of sexual size allometry. Taken together, our results provide compelling evidence in support of the sexual selection hypothesis for Rensch''s rule and highlight the potential importance of individual growth modification in the shaping of morphological patterns in Nature.     

Function‐related Drivers of Skull Morphometric Variation and Sexual Size Dimorphism in a Subterranean Rodent,Plateau Zokor (Eospalax baileyi)

Sexual dimorphism is prevalent in most living organisms. The difference in size between sexes of a given species is generally known as sexual size dimorphism (SSD). The magnitude of the SSD is determined by Rensch's rule where size dimorphism increases with increasing body size when the male is the larger sex and decreases with increasing average body size when the female is the larger sex. The unique underground environment that zokors (Eospalax baileyi) live under in the severe habitat of the Qinghai‐Tibetan Plateau (QTP) could create SSD selection pressures that may or may not be supported by Rensch's rule, making this scientific question worthy of investigation. In this study, we investigated the individual variation between sexes in body size and SSD of plateau zokors using measurements of 19 morphological traits. We also investigated the evolutionary mechanisms underlying SSD in plateau zokors. Moreover, we applied Rensch's rule to all extant zokor species. Our results showed male‐biased SSD in plateau zokors: The body‐ and head‐related measurements were greater in males than in females. Linear regression analysis between body length, body weight, and carcass weight showed significant relationships with some traits such as skull length, lower incisor length, and tympanic bulla width, which might support our prediction that males have faster growth rates than females. Further, the SSD pattern corroborated the assumption of Rensch's rule in plateau zokors but not in the other zokor species. Our findings suggest that the natural underground habitat and behavioral differences between sexes can generate selection pressures on male traits and contribute to the evolution of SSD in plateau zokors.     

Sexual size dimorphism in musteloids: An anomalous allometric pattern is explained by feeding ecology

Rensch's rule states that sexual size dimorphism (SSD) increases with body size in taxa where males are larger, and decreases when females are larger. The dominant explanation for the trend is currently that competitive advantage for males is greater in larger individuals, whereas female size is constrained by the energetics of rearing offspring. This rule holds for a variety of vertebrate taxa, and opposing trends are rare. We examine the allometry of SSD within the Musteloidea and demonstrate a hypo‐allometry contrary to Rensch's rule, with lower SSD associated with larger body size. We provide evidence that feeding ecology is involved. Where diet promotes group‐living, the optimal strategy for the males of larger species is often not to attempt to defend access to multiple females, obviating any competitive advantage of relatively greater size. We conclude that the effect of feeding ecology on mating systems may be a hitherto neglected factor explaining variation in SSD.     

Lack of support for Rensch's rule in an intraspecific test using red flour beetle (Tribolium castaneum) populations

Rensch's rule proposes a universal allometric scaling phenomenon across species where sexual size dimorphism (SSD) has evolved: in taxa with male‐biased dimorphism, degree of SSD should increase with overall body size, and in taxa with female‐biased dimorphism, degree of SSD should decrease with increasing average body size. Rensch's rule appears to hold widely across taxa where SSD is male‐biased, but not consistently when SSD is female‐biased. Furthermore, studies addressing this question within species are rare, so it remains unclear whether this rule applies at the intraspecific level. We assess body size and SSD within Tribolium castaneum (Herbst), a species where females are larger than males, using 21 populations derived from separate locations across the world, and maintained in isolated laboratory culture for at least 20 years. Body size, and hence SSD patterns, are highly susceptible to variations in temperature, diet quality and other environmental factors. Crucially, here we nullify interference of such confounds as all populations were maintained under identical conditions (similar densities, standard diet and exposed to identical temperature, relative humidity and photoperiod). We measured thirty beetles of each sex for all populations, and found body size variation across populations, and (as expected) female‐biased SSD in all populations. We test whether Rensch's rule holds for our populations, but find isometry, i.e. no allometry for SSD. Our results thus show that Rensch's rule does not hold across populations within this species. Our intraspecific test matches previous interspecific studies showing that Rensch's rule fails in species with female‐biased SSD.     

Sexual size dimorphism and Rensch's rule in Canidae

The size variation between males and females of a species is a phenomenon known as sexual size dimorphism (SSD). The observed patterns of variation in SSD among species has led to the formulation of Rensch's rule, which establishes that, in species showing a male size bias, SSD increases with an increase in the body size of the species. However, for species in which there is a female size bias, the SSD would decrease when the body size of the species increases. In the present study, we examined the variation in body size and SSD of 33 species of canids from estimates of body mass and body length. We studied its relationship with life‐history characteristics and tested Rensch's rule using phylogenetic generalized least squares and phylogenetic reduced major axis regressions, respectively. We observed the existence of correlation between body mass and body length, although the SSDs from these estimators are uncorrelated. SSD did not show the pattern predicted by Rensch's rule. SSD also did not show any correlation with life‐history traits. It is likely that the low SSD observed in canids is related to the monogamy observed in the family, which is a rare situation in mammals.     

Allometry of sexual size dimorphism in dioecious plants: do plants obey Rensch's rule?

Rensch's rule refers to a pattern in sexual size dimorphism (SSD) in which SSD decreases with body size when females are the larger sex and increases with body size when males are the larger sex. Many animal taxa conform to Rensch's rule, but it has yet to be investigated in plants. Using herbarium collections from New Zealand, we characterized the size of leaves and stems of 297 individuals from 38 dioecious plant species belonging to three distantly related phylogenetic lineages. Statistical comparisons of leaf sizes between males and females showed evidence for Rensch's rule in two of the three lineages, indicating SSD decreases with leaf size when females produce larger leaves and increases with leaf size when males produce larger leaves. A similar pattern in SSD was observed for stem sizes. However, in this instance, females of small-stemmed species produced much larger stems than did males, but as stem sizes increased, SSD often disappeared. We hypothesize that sexual dimorphism in stem sizes results from selection for larger stems in females, which must provide mechanical support for seeds, fruits, and dispersal vectors, and that scaling relationships in leaf sizes result from correlated evolution with stem sizes. The overall results suggest that selection for larger female stem sizes to support the weight of offspring can give rise to Rensch's rule in dioecious plants.