Song Perception in the Song Sparrow: Importance of Different Parts of the Song in Song Type Classification

Song sparrow (Melospiza melodia) males have repertoires of 6 to 12 song types, each song consisting of four or five contrasting phrases. Song types vary both within individuals (a singer varies successive renditions of a type within a singing bout) and between individuals (neighbors sing slightly different versions of a type), and in both cases this variation is concentrated in the later parts of the song. We speculated that type variation in the later parts of the song might be correlated with a perceptual tendency to classify song types primarily on the basis of the earlier parts of the song. We tested this hypothesis using a laboratory conditioning technique, supplemented by a field playback experiment. In the lab, song sparrows and white crowned sparrows were trained to discriminate between two distinct song types. In test sessions, they were presented with hybrid songs synthesized from varying proportions of the two training song types. For most birds and most song pairs, song classification was influenced by all parts of the song, with the beginning elements being most important. The field playback experiment used song type matching as the response measure. Each subject was presented a hybrid stimulus song consisting of the first half of one of his song types and the second half of another of his song types. Subjects replied with both ‘front matches’ and ‘back matches’ (60% were front matches).     

Sexual Dimorphism in the Response of the GABAergic System to Estrogen Administration

Abstract: Administration of estradiol benzoate to gonadectomized female rats results in up-regulation of CNS γ-aminobutyric acid (GABA) receptors. The increase of [³H]muscimol binding activity is observed in six of the seven brain areas examined. The same treatment, performed in castrated male or and rogenized female rats, induced an increase of [³H]muscimol binding only in the striatum. Evidence is provided suggesting that the dimorphic sensitivity of GABA receptor is not correlated with the difference in spontaneous motor activity reported between male and female rats.     

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.     

Enzyme polymorphisms in the House Sparrow, Passer domesticus

Methods are described for the visualization of 20 enzymes from the house sparrow, Passer domesticus, in starch gels and by iso-electric focussing. Many of the methods are applicable to other avian species. Two samples of sparrows from the east midlands of England have been analysed. The patterns that are manifest in the gels can be ascribed to between 33 and 35 loci, of which the same nine are polymorphic in both samples. The level of heterozygosity in these birds is about 15%, which at first sight is higher than an introduced population in Australia. However, this difference disappears when homologous loci are compared.     

脊椎动物雌雄生长差异的研究进展

综述了有关脊椎动物雌雄生长差异的研究,分别从摄食消化、生长与生殖能量配置、物种遗传、基因型与表现型、类固醇激素水平和生长轴基因表达等几个方面分析了脊椎动物雌雄生长差异的原因.     

The spread of the House Sparrow Passer domesticus in Bolivia

Bolivia lies within the Tropics and contains extremes from desert to jungle and from low to high altitudes. House Sparrows entered the south of Bolivia from Argentina about 1930 and have now spread to towns and villages scattered through about half of the country. These are principally in the semi-arid Andean descents of south and central Bolivia and in the lowlands in Santa Cruz city and certain nearby towns. In the high altiplano they have reached only two cities and are not numerous in either. They appear to be absent from the humid Andean slopes and from most of the eastern and northern lowlands, with the exception of two isolated towns which they could have reached either from Brazil or from elsewhere in Bolivia. House Sparrows do not occur away from human settlements in Bolivia.     

Disentangling the Size and Shape Components of Sexual Dimorphism

Evolutionary Biology - Many organisms are sexually dimorphic, reflecting sex-specific selection pressures. But although sexual dimorphism may consist of different variables from size to shape and...     

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.     

An Ecological Theory of Sexual Dimorphism in Animals

Both male ornamentation and male combat result in increased male mortality. Because population sizes are limited by a carrying capacity, increased age-specific adult male mortality will result in decreased age-specific adult female mortality, as well as decreased juvenile mortality. As intersexual competition is one form of intraspecific competition, through choosing to mate with ornamented and/or combative males, females in polygamous systems reduce intraspecific competition. Because average male fitness must exactly equal average female fitness, male fitness will paradoxically rise with increasing male mortality. This theory also offers new perspectives on peripheral problems to sexual theory, such as mate location, resource guarding, leks, harems, and others.     

Developmental Aspects of Sexual Dimorphism in Hominoid Canines

We examined the histology of canine teeth in extant hominoids and provided a comparative database on several aspects of canine development. The resultant data augment the known pattern of differences in aspects of tooth crown formation among great apes and more importantly, enable us to determine the underlying developmental mechanisms responsible for canine dimorphism in them. We sectioned and analyzed a large sample (n = 108) of reliably-sexed great ape mandibular canines according to standard histological techniques. Using information from long- and short-period incremental markings in teeth, we recorded measurements of daily secretion rates, periodicity and linear enamel thickness for specimens of Pan troglodytes, Gorilla gorilla, Pongo pygmaeus and Homo sapiens. Modal values of periodicities in males and females, respectively, are: Pan 7/7; Gorilla 9/10; Pongo 10/10; and Homo 8/8. Secretion rates increase from the inner to the outer region of the enamel cap and decrease from the cuspal towards the cervical margin of the canine crown in all great ape species. Female hominoids tend to possess significantly thicker enamel than their male counterparts, which is almost certainly related to the presence of faster daily secretion rates near the enamel-dentine junction, especially in Gorilla and Pongo. Taken together, these results indicate that sexual differences in canine development are most apparent in the earlier stages of canine crown formation, while interspecific differences are most apparent in the outer crown region. When combined with results on the rate and duration of canine crown formation, the results provide essential background work for larger projects aimed at understanding the developmental basis of canine dimorphism in extant and extinct large-bodied hominoids and eventually in early hominins.     

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.     

根田鼠气味识别的性二型

以新鲜尿和粪作气味源,在行为选择箱中观察根田鼠的行为识别模式,结果表明：雌鼠对陌生同性尿、粪气味源行为识别的差异不显,雄鼠对陌生同性尿、粪气味源的行为识别在多个指标上存在显差异;根田鼠对陌生异性尿、粪的行为响应模式无明显差异;除嗅舔时间外,雌、雄鼠对粪气味的行为识别在其他指标上不存在明显差异;比较雌、雄鼠对尿刺激的行为识别发现,雄鼠对尿刺激的访问频次和反标记显大于雌鼠,雌性嗅舔时间显大于雄性,其他方面二之间并无显差异。因此,雌、雄性根田鼠对粪气味的行为识别模式不存在性别差异;对尿气味的行为识别模式存在性别差异。