雉鸡(Phasianus colchicus)营巢生境的模拟分析研究

将多元统计学方法与地理信息系统结合对动物的栖息地进行适宜性分析,是近年动物栖息地研究者和管理者都十分感兴趣的方面。本研究采用马氏距离法,利用地理信息系统模拟甘肃雉鸡的营巢生境。模拟结果表明,与已知营巢生境相似水平为0.95的区域面积,仅占整个研究区的0.68%,而与已知营巢生境迥然不同（P＜0.05）的区域面积占79.08%。营巢生境与非营巢生境在生境类型组成和地形因素上存在多方差异,营巢生境中农田和草坡占有极大比例,用于营巢的区域总是更接近生境的边缘。特别是接近于农田、草坡和白桦阔叶林等生境,表明倾向于在这几种生境的边缘附近营巢。营巢生境的平均海拔比非营巢生境低,坡度也较缓,坡向则更偏于东南方。在同一生境类型内部,用于营巢的区域和不利用的区域之间也存在很大差别,营巢区域总是更接近生境的边缘。某一生境周围的其它生境类型也会影响雉鸡的营巢选择。     

Winter foraging habitat selection of brown-eared pheasant (Crossoptilon mantchuricum) and the common pheasant (Phasianus colchicus) in Huanglong Mountains, Shaanxi Province

The foraging habitat selections of brown-eared pheasant (Crossoptilon mantchuricum) and the common pheasant (Phasianus colchicus) were studied in Huanglongshan Nature Reserve Shaanxi, China. Foraging habitat characteristics were measured on the basis of expected differences between species at 183 sites from November to December 2006 and January 2007. The results showed that both species selected foraging habitats with altitude (<1200 m), conifer forest, half sunny and half shady slope, sunny slope, density of trees (<5 individuals/100 m²), cover of shrub (>50%), visibility class (<10%) and distance to water source (<300 m). However, the brown-eared pheasant selected habitats with cover of trees (30–50%), middle or lower slope location, distance to edge of woods (<300 m) and human disturbance (<500 m), and the selection on density of shrub was not observed, compared to the selections on cover of trees (<30%), lower slope location, distance to edge of woods (<500 m) and human disturbance (<300 m), and density of shrub (>500 individuals/100 m²) for common pheasant. We also found that the common pheasant avoid predators by concealment whereas brown-eared pheasant evade predations by running away strategy.     

Effects of testosterone on the development of neuromuscular systems and their target tissues involved in courtship and copulation in green anoles (Anolis carolinensis)

Male green anole lizards court females using a red throat fan (dewlap) and copulate by intromitting one of two penises (hemipenes). These structures begin sexually monomorphic, but by adulthood males have larger dewlaps, only males have hemipenes, and many of the neuromuscular components of both systems show male-biased dimorphisms. We hypothesized that testosterone (T), which increases in juvenile males but not females about a month after hatching, facilitates masculinization. To test this idea, on post-hatching day 30, gonadally intact females received either a blank or T implant, and males were either castrated or sham-castrated. At day 90, juveniles were euthanized and the length of the cartilage and cross-sectional areas of the muscle fibers and motoneurons required for dewlap extension were examined. We also measured the cross-sectional areas of the hemipenes and associated muscle fibers and motoneurons, and counted the motoneurons. T-treated females had longer cartilages and larger dewlap muscle fibers compared to those with blank implants. No effects on motoneurons were detected, and no females possessed hemipenes or associated musculature. In males, castration produced shorter dewlap cartilages and smaller hemipenes; other measures were not affected by treatment. These data indicate that components of the dewlap system differentiate relatively late in development, that T likely mediates the process, and that although components of the copulatory system are plastic in juvenile males, sexual differentiation of peripheral features is complete before day 30. The data also suggest that target structures (dewlap cartilage and hemipenes), compared to their neuromuscular effectors, are particularly sensitive to developmental T exposure.     

Female presence affects male behavior and testosterone levels in the European starling (Sturnus vulgaris)

In this study, we confronted individually housed male European starlings (Sturnus vulgaris) with a female conspecific for 60 min to study the consequences on behavior and plasma testosterone (T) concentrations. Control males experienced a similar procedure, the only difference being that they were tested in the absence of a female. Female presence significantly affected both behavior and plasma T levels of male starlings. Experimental males spent significantly more time singing in the nest box and flew significantly more into the nest box with green nesting material during female presentations than during control periods. Control males never showed these mate attraction behaviors. In total 5 of the 16 experimental males did not respond behaviorally to the female stimulus bird (NR males). In contrast to T levels of control males, plasma T concentrations of both experimental males that did respond to the female (R males) and of NR males (which only perceived the female stimulus) were positively influenced by female presentation. The time spent singing in the nest box by experimental males (R and NR males combined) during female presence tended to be positively correlated with changes in plasma T levels. Finally, before introduction of a female, plasma T levels of R males were significantly higher than those of NR males indicating that individually housed males respond to the presence of a female conspecific by increasing their mate attraction behaviors only when a threshold plasma T concentration has been reached.     

Serum testosterone,progesterone, and estradiol concentrations and sexual maturation in spotted seals (Phoca largha)

Spotted seals (Phoca largha) are ice-breeding phocid found in eight different breeding colonies all over the world. They exhibit a seasonal breeding pattern, with annual and synchronous cycles; however, little is known about their reproductive endocrinology. In this study, we measured serum testosterone, progesterone, and 17β-estradiol concentrations in captive spotted seals (simple number: female n = 68; male n = 89) throughout a full reproductive cycle. Males that were older than 4 years had significant testosterone fluctuations and were, therefore, classified as sexually mature. These animals show significant seasonal changes in testosterone levels, with average peak concentrations of 10.81 ± 9.57 nmol/L (±SD) from November to February, compared with mean concentrations of 1.42 ± 3.09 nmol/L throughout the remainder of the year. Females that reported a significant variation in progesterone concentrations and were older than 4 years were considered to be sexually mature. In these females, progesterone levels increased in February, remained elevated for 7 months with a mean value of 37.39 ± 17.03 nmol/L, and then dropped to 0.74 ± 0.54 nmol/L. Serum 17β-estradiol levels were also found to be significantly increased in January, remained so for 8 months (15.80 ± 14.15 ng/L), and then declined after August (7.77 ± 6.78 ng/L). In seals, mating typically occurs in February and March, 1 month after the observed peaks in testosterone and estradiol concentrations and corresponding to the increase in progesterone. A moderate positive correlation between testosterone and progesterone concentrations in sexually mature males was also observed (Spearman rho, r = 0.63, P < 0.01). In sexually immature females, progesterone and estradiol concentrations were found to be significantly lower than those in mature females. Finally, the observed patterns of estradiol and progesterone in sexually mature females suggest that embryonic diapause or successful implantation occurs in August.     

Intrasexual selection in Verreaux's sifaka (Propithecus verreauxi verreauxi)

Studies of sexual selection show that both female choice and male-male competition can influence the evolution and expression of male phenotypes. In this regard, it is important to determine the functional basis through which male traits influence variation in male reproductive success. In this study, we estimate the strength and type of sexual selection acting on adult males in a population of wild lemur, Verreaux's sifaka (Propithecus verreauxi verreauxi). The data used in this study were collected at Beza Mahafaly Special Reserve, southwest Madagascar. We conducted paternity analyses on 70 males in order to estimate the distribution of reproductive success in this population. Paternity data were combined with morphometric data in order to determine which morphological traits covary with male fitness. Five morphological traits were defined in this analysis: body size, canine size, torso shape, arm shape, and leg shape. We utilized phenotypic selection models in order to determine the strength and type of selection acting directly on each trait. Our results show that directional selection acts on leg shape (a trait that is functionally related to locomotor performance), stabilizing selection acts on body mass and torso shape, and negative correlational selection acts on body mass and leg shape. We draw from biomechanical and kinematic studies of sifaka locomotion to provide a functional context for how these traits influence male mating competition within an arboreal environment. Verreaux's sifaka and many other gregarious lemurs are sexually monomorphic in body mass and canine size, despite a high frequency and intensity of male-male aggressive competition. Our results provide some insight into this paradox: in our population, there is no directional selection acting on body mass or canine size in males. The total pattern of selection implicates that behaviors relating to locomotor performance are more important than behaviors relating to fighting ability during intrasexual contests.     

Paternal behavior increases testosterone levels in offspring of the California mouse

Paternal care during early development influences pup survivorship in the monogamous and biparental California mouse, Peromyscus californicus. Moreover, paternal pup retrievals impact development of adult offspring aggression and the neuropeptide vasopressin, yet little is known about the underlying mechanisms of these developmental changes. Because testosterone can increase arginine vasopressin and aggression, we hypothesized that paternal pup retrievals increase testosterone levels in prepubertal male P. californicus pups. Male pups were assigned to one of three groups: hormonal baseline, nonretrieval control, or retrieval. On postnatal days 18-21, all pups and the mother were removed from the cage, and the focal male pup was placed either outside of the nest to elicit paternal retrievals (retrieval group) or in the nest to discourage paternal retrievals (nonretrieval group). Testosterone was elevated at 45-min, but not 90-min, post-manipulation in retrieved compared to nonretrieved pups. Moreover, there was a significant positive correlation between pup retrievals and testosterone in the 45-min group. This rapid testosterone rise in response to paternal retrievals may facilitate an increase in aggression and vasopressin in adult offspring. Therefore, this period of development previously viewed as hormonally quiescent may be more active in response to paternal behavior than previously thought.     

Experimental manipulation of testosterone and condition during molt affects activity and vocalizations of male blue tits

Testosterone (T) is a key hormone regulating behavioral trade-offs in male birds, shifting investment towards sexual and competitive behaviors. However, the role of T in regulating male behavior during the molt has received very little attention, although this is a crucial life-history stage. Since the effect of T on behavior may be condition-dependent, particularly during the costly molt period, we studied the effects of T and condition in a two-way design. We manipulated T under two dietary regimes (standard and improved, resulting in an enhanced condition) in captive blue tits (Cyanistes caeruleus) undergoing the first pre-basic molt. T treatment increased song frequency, indicating that song is T-dependent also at this time of year. Males on the improved diet sang less than males in relatively worse condition, providing no support for song as an indicator of male condition. T-treated males exhibited greater locomotor activity than control males, but only when fed the standard diet. Neither T- nor diet-treatment affected plumage maintenance (preening). Although T treatment resulted in a delay in molt progress all birds completed the molt. Taken together our results show that during the molt male birds are sensitive to relatively small fluctuations in T. Similar to its commonly observed effects during the breeding season, T stimulated an increase in song and locomotion. While there might be some benefits associated with such T effects, these must be traded-off against costs associated with conspicuous behavior and increased molt duration.     

Sexual dimorphism of craniological characters in Eurasian badgers, Meles spp. (Carnivora, Mustelidae)

An analysis of 30 craniological characters of Eurasian badgers (Meles spp.) revealed different levels of sexual size dimorphism (SSD) and geographic variation in the three different species. SSD is displayed mostly in the general size of the skull (condylobasal length, zygomatic width, width of rostrum, and cranial height) and mandible (height of the vertical mandibular ramus, total length of the mandible, and length between the angular process and infradentale), and in some dental characters (length of the upper molar M¹). The most stable size dimorphism is manifested in the size of the canines, which is pronounced in all studied samples. SSD is not apparent in the length of the auditory bulla, the postorbital width, the minimum palatal width, the length of the lower molar M₂, and the talonid length of the lower carnassial tooth M₁.In both the European badgers, Meles meles, and the Asian badgers, Meles leucurus, two geographic forms that differ in the degree of SSD have been found. The most pronounced SSD of cranial characters is found in the Transcaucasian form of Meles meles and the Far-Eastern form of Meles leucurus. In the large European form of Meles meles, SSD is less pronounced in both absolute and relative criteria than in the smaller Transcaucasian form. An analogous situation is observed in the larger Siberian and smaller Far-Eastern forms of Meles leucurus. In the Japanese badgers, Meles anakuma, a downsizing of the skull is accompanied by a decrease in SSD (except in canine size) in comparison to the continental species. The significant differences in the manifestation of SSD in the Eurasian badgers support an earlier hypothesis (Abramov, 2001. Proc. Zool. Inst. Russ. Acad. Sci. 288, 221-233; Abramov, 2002. Russ. J. Theriol. 1 (1), 57-60; Abramov, 2003. Small Carnivore Conserv. 29, 5-7) that Meles meles, Meles leucurus, and Meles anakuma are separate species. The differences in the level of SSD among and within these three species of badgers may be attributed not to differences in the diet or social structure, but to the history of speciation events and formation of intraspecific distribution ranges.     

Ontogenetic changes and sexual dimorphism in the mandible of adult woolly mammoths (Mammuthus primigenius)

Morphometric studies are a fundamental tool in paleontology to answer taxonomic, functional and evolutionary questions. In particular, appropriate functional interpretation often requires consideration of ontogenetic changes in the structures studied. The woolly mammoth (Mammuthus primigenius) is one of the most representative large mammal species of the Eurasian Pleistocene. Available ontogenetic studies on woolly mammoth mandible have focused on the first ontogenetic stages of the mandible development up to 4-5 years and have suggested that the symphysial process is sexually dimorphic. In the present work, we studied ontogenetic changes and sexual dimorphism in 45 mandibles from subadult and adult stages (8-56 African Elephant Years). Our results show positive correlations among almost all the morphometric variables measured, as well as an increase of mandible size with age. This increase does not differ among the variables examined, although the highest values are related with the symphysis height and the opening of the horizontal branches, and the lower ones with the greatest length (dimension), which implies the increase in the relative mandible width and height throughout the individual life. Sexual dimorphism in the mandible is at best slight, and the symphysial process is not diagnostic for sexing purposes. In addition, differences in age were an important confounding factor to assess sexual dimorphism and should be considered in future uses of sexual dimorphism assessment techniques.     

Androgen receptors are required for full masculinization of the ventromedial hypothalamus (VMH) in rats

The ventromedial hypothalamus (VMH) is one of several sexually dimorphic nuclei that regulate mating behavior, and is rich in steroid hormone receptors and aromatase activity. We looked at the contribution of the androgen receptor (AR) to the volume of the VMH in rats by measuring each of the four subdivisions of the VMH in 90 day old male, female, and XY male rats carrying a mutant AR allele (tfm), which renders animals largely unresponsive to androgens. Confirming published reports, total VMH volume was greater in wild-type males than in females (P<0.01). The mean total volume of the VMH in TFM males was intermediate, but not significantly different from either females or males (Ps>0.10). The sex difference in VMH volume was primarily accounted for by the ventrolateral subdivision (VMHvl), which in both females and TFM males was significantly smaller than in wild-type males (Ps<0.005). There was no significant sex difference in the volume of the other three subdivisions of the VMH. Neuronal somata were larger in males than females in VMHvl, central VMH (VMHc) and the dorsomedial VMH (VMHdm), with TFM males having feminine neuronal somata in the VMHdm and VMHc. These data suggest that AR plays a role during sexual differentiation of the VMH, imparting its greatest effect in the VMHvl. ARs may regulate aromatase expression or activity to affect estrogen receptor activation, or may act independently of estrogen receptors to influence VMH morphology.     

Intercontinental effect on sexual shape dimorphism and allometric relationships in the beetle pest Diabrotica virgifera virgifera LeConte (Coleoptera: Chrysomelidae)

Hind wing shape variation was examined in 686 adult Diabrotica virgifera virgifera collected from maize plants in Europe and the USA Corn Belt, using geometric morphometric techniques. Sexual dimorphism at an Intercontinental scale was assessed using canonical variates analysis, a multivariate statistical method used to find the shape characters that best distinguish among groups of specimens. Our results showed that each of the populations of D. v. virgifera investigated in this study showed high levels of sex based hind wing shape dimorphism. In particular a stronger and more obvious pattern of hind wing shape variation was found in the USA than in Europe. These results support previous studies on D. v. virgifera wing shape that show that female D. v. virgifera have more elongated wings than males. These differences raise the question of whether sexual dimorphism may be modulated by natural selection.     

Causes of secondary sexual differences in plants — Evidence from extreme leaf dimorphism in Leucadendron (Proteaceae)

In extreme cases leaves in male plants of the dioecious genus Leucadendron (Proteaceae) are up to an order of magnitude smaller than female leaves. This secondary sexual dimorphism (SSD) in leaf size has previously been suggested to be due to intra-male sexual selection, leading to an increase in male allocation to reproduction in dimorphic species. After critically evaluating previous data provided to support this hypothesis, I suggest on both theoretical grounds and on re-analysis that this argument is unlikely and unsupported. Leaf size dimorphism could theoretically evolve directly due to disruptive ecological selection between genders, leading to niche dimorphism either within or between habitats. I test this ecological causation hypothesis by providing data on specific leaf area (sla) and water use efficiency (δ ¹³C) of leaves from males and females of several Leucadendron species. Results confirm the expectation of minimal gender differences. I argue that leaf dimorphism is a consequence of selection on flower size and architecture.     

Increased sibling competition does not increase testosterone or corticosterone levels in nestlings of the spotless starling (Sturnus unicolor)

Nestling begging in passerine birds is a complex behaviour that is shaped by a multitude of ecological factors and could be physiologically mediated by varying levels of steroid hormones. Previous research has shown links between sibling competition and testosterone and corticosterone in several bird species. The spotless starling (Sturnus unicolor) is a medium sized passerine in which nestlings compete intensively for resources, often resulting in marked size hierarchies that can have profound effects on their fitness. We tested the hypothesis that an increase in sibling competition levels would result in increases in testosterone and corticosterone in this species. To this end we conducted a brood size manipulation, creating small, medium and large broods. This manipulation had the expected effect on morphology: nestling size and mass decreased with increasing brood size. Androgen levels varied in response to brood size manipulation but, contrary to expectations, the largest concentrations were found in reduced brood sizes. Corticosterone levels increased with increasing brood size, but this effect disappeared when we corrected for the time taken to process nestlings. Cell-mediated immune response was found to decrease with increasing brood size and testosterone levels. The results suggest that the proposed link between testosterone and corticosterone and sibling competition does not hold in this species, and underlines the diversity of species-specific responsiveness to steroids.     

Development in Japanese macaques (Macaca fuscata): Sexually dimorphic behavior during the first year of life

We have documented several sexually dimorphic patterns of behavior that develop during the first year of life in infant Japanese macaques and their mothers. Mothers treated their infants differently by sex—mothers of males broke contact with them and retrieved them more frequently than did mothers of females. And mothers of male infants moved more frequently than did mothers of female infants. Male infants played more, played in larger groups, and mounted more frequently; female infants groomed and spent more time close to other monkeys in larger social groups than did males. Female infants were also punished by other group members more frequently than were male infants. We conclude that male and female Japanese macaque infants receive differential treatment early in life by both their own mothers and other animals, and males and females in turn treat their mothers and other animals differently. There appears to be a reciprocal relationship between the behavior of infants, mothers and other social partners that contributes to the development of sexually dimorphic patterns of behavior.     

Social modulation of testosterone levels in male black howlers (Alouatta pigra)

The influence of social factors on the modulation of male testosterone levels has been demonstrated among several vertebrate species. In addition to sexual activity, parental care and reproductive competition affect testosterone secretion. We examined variations in testosterone levels among male black howlers (Alouatta pigra) in various social contexts. Fecal samples were collected from nine males living in five different groups in the Mexican state of Campeche. The potential for intragroup and extragroup competition varied among the groups. The number of resident males living in the groups was the only variable that significantly explained variations in testosterone levels. Males living in unimale groups had higher testosterone levels; the highest testosterone levels were recorded for males that had experienced a shift from multimale to unimale group compositions. In this species, the probability of being challenged by extragroup males and evicted from the group during immigration events increases when males live in unimale groups. Therefore, our results suggest that male black howlers respond to competition for group membership by increasing their testosterone levels. In this context, testosterone secretion represents an anticipatory response to reproductive conflicts. Therefore, although males living in unimale groups have exclusive access to females, they face higher physiological costs associated with sustaining high testosterone levels for extended time periods.     

Neither testosterone levels nor aggression decrease when the male Mongolian gerbil (Meriones unguiculatus) displays paternal behavior

The first studies that correlated mammalian paternal behavior and testosterone levels indicated that the concentration of this steroid hormone decreases when males exhibit paternal care. However, recent studies have also shown that testosterone levels do not decrease when males display paternal behavior. In this study, we measured testosterone levels in plasma throughout the reproductive cycle of the Mongolian gerbil. Testosterone concentrations were correlated with paternal care as well as aggression. We also examined whether there is a trade-off between paternal behavior and aggression in this mammal. Our results show that Mongolian gerbil testosterone levels do not decrease when the males give paternal care. Likewise, male Mongolian gerbils exhibit high levels of aggression while displaying paternal behavior, indicating that there is no trade-off between aggression and paternal behavior. More studies are needed to determine whether testosterone is involved in the regulation of paternal behavior in this rodent.     

不同鸟类生境网络复合与优化——以苏锡常地区白鹭、鸳鸯、雉鸡为例

通过复合优化不同焦点物种的生境网络表征多数物种生境网络实现物种多样性保护,具有重要理论价值和实践意义。以苏锡常地区为研究区域,以白鹭、鸳鸯和雉鸡3种鸟类为焦点物种,通过采用生境斑块约束条件模型与最小成本路径法相结合的方法识别出生境网络;从满足集合覆盖问题视角出发,通过采用网络构成要素复合的方法进行网络复合,其中廊道与廊道的复合通过采用评价生态系统服务价值的方法实现;通过采用观测数据为生境斑块和迁移廊道增补依据的方法进行复合生境网络优化。结果表明:生境网络经过复合,廊道总面积、总长度及生态系统服务价值在分别减少了16%、68%和10%的情况下,保持了斑块间的连接度、兼顾到经济效益和生态效益最大化、覆盖了占总数86%以上的75处观测点;复合生境网络经过优化,覆盖了2010年及以后所有84处观测点,廊道总面积、总长度及生态系统服务价值分别增加了19%、21%和27%;说明生境网络复合优化定量分析方法和思路具有可行性,为网络复合研究提供了借鉴。     

Regulation of hhex expression in the yolk syncytial layer, the potential Nieuwkoop center homolog in zebrafish

The Nieuwkoop center is the earliest signaling center during dorsal-ventral pattern formation in amphibian embryos and has been implied to function in induction of the Spemann-Mangold organizer. In zebrafish, Nieuwkoop-center-like activity resides in the dorsal yolk syncytial layer (YSL) at the interface of the vegetal yolk cell and the blastoderm. hex homologs are expressed in the anterior endomesoderm in frogs (Xhex), the anterior visceral endoderm in mice, and the dorsal YSL in zebrafish (hhex). Here, we investigate the control of hhex expression in the YSL. We demonstrate that bozozok (boz) is absolutely required for early hhex expression, while overexpression of boz causes ectopic hhex expression. Activation of Wnt/beta-catenin signaling by LiCl induces hhex expression in wild-type YSL but not in boz mutant embryos, revealing that boz activity is required downstream of Wnt/beta-catenin signaling for hhex expression. Further, we show that the boz-mediated induction of hhex is independent of the Boz-mediated repression of bmp2b. Our data reveal that repressive effects of both Vega1 and Vega2 may be responsible for the exclusion of hhex expression from the ventral and lateral parts of the YSL. In summary, zebrafish hhex appears to be activated by Wnt/beta-catenin in the dorsal YSL, where Boz acts in a permissive way to limit repression of hhex by Vega1 and Vega2.     

Fin-mutant female zebrafish (Danio rerio) exhibit differences in association preferences for male fin length

Females often choose to associate with males that have exaggerated traits. In fishes, this may reflect an overall preference for larger size in a potential mate. Female zebrafish (Danio rerio) prefer males with larger bodies but not longer fins. The availability of mutant and transgenic strains of zebrafish make this a unique model system in which to study the role of phenotypic variation in social and sexual behavior. We used mutant strains of zebrafish with truncated (short fin) and exaggerated (long fin) fins to further examine female preferences for fin length in dichotomous association tests. Wild type females showed no preferences between wild type males and short fin mutant males or between wild type males and long fin mutant males. short fin females also showed no preference for short fin males or wild type males while long fin females preferred to associate with long fin males over wild type males. These results suggest that the single gene long fin mutation that results in altered fin morphological may also be involved in a related female association preference.