Multiple mate choice criteria and the importance of age for male mating success in the microhylid frog, Cophixalus ornatus

We examined multiple mate choice criteria in Cophixalus ornatus, a terrestrial breeding, microhylid frog. Mate choice consisted of three stages: mate attraction (male calling), courtship (male behavior between the call site and the nest), and nest site selection by the female. For male C. ornatus, the possession of a call with low dominant frequency relative to calling neighbors increased the probability that they would attract females. Dominant frequency was negatively correlated with age independent of male mass and snout vent length. When escorting the female from the call site to their nest, males traveled along more convoluted paths than when returning to the nest alone. The convolution of the path was, therefore, considered an aspect of courtship. Females released eggs into nests with structural characteristics typical of nests constructed by older males. Thus, females increased their chances of locating an acceptable nest by preferentially approaching males with lower dominant frequencies. This study is the first to demonstrate that age, independent of mass or snout-vent length, can influence call characteristics in anurans, and it is also the first to demonstrate the importance of male age to female mate choice in an amphibian.     

基于DEMATEL方法的海运行为形成因子影响关系分析

为揭示并量化海运人因可靠性分析(HRA)中行为形成因子(PSF)间复杂的影响关系,采用DEMATEL方法对航海人员值班任务中9个PSF的依赖关系进行建模和分析,并验证该方法的有效性。结果表明:船上组织的完善程度、驾驶台班组成员的合作质量、可用时间等PSF在系统中的作用大;船上组织的完善程度、人机界面(MMI)与运行支持的完善性、值班区间以及培训和准备的充分性4个PSF为原因因素,驾驶台班组成员的合作质量、同时出现的目标任务数量、可用时间、船上工作及船舶航行条件和操作规程/计划的可用性5个PSF为结果因素。安全管理人员应针对作用大或原因因素中的PSF制定安全管理措施,改善情景环境,提高人因可靠性。     

Oil dependency,political institutions,and urban–rural disparities in access to electricity in Africa

In line with the resource curse literature, this paper examines the effect of oil dependency on the disparities in access to electricity between urban and rural areas in Africa, conditional on the quality of political institutions. Based on data from 36 African countries over the period 2000–2017, our investigation suggests that oil rents (% of GDP) increase urban–rural disparities in access to electricity. However, the quality of institutions shapes the effect of oil dependency on these disparities. Specifically, a 10% increase in the institutional quality score reduces the adverse effects of oil rent on electricity access disparity by around 19%, and the negative impact of oil dependency on urban–rural disparities is reversed when institutional quality reaches a score of 52% on a scale from 0 to 100. The robustness tests support these results and call for strengthening the quality of institutions to overcome the resource curse in Africa.     

Differential responses of honeybee (<Emphasis Type="BoldItalic">Apis mellifera</Emphasis>) patrilines to changes in stimuli for the generalist tasks of nursing and foraging

Which task a social insect worker engages in is influenced by the worker’s age, genotype and the colony’s needs. In the honeybee, Apis mellifera, genotype influences both the age a worker switches tasks and its propensity of engaging in specialist tasks, such as water collecting, which only some workers will perform. In this study, we used colonies with natural levels of genetic diversity and manipulated colony age demography to drastically increase the stimuli for the generalist tasks of foraging and nursing, which all workers are thought to engage in at some point in their lives. We examined the representation of worker patrilines engaged in nursing and foraging before and after the perturbation. The representation of patrilines among foragers and nurses differed from that of their overall colony’s population. In the case of foraging, over- and underrepresentation of some patrilines was not simply due to differences in rates of development among patrilines. We show that replacement foragers tend to be drawn from patrilines that were overrepresented among foragers before the perturbation, suggesting that there is a genetic component to the tendency to engage in foraging. In contrast, the representation of patrilines in replacement nurses differed from that in the unperturbed nursing population. Our results show that there is a genetic influence on even the generalist tasks of foraging and nursing, and that the way patrilines in genetically diverse colonies respond to increases in task stimuli depends upon the task. The possible significance of this genetic influence on task allocation is discussed. Electronic supplementary material Supplementary material is available in the online version of this article at doi: and is accessible to authorized users.     

Age,experience and reproductive performance in a long-lived bird: a hormonal perspective

The ultimate factors influencing age-specific reproductive performance in birds have been widely discussed, and several hypotheses have been suggested to explain why young/inexperienced breeders have lower reproductive success than older individuals. In comparison, proximate factors and, particularly, hormonal mechanisms influencing age-related reproductive performance have received lesser attention. In this paper, we examined how baseline levels of corticosterone and prolactin, two hormones involved in reproduction, changed with age and experience in a long-lived bird, the Black-browed albatross (Thallasarche melanophris) during the brooding stage. Corticosterone levels were not linked to age, whereas prolactin levels increased until individuals reached 15 years of age. First-time breeders had higher corticosterone levels and lower prolactin levels than experienced ones. Corticosterone levels were not correlated with breeding experience among experienced birds, whereas prolactin levels slightly increased with advancing experience. Among experienced breeders, there was no effect of individual quality on corticosterone and prolactin levels. Baseline corticosterone and prolactin levels were respectively, positively and negatively correlated to time spent fasting/brooding on the nest. Moreover, the probability of successfully fledging a chick was negatively related to corticosterone levels, but not to prolactin levels. Elevated corticosterone levels in first time breeders may serve as evidence for depleted body reserves resulting from lower foraging/brooding capabilities and therefore support the constraint hypothesis. Low prolactin levels in young/inexperienced birds may be interpreted either as evidence for their lower breeding capacities (constraint hypothesis) or for their limited breeding investment (restraint hypothesis). Finally, we report, for the first time, the hormonal changes associated with the onset of senescence. The very old and most experienced birds, which had the lowest probability of successfully fledging a young, displayed elevated corticosterone levels and low prolactin levels, possibly indicating a degradation of breeding skills and/or a disruption of the endocrine system in senescent birds.     

海洋环境数据库的数据依赖识别方法

设计达到第三范式标准的数据库模式,是数据库建设的关键.本文针对海洋环境数据基本为调查数据、数据之间因缺乏业务逻辑无法确立依赖关系的现状,提出了根据现有数据模式识别数据依赖的方法,并应用于数据库模式的规范化设计,通过理论和实践证明海洋环境数据库模式设计达到第三范式标准,成功应用于城市风暴潮防灾减灾辅助决策支持系统等项目建...     

Age- and state-dependent reproductive effort in male mountain goats, Oreamnos americanus

In mammalian polygynous mating systems, male reproductive effort consists mainly of male–male competition and courting of females, which entail substantial somatic costs. Males are thus expected to adjust their reproductive effort according to their age and condition. In this study, we examined how activity budgets of male mountain goats (Oreamnos americanus), a polygynous ungulate, varied with age in a marked population over two periods: (1) summers 1995–2006 and (2) ruts 2004–2006. We then assessed if the proportions of time spent in male–male competition and courtship behaviors were influenced by age-specific body mass and social rank during the rut. Males spent most of their time foraging and resting during summer, and rested more and foraged less with increasing age. During the rut, pronounced shifts in activity budgets occurred as juveniles (1–2 years) increased time spent foraging, whereas adults (≥3 years) increased standing and time spent in social interactions at the expense of foraging. At old age, reproductive effort either stabilized or decreased slightly, providing weak support for the ‘mating strategy–effort’ hypothesis, predicting that courtship behaviors should peak in prime-aged males. Age-specific body mass did not affect time spent in male–male competition, but was positively related with time spent in courtship behaviors, providing support for the ‘individual quality’ hypothesis, predicting that males with more resources at the start of the rut should spend more time in mating-related activities. Age-specific social rank did not affect reproductive effort. Surviving to prime age while increasing mass each year should thus allow male ungulates to gain greater ability to court estrus females.     

Mercury concentrations in wild mink (Mustela vison) and river otters (Lontra canadensis) collected from eastern and Atlantic Canada: relationship to age and parasitism

Total mercury (Hg) concentrations were measured in the fur, brain and liver of wild mink (Mustela vison) and river otters (Lontra canadensis) collected from eastern and Atlantic Canada. Total Hg concentrations in fur were strongly correlated with levels in the brain and liver. There was no difference in tissue concentrations between male and female mink; however, female otters had significantly higher fur, brain and liver Hg levels than males. Similarly, there was not a significant relationship between Hg concentration and age of mink, whereas in otters, Hg concentrations in all three tissues decreased significantly with age. In both species, only a very small percentage of the variability in Hg concentration was explained by age. After adjusting the data for site-to-site differences in Hg levels, Hg concentrations in the fur of mink infected by the parasite, Dioctophyma renale, were found to be significantly higher than Hg levels in uninfected mink.     

Invasion of Pinus halepensis Mill. following a wildfire in an Argentine grassland nature reserve

The Ernesto Tornquist nature reserve is a relict of native Pampas vegetation in Argentina. Alien trees were introduced to the reserve in the 1950s, mainly to "improve" the natural landscape, resulting in the arrival of a totally new life form. In 1987, a fire affected an area planted with Pinus halepensis resulting in its massive expansion. In 1999, we removed trees from 17 circular plots of 10 m diameter placed systematically within the area that was colonized after the fire. Trunks were cut 20 cm from the ground and growth rings were counted. We studied the age structure of the population in order to reconstruct the colonizing events after the fire. We found that recruitment occurred throughout this period, except in the three years after the disturbance. We suggest that this delay in recruitment might be caused by low seedling survival under water stress conditions due to low rainfall, combined with scarce vegetation cover after fire. This could have been associated with an initial reduction in propagule pressure due to the scarcity of surviving trees in the vicinity and with the fact that fire occurred after the peak of seed release, during an extremely dry summer, probably killing a great number of seeds that were already in the soil. In the following years, recruitment was probably aided by pioneer trees and later by seeds shed from established pines. Alien trees had been allowed to reach maturity due to wildfire prevention and control in the years preceding the fire and the accumulated dry matter resulted in increased fire intensity that reduced the ability of grasses to re-sprout. As a consequence, the invasion window that allowed the expansion of pines remained open for at least 12 years.