Condition explains individual variation in mobbing behavior

During mobbing, individuals approach predators with the apparent aim of reducing the risk of predation. The intensity of mobbing may depend on the costs and benefits of this behavior, which likely vary among individuals and between different social contexts. We studied whether Dark‐eyed junco male mobbing behavior is related to social environment, individual condition, and age during experimentally induced mobbing events. Based on risk‐taking theory, we predicted that individuals with high residual reproductive value—younger individuals and those in better condition—would show weaker mobbing behavior. We also expected to see weaker mobbing when the total number of individuals in the mobbing assemblage was small. All subjects were caught to assess condition and age. Focal males were then attracted to simulated mobbing events using heterospecific alarm calls. Social environment did not explain individual variation in mobbing behavior in focal juncos. Community‐wise, the relationship between the closest approach and group size was not significantly different from chance. Junco males in better condition approached the predator less closely and were less likely to give alarm calls. Age did not explain variation in mobbing. Both the mean approach and probability of giving alarm calls by junco males were repeatable, in contrast to the size and composition of mobbing assemblages in junco territories, which were inconsistent. Our results show that variation in mobbing can be linked to individual state, which likely affects the costs and benefits of mobbing.     

Stability in prey abundance may buffer Black Sparrowhawks Accipiter melanoleucus from health impacts of urbanization

As the global trend towards urbanization continues, the need to understand its impact on wildlife grows. Species may have different levels of tolerance to urban disturbance; some even appear to thrive in urban areas and use human‐subsidized resources. However, the physiological costs and trade‐offs faced by urban‐dwelling species are still poorly understood. We assess the evidence for a negative impact of urbanization on the Black Sparrowhawk Accipiter melanoleucus, a raptor that recently colonized Cape Town, South Africa, and explore the potential mechanisms behind any such effect. We predicted that birds in more urbanized areas may be in poorer health and that this may be partially driven by differences in prey quantity and quality along an urban habitat gradient. The health of Black Sparrowhawk nestlings was evaluated through measures of their physiological stress (heterophil/lymphocyte ratio), body condition and blood parasite infection (infection risk and intensity of Haemoproteus and Leucocytozoon). Diet composition was determined through an analysis of prey remains collected around nests, and prey abundance was determined through point counts in different habitat types. We could find no negative effects of urbanization on nestling health, with no significant relationships with heterophil/lymphocyte ratio, body condition, risk and intensity of infection by Haemoproteus or intensity of infection by Leucocytozoon. Risk of infection by Leucocytozoon did, however, decline with increasing urban cover, perhaps because urbanized areas contain less habitat for blackflies, the vectors of this parasite, which require moving fresh water. We found no change in diet breadth or composition with increasing urban cover. Although some prey species were abundant or less abundant in certain habitat types, all habitat types contained ample prey for Black Sparrowhawks. The widespread abundance of food resources and resulting lack of nutritional stress may explain why Black Sparrowhawks are seemingly free of the negative health impacts expected to arise from urbanization. These findings may explain the success of the species in Cape Town and suggest that for urban‐dwelling, bird‐eating raptors the abundance of prey in cities may override any potential negative impacts of urbanization on health due to disturbance or other sources of stress.     

Evaluating morphometric and metabolic markers of body condition in a small cetacean,the harbor porpoise (Phocoena phocoena)

Mammalian body condition is an important individual fitness metric as it affects both survival and reproductive success. The ability to accurately measure condition has key implications for predicting individual and population health, and therefore monitoring the population‐level effects of changing environments. No consensus currently exists on the best measure to quantitatively estimate body condition in many species, including cetaceans. Here, two measures of body condition were investigated in the harbor porpoise (Phocoena phocoena). First, the most informative morphometric body condition index was identified. The mass/length² ratio was the most appropriate morphometric index of 10 indices tested, explaining 50% of the variation in condition in stranded, male porpoises with different causes of death and across age classes (n = 291). Mass/length² was then used to evaluate a second measure, blubber cortisol concentration, as a metabolic condition marker. Cortisol is the main glucocorticoid hormone involved in the regulation of lipolysis and overall energy balance in mammals, and concentrations could provide information on physiological state. Blubber cortisol concentrations did not significantly vary around the girth (n = 20), but there was significant vertical stratification through the blubber depth with highest concentrations in the innermost layer. Concentrations in the dorsal, outermost layer were representative of concentrations through the full blubber depth, showed variation by sex and age class, and were negatively correlated with mass/length². Using this species as a model for live cetaceans from which standard morphometric measurements cannot be taken, but from which blubber biopsy samples are routinely collected, cortisol concentrations in the dorsal, outermost blubber layer could potentially be used as a biomarker of condition in free‐ranging animals.     

Spontaneous vegetation succession in human‐disturbed habitats: A pattern across seres

Abstract. Vegetation samples from 15 successional seres in various disturbed habitats in the western part of the Czech Republic were analysed to detect possible trends. For particular seres, data on species cover were available from the onset to 10–76 yr of succession. All seres started on bare ground. Species which attained at least 1% cover in any sere in any year were used as input data for Canonical Correspondence Analysis, assessing the effect of time as the environmental variable, for Detrended Correspondence Analysis and TWINSPAN classification. Two distinct groups ofseres were distinguished: ‘ruderal’, occurring in agricultural, industrial or urban landscapes altered by men, usually on fertile sites; and ‘non‐ruderul’, occurring in less altered, mostly forested landscapes, usually on acid, nutrient‐poor and wetter soils. The former type of succession starts with ruderal annuals, being followed by ruderal perennials. In the latter case non‐ruderal clonal perennials prevail from the onset of succession. The landscape frame is emphasized, beside site environmental conditions, as influencing the type of succession. The character of species attaining dominance in succession, participation of dominant woody plants and the character of late successional stages, i.e. features important from the point of view of potential restoration of human‐disturbed habitats, are discussed.     

Condition-dependent reproductive effort in frogs infected by a widespread pathogen

To minimize the negative effects of an infection on fitness, hosts can respond adaptively by altering their reproductive effort or by adjusting their timing of reproduction. We studied effects of the pathogenic fungus Batrachochytrium dendrobatidis on the probability of calling in a stream-breeding rainforest frog (Litoria rheocola). In uninfected frogs, calling probability was relatively constant across seasons and body conditions, but in infected frogs, calling probability differed among seasons (lowest in winter, highest in summer) and was strongly and positively related to body condition. Infected frogs in poor condition were up to 40% less likely to call than uninfected frogs, whereas infected frogs in good condition were up to 30% more likely to call than uninfected frogs. Our results suggest that frogs employed a pre-existing, plastic, life-history strategy in response to infection, which may have complex evolutionary implications. If infected males in good condition reproduce at rates equal to or greater than those of uninfected males, selection on factors affecting disease susceptibility may be minimal. However, because reproductive effort in infected males is positively related to body condition, there may be selection on mechanisms that limit the negative effects of infections on hosts.     

阿尔泰山前荒漠两种沙蜥体况指数特征及其与生态因子的关系

为明确奇台沙蜥(Phrynocephalus grumgrzimailoi)和旱地沙蜥(P. helioscopus)体况指数的年龄性别特征, 及其与海拔、年均温、年降水量、平均日较差之间的关系, 我们测量了阿勒泰地区84只奇台沙蜥与176只旱地沙蜥的体况数据, 用log体重/log头体长表示体况指数。结果显示: (1)旱地沙蜥与奇台沙蜥间体况指数差异显著。(2)旱地沙蜥体况指数雌雄两性差异不显著, 奇台沙蜥体况指数雌雄两性差异显著。(3)两种蜥蜴成体与亚成体间体况指数均差异明显。(4)以月份为单位, 奇台沙蜥体况指数月份差异明显, 旱地沙蜥体况指数月份差异不明显。(5)年均温对奇台沙蜥体况指数有重要影响, 而年降水量为补充因子, 主要通过与其他生态因子组合发挥作用, 海拔对旱地沙蜥体况指数有影响。这些结果表明两种沙蜥对不同环境因子的反应不同, 在不同环境的适应度也不同。     

Visible skin color distribution plays a role in the perception of age, attractiveness, and health in female faces

Evolutionary psychologists have proposed that preferences for facial characteristics, such as symmetry, averageness, and sexual dimorphism, may reflect adaptations for mate choice because they signal aspects of mate quality. Here, we show that facial skin color distribution significantly influences the perception of age and attractiveness of female faces, independent of facial form and skin surface topography. A set of three-dimensional shape-standardized stimulus faces—varying only in terms of skin color distribution due to variation in biological age and cumulative photodamage—was rated by a panel of naive judges for a variety of perceptual endpoints relating to age, health, and beauty. Shape- and topography-standardized stimulus faces with the homogeneous skin color distribution of young people were perceived as younger and received significantly higher ratings for attractiveness and health than analogous stimuli with the relatively inhomogeneous skin color distribution of more elderly people. Thus, skin color distribution, independent of facial form and skin surface topography, seems to have a major influence on the perception of female facial age and judgments of attractiveness and health as they may signal aspects of underlying physiological condition of an individual relevant for mate choice. We suggest that studies on human physical attractiveness and its perception need to consider the influence of visible skin condition driven by color distribution and differentiate between such effects and beauty-related traits due to facial shape and skin topography.     

Data composition and taxonomic resolution in macroinvertebrate stream typology

In the EU water framework directive (WFD) a typological framework is defined for assessing the ecological quality of water bodies in the future. The aim of this study was to test the effect of data composition and taxonomic resolution on this typology. The EU research projects AQEM and STAR provided 1660 samples of 48 stream types sampled all over the major geographical gradients in Europe. These stream types fit the WFD typological demands and fit to the major European geographic regions (ecoregions). The samples included gradients from reference conditions to samples with bad ecological quality. Despite standardisation, there were large differences between the participating countries concerning the number of taxa, the number of specimens, and the taxonomic resolution. The macroinvertebrate data were analysed by using detrended correspondence analysis (DCA). The distribution patterns using all samples, only reference samples, and only degraded samples showed that the use of species-level (or ‘best available taxonomic’ level) performed better at a practical (fine) scale in comparison to family-level. The analyses further showed that even the use of a standardised protocol can not easily overcome (i) differences in site conditions that force the researcher to deviate from the protocol as well as (ii) the experiences of the researcher(s) and (iii) the available taxonomic knowledge.     

不同生态条件下水稻籼粳交后代亚种分化机制

籼粳交育种已成为国内最重要的育种方法之一,明确籼粳亚种分化机制是指导籼粳交育种的关键.本文用InDel(插入/缺失)和ILP(内含子长度多态性)标记,对在辽宁省和广东省种植并用单粒传法、混合法及系谱法构建的籼粳交(七山占/秋光)F₆代群体进行分析.结果表明: 混合法与单粒传法群体无偏分离,粳型判别值(Dj)集中在40%～60%之间;两地系谱法群体总体偏籼(30%～55%),且广东群体(38%)比辽宁(42%)偏籼,两地群体分布呈显著差异.混合法与单粒传法群体中Dj与重要农艺性状基因区域血缘呈显著正相关;而在系谱法中部分正相关被打破,且两地群体籼粳血缘呈规律性分布.表明人工选择是影响籼粳分化的主要因素,并与自然选择协同作用引起群体偏分离现象;群体中一些重要农艺性状的变化与籼粳分化间存在紧密的关系,这可能是影响籼粳交育种在综合亚种优势上未达到预期效果的关键.