The superseded female's dilemma: ultimate and proximate factors that influence guarding behaviour of the carpenter bee Xylocopa pubescens

Both solitary and primitively social nests of the facultatively social carpenter bee Xylocopa pubescens can be found throughout most of the breeding season. In social nests there is reproductive division of labour between a dominant forager and a guarding female. Two types of guarding females can be discerned: the young pre-reproductive guards, and older, formerly reproductive guards. The latter type of guard is found when, after a take-over of reproductive dominance either by a nestmate (mostly a daughter) or an intruder, the defeated female stays in the nest instead of leaving to try and found or usurp another nest. She is then manipulated into the role of a guard. The dominant female profits from the presence of the guard since she protects the nest against pollen robbery by conspecifics (Hogendoorn and Velthuis 1993). We have studied why superseded females might prefer to remain as a guard, rather than try their luck somewhere else. The hypotheses investigated pertain to (1) the difficulty for the defeated female of finding a new nest and of restarting reproductive activities due to (a) ecological constraints (nest and pollen shortage) and (b) the effect of age and wear on the defeated female; (2) the effects of guarding in terms of inclusive fitness. We found that superseded females remained as guards significantly more often when a nestmate (not necessarily close kin) took over reproductive dominance than when an intruder did so. Other factors associated with the decision of the defeated female to stay or leave were her age and the number of her own young still present after the supersedure. The probability of finding or constructing a new nest was lower for old than for young females. After finding a nest, old females produced less brood than young foundresses. As a result of these two factors old superseded females gained, in terms of inclusive fitness, by staying as guards, whereas young females profited from leaving the nest. We interpret these results as an indication that guarding behaviour has evolved due to kin selection. However, kin discrimination apparently did not occur. Therefore we conclude that in this species kin selection is not, in the proximate frame of reference, based on kin recognition and preference for helping kin. Correspondence to: K. Hogendoorn     

生态城市特征性指标的辨析及其应用

生态城市是依据生态学原理提出的一类社会、经济、自然协调发展的城市.基于生态城市内涵建立的城市特征性指标对城市特征性要素的量化和评价,是将生态城市个性这一主观观念变为可操作性目标的主要途径.基于城市复合生态系统理论和生态城市"健康、安全和发展"内涵,探讨了生态城市特征性指标的辨析方法.以厦门为例构建了厦门生态城市特征性指标体系.评价结果揭示了厦门城市特有的生态环境和资源的总体状态为亚健康状态(0.69)、比较脆弱的中警状态(0.39)和一般持续的发展状态(0.63).与现实的分析调研结果相符.这表明生态城市特征性指标有助于研究者辨识和评价城市生态系统的特定复合特征,更有针对性地明确城市生态规划和建设的重点行动领域,从而为城市实施可持续发展战略提供决策依据.     

基于数字图像处理技术的金相分析研究

采用和改进了人际交互式图像分割算法Live-wire,对电气火灾中的典型火烧金相图和一次短路金相图进行处理,结合数字形态学操作,精确提取了两类金相图中的典型胞状晶和柱状晶结构;分析和讨论了多种结构描述子对晶格分类的作用,结果表明,离心率和晶格标记方差两个描述子能有效区分两类晶格结构;采用聚类分析和Fisher判别法,实现了对两类金相图的自动分类.     

Interpreting the relationship between pheromone component emission from commercial lures and captures of Helicoverpa zea (boddie) in bucket and cone traps

Abstract

Male corn earworm moths, Helicoverpa zea (Boddie), were captured in conical Texas pheromone traps (cone traps) and bucket traps baited with four different commercial lures manufactured by three different manufacturers. Because significant numbers were captured in bucket traps baited with some of the lures, and none with others, the volatile emissions from all of the lures were sampled and analyzed by gas Chromatographic methods. The numbers of males captured in two types of trap were compared with bait emissions in an endeavor to define a more effective lure for bucket traps. The lure from one manufacturer captured the same numbers of males in both trap types; one captured more in bucket traps than in cone traps, and another captured only a small number in bucket traps. The emission rate of all active compounds from each of the different lures was approximately linear for the duration of the assays. A gas‐liquid Chromatographic peak associated with a third compound, (Z)‐9‐tetradecenal, which reduces behavioral responses, was observed in the emissions from all lures evaluated. The effectiveness of the Hercon (Emmigsville, PA) lure in capturing males in both types of trap was associated with a lower emission of (Z)‐l 1‐hexadecenal, (Z)‐9‐hexadecenal and (Z)‐9‐tetradecenal than from the other lures.     

Absence of sex-differential brood raising by workers in Diacamma sp. from Japan

To optimally allocate resources between workers, reproductive females, and males, ant workers have to be able to identify the sex of larvae and raise them differently. The ability of workers to discriminate between the sexes in the brood was tested in colonies of queenless ponerine ants, Diacamma sp., from Japan. The ratio of male eggs in the egg pile was increased experimentally. This manipulation resulted in a corresponding increase in the ratio of adult males, suggesting that Diacamma workers do not raise the sexes differently. Received: 4 November 1997 / Accepted after revision: 14 March 1998     

A multilevel study of the relationships between diversity training,ethnic discrimination and satisfaction in organizations

The prevalence of diversity training has not been matched by empirical research on its effectiveness. Among the most notable gaps are an absence of attention to its impact on discrimination and limited consideration of organizational‐level factors. Results from employee surveys across 395 healthcare organizations reveal an effect of the extent of diversity training in organizations on ethnic minorities' experiences of discrimination. In addition, the results demonstrate that the consequences of ethnic discrimination for individuals' job attitudes are influenced by organizational‐level phenomenon. These findings highlight the importance of attending to ethnic discrimination as an outcome of diversity training with implications for employee attitudes. Copyright © 2010 John Wiley & Sons, Ltd.     

Gender and career success: A typology and analysis of dual paradigms

Despite women's advancements in the workplace, gender inequality persists. We classify and test two frameworks used to explain gender differences in career success: unequal attributes and unequal effects. The unequal attributes framework suggests that gender is related to other attributes, which result in unequal career outcomes for men and women (i.e., a mediated effect). The unequal effects framework suggests that even when men and women share the same attribute or circumstances, they are rewarded differently, such that individual attributes have unequal effects on career outcomes for men and women (i.e., a moderated effect). We collected survey data from a gender‐balanced sample of 394 business school alumni. Using structural equation modeling to test the unequal attributes framework, we found that work hours, career orientation, having a nonemployed spouse, and working in a predominantly female job were unequal attributes that explained gender differences in career success. Using multigroup path analysis to examine unequal effects, we found that being agentic, married, having children at home, and working in a predominantly female workplace had unequal effects in relation to career success for men and women. We find support for both models across three categories of career success antecedents (i.e., personal, family, and job attributes).     

Delayed dispersal as a potential route to cooperative breeding in ambrosia beetles

Xyleborini are a species-rich tribe of ambrosia beetles, which are haplodiploid and typically mate among siblings within their natal brood chamber. Several characteristics of this tribe would predict the evolution of higher levels of sociality: high genetic relatedness within galleries due to inbreeding, high costs of dispersal and the potential benefit of cooperation in brood care within the natal gallery (e.g. by fungus gardening, gallery extension, offspring feeding and cleaning). However, information on the social system of these beetles is very limited. We examined the potential for cooperative breeding in Xyleborinus saxeseni by monitoring dispersal in relation to brood size and composition. Results show that adult female offspring delay dispersal despite dispersal opportunities, and apparently some females never disperse. The females’ decision to stay seems to depend on the presence of eggs and dependent siblings. We found no indication that female offspring reproduce in their natal gallery, as colonies with many mature daughters do not contain more eggs than those with few or no daughters. There is a significant positive relationship between the number of females present and the number of dependent siblings (but not eggs), which suggests that cooperative brood care of female offspring raises colony productivity by improving survival rates of immatures. Our results suggest that cooperative breeding is likely to occur in X. saxeseni and possibly other xyleborine species. We argue that a closer look at sociality within this tribe may yield important information on the factors determining the evolution of cooperative breeding and advanced social organization.     

A test of reproductive skew models in a field population of a multiple-queen ant

Determining the evolutionary basis of variation in reproductive skew (degree of sharing of reproduction among coexisting individuals) is an important task both because skew varies widely across social taxa and because testing models of skew evolution permits tests of kin selection theory. Using parentage analyses based on microsatellite markers, we measured skew among female eggs (n=32.3 eggs per colony, range=20–68) in 17 polygynous colonies from a UK field population of the ant Leptothorax acervorum. We used skew among eggs as our principal measure of skew because of the high degree of queen turnover in the study population. Queens within colonies did not make significantly unequal contributions to queen and worker adult or pupal offspring, indicating that skew among female eggs reflected skew among daughter queens. On average, both skew among female eggs (measured by the B index) and queen–queen relatedness proved to be low (means±SE=0.06±0.02 and 0.28±0.08, respectively). However, contrary to current skew models, there was no significant association of skew with either relatedness or worker number (used as a measure of productivity). In L. acervorum, predictions of the concession model of skew may hold between but not within populations because queens are unable to assess their relatedness to other queens within colonies. Additional phenomena that may help maintain low skew in the study population include indiscriminate infanticide in the form of egg cannibalism and split sex ratios that penalize reproductive monopoly by single queens within polygynous colonies.     

Male approach and female avoidance as mechanisms of population discrimination in sagebrush lizards

Reproductive isolation and speciation can result from female choice for particular males. Isolation can also result, however, from male mating preferences or from aggressive encounters which then influence mating decisions. In this study, we use laboratory discrimination trials to study the behavioral mechanisms of population discrimination in sagebrush lizards (Sceloporus graciosus). We specifically ask three questions about population-level discrimination: (1) Does it vary in strength in relation to the geographic distance between the populations? (2) Is it more apparent in inter- or intra-sexual interactions? (3) Does it take the form of attraction or avoidance? We ran 890 trials that tested the ability of male and female sagebrush lizards from one population to discriminate their own population from four other populations. In addition, we utilized both sequential and simultaneous-choice designs, which enabled us to distinguish between attraction and avoidance. We found that most population-level discrimination was exhibited by male lizards preferring to associate with particular types of females, as well as female avoidance of particular types of males. The strength and direction of both discriminations depended on the populations compared and on whether the tests were conducted as sequential- or simultaneous-choice tests, producing a complex relationship between geographic distance and behavioral discrimination. Our results suggest that there are roles for male attraction and female avoidance in population discrimination, reproductive isolation, and speciation.