Target and nontarget discrimination of herbicides applied to vegetation in a power-line corridor

We tested two cutting regimens (cut/spray and cut/delay spray) and four radiarc-applied herbicides (Garlon + Tordon, Accord, Accord + Escort, and Krenite) in an Ohio power-line corridor to determine which management combination best eliminated target species (i.e., trees) and preserved nontarget species (i.e., low shrubs, vines, perennial herbs, and grasses). When spraying was delayed after cutting, the herbicide with the least impact on nontarget species (Krenite) also was least efficient at killing target trees. Spraying soon after cutting improved tree-killing efficiency of several herbicides, but it also increased the negative impact on nontarget species. The herbicide with the most consistent tree-killing ability (Accord + Escort) had the most impact on nontarget species. Because none of the herbicide/cutting treatments performed ideally, resource managers must decide the acceptable impact on nontarget species when considering herbicide use. Future success of herbicides as part of an integrated succession management approach requires more selective application methods and formulations so that target effects can be maximized and nontarget effects can be minimized.     

Host intra-clutch variation,cuckoo egg matching and egg rejection by great reed warblers

Prevailing theory predicts that lower levels of intra-clutch variation in host eggs facilitate the detection of brood parasitism. We assessed egg matching using both human vision and UV-VIS spectrophotometry and then followed the nest fate of great reed warblers naturally parasitised by European cuckoos. Rejection was predicted by the following three variables: matching between cuckoo and host eggs on the main chromatic variable defined by principal components analysis of the egg spectra (which has a strong loading in the UV); the number of host eggs in the nest; and human estimates of intra-clutch variation. The first variable is not correlated to human estimates of matching, which do not predict rejection. In line with another recent study, rejection rates were predicted by higher levels of intra-clutch variation in the host eggs, suggesting that higher rather than lower levels of intra-clutch variation can facilitate the discrimination of cuckoo eggs by hosts. We suggest that the importance of intra-clutch variation is context dependent, with intra-clutch variation being important when there is good matching between the host and the cuckoo eggs. Our results also suggest that both spectrometric and human visual assessments of egg matching and intra-clutch variation are prudent: the former provide the best method of estimating reflectance variation, whereas the latter include some assessment of patterns of maculation.     

Worker discrimination among queens in newly founded colonies of the fire ant Solenopsis invicta

Although colonies of the fire ant Solenopsis invicta are often founded by small groups of queens, all but one of the queens are soon eliminated due to worker attacks and queen fighting. The elimination of supernumerary queens provides an important context for tests of discrimination by the workers, since the outcome of these interactions strongly affects the workers' inclusive fitness. To test whether workers in newly founded colonies discriminate among nestmate queens, paired cofoundresses were narrowly separated by metal screens that prevented direct fighting, but through which the workers could easily pass. Soon after the first workers completed development, they often attacked one of the queens; these attacks were strongly associated with queen mortality. When one queen's brood was discarded, so that the adult workers were all the daughters of just one queen, the workers were significantly less likely to bite their mother than the unrelated queen; however, this tendency was comparatively weak. Queens kept temporarily at a higher temperature to increase their rate of investment in brood-rearing lost weight more rapidly than paired queens and were subsequently more likely to be attacked and killed by workers. Workers were more likely to bite queens that had been temporarily isolated than queens that remained close to brood and workers. When queens were not separated by screens, the presence of workers stimulated queen fights. These results show that workers discriminate strongly among equally familiar queens and that discrimination is based more on the queens' condition and recent social environment than on kinship. Received: 9 June 1998 / Accepted after revision: 10 October 1998     

Prey chemical discrimination in ambush foragers: absence in representatives of two additional iguanian lizard families and probable olfactory mediation in a gekkonine gecko

Summary. Lingually mediated prey chemical discrimination in lizards has evolved in active foragers, been lost in taxa that have reverted to ambush foraging, and has not evolved in taxa that have retained the ancestral ambushing. Previous studies have shown that all families of insectivorous ambushers lack prey chemical discrimination, including most families of iguanian lizards and two gekkonid species. I conducted experimental studies of prey chemical discrimination in representatives of two additional iguanian families and a third gekkonid lizard. An oplurid species, Oplurus cuvieri and a corytophanid, Corytophanes cristatus, did not discriminate among prey chemicals and control substances. Prey chemical discrimination is now known to be absent in insectivorous ambush foragers in all but one of the families in Iguania, one of the two major lizard radiations. Hoplocercidae remains unstudied. Like other ambushing gekkonid lizards, Pachydactylus turneri did not exhibit elevated tongue-flick rates in response to prey chemicals. However, after tongue-flicking or being touched on the labial scales by cotton swabs, these lizards bit swabs bearing prey chemicals more frequently than control stimuli. They also exhibited buccal pulsing more frequently in response to prey chemicals than deionized water, suggesting olfactory sampling. The unusually highly developed olfactory organs of gekkonid lizards and their nocturnal habits suggest that olfaction may be more important to foraging than in other lizards. Further studies are needed to determine relative roles of olfaction and vomerolfaction in selective response to prey chemicals and to ascertain whether and to what extent the tongue may be used to locate and identify prey. Received 30 March 1999; accepted 26 July 1999     

水源地水污染风险等级判别方法及应用

以广西柳州市柳南水厂水源地为研究对象,建立了水源地风险等级判别模型,模型主要考虑企业风险等级,以及风险影响后水源地水质超标倍数、水质超标持续时间、污染团到达时间等因子,模型参数根据调查及分析得到。通过风险判别模型,计算得到柳南水厂取水口的风险等级,为该区域进行环境风险管理提供了技术支撑。     

Kinship and aggression: do house sparrows spare their relatives?

Kin-selection theory predicts that relatedness may reduce the level of aggression among competing group members, leading to indirect fitness benefits for kin-favoring individuals. To test this hypothesis, we investigated whether relatedness affects aggressive behavior during social activities in captive house sparrow (Passer domesticus) flocks. We found that sparrows did not reduce their aggression towards kin, as neither the frequency nor the intensity of fights differed between close kin and unrelated flock-mates. Fighting success was also unrelated to kinship and the presence of relatives in the flock did not influence the birds’ dominance rank. These results suggest that the pay-offs of reduced aggression towards kin may be low in non-breeding flocks of sparrows, e.g. due to competition among relatives as predicted by a recent refinement of kin-selection theory. Our findings indicate that the significance of kin selection may be restricted in some social systems such as winter aggregations of birds. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Opportunistic discrimination of alien eggs by social wasps (Polistes biglumis, Hymenoptera Vespidae): a defense against social parasitism?

Foundresses of the social wasp Polistes biglumis were tested to see whether they were able to recognize alien eggs experimentally introduced into their own nests. Foundresses removed alien conspecific reproductive-destined eggs while they accepted worker-destined eggs. The results indicate that social wasps discriminate among eggs and that they discriminate against alien eggs destined to produce unrelated reproductives. P. biglumis is a strictly solitary founding species, with no reproductive competition within colonies; thus, brood discrimination abilities could have evolved as a counteradaptation against intra- and inter-specific brood parasitism. Received: 12 May 2000 / Revised: 15 July 2000 / Accepted 20 July 2000     

The effects of age and relatedness on mating patterns in thornbug treehoppers: inbreeding avoidance or inbreeding tolerance?

The social environment of many species includes synchronous maturation of siblings in family groups, followed by limited dispersal of adults from their natal site. Under these conditions, females may experience high encounter rates with same-age siblings during mate searching, increasing their risk of inbreeding. If inbreeding depression occurs, mating with a sibling is often considered maladaptive; however, in some contexts, the inclusive fitness benefits of inbreeding may outweigh the costs, favoring females that tolerate some level of inbreeding depression. We evaluated mating patterns in the treehopper Umbonia crassicornis, a semelparous species in which females encounter same-age siblings during mate searching. A female U. crassicornis that mates with a brother suffers from inbreeding depression. We used a free-choice mating design that offered females simultaneous mating opportunities with three groups of males: siblings, same-age nonsiblings, and older nonsiblings. These groups represent the types of males typically encountered by females during mate searching. Our goal was to assess whether mating patterns were influenced by inbreeding avoidance by evaluating two hypotheses: kin discrimination and age-based mating (older males cannot be siblings in this species). There was no difference in the proportions of females mating with siblings vs nonsiblings, suggesting an absence of kin discrimination. However, females mated with a greater proportion of older vs younger males. Given that females do not avoid siblings as mates despite a cost to inbreeding, our results provide a possible example of inbreeding tolerance. We also discuss some factors that may have contributed to the mating advantage of older males.     

Learning affects host discrimination behavior in a parasitoid wasp

Learning is generally predicted not to be important in host discrimination by parasitoids, because the stimuli involved are less variable than those used in habitat location. However, Anaphes victus (Hymenoptera: Mymaridae), an egg parasitoid of Listronotus oregonensis (Coleoptera: Curculionidae) apparently learns to associate external pheromones with the presence of a conspecific in a host. In this species, females can reject a parasitized host either after antennal drumming (antennal rejection) or after the insertion of their ovipositor (sting rejection). When they encountered a series of parasitized hosts, females A. victus learned to associate the presence of the external pheromone with the presence of the internal one. Learning lasted less than 4 h and occurred earlier in a series when the female marking the egg and the one detecting that mark were close relatives. This behavior could be adaptive because antennal rejection is faster than sting rejection. Received: 11 March 1997 / Accepted after revision: 30 August 1997     

基于改进的未确知聚类模型的岩爆倾向性预测

在采用未确知聚类评价模型进行多指标分级评价时,常采用置信度识别准则作为待测对象的属性识别,该准则中置信度的取值由人为取定,当置信度取值不同时,得到的分级判定结果往往出现差异,甚至产生完全不同的判定结果。通过距离判别的思想将未确知聚类理论中的置信度识别准则进行改进,并运用到岩爆烈度的分级预测中。根据岩爆发生的主要影响因素,选取岩石单轴抗压强度σ_c、单轴抗拉强度σ_t、最大切应力σ_θ及岩石的弹性变形能指标W_(et)为岩爆主要影响因子。并以σ_c/σ_1、σ_θ/σ_c、W_(ey)为岩爆烈度等级评价因子,建立未确知测度模型,以距离判别改进后的属性识别方法进行分级预测,并与原置信度识别准则得到的判别结果进行分析和比较。为验证改进模型的实用性,以贵州开磷集团马路坪矿区为例,采用改进的未确知聚类模型对其岩爆烈度等级进行预测分析。结果表明,预测结果与实际情况基本吻合,证明采用改进后的未确知测度模型的判别结果不仅消除了由于置信度取值不同造成的判别结果误差,降低了人为主观因素的影响,而且具有较高的判别准确性和可行性。