Kin recognition in a semi-natural context: Behaviour towards foreign conspecifics in the social waspRopalidia marginata (Lep.) (Hymenoptera: Vespidae)

Summary Female wasps of the tropical primitively eusocial speciesRopalidia marginata are known to discriminate unfamiliar nestmates from unfamiliar non-nestmates outside the context of their nests. Here, we show that when foreign conspecifics are introduced in the context of a nest in laboratory cages, genetic relatives among them are treated by nest inhabitants more tolerantly than non-relatives, but that no foreign conspecifics are accepted into the nests. However, some wasps may leave their nest and join the foreign relatives and non-relatives to found new colonies cooperatively. Very few of the introduced animals are severely attacked or killed; most are allowed to remain in parts of the cage away from the nest. These results suggest that factors other than genetic relatedness may be involved in regulating tolerance and acceptance of foreign conspecifics on a nest and its vicinity. Our results are different from those of similar experiments with ants, which have demonstrated that former nestmates that are removed as pupae and later introduced as adults are either accepted into the nest or attacked and killed. We attribute this difference to the fact that in a primitively eusocial species such asR. marginata, the rules governing tolerance and acceptance of foreign conspecifics must be quite different from those in highly eusocial species. We also attempt to test some predictions of the conspecific acceptance threshold models of Reeve (Am. Nat. 133:407–435, 1989). Our results uphold the predictions of his fitness consequence submodel but do not support those of his interaction frequency sub-model.     

Hard working nurses rather than over-aged nurses permit <Emphasis Type="Italic">Ropalidia marginata</Emphasis> to respond to the loss of young individuals

Summary The primitively eusocial wasp Ropalidia marginata exhibits a remarkably well-developed honey bee like age polyethism. Individuals perform different tasks sequentially as they age, starting with intranidal tasks (nursing and building in that order) and ending with extranidal tasks (foraging for pulp and food in that order). As in the case of honey bees such age polyethism is rather flexible; in the absence of old individuals (in young-cohort colonies), precocious foragers forage at abnormally young ages. Here we demonstrate that the absence of young individuals (in old-cohort colonies) does not result in over-aged nurses nursing at abnormally old ages, as seen in the case of honey bees. Instead it results in hard working nurses who nurse at abnormally high rates. The possible reasons for the absence of over-aged nurses and the presence of hard working nurses are discussed.Received 30 April 2003; revised 18 November 2003; accepted 5 January 2004.     

Social insects and social amoebae

The evolution of social groupings in insects, especially wasps, is compared to that of social amoebae (cellular slime moulds). They both show a gamut of colony sizes, from solitary forms to complex colonies with a division of labour. The various ideas as to how there might have been an evolution of complexity within insect societies, such as the role of genetic relatedness, the role of mutualism, the origin of sterility, the manipulation and exploitation of some individuals by others within a colony, are discussed, and then applied to social amoebae. The result is both interesting and instructive: despite some differences, there are many striking parallels, which suggests that there are some common denominators in the formation and evolution of a social existence among organisms.     

A possible novel function of dominance behaviour in queen-less colonies of the primitively eusocial wasp Ropalidia marginata

Unlike the queens of other primitively eusocial species, Ropalidia marginata queens are strikingly docile and non-aggressive individuals, never at the top of the behavioural dominance hierarchy of their colonies. Nevertheless, these queens are completely successful at suppressing worker reproduction, suggesting that they do not use aggression but employ some other mechanism (e.g. pheromones) to do so. Upon removal of the queen from a colony, a single worker, the 'potential queen', immediately begins to display highly elevated levels of aggression towards her nest mates. This individual becomes the next docile queen if the original queen is not returned. We attempt to understand the function of the temporary and amplified dominance behaviour displayed by the potential queen. We find that the dominance behaviour shown by the potential queen is unrelated to the number of her nest mates, their dominance ranks or ovarian condition. This suggests that aggression may not be used to actively suppress other workers and counter threat. Instead we find evidence that dominance behaviour is required for the potential queen's rapid ovarian development, facilitating her speedy establishment as the sole reproductive individual in the colony.     

Factors affecting the acceptance of alien conspecifics on nests of the primitively eusocial wasp,Ropalidia marginata (Hymenoptera: Vespidae)

In the primitively eusocial wasp, Ropalidia marginata,individual females are known to drift from one newly founded nest to another. In the laboratory, young (<6- to 8-day-old) alien wasps are accepted onto unrelated colonies, while older (>6- to 8-day-old) wasps are not. Here we have investigated the factors that could influence the acceptance of foreign conspecifics onto unrelated nests. Individually marked wasps of different ages, isolated immediately after eclosion from the natal nest and from each other, were introduced onto unrelated recipient nests. Considered separately, both age and ovarian condition seemed to influence the probability of acceptance as well as the levels of aggression and tolerance received by the introduced wasps. However, partial correlation analysis and multiple regression analysis indicated that only age had a direct influence and that the ovarian condition acts only through age, a variable with which it is highly correlated. The observed acceptance of young aliens and rejection of old aliens are less likely to be due to the perception of older wasps as a reproductive threat rather than some age-related factor, other than ovarian condition, for example, the relative ease with which younger wasps can be molded into desired roles.     

Juvenile hormone accelerates ovarian development and does not affect age polyethism in the primitively eusocial wasp,Ropalidia marginata

Juvenile hormone modulates post-imaginal reproductive division of labor in primitively eusocial species and promotes the production of queens (e.g., Polistes) while it modulates age polyethism and promotes the production of foragers in highly eusocial species (e.g., the honey bee). Ropalidia marginata is a primitively eusocial wasp that shows both post-imaginal regulation of reproductive division of labor as well as age polyethism. Hence, R.marginata is a particularly interesting model system to study the effect of juvenile hormone. We demonstrate here that a single, topical application of 100 micro g of juvenile hormone-III per female wasp accelerates ovarian development of wasps held in isolation. Similar application to wasps released back on to their natal nests has no effect on their rate of behavioral development as witnessed from the age of first performance of feed larva, build, bring pulp and bring food. We conclude therefore that in R.marginata, juvenile hormone has retained its function of modulating reproductive division of labor and has not acquired the function of modulating age polyethism.     

Evolution of social behaviour in the primitively eusocial wasp Ropalidia marginata: do we need to look beyond kin selection?

Ropalidia marginata is a primitively eusocial wasp widely distributed in peninsular India. Although solitary females found a small proportion of nests, the vast majority of new nests are founded by small groups of females. In such multiple foundress nests, a single dominant female functions as the queen and lays eggs, while the rest function as sterile workers and care for the queen''s brood. Previous attempts to understand the evolution of social behaviour and altruism in this species have employed inclusive fitness theory (kin selection) as a guiding framework. Although inclusive fitness theory is quite successful in explaining the high propensity of the wasps to found nests in groups, several features of their social organization suggest that forces other than kin selection may also have played a significant role in the evolution of this species. These features include lowering of genetic relatedness owing to polyandry and serial polygyny, nest foundation by unrelated individuals, acceptance of young non-nest-mates, a combination of well-developed nest-mate recognition and lack of intra-colony kin recognition, a combination of meek and docile queens and a decentralized self-organized work force, long reproductive queues with cryptic heir designates and conflict-free queen succession, all resulting in extreme intra-colony cooperation and inter-colony conflict.     

TwoAscochyta species onAlthaea officinalis andAralia elata

Two brown zonate leaf spot fungi new to Japan are described.Ascochyta malvicola onAlthaea officinalis andA. marginata onAralia elata were recorded in Kyoto Prefecture in 1988.     

Life span of queens in the antFormica exsecta

Summary The antFormica exsecta commonly has two types of colonies: either polygynous and polydomous or monogynous and monodomous. The longevity of queens was studied in monogynous colonies in southern Finland by indirect methods using genetic markers; these data were also used to estimate the number of matings and queen replacement. The average genetic relatedness among worker nest mates was 0.72. Taking inbreeding into account (the inbreeding coefficient wasF=0.16), this value agrees with the assumption that 40% of the queens mated with one male and 60% with two males. The distribution of genotypes within colonies remained stable in successive years, indicating that queen replacement did not occur or was extremely rare. This means that the life span of nests reflects directly the life span of the queens. Eleven of the 16 nests found in 1979 were still alive ten years later. This corresponds to an annual mortality of 3.7% and a mean life span of 27 years. A total of 57 colonies were mapped in the population over a period of ten years. Averaging over the years, the annual mortality was estimated to be 4.9%. This represents a mean life span of 20 years if mortality was independent of age.     

Ropalidia rufoplagiata: a polistine wasp society probably lacking permanent reproductive division of labour

Summary Ropalidia rufoplagiata Cameron (Hymenoptera: Vespidae), a polistine species from penisular India, appears to be unique among all known primitively eusocial wasps. A total of 33 out of 46 identified females from an observed colony were found to oviposit on 1–17 occasions. No single predominant egg-layer could be identified during the 45-day period. Of the 17 dissected egg-layers, 12 were mated. All egg-layers showed several oviposition-related behavioural patterns including systematic, but indiscriminate, cannibalism of eggs and larvae, cleaning of empty cells, and guarding of freshly-laid eggs. There was no correlation between the egg-laying activity of the females (whether mated or not), oophagy, and their position in the dominance hierarchy. All nest-maintenance activities were performed exclusively by the egg-layers, while the non-egg-layers were mainly involved in the extranidal task of foraging. No significant morphometric differences between egg-layers and foragers could be discerned. Almost all the older individuals in the colony were egg-layers, while foragers were mainly younger animals. Such a temporal differentiation in reproductive labour suggests the absence of a permanent reproductive caste in this species.     

Patriline differences in emergency queen rearing in the honey bee, <Emphasis Type="Italic">Apis mellifera</Emphasis>

Summary In the polyandrous honey bee, Apis mellifera, workers can potentially increase their inclusive fitness by rearing full-sister queens. If the mother queen dies suddenly, workers feed a few larvae in worker cells with royal jelly and rear them into queens (emergency queen rearing). Using DNA microsatellite markers we determined the patriline of emergency queens reared in two colonies headed by naturally-mated queens before being made queenless. We found that some patrilines were reared more than others in one colony, but not in the other. These differences between colonies suggest that selective rearing is not always present and this might explain the mixed results of previous nepotism studies in the honey bee.Received 10 February 2003; revised 7 March 2003; accepted 17 March 2003.     

How to fool a virgin: Artificial dealation triggers oviposition in virgin Lasius niger queens

Once inseminated, ant queens rapidly shed their wings and start to lay eggs. Here we test whether there is a causal link between dealation and oviposition in the ant Lasius niger. We show that artificially dealated virgin queens start to lay eggs shortly after wing removal, whereas winged virgin queens hardly ever lay eggs. Dealate virgins do, however, produce fewer eggs than mated queens. These findings indicate that dealation does induce egg-laying, and that other factors, such as mating and/or insemination, further stimulate oviposition under natural conditions. Received 2 January 2006; revised 8 February 2006; accepted 4 April 2006.     

<Emphasis Type="Italic">hedgehog</Emphasis> is a segment polarity gene in a crustacean and a chelicerate

The evolution of arthropod segmentation has been studied by comparing expression patterns of pair-rule and segment polarity genes in various species. In Drosophila, the formation and maintenance of the parasegmental boundaries depend on the interactions between the wingless (wg), engrailed (en) and hedgehog (hh) genes. Until now, the expression pattern of hh has not been analysed to such a great extent as en or wg. We report the cloning and expression analysis of hh genes from Euscorpius flavicaudis, a chelicerate, and Artemia franciscana, a branchiopod crustacean. Our data provide evidence that hh, being expressed in the posterior part of every segment, is a segment polarity gene in both organisms. Additional hh expression sites were observed in the rostrum and appendages of Euscorpius and in the gut of Artemia. From the available data on hh expression in various bilaterians, we review the various hypotheses on the evolution of hh function and we suggest an ancestral role of hh in proctodeum specification and gut formation.Edited by D. Tautz     

Facultative schooling behavior in the spottail shiner (Notropis hudsonius): possible costs and benefits

Synopsis If an individual is less susceptible to predation in a group it should be able to reduce its vigilance for predators and perhaps also its tendency to flee from predators, thereby gaining time and energy for feeding and other activities. These predictions were examined in the field (Veronica Lake, northwestern Ontario) using a facultative schooling species, the spottail shiner (Notropis hudsonius). Schools of various sizes attacked with a fish predator model had a significantly lower reaction distance to the predator than solitary shiners. Solitary shiners must therefore invest more time and energy in defense but may gain a feeding advantage because their visual field does not overlap with conspecific competitors.     

缘座壳孢菌抑菌活性化合物的分离及鉴定

【目的】座壳孢菌是粉虱和蚧壳虫的一种重要昆虫病原真菌,其代谢产物具有抑菌、杀虫、抗肿瘤和抗氧化等生物活性。本研究旨在分离并鉴定缘座壳孢发酵物中的代谢物,以期为拓展该生防菌的应用提供依据。【方法】基于色谱技术从缘座壳孢菌A. marginata WYTF2017-01发酵培养物中分离化合物,借助波谱手段鉴定其化合物结构,分析化合物的抑菌活性。【结果】本研究共鉴定了12种化合物,包括Methyl 24-methylene-3-oxolanost-8-en-26-oic ester (1)、Ergosta-5,7,22-trien-3-ol,4-methyl-,(3β,4α,22E) (2)、杜斯塔宁(3)、3β-acetoxy-15α,22-dihydroxyhopane (4)、麦角固醇(5)、4-(Hydroxymethyl)-3-furancarboxylic acid (6)、Eupenicisirenin B (7)、4,6-dihydroxy-1(3H)-isobenzofuranone (8)、β-谷甾醇(9)、对叔丁基苯甲酸甲酯(10)、2-benzyl-4H-pyran-4-one(11)和6-benzyl-4-oxo-4H-pyran-3-carboxamide (12),其中化合物1、2、6~12为首次从昆虫病原真菌中分离鉴定。化合物1、2、3、6、7、8、11和12对真菌或细菌具有不同程度的抑制活性,MIC值为3.13~50.00 μg·mL^-1。化合物7、8和12抑菌活性较为突出,化合物7对大肠杆菌的MIC值为3.13 μg·mL^-1,效果与阳性对照链霉素相同,而8和12对青枯劳尔氏菌的MIC值分别为6.25和12.50 μg·mL^-1,优于或等同于链霉素(MIC值为12.50 μg·mL^-1)。【结论】从缘座壳孢菌分离的多种代谢物具有良好的抑菌活性,显示了防治植物病害的潜力。     

Social and ecological contexts of trophallaxis in facultatively social sweat bees, Megalopta genalis and M. ecuadoria (Hymenoptera, Halictidae)

Exchange of liquid food among adults (trophallaxis) is documented for the first time in New World sweat bees (Halictinae). Megalopta genalis and M. ecuadoria are facultatively social, and in social groups foragers regularly give food to the oldest resident female bee, which dominates social interactions. In turn, the oldest resident sometimes re-distributes this food, and shares it with younger foragers. Food is sometimes offered freely, but often the dominant bee exhibits escalating aggressive behavior until she is fed, whereupon she immediately ceases to be aggressive. The occurrence of trophallaxis in a species with mass-provisioned larvae provides an opportunity to examine the ritualization of social behavior. Trophallaxis also increases survivorship of males and females by almost 50% under experimental conditions, suggesting the behavior is also important in ecological contexts. Received 25 July 2005; revised 22 November 2005; accepted 23 December 2005.     

Foraging behavior of the communal spider,Philoponella republicana (Araneae: Uloboridae)

The communal orb-weaving spider, Philoponella republicana,was observed in the subtropical moist forest of Southeast Peru. These spiders live in colonies of conspecifics whose individual orbs are connected by silk. The wrapping of a prey prior to feeding is a large component of the prey capture process because P. republicanahas no venom with which to kill an insect. Wrapping time was the only aspect of prey capture that was strongly correlated with the size of the insect captured. Occasionally we observed several individuals working together to wrap a prey item. These joint efforts were more frequent on prey larger than the capturing spider. Although group captures accounted for only 5.5% of captures, they represented 14.7% of the biomass obtained. A comparison of the relationship between wrapping time and prey size for solitary and group efforts suggested that, by working together, the spiders reduced their total handling time. In most cases only one spider fed on the captured prey.