Use of artificial arenas to predict the social organisation of halictine bees: Data for fourteen species from Chile

I studied the behavioural profiles of fourteen species of Chilean halictine bee using the circle tube apparatus. Interactions were classified as aggressive, avoidance or cooperative. One species, Corynura chloris, is believed to be semisocial and its behaviour was largely aggressive, Ruizantheda mutabilis is known to be communal and its behaviour was predominantly cooperative whereas Penapis toroi is a member of a subfamily from which only solitary behaviour is known and it primarily exhibited avoidance behaviours. As a result, I suggest that the relative frequency of these different behaviours may be useful in establishing the social organisation of species. Based upon comparisons of behavioural profiles, I predict the social organizations of the remaining species and suggest that at least some of the bees in the populations of Ruizantheda proxima, Caenohalictus dolator, Ca. species A and Pseudagapostemon pississi investigated exhibit communal behaviour; those of Co. patagonica and Co. herbsti likely have a reproductive division of labour, probably within semisocial societies, and that the populations of Co. corinogaster, Co. melanocladius, Ca. pygosinuatum, Ca. cuprellus and Lasioglossum aricense studied are probably solitary. Phylogenies suggest that solitary behaviour in Ca. pygosinuatum and Ca. cuprellus is reversed from communal behaviour and solitary behaviour in L. aricense may be a reversal from eusociality. The response “back and follow” is not indicative of dominance or cooperation as it correlated only with the frequency of avoidance interactions among the taxa studied. I discuss the utility of the circle tube apparatus in the identification of populations worthy of more detailed sociobiological investigation. Received 10 August 2005; revised 8 March 2006; accepted 21 March 2006.     

A new Chlerogelloides from northeastern Brazil and French Guiana, with a key to the species (Hymenoptera, Halictidae)

A third species of the rare augochlorine bee genus Chlerogelloides Engel et al. (Halictinae, Augochlorini) is described and figured. Chlerogelloides nexosasp. n. is most similar to the type species, Chlerogelloides femoralis Engel et al., in that both have modified midlegs in the males. The former, however, can be distinguished on the basis of its terminalia, which in some respects more closely resembles those of Chlerogelloides simplex Engel and Brooks. Brief comments on the secondary features of males and relationships of the genus are provided. A key to the species of the genus is provided and floral records of Cordia nodosa Lam. (Boraginaceae) and Gonzalagunia dicocca Cham. & Schltdl. (Rubiaceae) are noted.     

Spatio-temporal variation of colony structure and eusociality level of the Japanese sweat bee<Emphasis Type="Italic"> Lasioglossum</Emphasis> (<Emphasis Type="Italic">Evylaeus</Emphasis>)<Emphasis Type="Italic"> duplex</Emphasis> (Hymenoptera: Halictidae)

Colony structure and eusociality level of the sweat bee Lasioglossum (Evylaeus) duplex were studied in 2001 in Sapporo and Assabu, Hokkaido, northern Japan. Sakagami and his colleagues had also studied this species in Sapporo in 1957–1968. Brood size, sex ratio and queen–worker size dimorphism were geographically and temporally variable, indicating spatio-temporal variation at the eusociality level. Inseminated workers constituted only 7.9% of the populations in 1957–1968 Sapporo but about 60% in 2001 in Sapporo and Assabu. A few of the inseminated workers were believed to leave natal nests for independent colony founding. Thus, partial bivoltinism is likely in this sweat bee species. The presence of workers with developed ovaries and/or corpora lutea suggests the occurrence of worker oviposition.     

It's good to be queen: classically eusocial colony structure and low worker fitness in an obligately social sweat bee

Lasioglossum malachurum, a bee species common across much of Europe, is obligately eusocial across its range but exhibits clear geographic variation in demography and social behaviour. This variation suggests that social interactions between queens and workers, opportunities for worker oviposition, and patterns of relatedness among nest mates may vary considerably, both within and among regions. In this study, we used three microsatellite loci with 12-18 alleles each to examine the sociogenetic structure of colonies from a population at Agios Nikolaos Monemvasias in southern Greece. These analyses reveal that the majority of colonies exhibit classical eusocial colony structure in which a single queen mated to a single male monopolizes oviposition. Nevertheless, we also detect low rates of multiqueen nest founding, occasional caste switching by worker-destined females, and worker oviposition of both gyne and male-producing eggs in the final brood. Previous evidence that the majority of workers show some ovarian development and a minority (17%) have at least one large oocyte contrasts with the observation that only 2-3% of gynes and males (the so-called reproductive brood) are produced by workers. An evaluation of the parameters of Hamilton's Rule suggests that queens benefit greatly from the help provided by workers but that workers achieve greater fitness by provisioning and laying their own eggs rather than by tending to the queen's eggs. This conflict of interest between the queen and her workers suggests that the discrepancy between potential and achieved worker oviposition is due to queen interference. Comparison of relatedness and maternity patterns in the Agios Nikolaos Monemvasias population with those from a northern population near Tübingen, Germany, points to a north-south cline of increasingly effective queen control of worker behaviour.     

Bee-pollination inHibbertia fasciculata (Dilleniaceae)

In direct contrast to mostHibbertia spp., the flowers ofH. fasciculata R. Br. ex D. C. bear only a single whorl of stamens and these stamens are arranged separately (not in typical bundles). The short filaments are appressed to the three carpels so that the inflated, porose and introrsive anthers form a centralized cluster obscuring the three ovaries. The three slender styles emerge at right angles from between the filaments. These styles curve upward and the stigmas form the three points of a triangle; each stigma is approximately one millimeter outside the centralized cluster of anthers. The flowers are nectarless and bear a bright yellow corolla. A pungent and unpleasant fragrance appears to be concentrated within the pollenkitt. When native bees attempt to forage for the pollen, within the cluster of anthers, the ventrally deposited loads of pollen, on the bees' abdomens, contact the outer triangle of stigmas. The major pollinators ofH. fasciculata are female bees in the polylectic genera,Lasioglossum (subgenusChilalictus, Halictidae) andLeioproctus (Colletidae). These bees carry an average of more than two pollen taxa when they are caught foraging onH. fasciculata. 78% of the 47 bees, captured onH. fasciculata carried the pollen from at least one sympatric taxon bearing nectariferous flowers (e.g., genera in theMyrtaceae, Compositae, andEpacridaceae). The pollination biology ofH. fasciculata is assessed in relation to the known radiation of bee-pollinated flowers in the genusHibbertia, and within theDilleniaceae s. l.     

Environmental influences on male production and social structure inHalictus rubicundus (Hymenoptera: Halictidae)

Summary Several years' observations of population of a primitively social halictine bee,Halictus rubicundus, revealed the following: (1) there is a correlation between ambient temperatures during the spring provisioning phase and the sex ratio of the resulting brood, such that warmer temperatures are associated with an increase in male bias; (2) over the course of the season, the degree of male bias of eggs laid appears to correspond with photoperiod; and (3) increasing male bias in the first brood is associated with decreasing proportions of social colonies formed in the population, and this effect may be accentuated by small population size. These phenomena suggest that abiotic environmental conditions at the time of brood production may profoundly influence the demography of this population, and that the demography in turn determines the degree to which sociality is expressed. These findings are related to hypotheses dealing with caste determination in temperate halictine bees, viewed in the context of the evolution and maintenance of sociality, and it is proposed that these phenomena reveal a mechanism by which social behavior (the occurrence of a worker caste, in particular) is facultatively fine-tuned to suit the characteristics of the environment.     

Nesting biology of tropical solitary and social sweat bees,Lasioglossum (Dialictus) figueresi Wcislo andL. (D.) aeneiventre (Friese) (Hymenoptera: Halictidae)

Summary The nesting biology of a mainly solitary bee,Lasioglossum (Dialictus) figueresi, is compared with that of a possible relative and mainly eusocial bee,L. (D.) aeneiventre. These bees nest in the ground in highly disturbed areas in the Meseta Central of Costa Rica. Information is provided on social organization, male production, diel and seasonal activity patterns, pollen utilization, natural enemies and nest architecture. L. (D.) figueresi nests within aggregations in vertical earthen banks, and 80–90 % of females are solitary during the nest-provisioning phase. Social nests contain two (or rarely three) females which may be either equal or unequal in reproductive status (i.e. mated with developed ovaries or not). Solitary nests and two-female nests do not experience different rates of parasitism. Mid-way through the dry season, females cease provisioning at a time when otherL. (Dialictus) remain active. Females typically remain within their nests, although they occasionally forage for nectar. This behavior is similar of that of spring gynes of temperate eusocial species. The egg-to-adult developmental rate ofL. (D.) figueresi is unusually slow for halictine bees, however, so that all the adult females die before their brood eclose in April and May, precluding overlap of generations. The eclosed offspring remain in open cells within their natal nests until mid-June, when both males and females emerge to mate. These newly mated females either establish new nests or re-use old ones. L. (D.) aeneiventre nests within aggregations in horizontal ground or in vertical banks. A foundress female digs a nest at the beginning of the dry season, although some re-activate old nests. Foundress nests develop into colonies with various kinds of social organization. In contrast toL. (D.) figueresi, L. (D.) aeneiventre is active nearly all year round, except during periods of heavy rain, and produces up to three broods per year.Sweat bees (Hymenoptera: Halictinae) are a socially heterogeneous group of mainly ground-nesting bees which are abundant world-wide. Intra-specific variation in social behavior is prevalent both within and among populations, presumably indicating social and environmental control of behavioral modifications (see e.g. Sakagami and Munakata, 1972; Eickwort, 1986; Packer, 1990; Yanega, 1988; reviewed in Michener, 1990). The initial stages of hymenopteran social evolution are represented by solitary individuals and those in undifferentiated societies, yet their biology is not well known, as is true for the numerous tropical halictine species or populations (see Michener, 1990).The subgenusDialictus ofLasioglossum is a primarily New World group of several hundred species (Moure and Kurd, 1987). These bees are monotonously similar in structure and appearance, yet diverse in social behavior. FemaleLasioglossum (Dialictus) figueresi are usually solitary, and structurally are very similar to their social relativeL. (D.) aeneiventre (Wcislo, 1990 a). The systematic placement of these species with respect to otherL. (Dialictus) is uncertain, but they have no obvious affinities to other recognized species groups (G. C. Eickwort, pers. comm.). Unusual morphological features, such as large size, yellowish wings and pubescence, and features of the genital organs, may indicate thatL. (D.) figueresi is the more derived of the pair, and may therefore be secondarily solitary, as is known for other sweat bees (Packer, 1991).     

外群选择对隧蜂科（膜翅目：蜜蜂总科）系统重建的影响

外群用于给树附根和推断祖先性状状态。通常,来自内群的姐妹群中的多个分类单元被共同选择作为外群。为了在经验上验证这一方法, 我们采用了3种外群选择策略： 姐妹群中的单一分类单元, 姐妹群中的多个分类单元和连续姐妹群中的多个分类单元。以隧蜂科（膜翅目： 蜜蜂总科）的系统发育重建为例, 我们评估了这3种策略对树拓扑结构的影响, 包括最大似然树、 最大简约树和贝叶斯树。初步结果表明： 相比其他两种策略, 采用姐妹群中的多个分类单元作为外群更有利于系统发育重建得到现已被广泛认可的隧蜂科系统发育关系; 相比最大似然法和贝叶斯法, 虽然隧蜂科系统发育关系没有被很好地解决, 但最大简约法在不同外群选择策略下得到了较为一致的拓扑结构     

Pollination of Campomanesia phaea (Myrtaceae) by night‐active bees: a new nocturnal pollination system mediated by floral scent

• Bees are the most important diurnal pollinators of angiosperms. In several groups of bees a nocturnal/crepuscular habit developed, yet little is known about their role in pollination and whether some plants are adapted specifically to these bees. We used a multidisciplinary approach to investigate the reproductive biology and to understand the role of nocturnal/crepuscular bees in pollination of Campomanesia phaea (Myrtaceae), popularly named cambuci.
• We studied the floral biology and breeding system of C. phaea. We collected the floral visitors and tested the pollinators' effectiveness. We also determined the floral scents released at night and during daytime, and studied behavioural responses of crepuscular/nocturnal bees towards these scents.
• The flowers of cambuci were self‐incompatible and had pollen as the only resource for flower visitors. Anthesis lasted around 14 h, beginning at 04:30 h at night. The flowers released 14 volatile compounds, mainly aliphatic and aromatic compounds. We collected 52 species of floral visitors, mainly bees. Nocturnal and crepuscular bees (four species) were among the most frequent species and the only effective pollinators. In field bioassays performed at night, nocturnal/crepuscular bees were attracted by a synthetic scent blend consisting of the six most abundant compounds.
• This study describes the first scent‐mediated pollination system between a plant and its nocturnal bee pollinators. Further, C. phaea has several floral traits that do not allow classification into other nocturnal pollination syndromes (e.g. pollinator attraction already before sunrise, with pollen as the only reward), instead it is a plant specifically adapted to nocturnal bees.

     

The influence of soil temperature on the nesting cycle of the halictid bee Lasioglossum malachurum

The physiology and behavior of ectothermic organisms is strongly influenced by temperature. For ground nesting species like the primitively eusocial halictid bee, Lasioglossum malachurum, soil temperature might influence the life cycle as well as the complexity of the social group since the number of broods that can be fitted into the flight season might increase with increasing temperature. Our study populationof L. malachurum at Wuerzburg exhibits a remarkable variability with respect to the number of broods and the pattern of sexual production. Broods are separated by activity pauses during which the larvae develop. In this study we investigate the influence of soil temperature on the pattern of nesting activity (duration of broods and pauses) and on the number of broods in L. malachurum. We observed a total of 1138 nests in 13 aggregations near Wuerzburg. As expected, soil temperature shortened the duration of the pauses, resulting in an overall shortening of the nesting cycle. This is most probably due to a physiological effect of soil temperature on the development of the larvae. With regard to the nesting strategies, we hypothesized that a shortening of the nesting cycle within the limited flight season should enhance the success of a strategy with more worker broods. In fact, patches with higher soil temperature showed more broods. However, this effect was rather weak, suggesting that other factors might have a stronger impact on the variability in nesting strategy within our study population of L. malachurum. Received 20 December 2005; revised 25 April 2006; accepted 2 May 2006. An erratum to this article is available at .