Characterization of microsatellite loci from the solitary sweat bees Lasioglossum leucozonium and Lasioglossum oenotherae (Hymenoptera,Halictidae)

Microsatellite loci were isolated from two solitary sweat bees: the polylectic Lasioglossum leucozonium (10 loci) and the oligolectic Lasioglossum oenotherae (9 loci) (Hymenoptera, Halictidae). All loci were polymorphic with high observed heterozygosities (0.07–0.75 for L. leucozonium; 0.06–0.92 for L. oenotherae). These loci will be used to study the consequences of diet specialization on the population and conservation genetics of bees.     

Lasioglossum (Dialictus) tenax (Sandhouse) (Hymenoptera: Halictidae) as a solitary sweat bee

Summary Nine nests ofLasioglossum (Dialictus) tenax were excavated near Calgary, Alberta, Canada over a time period encompassing the entire brood production period in 1988. Each nest contained a maximum of one active adult female, nest productivity peaked in mid July, protandry was noted and no significant size difference between foundresses and the earlier emerging females was detected. These data suggest that this species is solitary. These results are compared with data for the sympatrically nesting eusocial speciesL. (D.) laevissimum.     

Microsatellite loci for the eusocial Lasioglossum malachurum and other sweat bees (Hymenoptera,Halictidae)

Sweat bees (family Halictidae) comprise a numerous and diverse group that are arguably among the most socially labile of all insect taxa. Given the lack of highly variable markers for eusocial species of the family, we developed a suite of dinucleotide and trinucleotide markers for one of its members, the Eurasian Lasioglossum malachurum, and used them to amplify DNA from other halictids. Loci were highly variable in L. malachurum and amplified DNA from many other halictids.     

Segregation of temporal and spatial distribution between kleptoparasites and parasitoids of the eusocial sweat bee, Lasioglossum malachurum (Hymenoptera: Halictidae, Mutillidae)

Cuckoo bees and velvet ants use different resources of their shared host bees, the former laying eggs on the host pollen stores and the latter on immature stages. We studied the activity patterns of the cuckoo bee Sphecodes monilicornis and the velvet ant Myrmilla capitata at two nesting sites of their host, the social digger bee Lasioglossum malachurum , over a 3 year period. Due to the difference in host exploitation, we expected different temporal patterns of the two natural enemies as well as a positive spatial association with host nest density for both species. At a daily level, S. monilicornis was more abundant between 10.00 and 15.00 h, while M. capitata was most active in the early morning and late afternoon; both species activities were independent from host provisioning activity. The activity of cuckoo bees was in general positively correlated with the density of open host nests (but not with the total number of nests), while that of velvet ants was rarely correlated with this factor. Sphecodes monilicornis was seen both attacking the guard bees and directly entering into the host nests or digging close to nest entrances, while M. capitata only gained access to host nests through digging. We conclude that the temporal and spatial segregation between the two species may be, at least partially, explained both by the different resources exploited and by the different dynamics of host interactions.     

Lasiocepsin, a novel cyclic antimicrobial peptide from the venom of eusocial bee Lasioglossum laticeps (Hymenoptera: Halictidae)

In the venom of eusocial bee Lasioglossum laticeps, we identified a novel unique antimicrobial peptide named lasiocepsin consisting of 27 amino acid residues and two disulfide bridges. After identifying its primary structure, we synthesized lasiocepsin by solid-phase peptide synthesis using two different approaches for oxidative folding. The oxidative folding of fully deprotected linear peptide resulted in a mixture of three products differing in the pattern of disulfide bridges. Regioselective disulfide bond formation significantly improved the yield of desired product. The synthetic lasiocepsin possessed antimicrobial activity against both Gram-positive and -negative bacteria, antifungal activity against Candida albicans, and no hemolytic activity against human erythrocytes. We synthesized two lasiocepsin analogs cyclized through one native disulfide bridge in different positions and having the remaining two cysteines substituted by alanines. The analog cyclized through a Cys8-Cys25 disulfide bridge showed reduced antimicrobial activity compared to the native peptide while the second one (Cys17-Cys27) was almost inactive. Linear lasiocepsin having all four cysteine residues substituted by alanines or alkylated was also inactive. That was in contrast to the linear lasiocepsin with all four cysteine residues non-paired, which exhibited remarkable antimicrobial activity. The shortening of lasiocepsin by several amino acid residues either from the N- or C-terminal resulted in significant loss of antimicrobial activity. Study of Bacillus subtilis cells treated by lasiocepsin using transmission electron microscopy showed leakage of bacterial content mainly from the holes localized at the ends of the bacterial cells.     

Phylogeny of the bee genus Lasioglossum (Hymenoptera: Halictidae) based on mitochondrial COI sequence data

The bee genus Lasioglossum Curtis is a model taxon for studying the evolutionary origins of and reversals in eusociality. This paper presents a phylogenetic analysis of Lasioglossum species and subgenera based on a data set consisting of 1240 bp of the mitochondrial cytochrome oxidase I (COI) gene for seventy-seven taxa (sixty-six ingroup and eleven outgroup taxa). Maximum parsimony was used to analyse the data set (using paup *4.0) by a variety of weighting methods, including equal weights, a priori weighting and a posteriori weighting. All methods yielded roughly congruent results. Michener’s Hemihalictus series was found to be monophyletic in all analyses but one, while his Lasioglossum series formed a basal, paraphyletic assemblage in all analyses but one. Chilalictus was consistently found to be a basal taxon of Lasioglossum sensu lato and Lasioglossum sensu stricto was found to be monophyletic. Within the Hemihalictus series, major lineages included Dialictus + Paralictus, the acarinate Evylaeus + Hemihalictus + Sudila and the carinate Evylaeus + Sphecodogastra. Relationships within the Hemihalictus series were highly stable to altered weighting schemes, while relationships among the basal subgenera in the Lasioglossum series (Lasioglossum s.s., Chilalictus, Parasphecodes and Ctenonomia) were unclear. The social parasite of Dialictus, Paralictus, is consistently and unambiguously placed well within Dialictus, thus rendering Dialictus paraphyletic. The implications of this for understanding the origins of social parasitism are discussed.     

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).     

Phylogeny of the bee genus Agapostemon (Hymenoptera: Halictidae)

Abstract. A phylogeny for genus Agapostemon (Hymenoptera: Halictidae) is reconstructed from morphological characters, using all species, with four representatives of Agapostemonini as outgroup taxa. Parsimony analysis using 150 unordered characters resulted in eighteen equally parsimonious trees, a strict consensus of which is highly resolved for Agapostemon. Based on this analysis, Agapostemonoides Roberts & Brooks is returned to generic status, and a new subgenus is described: Notagapostemon, which includes the rhopalocerus, heterurus, atrocaeruleus, erebus, kohliellus, nasutus and intermedius groups of Moure & Hurd. Species groups are proposed for Notagapostemon and revised in A. (Agapostemon). Agapostemon cockerelli Crawford is synonymized with A. obliquus (Provancher), A. epichryseus (Morelos) with A. leunculus Vachal, A. inca Roberts with A. heterurus Cockerell, A. hispaniolicus Roberts female with A. centratus (Vachal) and A. hispaniolicus Roberts male with A. alayoi Roberts. Optimization of known behaviours suggests communal ancestry for the genus and infers the prevalence of this behaviour in Agapostemon. Optimization of geographical range suggests a Central American or Caribbean origin of Agapostemon, with one invasion of North America and multiple invasions of South America and the Caribbean. One invasion of the Caribbean suggests arrival from North America via Florida.     

Invasion of Nests of Lasioglossum imitatum by a Social Parasite,Paralictus asteris (Hymenoptera: Halictidae)

Paralictus asteris Mitchell is a socially parasitic sweat bee that invades nests and becomes the dominant reproductive in colonies of a phylogenetically related host, Lasioglossum (Dialictus) imitatum (Smith). The parasite has a greatly enlarged quadrate head, with elongate scythe-like mandibles, and other morphological modifications apparently associated with a parasitic lifestyle. Nevertheless, the parasite did not forcefully enter nests. Host guards adopted a defensive posture at the nest entrance when they contacted a dead, frozen parasite, suggesting that they recognized the intruders as parasites. Living parasites, however, only sometimes induced this guarding response, while in other cases parasites entered host nests without obvious signs of aggression from the guard. Guards also responded aggressively to both frozen and living conspecifics from other nests, but were not aggressive to living or frozen nest-resident conspecifics, suggesting that the cues used for recognition of both unrelated conspecifics and parasites are chemical ones. More than one parasite can invade and occupy a nest, and successful invasion was not influenced by whether a parasitic female was mated or had developed ovaries.     

The effect of pollen protein concentration on body size in the sweat bee Lasioglossum zephyrum (Hymenoptera: Apiformes)

Adult bees and wasps provide all the food their offspring require to grow from egg to adult. For a given diet, offspring body size generally increases with an increase in the amount of food consumed as a larva, but the extent to which body size is influenced by the type of food consumed is poorly known. Pollen ranges from 2–60% protein among plant species, and bees are extremely efficient at assimilating nitrogen; therefore, it seems likely that either parent bees adjust the size of larval provisions to compensate for differences in pollen protein concentration or bee offspring attain different body size depending on the pollen type(s) consumed as a larva. We presented the generalist sweat bee Lasioglossum zephyrum with pollen diets that differed in protein content and monitored offspring body size during two experiments. In a protein supplementation experiment, diets ranged from 20–66% protein and consisted of Typha pollen amended with soy protein. On a pollen/soy diet, offspring body size increased 25% with a shift from 20–37% protein, but did not increase further at greater protein concentrations. In a multiple pollen experiment, pollen diets ranged from 20–39% protein and consisted of eight pollens that differed naturally in protein concentration. The largest offspring arose from the most protein-rich pollens, whereas much smaller bees developed on protein-poor pollens. Provision size only predicted offspring size when pollen type, and therefore protein quantity, was considered. Adult foragers did not adjust provision size to compensate for pollen protein. Therefore, offspring body size appears to result from a combination of controlled (provision size) and uncontrolled (pollen quality) factors that arise out of bee foraging decisions.     

Proventricular structure in the bee tribe Augochlorini (Hymenoptera: Halictidae)

Characters of the digestive tract have received little attention in modern phylogenetic analyses regarding relationships among bees, in part because studies on the internal morphology of bees generally concentrate on physiological and behavioural aspects. This paper presents a comparative study of the proventricular structure, analysed with scanning electronic microscopy, in bees of the tribe Augochlorini. Eleven species of Augochlorini were analysed as the ingroup, versus one each of Halictini and Caenohalictini, and two of Crabronidae as outgroups. The presence of a long columnar proventricular fold is an apomorphy for Augochlorini, whereas a proventricular fold with a keel-shaped structure at the moving lip level is an apomorphy for Augochlorina. Together these data corroborate the monophyly of Augochlorini and Augochlorina, respectively.     

Social polymorphism in the sweat bee <Emphasis Type="Italic">Lasioglossum (Evylaeus) baleicum</Emphasis> (Cockerell) (Hymenoptera,Halictidae) in Hokkaido,northern Japan

Summary The life cycle and social behaviour of the sweat bee Lasioglossum (Evylaeus) baleicum (Cockerell) was investigated in two geographically separate populations in Hokkaido, northern Japan. Colonies were excavated throughout the brood rearing season from an aggregation in Nishioka forest park, Sapporo, and near Kawakita in eastern Hokkaido during 2000 and 2001. The Nishioka population produced two discrete broods during the year and was weakly eusocial; 57% of workers were mated and 28% exhibited some ovarian development, 12–16% of the first brood was male, and workers were on average 4.5% smaller than their respective queen. In contrast, the population at Kawakita was solitary, and produced a single brood per year with an unbiased sex ratio. In addition however, there were some solitary colonies in the Nishioka population and evidence of a partial second brood in some colonies at Kawakita, suggesting differences between the populations are not fixed and that this species is truly socially polymorphic. L. (E.) baleicum is a member of the fulvicorne species group, which includes other examples of social polymorphic species as well as solitary and eusocial species, though this is the only species of this group so far known to exhibit a solitary/non-delayed eusocial polymorphism. Recent studies suggest that social polymorphism has both genetic and environmental influences, raising questions as to the relative import of each.     

Seasonal changes in ovarian state in a eusocial halictine bee,Lasioglossum duplex,based on stages of the oldest oocytes in each ovariole (Hymenoptera: Halictidae)

Summary The changes in ovarian activity in the life cycle of the eusocial halictine beeLasioglossum (Evylaeus) duplex (Dalla Torre) was studied in both queens and workers by examining the stages of the terminal follicle in each of the six ovarioles. By this method, ovarian activities of both queens and workers were more quantitatively determined than by observation of gross ovarian features as usually conducted. Queen ovaries clearly exhibited two active periods, corresponding to the spring solitary phase and the summer eusocial phase, with distinctly greater activity in the latter. In ovaries of overwintering queens oosorption of young follicle was observed. Worker ovaries were found more active in orphan than in queenright colonies. The order of ovarian activity obtained from pooled data, summer queens>spring queens>orphan workers>queenright workers, was also recognized by comparison of individual females. Bionomics of the eusocial halictine beeLasioglossum duplex IX. Contribution No. 3107 from the Inst. Low Temp. Sci.     

Ontogenetic patterns of volatiles identified in Dufour's gland extracts from queens and workers of the primitively eusocial halictine bee,Lasioglossum malachmum (Hymenoptera: Halictidae)

Summary Ontogenetic patterns of volatile compounds identified in Dufour's gland extracts from queens and workers of the primitively eusocial sweat beeLasioglossum malachurum (K.) were compared. Only young unmated queens showed high proportions of isopentenyl esters, while macrocyclic lactones were dominant in old breeding queens, spring queens, and workers. In young queens the relative and absolute amounts of volatiles changed one day after mating. A discriminant analysis revealed significant differences in odor patterns of unmated and mated young queens. The fat body was the largest in young females, while eggs could be recorded only in breeding queens. Possible functions of different odor components in the investigated female groups are discussed.