Nest-moving by the polydomous ant <Emphasis Type="Italic">Cataglyphis iberica</Emphasis>

In this paper we analyze emigration from nests by the polydomous ant Cataglyphis iberica. Social carrying of workers of this species between different nests of the colony is frequent. In Bellaterra (Barcelona, NE Spain), we monitored field emigration of C. iberica by noting for each nest the migratory behavior of C. iberica workers and, when the nests were attacked by another ant species, Camponotus foreli, we noted the number of C. foreli workers involved in the attacks. Emigration of C. iberica from nests was highly variable. We suggest the main factor determining emigration by this species was attack by workers of C. foreli, so emigration from C. iberica nests was much faster when harassment by C. foreli increased. The system of multiple nests of C. iberica enables this species to abandon attacked nests and to reinstall their population in other nests of the same colony. This reduces risk to the colonies because the route between the different nests is well known by transporter workers.     

Decision-making conditions for intra- or inter-nest mating of winged males in the male-dimorphic ant <Emphasis Type="Italic">Cardiocondyla minutior</Emphasis>

Only winged male and female ants generally mate through nuptial flight during the reproductive season. In the ants of Cardiocondyla, the males show wing dimorphism and their reproductive strategies differ depending on the differences in wing morphology. It has been suggested that wingless “ergatoid” males bearing very similar external morphologies to workers mate within natal nests, whereas winged males bearing typical ant male morphology disperse from their nests to mate. However, some behavioral observations suggest that the winged males of some Cardiocondyla ants such as C. obscurior and C. minutior may mate within natal nests before dispersion. We evaluated the factors affecting the mating behaviors of the winged males of C. minutior under laboratory conditions. We found that (1) the winged males remained and mated with virgin females in natal nests when either virgin winged females or the relatively mature pupae of winged females (i.e., at least 10 days) were present in the nest, (2) the winged males dispersed to adjacent nests with virgin winged females when only mated queens and the relatively young pupae of winged females (i.e., <9 days) were present in the nest, and (3) all winged males were accepted by the workers of non-natal nests irrespective of the distance from the natal nests in the field. Although most ergatoid males were accepted by the workers of close non-natal nests, they were all attacked and killed by the workers of distant non-natal nests. These results suggest that intra-nest mating and the dispersion of the winged males of C. minutior are facultatively determined by the condition of winged females (virginity and relative pupal age) in natal nests. Furthermore, our results suggest that winged males are likely to seek mating partners chemically and to mate with virgin winged females.     

Sperm reduces female longevity and increases melanization of the spermatheca in the bumblebee <Emphasis Type="Italic">Bombus terrestris</Emphasis> L.

Here we present evidence that the male mating products (sperm and gland products) reduce survival during hibernation of queens of the bumblebee B. terrestris. Most remarkably, the inseminated queens are significantly more likely to have melanized spermathecae than their virgin sisters. Although we could not detect a direct relationship between these two findings they are quite remarkable since B. terrestris is a monandrous and comparably long-lived insect where sexual conflict is unlikely to evolve. The reduced survival can probably be attributed to a general cost of maintaining the sperm, whereas the presence of melanized spermathecae in the inseminated queens may indicate a pathogen transferred during mating or genetic incompatibilities between males and queens. Received 30 December 2007; revised 27 April 2008; accepted 1 May 2008.     

Colony kin structure and breeding patterns in the social wasp, <Emphasis Type="Italic">Polistes biglumis</Emphasis>

We used DNA microsatellites to study colony kin structure and breeding patterns in the primitively eusocial wasp Polistes biglumis. P. biglumis inhabits cool areas at high altitudes and, as a consequence, has a reduced colony cycle compared to more temperate Polistes. P. biglumis colonies are always founded and controlled by a single foundress, but nest failure is common and foundresses losing their nests do not have time to start new ones due to the short season. Instead, nests are characterized by frequent female turnover, in the form of females taking over (usurpation) other con-specific nests. Our results showed that most nests had offspring from multiple unrelated females, including some where multiple females were not observed in monitoring. Reconstruction of behavioural events from the genetic data revealed three types of multiple matriline nests: (a) nests that were usurped by another female, where the original nest owner disappeared following the usurpation event, (b) nests that were joined by another female, where the original nest owner stayed following the joining event, (c) nests that were both usurped and joined by other females. We also found, for the first time, a clear indication of multiple mating by Polistes females. Moreover, males mating with the same female were related, which may be explained by the lek mating system of P. biglumis. Finally, we analysed the nest sex ratios and how it changed during the season and found that sexes were produced sequentially, males before females.     

<Emphasis Type="Italic">Wolbachia</Emphasis> infection increases recapture rate of field-released <Emphasis Type="Italic">Drosophila melanogaster</Emphasis>

Wolbachia pipientis is a commonly occurring endosymbiont with well-characterised effects on host reproductive biology associated with its infection of the gonads. Wolbachia infections are also widespread in somatic tissues and consequently they have the potential to play a much broader role in host biology. Recently, Wolbachia was shown to alter the locomotion of Drosophila melanogaster in response to food cues in the laboratory. To determine whether this laboratory-based phenotype might translate to real differences for insects in the field, we performed a simple mark-release-recapture experiment with Wolbachia-infected D. melanogaster in a forested habitat. We demonstrate that infected flies are recaptured at twice the rate of uninfected flies, although infection does not affect the distance traveled by those flies recaptured. The differences in recapture could be explained by infection-induced changes in physiology or behavior. If generalizable, such changes may affect the interpretation of behavioral studies for Wolbachia-infected insects and have potential implications for the dynamics of Wolbachia infections in natural populations, including situations where Wolbachia-infected insects are being released for biological control.     

Population dynamics of a maternally-transmitted <Emphasis Type="Italic">Spiroplasma</Emphasis> infection in <Emphasis Type="Italic">Drosophila hydei</Emphasis>

A maternally-inherited spiroplasma endosymbiont of Drosophila hydei does not exert apparent phenotypes on both sexes of its host and is prevalent in natural populations of D. hydei. Our previous experiments using a laboratory stock of D. hydei revealed that low temperatures (such as 15°C and 18°C) dramatically lower the vertical transmission rates of this spiroplasma. Therefore, we hypothesized that, in temperate regions, the infection frequencies may decrease in cool seasons but increase in the summer season. To clarify the temporal population dynamics of the spiroplasma infection, D. hydei were collected from two Japanese populations in 2006–2008 from May to early August, representing the only period when a number of D. hydei are collectable in Japan, and examined for spiroplasma infection. Within each year, the frequency of spiroplasma infection fluctuated considerably in both populations. Consistent with our hypothesis, the infection frequency showed an increasing trend in both populations in 2007. However, the data in 2006 and 2008 did not show consistent patterns of increase. The population dynamics of spiroplasma infection may be affected but not critically determined by temperature. Moreover, despite the fluctuation within each year, the infection frequencies seemed to be stable across the years. The frequencies of spiroplasma infection in D. hydei populations may be stabilized by multiple factors. One of these factors may involve a context-dependent positive effect of spiroplasma on the fitness of D. hydei, as was recently observed in laboratory experiments.     

Genetic and morphological variation over space and time in the invasive fire ant <Emphasis Type="Italic">Solenopsis invicta</Emphasis>

Social insects are among the most successful and damaging of invasive taxa. We studied spatial and temporal variation in two traits, colony genetic structure and worker mass, associated with social insect success in the introduced fire ant Solenopsis invicta. Our aim was to determine if changes in social structure occurred over time and if variation in worker size was related to worker genotype. We sampled 1139 workers from five multiple-queen S. invicta nests on six dates over a one-year period. The genotypes of workers were determined at ten microsatellite loci and at the selected locus general protein-9 (Gp-9). We found little evidence for genetic differentiation of workers sampled from distinct nests or from different dates at the microsatellite loci. However, worker Gp-9 genotype frequencies varied among nests and over time. In addition, worker mass was affected by nest-of-origin, sampling date, ploidy level, and Gp-9 genotype. Our results suggest that large numbers of queens contribute to the production of workers in introduced S. invicta nests throughout the year. Colony boundaries are semi-permeable, although the among-nest variation in Gp-9 genotype frequencies and worker mass does suggest that boundaries are present. In addition, selection operating on Gp-9 genotype depends on nest environment. Finally, worker mass is affected by both endogenous and exogenous factors in S. invicta. Overall, our data suggests that the key traits of colony social structure and worker size reflect the effects of variable selection in invasive social insects.     

<Emphasis Type="Italic">Chlamydia psittaci</Emphasis> infection in canaries heavily infested by <Emphasis Type="Italic">Dermanyssus gallinae</Emphasis>

Dermanyssus gallinae is a haematophagous ectoparasite responsible for anemia, weight loss, dermatitis and a decrease in egg production. Dermanyssus gallinae may play a role in the modulation of the host immune system, maybe predisposing the host to some bacterial infections such as chlamydiosis. This is an important zoonosis. Humans are exposed to Chlamydia psittaci through inhalation of the agent dispersed from the infected birds. In this study, a syndrome observed in an aviary of canaries was investigated. A heavy infestation by D. gallinae was reported. Simultaneously, a C. psittaci infection was molecularly confirmed in the canaries. Combined therapy was applied successfully. The association of C. psittaci with the examined mites has been confirmed. Therefore, we think that D. gallinae have played a role in the spreading of C. psittaci infection among the canaries. Moreover, D. gallinae could have played an important role predisposing the canaries to the development of chlamydiosis, by inducing anemia and debilitation. The control of mites in the aviaries may represent a crucial step for the prevention of important infection such as chlamydiosis in birds and humans.     

Fungus garden platforms improve hygiene during nest establishment in <Emphasis Type="Italic">Acromyrmex</Emphasis> ants (Hymenoptera,Formicidae, Attini)

Physically isolating organisms from disease agents should reduce the likelihood of disease transmission and infection, and increase survival and growth, particularly in more vulnerable, early ontogenetic stages. During nest founding in fungus-growing ants, foundresses of most genera use a garden platform to isolate the incipient fungal garden from the soil of the underground chamber. We studied nest founding in Acromyrmex octospinosus to test the hypotheses that the use of a platform (rootlets used to suspend the fungus garden): (i) reduces the likelihood that the garden will be contaminated by soil-borne microbial pathogens; (ii) results in more rapid growth of a young colony; and (iii) increases colony survival. We manipulated natural incipient nests to have gardens either in contact with or isolated from soil surrounding the chamber, and nests with and without foundresses present. We found a higher incidence of infection in gardens that were in contact with the chamber soil and without queens, compared with gardens isolated from the chamber soil with and without foundresses. The production of eggs, larvae and pupae, as well as leaf area harvested, were significantly different between nests with and without platforms, but there were no differences in the production of workers nor garden biomass. Likewise, there were no differences between treatments in colony survival rates over 8 weeks. Using smaller incipient gardens, however, gardens with and without platforms differed in survivorship rates after 24 hours. The results indicate that the use of a platform to cultivate an incipient fungal garden is an adaptation to reduce soil-borne diseases and increase colony performance. Received 28 July 2006; revised 15 November 2006; accepted 22 November 2006.     

Negative Evidence of <Emphasis Type="Italic">Wolbachia</Emphasis> in the Predaceous Mite <Emphasis Type="Italic">Phytoseiulus persimilis</Emphasis>

The cytoplasmically inherited bacterium Wolbachia is widespread in arthropod species and has been repeatedly detected in the predaceous mite Phytoseiulus persimilis. Our original goal was to assess the prevalence of Wolbachia infection in P. persimilis and the potential fitness consequences for this host. To accomplish that goal, seven P. persimilis strains were obtained from Europe, Africa and the USA and reared on the phytophagous mite Tetranychus urticae as prey. After preliminary results showed that the T. urticae used was infected with Wolbachia, the minimum starvation time of the predators to prevent false positive results from undigested prey was determined. We tested DNA samples by PCR (polymerase chain reaction) after starving the predators or feeding them Wolbachia-free T. urticae for various periods. Those experiments showed that Wolbachia could not be detected after 16 h at 25 °C and 48 h at 20 °C. To verify the results of the PCR analyses, we furthermore conducted crossing experiments with antibiotic-treated and untreated individuals. No indications of Wolbachia effects were recorded. Additionally, we screened live eggs of four of the seven strains reared in our laboratory and alcohol samples of 10 other P. persimilis strains for the occurrence of Wolbachia by PCR, none of which tested positive. Synthesis of our study and previous reports suggests that infection of P. persimilis with Wolbachia is extremely rare and of minor importance. We discuss the significance of our findings for future studies on the presence of Wolbachia in predaceous arthropods.     

Fitness consequences of infection of <Emphasis Type="Italic">Arabidopsis thaliana</Emphasis> with its natural bacterial pathogen <Emphasis Type="Italic">Pseudomonas viridiflava</Emphasis>

Variation in plant resistance to pathogen infection is commonly observed in interactions between wild plants and their foliar pathogens. Models of host–pathogen interactions indicate that a large cost of infection is generally necessary to maintain this variation, yet there is limited evidence that foliar pathogens cause detectable fitness reductions in wild host plants. Most published work has focused on fungal pathogens. Pseudomonas viridiflava, a common bacterial pathogen of the annual weed Arabidopsis thaliana across its range, comprises two distinct genetic clades that cause disease symptoms of different severity. Here we measured the extent of infection of wild A. thaliana populations in the Midwest, USA, and examined the effect on seed production, in field and growth-chamber experiments, of experimental inoculation with isolates from the two clades. We found infection with P. viridiflava varied from 0 to 56% in Midwest A. thaliana populations, with the possibility of several leaves per plant infected later in the growing season. In the growth chambers, experimental inoculation reduced seed set by averages of 15 and 11% for clades A and B, respectively. In the field experiment, only clade A affected plant fitness significantly, reducing seed set by an average of 38%. Underlying these average effects we observed both negative and positive effects of infection, and variation in both fitness among plant genotypes and sensitivity to environmental conditions.     

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.     

The first record of infection and sterilization by the nematode <Emphasis Type="Italic">Sphaerularia</Emphasis> in hornets (Hymenoptera,Vespidae, <Emphasis Type="Italic">Vespa</Emphasis>)

Parasitic nematodes of the genus Sphaerularia are known to infect and sterilize the overwintering gynes (potential queens) of bumblebees.We found that 70% of the overwintered gynes of the hornet Vespa simillima collected using bait traps were infected and sterilized by Sphaerularia sp. This is the first solid record of parasitism by Sphaerularia in hornets (Vespa spp.). Received 22 June 2006; revised 24 October 2006; accepted 3 November 2006.     

Permanent loss of wings in queens of the ant <Emphasis Type="Italic">Odontomachus coquereli</Emphasis> from Madagascar

Winged queens are the most common reproductives in ants. They are morphologically specialized for independent colony foundation, with wings for long-range dispersal and metabolic reserves to raise the first brood. However independent foundation can sometimes be selected against and replaced by fission, featuring short-range dispersal on the ground and reproductives that are dependent on the wingless workers for all non-reproductive tasks. We investigated the evolutionary consequences of this transition on the morphology of the reproductives by collecting 30 colonies of Odontomachus coquereli from Madagascar, the only species in the genus where winged queens have never been found. Data about colony demography, morphometry, allometry and ovarian dissections showed that the winged queen caste has been replaced by a wingless reproductive caste with distinct body proportions relative to the workers or to congeneric winged queens. The 17 reproductives that we measured exhibited little size variability. A single wingless reproductive was found in each colony, corresponding to ‘ergatoids’ in literature. Several facts suggest that colonies reproduce by fission, notably the relatively constant colony size (19±11 workers). The developmental origins of wingless reproductive phenotypes need investigation; little genetic change may be involved, as seen when Odontomachus larvae are parasitized by nematodes. The sole function of wingless reproductives in O. coquereli is reproduction, and they contrast with multi-purpose wingless reproductives found in other ants, where numerous intermorphs occur in each colony and contribute to sterile tasks. Received 15 December 2006; revised 26 February 2007; accepted 1 March 2007.     

Life-cycle and foraging patterns of native <Emphasis Type="Italic">Bombus terrestris</Emphasis> (L.) (Hymenoptera,Apidae) in the Mediterranean region

Life-cycle and foraging patterns of native Bombus terrestris populations were investigated at two sites in the Mediterranean region of Turkey, Phassalis (0 – 100 m above sea level [a.s.l.]) and Termessos (500 – 700 m a.s.l.). Bumble-bee activity was recorded during standard bee walks from November 2003 until the end of October 2004, each site being visited three times every month during the one-year period. The yearly dynamics of flight, the flowering plant species visited, and the visitation frequencies of these plants were recorded during every bee walk at both sites. There were considerable differences between the two populations with regard to the dates when the queens emerged from diapause (the emerging season), the timing of the appearance of sexuals (young queens and males), and the total number of plant species visited. Bombus terrestris queens emerged from diapause in November-December at the Phassalis site (coastal area) and in February-March at the Termessos site. The queens aestivated at the Phassalis site, whereas they hibernated at the Termessos site. Only one generation per year was produced at each site. The duration of the queens’ diapause lasted 5 – 8 months and length of the life cycle 190 – 215 days. Native B. terrestris populations were noted to forage on 47 flowering plant species from 20 families (10 at the Phassalis site and 40 at the Termessos site) during the study period. Two of the plant species (Arbutus unedo L. and Vitex agnus-castus L.) have long flowering periods and play a crucial role in the life cycle of native B. terrestris populations. The emergence of queens at the aestivation site was synchronized with the flowering of Arbutus unedo L., while the emergence of sexuals coincided with the flowering of Vitex agnus-castus L. at both sites. Received 30 May 2007; revised 5 December 2007; accepted 8 January 2008.     

Colony genetic structure in the Australian jumper ant <Emphasis Type="Italic">Myrmecia pilosula</Emphasis>

Eusocial insects vary significantly in colony queen number and mating frequency, resulting in a wide range of social structures. Detailed studies of colony genetic structure are essential to elucidate how various factors affect the relatedness and the sociogenetic organization of colonies. In this study, we investigated the colony structure of the Australian jumper ant Myrmecia pilosula using polymorphic microsatellite markers. Nestmate queens within polygynous colonies, and queens and their mates, were generally unrelated. The number of queens per colony ranged from 1 to 4. Queens were estimated to mate with 1–9 inferred and 1.0–11.4 effective mates. This is the first time that the rare co-occurrence of polygyny and high polyandry has been found in the M. pilosula species group. Significant maternity and paternity skews were detected at the population level. We also found an isolation-by-distance pattern, and together with the occurrence of polygynous polydomy, this suggests the occurrence of dependent colony foundation in M. pilosula; however, independent colony foundation may co-occur since queens of this species have fully developed wings and can fly. There is no support for the predicted negative association between polygyny and polyandry in ants.     

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.     

Detection of <Emphasis Type="Italic">Candida</Emphasis><Emphasis Type="Italic">dubliniensis</Emphasis> in Venezuela

Over the past decades there has been a significant increase in fungal infections caused by Candida species, and continues to be common in immunocompromised individuals infected with the human immunodeficiency virus (HIV). Although Candida albicans remains the fungal species most frequently isolated as an opportunistic oral pathogen, other non-albicans are often identified in this cohort of patients, including C. dubliniensis. This yeast is closely related to and shares many phenotypic characteristics with C. albicans. Colonies of these two species appear morphologically identical when not grown on special media. The shared phenotypic characteristics of C. dubliniensis and C. albicans suggest that many C. dubliniensis isolates may have been misidentified as C. albicans in the past. The present studies aim is to recover and identify C. dubliniensis, and presumptive clinical C. albicans, from the oral cavities of HIV-seropositive individuals, comparing conventional media to obtain a simple, low-cost and reliable identification system for C. dubliniensis. A total of 16 isolates (3,98%) had been obtained from 402 HIV infected individuals with recurrent oropharyngitis and were identified as C. dubliniensis. Out of these C. dubliniensis isolates 19% were resistant, with MICs above 64 μg/ml to fluconazole. This constitutes, to the authors knowledge the first recovery of this organism in Venezuela.     

Both cooperation and nest position improve larval survival in the sweat bee, <Emphasis Type="Italic">Lasioglossum</Emphasis> (<Emphasis Type="Italic">Evylaeus</Emphasis>) <Emphasis Type="Italic">baleicum</Emphasis>

Nesting by multiple females in sweat bees raises the question of the benefits associated with grouping. Adult numbers of the sweat bee, Lasioglossum (Evylaeus) baleicum, exhibited variation within a nest population. The effects of adult number and nest position on larval survival were analyzed in a nest aggregation. Both variables independently affected larval survival, with the presence of multiple adults in a nest markedly improving survival rate. Nests located near the periphery of the aggregation of nests suffered high larval mortalities. Increased frequency of cell-inspection in multiple-female nests seems to be associated with a concomitant increase in larval cell protection from external predation. Such predation pressure was assumed, given the existence of an underground ant colony that employs a recruitment system while foraging in the study area.