Genetic improvement of Amblyseius finlandicus (Acari: Phytoseiidae): laboratory selection for resistance to azinphosmethyl and dimethoate

Amblyseius finlandicus (Oudemans) was selected in the laboratory for resistance to azinphosmethyl and dimethoate by subjecting adult females to increasing concentrations of dried residues of dimethoate and azinphosmethyl on detached bean leaves. The first eight selections were done with dimethoate. Slide-dip bioassays indicated selection with dimethoate increased dimethoate resistance 1.8-fold and azinphosmethyl resistance 2.6-fold. These resistances appeared to be quite stable: a 1.2 to 1.3-fold decrease in resistance ratios was observed in a subculture after 10 months without selections. No decrease was observed after 9 months without selections in a pooled colony that consisted of both resistant and susceptible mites. The dimethoate-selected colony was subsequently selected eight times with azinphosmethyl. About 15 % of the mites survived the last selection round with 2,500 ppm, which is 2.5 times the highest recommended field rate in Finnish apple orchards. At the end of the selection program, based on slide-dip bioassays, the total increase in resistance to dimethoate was about two-fold and to azinphosmethyl about 5.4-fold compared to the unselected base colony from which the selected colony was derived. The LC₅₀ value for azinphosmethyl was 14 times higher in the selected colony (451.3 ppm a.i.) compared to the most susceptible colony tested. A similar level of resistance to both pesticides was achieved after six azinphosmethyl selections on a mixed colony that was initiated by pooling mites from five field-collected colonies and the dimethoate-selected lines. Year-to-year variation in azinphosmethyl LC₅₀ values of the unselected base colony was high, with values varying from 83.8 to 348.7 ppm a.i., demonstrating the need to test a reference strain in each bioassay. Results of the azinphosmethyl selections and the subsequent slide-dip bioassays suggest that the resistant strain could tolerate field rates of azinphosmethyl (300–950 ppm a.i.) used in Finnish apple orchards.     

Genetic improvement of a parasitoid: Response of Trioxys pallidus to laboratory selection with azinphosmethyl

Colonies of Trioxys pallidus Haliday (Hymenoptera: Aphidiidae) were collected from California walnut orchards during 1985–86 and screened for variability of responses to azinphosmethyl. Variability was found and laboratory selection was initiated with four colonies. All colonies responded to selection; after seven to 12 selections, three colonies were combined (Select colony) and selection was conducted an additional 27 times. The corresponding base colonies were also combined and maintained for comparisons (Base). Concentration/mortality lines obtained for the Select and Base colonies after five and 27 selections indicated seven‐ and 9.2‐fold differences in LC₅₀ values respectively. Survival of the resistant strain varied with bioassay method and decreased in the order: clip cages on treated foliage > treated plastic cups with untreated mesh tops > treated plastic cups with treated mesh tops> treated cups with treated solid lids. The initial bioassay results with treated plastic cups suggested that the selection response was inadequate to allow the resistant strain to survive field rats of azinphosmethyl. When the resistant strain's survival was evaluated with bioassay methods more closely mimicking field conditions (clip cages on field‐treated foliage), we concluded the selected strain could survive field rates of azinphosmethyl.     

Mating compatibility, life-history traits, and RAPD-PCR variation in Bemisia tabaci associated with the cassava mosaic disease pandemic in East Africa

The pandemic of a severe form of cassava mosaic virus disease (CMVD) in East Africa is associated with abnormally high numbers of its whitefly vector, Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae). To determine whether a novel B. tabaci biotype was associated with the CMVD pandemic, reproductive compatibility, fecundity, nymphal development, and random amplified polymorphic DNA (RAPD) variability were examined in, and between, B. tabaci colonies collected from within the CMVD pandemic and non-pandemic zone in Uganda. In a series of reciprocal crosses carried out over two generations among the six CMVD pandemic and four non-pandemic zone cassava B. tabaci colonies, there was no evidence of mating incompatibility. All the crosses produced both female and male progeny in the F₁ and F₂ generations, which in a haplo-diploid species such as B. tabaci indicates successful mating. There also were no significant differences between the sex ratios for the pooled data of experimental crosses, between individuals from two different colonies and control crosses between individuals from the same colony. Only one instance of mating incompatibility occurred in a control cross between cassava B. tabaci from Uganda and cottonB. tabaci from India. Measures of fecundity of the pandemic and non-pandemic zone B. tabaci on four cassava varieties showed no significant differences in their fecundity, nymphal development or numbers surviving to adult eclosion. Cluster analysis of 26 RAPD bands using six 10-mer primers was concordant with the mating results, grouping the pandemic and non-pandemic zone colonies into a single large group, also including a B. tabaci colony collected from cassava in Tanzania. These results suggest that it is unlikely that the severe CMVD pandemic in East Africa is associated with a novel and reproductively isolated B. tabaci biotype.     

Analysing spatial and temporal variation in colony size: an approach using autoregressive mixed models and information theory

The spatial and temporal variation in population sizes of animal colonies are rarely studied simultaneously. I examined factors determining colony size (number of nests) for 23 colonies from the only breeding population of rook Corvus frugilegus in Spain over 7 years. Population sizes within colonies were highly predictable over time, with autocorrelations up to a distance (lag) of 6 years. Autoregressive mixed models were used to explain colony size as a function of environmental factors, while controlling for temporal autocorrelation. These factors included refuse tips, widely used as food resource, and a derived variable that incorporated the two factors most often related to avian colony size (inter-colony competition and foraging habitat around colonies). Autoregressive models provided a better fit to the data than models which did not consider temporal autocorrelation. The information-theoretic (AIC_c-based) approach revealed uncertainty in the selection of the best model explaining colony-size, but relatively strong support for certain variables. The highest weights of evidence were for year (ω _i  = 0.90) and the number of competitors per unit of foraging habitat (i.e., derived variable; ω _i  = 0.63), showing that the size of rook colonies in Spain was negatively affected by inter-colony competition relative to the foraging habitat surrounding the colonies. This variable measured within a 6-km radius from the colonies had ~30 times higher weight of evidence (more plausible) than the same variable measured within 3 km, indicating that food limitation may occur outside the breeding period. Sizes of colonies tended to decrease when distance between the colony and the nearest refuse tip increased. There was some evidence supporting the idea that the effect of the number of competitors per unit of foraging habitat on colony size varied from year to year, but statistical power was weak. These findings suggest that variation in number of rook nests within colonies reflects spatial and temporal heterogeneity of net food via both inter-colony competition and foraging habitat around the colony. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Intra-individual variation in the vocalized frequency of the Taiwanese leaf-nosed bat, Hipposideros terasensis, influenced by conspecific colony members

We examined the intra-individual variation in resting frequency of the constant-frequency component of the second harmonic of the pulse (F _rest) over 4 years in a laboratory colony of the Taiwanese leaf-nosed bat (Hipposideros terasensis). Patterns of change in F _rest were observed when individuals were added to or removed from the colony so that we investigated whether F _rest was affected by neighboring colony members. F _rest of each bat continually showed a long-term gradual change throughout the year, and all bats in the colony increased or decreased their F _rest in the same direction as a group non-seasonally. The greatest short-term changes were observed when new bats with a relatively low F _rest joined the colony and F _rest of new bats converged with those of the original colony members around 8 –16 days after their introduction. Conversely, a single individual showed sudden short-term decrease in F _rest after its isolation from other colony members. These findings strongly indicate that F _rest is flexible according to the presence of neighboring conspecific bats. We suggest that the audio-vocal feedback for conspecific pulses appears to be involved in the short- or long-term intra-individual variation in F _rest other than factors previously thought such as age or season.     

Ecological and genetic data indicate recovery of the endangered coral Acropora palmata in Los Roques, Southern Caribbean

The rapid decline of Acropora cervicornis and Acropora palmata has often been linked with coral reef deterioration in the Caribbean; yet, it remains controversial whether these species are currently recovering or still declining. In this study, the status of ten populations of A. palmata in Los Roques National Park (LRNP), Venezuela is presented. Six of these populations showed signs of recovery. Ten 80 m² belt-transects were surveyed at each of the ten reef sites. Within belt-transects, each colony was measured (maximum diameter and height) and its status (healthy, diseased or injured) was recorded. Populations in recovery were defined by a dominance of small to medium-sized colonies in densities >1 colony per 10 m², together with 75% undamaged colonies, a low prevalence of diseases (<10%), and a low density of predators (0.25 snails per colony). Based on allozyme analysis of seven polymorphic loci in four populations (N = 30), a moderate to high-genetic connectivity among these populations (F _ST = 0.048) was found with a predominance of sexual over asexual reproduction (N* : N = 1; N _go : N = 0.93–1). Both ecological and molecular data support a good prognosis for the recovery of this species in Los Roques.     

Diurnal changes in the photochemical efficiency of the symbiotic dinoflagellates (Dinophyceae) of corals: photoprotection, photoinactivation and the relationship to coral bleaching

The photochemical efficiency of symbiotic dinoflagellates within the tissues of two reef‐building corals in response to normal and excess irradiance at water temperatures < 30 °C were investigated using pulse amplitude modulated (PAM) chlorophyll fluorescence techniques. Dark‐adapted F_v/F_m showed clear diurnal changes, decreasing to a low at solar noon and increasing in the afternoon. However, F_v/F_m also drifted downwards at night or in prolonged darkness, and increased rapidly during the early morning twilight. This parameter also increased when the oxygen concentration of the water holding the corals was increased. Such changes have not been described previously, and most probably reflect state transitions associated with PQ pool reduction via chlororespiration. These unusual characteristics may be a feature of an endosymbiotic environment, reflective of the well‐documented night‐time tissue hypoxia that occurs in corals. F_v/F_m decreased to 0·25 in response to full sunlight in shade‐acclimated (shade) colonies of Stylophora pistillata, which is considerably lower than in light‐acclimated (sun) colonies. In sun colonies, the reversible decrease in F_v/F_m was caused by a lowering of F_m and F_o suggesting photoprotection and no lasting damage. The decrease in F_v/F_m, however, was caused by a decrease in F_m and an increase in F_o in shade colonies suggesting photoinactivation and long‐term cumulative photoinhibition. Shade colonies rapidly lost their symbiotic algae (bleached) during exposure to full sunlight. This study is consistent with the hypothesis that excess light leads to chronic damage of symbiotic dinoflagellates and their eventual removal from reef‐building corals. It is significant that this can occur with high light conditions alone.     

Gene flow is maintained by polyandry and male dispersal in the army ant <Emphasis Type="Italic">Eciton burchellii</Emphasis>

The combination of haplodiploidy, complementary sex determination and eusociality constrains the effective population size (N _e) of social Hymenoptera far more than in any other insect group. Additional limitations on N _e occur in army ants since they have wingless queens and colony fission, both of which are factors causing restricted maternal gene flow and high population viscosity. Therefore, winged army ant males gain a particular significance to ensure dispersal, facilitate gene flow and avoid inbreeding. Based on population genetic analyses with microsatellite markers, we studied a population of the Neotropical army ant Eciton burchellii, finding a high level of heterozygosity, weak population differentiation and no evidence for inbreeding. Moreover, by using sibship reconstruction analyses, we quantified the actual number of male contributing colonies represented in a queen’s mate sample, demonstrating that, through extreme multiple mating, the queens are able to sample the genes of males from up to ten different colonies, usually located within an approximate radius of 1 km. We finally correlated the individual mating success of each male contributing colony with the relative siring success of individual males and found a significant colony-dependent male fitness component. Our results imply that the dispersal and mating system of these army ants seem to enhance gene flow and minimise the deleterious effects associated with small effective population size. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Genetic structure in a swarming brown long-eared bat (<Emphasis Type="Italic">Plecotus auritus</Emphasis>) population: evidence for mating at swarming sites

Plecotus auritus, a small, gleaning bat species, lives in small, isolated summer colonies in which both males and females show a high degree of natal philopatry. Despite this, colonies have high gene diversities and low inbreeding coefficients. It has been suggested that inbreeding is avoided because mating occurs during autumnal and spring swarming at hibernation sites. We tested this hypothesis by comparing microsatellite profiles, based on eight loci, of bats from six summer colonies and two swarming sites they were known to visit from radiotelemetry studies. We found high gene diversities (H _s = 0.77) at both swarming sites and summer colonies which were not statistically different. There was no detectable isolation by distance and F_ST was low (0.001). Together, these results suggest high gene flow between sites. Despite this, there was small but significant genetic differentiation amongst summer colonies and between summer colonies and the primary swarming site. We suggest that swarming is important for gene flow and for maintaining genetic diversity in this highly philopatric species and discuss possible reasons for the genetic differentiation observed. The identification and protection of swarming sites should be a major conservation priority for this and other temperate bat species.     

Sexual and asexual colony foundation and the mechanism of facultative parthenogenesis in the termite <Emphasis Type="Italic">Reticulitermes speratus</Emphasis> (Isoptera,Rhinotermitidae)

Summary. Facultative parthenogenesis has great adaptive significance, especially with regard to low pairing efficiency. In the termite Reticulitermes speratus, females that fail to mate with males reproduce parthenogenetically and found colonies cooperatively with partner females or even alone. Comparison of colony foundation success at 400 days between colonies founded by single females (F), female-female pairs (FF), and male-female pairs (FM) showed that female-female cooperation promoted colony survivorship over monogamous foundation. We report here for the first time the mode of parthenogenesis in Isoptera. Combining chromosome observations and genetic analysis using microsatellites, we show that the mode of parthenogenesis is diploid thelytoky and that the restoration of ploidy is most likely accomplished by terminal fusion. Parthenogens show a higher mortality and a longer egg-development time than sexually produced offspring, probably due to reduced heterozygosity. In addition Wolbachia bacteria were detected in R. speratus. However, since Wolbachia was also detected in non-parthenogenetic R. flavipes, it is unlikely that Wolbachia is the cause of parthenogenesis in R. speratus.Received 30 October 2003; revised 4 March 2004; accepted 17 March 2004.     

Desiccation‐induced changes in photochemical processes of photosynthesis and spectral reflectance in Nostoc commune (Cyanobacteria,Nostocales) colonies from polar regions

Cyanobacterium Nostoc commune is a species highly resistant against desiccation. In this study, we investigated changes in photochemical processes of photosynthesis and spectral reflectance indices during controlled desiccation of the colonies from Antarctica. In a dehydration process, water potential (WP) reached ?3 MPa and values of potential (F _v/F _m) and effective quantum yields (ΦPSII) of photosystem II were kept to high value until 90% of water was lost from the colony, and these values decreased rapidly by further loss of water. This indicates that the colony loses water mostly from the exopolysaccharidic envelope, not from cells during the initial part of dehydration (relative water content, RWC = 100–10%). Other suggestions of inhibition of photosynthetic processes after 90% loss of water were the increase of the chlorophyll fluorescence parameter F _p/F _s. The F _m′ was higher than F _m in hydrated colonies because of state transition which change energy distribution between PS I and PS II, but decreased to same level as F _m in dehydrated colonies. The Normalized Difference Vegetation Index (NDVI) and Photochemical Reflectance Index (PRI) showed concave‐ and convex‐curvilinear relationship with RWC, respectively. The changes of NDVI values were, however, statistically insignificant. PRI values were predominantly below 0 because of phycobiliprotein involvement. These results were compared with the same species in the Arctic region. This is, according to our best knowledge, the first measurement of changes in spectral reflectance indices during desiccation of cyanobacteria.     

Domestication-related changes in sexual performance of Queensland fruit fly

In Sterile Insect Technique (SIT) programs, massive numbers of insects are reared, sterilized, and released in the field to impede reproduction of pest populations. The domestication and rearing processes used to produce insects for SIT programs may have significant evolutionary impacts on life history and reproductive biology. We assessed the effects of domestication on sexual performance of laboratory reared Queensland fruit fly, Bactrocera tryoni, by comparing an old (49 generations) and a young colony (5 generations). We evaluated mating propensity, mating latency, copula duration, sperm transfer, and ability to induce sexual inhibition in mates. Overall, both males and females from the old colony had greater mating propensity than those from the young colony. Copula duration was longer when females were from the old colony. There was no evidence of sexual isolation between the colonies as males and females from the two colonies had similar propensity to mate with flies from either colony. Males from the old colony transferred more sperm regardless of which colony their mate was from. Finally, males from both colonies were similarly able to induce sexual inhibition in their mates and were also similarly able to secure copulations with already-mated females. Positive effects of domestication on sperm transfer, coupled with maintained ability to induce sexual inhibition in mates and to secure copulations with previously mated females, highlights that domestication may have little effect, or even positive effects, on some aspects of sexual performance that may advantage mass-reared B. tryoni in SIT programs.     

Effects of Daphnia ‐Associated Infochemicals on the Morphology,Polysaccharides Content and PSII‐Efficiency in Scenedesmus obliquus

We investigated the effects of infochemicals from Daphnia carinata on the morphology, polysaccharides yield and PSII‐efficiency in Scenedesmus obliquus. Infochemicals released from D. carinata induced colony formation in S. obliquus. The contents of soluble extracellular polysaccharides, bounded extracellular polysaccharides, and the total polysaccharides per cell in the induced colonies of S. obliquus increased significantly relative to those of the unicells, which indicated that Daphnia ‐associated infochemicals could also stimulate S. obliquus to increase the synthesis of extracellular polysaccharides. The increased extracellular polysaccharides may play an important role in cementing S. obliquus cells together to form colonies. In addition, no significant differences in growth, the maximal efficiency of PSII photochemistry (F_v/F_m), and the effective quantum yields of PSII (Φ_PSII) were detected between unicellular and induced colonial populations, which showed that the cost of induced colony formation was not reflected on these indices. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Six weeks in the life of a reproducing army ant colony: male parentage and colony behaviour

The army ant Eciton burchellii is one of the most conspicuous ant species in New World tropical forests, but studies of colony life histories have been hampered by the nomadic lifestyle of these ants, which alternate between a nomadic phase when the colony relocates frequently, and a statary phase when the colony remains at a fixed site. Here we report on a colony from Venezuela that we studied continuously for six weeks, from the time that the queen produced a reproductive brood until the adult reproductives emerged and the colony entered the next cycle. Our findings support the contention that reproductive larvae develop faster than worker larvae, and that the nomadic phases of colonies with reproductive broods are significantly shorter than those of colonies with worker broods. This strongly suggests that the onset of pupation is linked to the onset of the statary phase. We used microsatellite genotyping to accurately identify male and queen larvae and we describe how they can be distinguished morphologically. Using the same genetic markers, we determined the parentage of 81 males produced by this colony. Only one of the males had a genotype that could not be directly derived from the observed queen genotype, but this mismatch is most probably due to a single mutation at one of the microsatellite loci, rather than this male being a worker son. We therefore conclude that this colony provides no evidence that workers lay eggs that develop into adult males in the presence of the queen, confirming the results of an earlier study on male parentage in an Old World army ant. Received 16 November 2006; revised 15 January 2007; accepted 16 January 2007.     

Genetic diversity and colony structure of Tapinoma melanocephalum on the islands and mainland of South China

Aim

Tapinoma melanocephalum is listed as one of the most important invasive pest species in China. Information regarding the patterns of invasion and effects of geographic isolation on the population genetics of this species is largely lacking.

Location

South China.

Methods

To address this problem, we genotyped 39 colonies (two colonies were collapsed due to genetic similarity) using microsatellite markers and mitochondrial DNA sequencing to compare colony genetic structure of T. melanocephalum on the mainland and islands of South China.

Results

An analysis of the colony genotypes showed that the genetic diversity of the mainland population was slightly higher than that of the island populations but not significantly so. However, the observed heterozygosity on Shangchuan Island (SCD) was significantly lower than that of the other colonies. We also found six haplotypes in 111 mitochondrial DNA COI sequences. The relatedness (r) value between colonies of SCD was 0.410, higher than that of the other populations. The genetic clusters among colonies were not related to geographic locations and exhibited admixture likely due to frequent human‐mediated dispersal associated with trade between the mainland population and the islands. Pairwise F_STs between populations showed differentiation among mainland populations, while SCD displayed high levels of divergence (F_ST > 0.15) from most mainland populations. There was no significant isolation by distance among colonies. Most populations showed signs of a bottleneck effect.

Main conclusions

Our study suggests that there was no significant difference in the genetic diversity among the islands and the mainland; however, the lower genetic diversity, the higher degree of genetic divergence from other colonies, and the higher relatedness among nestmates made the SCD population stand out from all the others.     

Population structure and interdemic selection in the cooperative spider Anelosimus eximius

The degree of relatedness among interacting individuals helps determine the fitness consequences of particular behaviors, whereas the partitioning (and amount) of genetic variation among and within groups controls the level at which selection will act most effectively. Three criteria are considered necessary for selection to act at the group or interdemic level: high rate of group initiation/extinction; differential survival and reproduction among groups; and highly subdivided population structure. The first two criteria have been demonstrated by earlier studies of Anelosimus eximius colonies. This study employs hierarchical analysis of allozyme polymorphisms to demonstrate the third criterion, subdivided population structure. Anelosimus eximius were collected from Suriname, Panama, Ecuador, Peru and Trinidad. Seven of 40 scorable enzyme loci revealed variation; 4 of these were polymorphic within colonies or regions. Expected heterozygosities were low, ranging from 0 (Ecuador, Peru) to ～0.03 (Suriname). For each polymorphic locus, hierarchical F -statistics were used to partition overall genetic variation into among-region (or among-population; F _rt ), among-colony ( F _sr ), and within-colony ( F _is ) components. Samples from Suriname (43 colonies, 4 local populations) were the most informative; lack of scorable variation limited the inferences that could be drawn from other regions. A. eximius colonies are highly inbred: negative estimates of F _is imply very small effective colony sizes (～6.5 for Suriname samples). By contrast, estimates of F _sr were very high: the mean for Suriname samples was 0.890, indicating neglibible gene flow among established colonies. Inbreeding within colonies, and genetic differentiation among colonies are consistent with demographic and behavioral observations of A. eximius . We suggest that interdemic selection is probable in this species and other cooperative spiders with this type of social system, and that mutual tolerance and absence of nest-mate recognition, as well as female-biased sex ratios, may have arisen by interdemic selection.     

Male parentage and queen mating frequency in the bumblebee <Emphasis Type="Italic">Bombus ignitus</Emphasis> (Hymenoptera: bombinae)

Kin selection theory predicts conflict between queens and workers in the social insect colony with respect to male production. This conflict arises from the haplodiploid system of sex determination in Hymenoptera that creates relatedness asymmetries in which workers are more closely related to the sons of other workers than to those of the queen. In annual hymenopteran societies that are headed by a single queen, the mating frequency of the queen is the only factor that affects the colony kin structure. Therefore, we examined the mating structure of queens and the parentage of males in a monogynous bumblebee, Bombus ignitus, using DNA microsatellites. In the seven colonies that were studied, B. ignitus queens mated once, thereby leading to the prediction of conflict between the queen and workers regarding male production. In each of the five queen-right colonies, the majority of the males (95%) were produced by the colony’s queen. In contrast, workers produced approximately 47% of all the males in two queenless colonies. These results suggest that male production in B. ignitus is a conflict between queen and workers.     

Population genetic structure and gene flow in a gleaning bat,Plecotus auritus

During summer the brown long-eared bat Plecotus auritus (Vespertilionidae) forms stable colonies, comprised of both adult females and males and young of the year. A long-term ringing study conducted in north-east Scotland has established that little movement occurs among colonies and that both sexes are recruited into their natal colony. The aim of the present study was to investigate, using microsatellite DNA markers, if genetic structure within the population reflects the spatial structure indicated by ringing. Inter-colony F_ST estimates obtained for all colony members, and for females and males separately, were low (0.019, 0.026 and 0.011, respectively), but all values differed significantly from zero. These data indicate high gene flow between colonies, although some coancestry among colony members is evident in both sexes. On combining the ringing and genetic data, it is concluded that gene flow occurs via extra-colony copulation, rather than natal dispersal, and that each colony behaves as a distinct subpopulation. Microgeographical genetic isolation by distance was demonstrated for, to our knowledge, the first time in a bat species, and found to be apparent both across the entire study area and along one river valley. The results suggest that extensive macrogeographical population genetic structure may be evident across the species'' range.     

Production of winged and wingless males in the ant, <Emphasis Type="Italic">Cardiocondyla minutior</Emphasis>

Summary Wingless (ergatoid) males of the tramp ant Cardiocondyla minutior attack and kill their young ergatoid rivals and thus attempt to monopolize mating with female sexuals reared in the colony. Because of the different strength of local mate competition in colonies with one or several reproductive queens, we expected the production of new ergatoid males to vary with queen number. Sex ratios were mostly female-biased, but in contrast to the sympatric species C. obscurior (Cremer and Heinze, 2002) neither the percentage of ergatoid males nor of female sexuals among the first 20 sexuals produced varied considerably with queen number. As in C. obscurior, experimental colony fragmentation led to the production of winged males, whereas in unfragmented control colonies only ergatoid males eclosed.Received 3 December 2003; revised 20 February 2004; accepted 23 February 2004.     

Behavior of ergatoid males in the ant,Cardiocondyla nuda

Summary Ergatoid males of the ant,Cardiocondyla nuda, attack and frequently kill young males during or shortly after eclosion. Smaller colonies therefore contain typically only one adult male, which may inseminate all alate queens which are reared in the colony over a few weeks. In larger colonies, several males may be present, however, fighting among adult males was not observed. We discuss the significance of male fighting behavior in ants.