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A heritable component in sex ratio and caste determination in a Cardiocondyla ant
Sabine Frohschammer, Jürgen Heinze
Frontiers in Zoology , 2009, DOI: 10.1186/1742-9994-6-27
Abstract: Because of the very short lifetime of their queens, ants of the genus Cardiocondyla are ideal model systems for the study of complete lifetime reproductive success, queen bias, and sex ratios. We found that lifetime sex ratios of the ant Cardiocondyla kagutsuchi have a heritable component. In experimental single-queen colonies, 22 queens from a genetic lineage with a highly female-biased sex ratio produced significantly more female-biased offspring sex ratios than 16 queens from a lineage with a more male-biased sex ratio (median 91.5% vs. 58.5% female sexuals). Sex ratio variation resulted from different likelihood of female larvae developing into sexuals (median 50% vs. 22.6% female sexuals) even when uniformly nursed by workers from another colony.Consistent differences in lifetime sex ratios and queen bias among queens of C. kagutsuchi suggest that heritable, genetic or maternal effects strongly affect caste determination. Such variation might provide the basis for adaptive evolution of queen and worker strategies, though it momentarily constrains the power of workers and queens to optimize caste ratios.Studies of intra- and interspecific variation of sex ratios in the social Hymenoptera (bees, wasps, and ants) provide among the most convincing support for the importance of inclusive fitness in evolution. Haplodiploid sex determination in the Hymenoptera (males arise from unfertilized eggs and females from fertilized eggs) results in a closer genetic relatedness of workers to their sexual sisters than to their brothers, while queens are equally related to their male and female offspring [1-3]. Consequently, workers in a colony with a single, singly-mated queen can optimize their inclusive fitness by allocating three times more resources into female than male sexuals, while the queens gain most from an equal sex allocation ratio. When queen numbers and queen mating frequencies vary among colonies relative to the population mean, evolution may lead to split sex ra
Queen pheromones in Temnothorax ants: control or honest signal?
Elisabeth Brunner, Johannes Kroiss, Andreas Trindl, Jürgen Heinze
BMC Evolutionary Biology , 2011, DOI: 10.1186/1471-2148-11-55
Abstract: We aimed at determining the tempo of the evolution of queen signals in two ways. First, we investigated whether queens of Temnothorax ants are capable of controlling egg laying by workers of their own, closely, and distantly related species. Second, we compared the species- and caste-specific patterns of cuticular hydrocarbons, which are assumed to convey information on reproductive status. In mixed-species colonies, queens were not able to fully suppress egg-laying and male production by workers of unrelated species, while workers did not reproduce under the influence of a queen from their own species. Furthermore, the chemical profiles differed more strongly among queens of different species than among the respective workers.Our results suggest that cuticular hydrocarbons associated with fecundity are not fully conserved in evolution and evolve slightly faster than worker-specific components in the blend of cuticular hydrocarbons. While this higher rate of evolution might reflect an arms race between queens and workers, the observation that workers still respond to the presence of a queen from another species support the honest signal hypothesis. Future studies need to examine alternative explanations for a higher rate of evolution of queen-specific substances, such as an involvement of such compounds in mating.The efficiency and integrity of the societies of ants, bees, and wasps relies on a well-controlled division of reproduction [1,2]. Workers rarely lay eggs in the presence of a fertile queen [3,4]. This is surprising, as workers are more closely related to their own sons (r = 0.5) than to the sons of the queen (r = 0.25) and in queenless conditions are usually capable of producing male offspring from their own, unfertilized eggs [5,6].Complete worker sterility benefits the queen, which should be selected to inhibit worker reproduction. However, overt aggression by the queen is very rare and appears restricted to very small colonies [7-10]. Instead, reproduct
Terminal Investment: Individual Reproduction of Ant Queens Increases with Age  [PDF]
Jürgen Heinze, Alexandra Schrempf
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0035201
Abstract: The pattern of age-specific fecundity is a key component of the life history of organisms and shapes their ecology and evolution. In numerous animals, including humans, reproductive performance decreases with age. Here, we demonstrate that some social insect queens exhibit the opposite pattern. Egg laying rates of Cardiocondyla obscurior ant queens increased with age until death, even when the number of workers caring for them was kept constant. Cardiocondyla, and probably also other ants, therefore resemble the few select organisms with similar age-specific reproductive investment, such as corals, sturgeons, or box turtles (e.g., [1]), but they differ in being more short-lived and lacking individual, though not social, indeterminate growth. Furthermore, in contrast to most other organisms, in which average life span declines with increasing reproductive effort, queens with high egg laying rates survived as long as less fecund queens.
Observation by microsatellite DNA analysis of sperm usage in naturally mated honeybee queens (Apis mellifera ligustica) over a period of two years  [cached]
Cristina Previtali,Graziella Bongioni,Cecilia Costa,Marco Lodesani
Italian Journal of Animal Science , 2010, DOI: 10.4081/ijas.2008.465
Abstract: The aim of this study was to observe sperm utilization in Apis mellifera ligustica naturally mated honeybee queens over a two year period. The study was conducted by microsatellite analysis of the progenies of 6 honeybee queens sampled during two consecutive egg-laying seasons (from June to October in the first year and from March to June in the second year). Four microsatellite markers were initially analysed. However, the most variable locus A76 alone was sufficient to distinguish the genotype of the queens and the patrilines of the six colonies. The effective number of matings based on the frequencies of the patrilines and corrected for the sample size, was computed and was 8.10, slightly lower than the number found by other authors. No significant differences were noted in the observed frequencies of the patrilines in the two reproductive seasons. Moreover, there was a similar distribution of the patrilines in the first month (June 2002) with respect to the last month (June 2003). These results indicated that there was a temporal conservation of the genetic structure of the colonies.
Asymmetric Dispersal and Colonization Success of Amazonian Plant-Ants Queens  [PDF]
Emilio M. Bruna, Thiago J. Izzo, Brian D. Inouye, Maria Uriarte, Heraldo L. Vasconcelos
PLOS ONE , 2011, DOI: 10.1371/journal.pone.0022937
Abstract: Background The dispersal ability of queens is central to understanding ant life-history evolution, and plays a fundamental role in ant population and community dynamics, the maintenance of genetic diversity, and the spread of invasive ants. In tropical ecosystems, species from over 40 genera of ants establish colonies in the stems, hollow thorns, or leaf pouches of specialized plants. However, little is known about the relative dispersal ability of queens competing for access to the same host plants. Methodology/Principal Findings We used empirical data and inverse modeling—a technique developed by plant ecologists to model seed dispersal—to quantify and compare the dispersal kernels of queens from three Amazonian ant species that compete for access to host-plants. We found that the modal colonization distance of queens varied 8-fold, with the generalist ant species (Crematogaster laevis) having a greater modal distance than two specialists (Pheidole minutula, Azteca sp.) that use the same host-plants. However, our results also suggest that queens of Azteca sp. have maximal distances that are four-sixteen times greater than those of its competitors. Conclusions/Significance We found large differences between ant species in both the modal and maximal distance ant queens disperse to find vacant seedlings used to found new colonies. These differences could result from interspecific differences in queen body size, and hence wing musculature, or because queens differ in their ability to identify potential host plants while in flight. Our results provide support for one of the necessary conditions underlying several of the hypothesized mechanisms promoting coexistence in tropical plant-ants. They also suggest that for some ant species limited dispersal capability could pose a significant barrier to the rescue of populations in isolated forest fragments. Finally, we demonstrate that inverse models parameterized with field data are an excellent means of quantifying the dispersal of ant queens.
Performance Evaluation of Naturally Mated and Instrumentally Inseminated Honeybee (Apis mellifera L.) Queens in Field Colonies
S. Abdulaziz,M. Al-Qarni,Brian H. Smith,Susan W. Cobey
Pakistan Journal of Biological Sciences , 2003,
Abstract: Apis mellifera queens were reared to evaluate the performance of Naturally Mated (NM) and instrumentally inseminated (II) queens, using Doolittle grafting method. A group of twelve queen cells was introduced to five frames nucleus colonies and virgins allowed to mate naturally. A second group of 14 queen cells was confined to cages and instrumentally inseminated once with 8 l of semen and placed back to their assigned nucleus colonies. At oviposition, nucleus colonies for both groups were transferred into a standard Langstroth hive filled with empty combs and all colonies were allowed to build up naturally into full-size colonies. A perusal of the data presented a slightly higher survival rate in NM queens but binary logistic regression test revealed no significant differences between the survival rates of both NM and II queens that ended up with 5 NM (41%) and 3 II (21.4%) queens after 23-months. A detail probe of ANOVA also indicated no significant difference in brood production which were recorded 1274.4 and 1304.3cm2 2-months after colony establishment, 1585.2 and 1534.6 cm2 during April 1997 and 1674.9 and 1541.5cm2 during spring 1998 for NM and II queens respectively. Likewise, honey production for NM remained statistically at par with that of II queens and was recorded 251.7 and 241.1 lbs. during fall season 1996 and 314.2 and 297.5 lbs. during fall 1997 for NM and II queens respectively.
Transcript levels of ten caste-related genes in adult diploid males of Melipona quadrifasciata (Hymenoptera, Apidae): a comparison with haploid males, queens and workers
Borges, Andreia A.;Humann, Fernanda C.;Campos, Lucio A. Oliveira;Tavares, Mara G.;Hartfelder, Klaus;
Genetics and Molecular Biology , 2011, DOI: 10.1590/S1415-47572011005000050
Abstract: in hymenoptera, homozygosity at the sex locus results in the production of diploid males. in social species, these pose a double burden by having low fitness and drawing resources normally spent for increasing the work force of a colony. yet, diploid males are of academic interest as they can elucidate effects of ploidy (normal males are haploid, whereas the female castes, the queens and workers, are diploid) on morphology and life history. herein we investigated expression levels of ten caste-related genes in the stingless bee melipona quadrifasciata, comparing newly emerged and 5-day-old diploid males with haploid males, queens and workers. in diploid males, transcript levels for dunce and paramyosin were increased during the first five days of adult life, while those for diacylglycerol kinase and the transcriptional co-repressor groucho diminished. two general trends were apparent, (i) gene expression patterns in diploid males were overall more similar to haploid ones and workers than to queens, and (ii) in queens and workers, more genes were up-regulated after emergence until day five, whereas in diploid and especially so in haploid males more genes were down-regulated. this difference between the sexes may be related to longevity, which is much longer in females than in males.
Morphological caste studies in the neotropical swarm-founding Polistinae wasp Angiopolybia pallens (Lepeletier) (Hymenoptera: Vespidae)
Gelin, Luiz F.F.;Cruz, Jucelho D. da;Noll, Fernando B.;Giannotti, Edilberto;Santos, Gilberto M. de M.;Bichara-Filho, Carlos C.;
Neotropical Entomology , 2008, DOI: 10.1590/S1519-566X2008000600011
Abstract: neotropical swarm-founding wasps present polygynic colonies and a great variation in relation to caste differentiation, ranging from species in which queens and workers are similar in shape and size to those where variation in shape and size is conspicuous. canonical discriminant analysis and bonferroni t-test analysis on morphometric data collected from eight body parts of specimens from nine colonies of angiopolybia pallens (lepeletier) were undertaken as a step towards to a better understanding on caste differenciation in epiponini. all specimens were dissected to verify the ovary developmental stage, and the spermatheca was removed to check for the mating status. females were then grouped as queens (mated with developed ovaries), intermediates (virgin with developed ovaries) and workers (virgin with undeveloped ovaries). even though differences were found for some measurements in seven out of the nine colonies evaluated, multivariate analysis (wilks' lambda values) indicated castes could not be reliably distinguished only by morphology. we conclude that morphological differences among a. pallens castes are low or absent, reflecting a possible groundplan for the epiponini, i.e. a post-imaginal pattern of caste differentiation.
Patterns of DNA Methylation in Development, Division of Labor and Hybridization in an Ant with Genetic Caste Determination  [PDF]
Chris R. Smith, Navdeep S. Mutti, W. Cameron Jasper, Agni Naidu, Christopher D. Smith, Jürgen Gadau
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0042433
Abstract: Background DNA methylation is a common regulator of gene expression, including acting as a regulator of developmental events and behavioral changes in adults. Using the unique system of genetic caste determination in Pogonomyrmex barbatus, we were able to document changes in DNA methylation during development, and also across both ancient and contemporary hybridization events. Methodology/Principal Findings Sodium bisulfite sequencing demonstrated in vivo methylation of symmetric CG dinucleotides in P. barbatus. We also found methylation of non-CpG sequences. This validated two bioinformatics methods for predicting gene methylation, the bias in observed to expected ratio of CpG dinucleotides and the density of CpG/TpG single nucleotide polymorphisms (SNP). Frequencies of genomic DNA methylation were determined for different developmental stages and castes using ms-AFLP assays. The genetic caste determination system (GCD) is probably the product of an ancestral hybridization event between P. barbatus and P. rugosus. Two lineages obligately co-occur within a GCD population, and queens are derived from intra-lineage matings whereas workers are produced from inter-lineage matings. Relative DNA methylation levels of queens and workers from GCD lineages (contemporary hybrids) were not significantly different until adulthood. Virgin queens had significantly higher relative levels of DNA methylation compared to workers. Worker DNA methylation did not vary among developmental stages within each lineage, but was significantly different between the currently hybridizing lineages. Finally, workers of the two genetic caste determination lineages had half as many methylated cytosines as workers from the putative parental species, which have environmental caste determination. Conclusions/Significance These results suggest that DNA methylation may be a conserved regulatory mechanism moderating division of labor in both bees and ants. Current and historic hybridization appear to have altered genomic methylation levels suggesting a possible link between changes in overall DNA methylation and the origin and regulation of genetic caste determination in P. barbatus.
Bigger Helpers in the Ant Cataglyphis bombycina: Increased Worker Polymorphism or Novel Soldier Caste?  [PDF]
Mathieu Molet, Vincent Maicher, Christian Peeters
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0084929
Abstract: Introduction The mechanisms by which development favors or constrains the evolution of new phenotypes are incompletely understood. Polyphenic species may benefit from developmental plasticity not only regarding ecological advantages, but also potential for evolutionary diversification. For instance, the repeated evolution of novel castes in ants may have been facilitated by the existence of alternative queen and worker castes and their respective developmental programs. Material and Methods Cataglyphis bombycina is exceptional in its genus because winged queens and size-polymorphic workers occur together with bigger individuals having saber-shaped mandibles. We measured seven body parts in more than 150 individuals to perform a morphometric analysis and assess the developmental origin of this novel phenotype. Results Adults with saber-shaped mandibles differ from both workers and queens regarding the size of most body parts. Their relative growth rates are identical to workers for some pairs of body parts, and identical to queens for other pairs of body parts; critical sizes differ in all cases. Conclusions Big individuals are a third caste, i.e. soldiers, not major workers. Novel traits such as elongated mandibles are combined with a mix of queen and worker growth rates. We also reveal the existence of a dimorphism in the queen caste (microgynes and macrogynes). We discuss how novel phenotypes can evolve more readily in the context of an existing polyphenism. Both morphological traits and growth rules from existing queen and worker castes can be recombined, hence mosaic phenotypes are more likely to be viable. In C. bombycina, such a mosaic phenotype appears to function both for defense (saber-shaped mandibles) and fat storage (big abdomen). Recycling of developmental programs may have contributed to the morphological diversity and ecological success of ants.
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