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Laurent Keller - One of the best experts on this subject based on the ideXlab platform.
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re in social insect
2015Co-Authors: Ne Beekman, Benjamin P Oldroyd, Tanja Schw, Laurent KellerAbstract:Reviewthat the majority of social insect species are characterized by ‘strict ’ environmental Caste Determination (ECD). Rather, it appears that Caste Determination systems vary along a continuum from ECD to genetic Caste determi-nation (GCD), where environmental factors no longer affect an individual’s Caste fate. We describe the proximate basis for genotype–Caste associations in the species where genetic effects on Castes are known to occur, and evaluate mechanisms generating and maintaining variation in Caste predisposition. Although we focus solely on the bifur-cation between royals and workers, most of the presented arguments should also apply to differentiation among worker Castes, such as that found between specialized soldiers and nurses. ducted in the western honey bee (Apis mellifera), a species generally recognized as having strict ECD. Independent experiments have revealed that a large amount of food, or a protein rich diet, are a necessary and sufficient condition for the development of new queens [9–12]. Queen devel-opment can also be induced by down-regulation of a DNA Glossary Environmental Caste Determination (ECD): a system of queen and worker differentiation that is determined by environmental stimuli and largely insensitive to genetic factors (phenotypic plasticity). Genetic Caste Determination (GCD): a system of queen and worker differentia-tion where an individual’s genotype predicts its Caste. Environmental stimuli do not affect the Caste fate of a given genotype although they might determine which set of genotypes are raised. Intermorphic queens: reproductive females morphologically intermediate between a typical queen and a typical worker. Queen traits include, for example, the presence of a spermatheca and large ovaries, worker traits include the lack of wings and associated thoracic structures and the absence (or reduction) of ocelli
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Genetic components to Caste allocation in a multiple-queen ant species.
Evolution, 2011Co-Authors: Romain Libbrecht, Tanja Schwander, Laurent KellerAbstract:Reproductive division of labor and the coexistence of distinct Castes are hallmarks of insect societies. In social insect species with multiple queens per colony, the fitness of nestmate queens directly depends on the process of Caste allocation (i.e., the relative investment in queen, sterile worker and male production). The aim of this study is to investigate the genetic components to the process of Caste allocation in a multiple-queen ant species. We conducted controlled crosses in the Argentine ant Linepithema humile and established single-queen colonies to identify maternal and paternal family effects on the relative production of new queens, workers, and males. There were significant effects of parental genetic backgrounds on various aspects of Caste allocation: the paternal lineage affected the proportion of queens and workers produced whereas the proportions of queens and males, and females and males were influenced by the interaction between parental lineages. In addition to revealing nonadditive genetic effects on female Caste Determination in a multiple-queen ant species, this study reveals strong genetic compatibility effects between parental genomes on Caste allocation components.
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genetic compatibility affects queen and worker Caste Determination
Science, 2008Co-Authors: Tanja Schwander, Laurent KellerAbstract:The development of queen and worker phenotypes in ants has been believed to be largely determined from environmental effects. We provide evidence that the production of discrete phenotypes is also influenced by genetic interaction effects. During the development of eggs into adults, some patrilines among offspring of multiply mated Pogonomyrmex rugosus ant queens became more common in workers while others became overrepresented in queens. Controlled crosses showed that these changes stem from some parental genome combinations being compatible for producing one phenotype but less compatible for the other. Genetic interaction effects on Caste may be maintained over evolutionary time because the fitness of an allele depends on its genetic background.
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maternal effect on female Caste Determination in a social insect
Current Biology, 2008Co-Authors: Tanja Schwander, Sara Helms Cahan, Jeanyves Humbert, Colin S Brent, Lucille Chapuis, Emanuela Renai, Laurent KellerAbstract:Caste differentiation and division of labor are the hallmarks of social insect colonies [1, 2]. The current dogma for female Caste differentiation is that female eggs are totipotent, with morphological and physiological differences between queens and workers stemming from a developmental switch during the larval stage controlled by nutritional and other environmental factors (e.g., [3-8]). In this study, we tested whether maternal effects influence Caste differentiation in Pogonomyrmex harvester ants. By conducting crossfostering experiments we identified two key factors in the process of Caste Determination. New queens were produced only from eggs laid by queens exposed to cold. Moreover, there was a strong age effect, with development into queens occurring only in eggs laid by queens that were at least two years old. Biochemical analyses further revealed that the level of ecdysteroids was significantly lower in eggs developing into queens than workers. By contrast, we found no significant effect of colony size or worker exposure to cold, suggesting that the trigger for Caste differentiation may be independent of the quantity and quality of resources provided to larvae. Altogether these data demonstrate that the developmental fate of female brood is strongly influenced by maternal effects in ants of the genus Pogonomyrmex.
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characterization and distribution of pogonomyrmex harvester ant lineages with genetic Caste Determination
Molecular Ecology, 2006Co-Authors: Tanja Schwander, Sara Helms Cahan, Laurent KellerAbstract:Genetic Caste Determination has been described in two populations of Pogonomyrmex harvester ants, each comprising a pair of interbreeding lineages. Queens mate with males of their own and of the alternate lineage and produce two types of diploid offspring, those fertilized by males of the queens' lineage which develop into queens and those fertilized by males of the other lineage which develop into workers. Each of the lineages has been shown to be itself of hybrid origin between the species Pogonomyrmex barbatus and Pogonomyrmex rugosus, which both have typical, environmentally determined Caste differentiation. In a large scale genetic survey across 35 sites in Arizona, New Mexico and Texas, we found that genetic Caste Determination associated with pairs of interbreeding lineages occurred frequently (in 26 out of the 35 sites). Overall, we identified eight lineages with genetic Caste Determination that always co-occurred in the same complementary lineage pairs. Three of the four lineage pairs appear to have a common origin while their relationship with the fourth remains unclear. The level of genetic differentiation among these eight lineages was significantly higher than the differentiation between P. rugosus and P. barbatus, which questions the appropriate taxonomic status of these genetic lineages. In addition to being genetically isolated from one another, all lineages with genetic Caste Determination were genetically distinct from P. rugosus and P. barbatus, even when colonies of interbreeding lineages co-occurred with colonies of either putative parent at the same site. Such nearly complete reproductive isolation between the lineages and the species with environmental Caste Determination might prevent the genetic Caste Determination system to be swept away by gene flow.
Chris Smith - One of the best experts on this subject based on the ideXlab platform.
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patterns of dna methylation in development division of labor and hybridization in an ant with genetic Caste Determination
PLOS ONE, 2012Co-Authors: Chris Smith, Navdeep S Mutti, Cameron W Jasper, Agni Naidu, Christopher D Smith, Juergen GadauAbstract: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.
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Caste Determination in a polymorphic social insect nutritional social and genetic factors
The American Naturalist, 2008Co-Authors: Chris Smith, Juergen Gadau, Kirk E Anderson, Chadwick V Tillberg, Andrew V SuarezAbstract:Abstract: We examined how dietary, social, and genetic factors affect individual size and Caste in the Florida harvester ant Pogonomyrmex badius, which has three discrete female Castes. The diet that a larva consumed, as indicated by δ13C, δ15N, and C:N, varied with Caste. Both N content and estimated trophic position of dietary input was higher for major than for minor workers and was highest for gynes (reproductive females). The size and resources of a colony affected the size of only minor workers, not that of gynes and major workers. Approximately 19% of patrilines showed a bias in which female Caste they produced. There were significant genetic effects on female size, and the average sizes of a major worker and a gyne produced by a patriline were correlated, but neither was correlated with minor worker size. Thus, genetic factors influence both Caste and size within Caste. We conclude that environmental, social, and genetic variation interact to create morphological and physiological variation among ...
Kirk E Anderson - One of the best experts on this subject based on the ideXlab platform.
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phylogeography of pogonomyrmex barbatus and p rugosus harvester ants with genetic and environmental Caste Determination
Ecology and Evolution, 2015Co-Authors: Juergen Gadau, Kirk E Anderson, Brendon M MottAbstract:We present a phylogeographic study of at least six reproductively isolated lineages of new world harvester ants within the Pogonomyrmex barbatus and P. rugosus species group. The genetic and geographic relationships within this clade are complex: Four of the identified lineages show genetic Caste Determination (GCD) and are divided into two pairs. Each pair has evolved under a mutualistic system that necessitates sympatry. These paired lineages are dependent upon one another because their GCD requires interlineage matings for the production of F1 hybrid workers, and intralineage matings are required to produce queens. This GCD system maintains genetic isolation among these interdependent lineages, while simultaneously requiring co-expansion and emigration as their distributions have changed over time. It has also been demonstrated that three of these four GCD lineages have undergone historical hybridization, but the narrower sampling range of previous studies has left questions on the hybrid parentage, breadth, and age of these groups. Thus, reconstructing the phylogenetic and geographic history of this group allows us to evaluate past insights and hypotheses and to plan future inquiries in a more complete historical biogeographic context. Using mitochondrial DNA sequences sampled across most of the morphospecies’ ranges in the U.S.A. and Mexico, we conducted a detailed phylogeographic study. Remarkably, our results indicate that one of the GCD lineage pairs has experienced a dramatic range expansion, despite the genetic load and fitness costs of the GCD system. Our analyses also reveal a complex pattern of vicariance and dispersal in Pogonomyrmex harvester ants that is largely concordant with models of late Miocene, Pliocene, and Pleistocene range shifts among various arid-adapted taxa in North America.
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Caste Determination in a polymorphic social insect nutritional social and genetic factors
The American Naturalist, 2008Co-Authors: Chris Smith, Juergen Gadau, Kirk E Anderson, Chadwick V Tillberg, Andrew V SuarezAbstract:Abstract: We examined how dietary, social, and genetic factors affect individual size and Caste in the Florida harvester ant Pogonomyrmex badius, which has three discrete female Castes. The diet that a larva consumed, as indicated by δ13C, δ15N, and C:N, varied with Caste. Both N content and estimated trophic position of dietary input was higher for major than for minor workers and was highest for gynes (reproductive females). The size and resources of a colony affected the size of only minor workers, not that of gynes and major workers. Approximately 19% of patrilines showed a bias in which female Caste they produced. There were significant genetic effects on female size, and the average sizes of a major worker and a gyne produced by a patriline were correlated, but neither was correlated with minor worker size. Thus, genetic factors influence both Caste and size within Caste. We conclude that environmental, social, and genetic variation interact to create morphological and physiological variation among ...
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distribution and evolution of genetic Caste Determination in pogonomyrmex seed harvester ants
Ecology, 2006Co-Authors: Kirk E Anderson, Jurgen Gadau, Brendon M Mott, Robert A Johnson, Annette Altamirano, Christophpeter Strehl, Jennifer H FewellAbstract:We examined the distribution and ancestral relationships of genetic Caste Determination (GCD) in 46 populations of the seed-harvester ants Pogonomyrmex barbatus and P. rugosus across the east-to-west range of their distributions. Using a mtDNA sequence and two nuclear markers diagnostic for GCD, we distinguished three classes of population phenotypes: those with GCD, no evidence of GCD, and mixed (both GCD and non-GCD colonies present). The GCD phenotype was geographically widespread across the range of both morphospecies, occurring in 20 of 46 sampled populations. Molecular data suggest three reproductively isolated and cryptic lineages within each morphospecies, and no present hybridization. Mapping the GCD phenotype onto a mtDNA phylogeny indicates that GCD in P. rugosus was acquired from P. barbatus, suggesting that interspecific hybridization may not be the causal agent of GCD, but may simply provide an avenue for GCD to spread from one species (or subspecies) to another. We hypothesize that the origin of GCD involved a genetic mutation with a major effect on Caste Determination. This mutation generates genetic conflict and results in the partitioning and maintenance of distinct allele (or gene set) combinations that confer differences in developmental Caste fate. The outcome is two dependent lineages within each population; inter-lineage matings produce workers, while intra-lineage matings produce reproductives. Both lineages are needed to produce a Caste-functional colony, resulting in two reproductively isolated yet interdependent lineages. Pogonomyrmex populations composed of dependent lineages provide a unique opportunity to investigate genetic variation underlying phenotypic plasticity and its impact on the evolution of social structure.
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behavioral regulation of genetic Caste Determination in a pogonomyrmex population with dependent lineages
Ecology, 2006Co-Authors: Rebecca M Clark, Kirk E Anderson, Jurgen Gadau, Jennifer H FewellAbstract:The fate of a social insect colony is partially determined by its ability to allocate individuals to the Caste most appropriate for the requirements for growth, maintenance, and reproduction. In pairs of dependent lineages of Pogonomyrmex barbatus, the allocation of individuals to the queen or worker Caste is constrained by genotype, a system known as genetic Caste Determination (GCD). In mature GCD colonies, interlineage female eggs develop into sterile workers, while intralineage eggs become reproductively capable queens. Although the population-level consequences of this system have been intensively studied, the proximate mechanisms for GCD remain unknown. To elucidate these mechanisms, we brought newly mated queens into the laboratory and allowed them to establish colonies, nearly half of which unexpectedly produced virgin queens only seven months after colony founding. We genotyped eggs, workers, and the virgin queens from these colonies. Our results showed that queens in young colonies produce both interlineage and intralineage eggs, demonstrating that queens of GCD colonies indiscriminately use sperm of at least two lineages to fertilize their eggs. Intralineage eggs were more frequent in colonies producing virgin queens. These findings suggest that intralineage eggs are predetermined to become queens and that workers may cull these eggs when colonies are not producing queens. Virgin queens produced by young GCD colonies were smaller than field-caught virgin queens, and often had developmental problems. Hence, they are probably nonfunctional and represent an intense resource drain for developing colonies, not a contribution to colony fitness.
Andrew F G Bourke - One of the best experts on this subject based on the ideXlab platform.
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micrornas associated with Caste Determination and differentiation in a primitively eusocial insect
Scientific Reports, 2017Co-Authors: David Collins, Irina Mohorianu, Matthew Beckers, Vincent Moulton, Tamas Dalmay, Andrew F G BourkeAbstract:In eusocial Hymenoptera (ants, bees and wasps), queen and worker adult Castes typically arise via environmental influences. A fundamental challenge is to understand how a single genome can thereby produce alternative phenotypes. A powerful approach is to compare the molecular basis of Caste Determination and differentiation along the evolutionary trajectory between primitively and advanced eusocial species, which have, respectively, relatively undifferentiated and strongly differentiated adult Castes. In the advanced eusocial honeybee, Apis mellifera, studies suggest that microRNAs (miRNAs) play an important role in the molecular basis of Caste Determination and differentiation. To investigate how miRNAs affect Caste in eusocial evolution, we used deep sequencing and Northern blots to isolate Caste-associated miRNAs in the primitively eusocial bumblebee Bombus terrestris. We found that the miRNAs Bte-miR-6001-5p and -3p are more highly expressed in queen- than in worker-destined late-instar larvae. These are the first Caste-associated miRNAs from outside advanced eusocial Hymenoptera, so providing evidence for Caste-associated miRNAs occurring relatively early in eusocial evolution. Moreover, we found little evidence that miRNAs previously shown to be associated with Caste in A. mellifera were differentially expressed across Caste pathways in B. terrestris, suggesting that, in eusocial evolution, the Caste-associated role of individual miRNAs is not conserved.
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differential gene expression in queen worker Caste Determination in bumble bees
Proceedings of The Royal Society B: Biological Sciences, 2005Co-Authors: J J M Pereboom, William C Jordan, Seirian Sumner, Robert L Hammond, Andrew F G BourkeAbstract:Investigating how differential gene expression underlies Caste Determination in the social Hymenoptera is central to understanding how variation in gene expression underlies adaptive phenotypic diversity. We investigated for the first time the association between differential gene expression and queen–worker Caste Determination in the bumble-bee Bombus terrestris. Using suppression subtractive hybridization we isolated 12 genes that were differentially expressed in queen- and worker-destined larvae. We found that the sets of genes underlying Caste differences in larvae and adults failed to overlap greatly. We also found that B. terrestris shares some of the genes whose differential expression is associated with Caste Determination in the honeybee, Apis mellifera, but their expression patterns were not identical. Instead, we found B. terrestris to exhibit a novel pattern, whereby most genes upregulated (i.e. showing relatively higher levels of expression) in queen-destined larvae early in development were upregulated in worker-destined larvae late in development. Overall, our results suggest that Caste Determination in B. terrestris involves a difference not so much in the identity of genes expressed by queen- and worker-destined larvae, but primarily in the relative timing of their expression. This conclusion is of potential importance in the further study of phenotypic diversification via differential gene expression.
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kin conflict over Caste Determination in social hymenoptera
Behavioral Ecology and Sociobiology, 1999Co-Authors: Andrew F G Bourke, Francis L W RatnieksAbstract:We argue that Caste Determination, the process whereby females in the social Hymenoptera develop into either queens or workers, is subject to kin-selected conflict. Potential conflict arises because developing females are more closely related to their would-be offspring than to those of other females. Therefore, they may favour becoming queens contrary to the interests of other developing females and of existing queens and workers. We suggest two contexts leading to potential Caste conflict. The first occurs when queens are reared in a reproductive phase following an ergonomic phase of worker production, while the second occurs when queens and workers are reared simultaneously. The first context assumes that workers' per capita contribution to colony survival and productivity falls with rising colony size. A critical feature influencing whether potential conflict is realized is the extent to which developing females can determine their own Caste (“self-Determination”). Self-Determination is facilitated when female larvae control their own food intake and when queen-worker size dimorphism is low. We know of no strong evidence for actual conflict over Caste fate arising in the first context. However, stingless bees and polygynous ants with excess queen-potential larvae that are either forced to develop as workers or are culled as adults demonstrate actual Caste conflict in the second context. Caste conflict does not preclude Caste regulation for “the good of the colony”, but such regulation is contingent on either the absence of potential conflict or on developing females losing control of their Caste fate.
Juergen Gadau - One of the best experts on this subject based on the ideXlab platform.
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phylogeography of pogonomyrmex barbatus and p rugosus harvester ants with genetic and environmental Caste Determination
Ecology and Evolution, 2015Co-Authors: Juergen Gadau, Kirk E Anderson, Brendon M MottAbstract:We present a phylogeographic study of at least six reproductively isolated lineages of new world harvester ants within the Pogonomyrmex barbatus and P. rugosus species group. The genetic and geographic relationships within this clade are complex: Four of the identified lineages show genetic Caste Determination (GCD) and are divided into two pairs. Each pair has evolved under a mutualistic system that necessitates sympatry. These paired lineages are dependent upon one another because their GCD requires interlineage matings for the production of F1 hybrid workers, and intralineage matings are required to produce queens. This GCD system maintains genetic isolation among these interdependent lineages, while simultaneously requiring co-expansion and emigration as their distributions have changed over time. It has also been demonstrated that three of these four GCD lineages have undergone historical hybridization, but the narrower sampling range of previous studies has left questions on the hybrid parentage, breadth, and age of these groups. Thus, reconstructing the phylogenetic and geographic history of this group allows us to evaluate past insights and hypotheses and to plan future inquiries in a more complete historical biogeographic context. Using mitochondrial DNA sequences sampled across most of the morphospecies’ ranges in the U.S.A. and Mexico, we conducted a detailed phylogeographic study. Remarkably, our results indicate that one of the GCD lineage pairs has experienced a dramatic range expansion, despite the genetic load and fitness costs of the GCD system. Our analyses also reveal a complex pattern of vicariance and dispersal in Pogonomyrmex harvester ants that is largely concordant with models of late Miocene, Pliocene, and Pleistocene range shifts among various arid-adapted taxa in North America.
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patterns of dna methylation in development division of labor and hybridization in an ant with genetic Caste Determination
PLOS ONE, 2012Co-Authors: Chris Smith, Navdeep S Mutti, Cameron W Jasper, Agni Naidu, Christopher D Smith, Juergen GadauAbstract: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.
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origin and evolution of the dependent lineages in the genetic Caste Determination system of pogonomyrmex ants
Evolution, 2011Co-Authors: Anu Sirvio, Robert A Johnson, Pekka Pamilo, Robert E Page, Juergen GadauAbstract:: Hybridizing harvester ants of the Pogonomyrmex barbatus/rugosus complex have an exceptional genetic Caste Determination (GCD) mechanism. We combined computer simulations, population genomics, and linkage mapping using >1000 nuclear AFLP markers and a partial mtDNA sequence to explore the genetic architecture and origin of the dependent lineages. Our samples included two pairs of hybridizing lineages, and the mitochondrial and nuclear data showed contradicting affinities between them. Clustering of individual genotypes based on nuclear markers indicated some exceptions to the general GCD system, that is, interlineage hybrid genes as well as some pure-line workers. A genetic linkage map of P. rugosus showed one of the highest recombination rates ever measured in insects (14.0 cM/Mb), supporting the view that social insects are characterized by high recombination rates. The population data had 165 markers in which sibling pairs showed a significant genetic difference depending on the Caste. The differences were scattered in the genome; 13 linkage groups had loci with F(ST)>0.9 between the hybridizing lineages J1 and J2.The mapping results and the population data indicate that the dependent lineages have been initially formed through hybridization at different points in time but the role of introgression has been insignificant in their later evolution.
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Caste Determination in a polymorphic social insect nutritional social and genetic factors
The American Naturalist, 2008Co-Authors: Chris Smith, Juergen Gadau, Kirk E Anderson, Chadwick V Tillberg, Andrew V SuarezAbstract:Abstract: We examined how dietary, social, and genetic factors affect individual size and Caste in the Florida harvester ant Pogonomyrmex badius, which has three discrete female Castes. The diet that a larva consumed, as indicated by δ13C, δ15N, and C:N, varied with Caste. Both N content and estimated trophic position of dietary input was higher for major than for minor workers and was highest for gynes (reproductive females). The size and resources of a colony affected the size of only minor workers, not that of gynes and major workers. Approximately 19% of patrilines showed a bias in which female Caste they produced. There were significant genetic effects on female size, and the average sizes of a major worker and a gyne produced by a patriline were correlated, but neither was correlated with minor worker size. Thus, genetic factors influence both Caste and size within Caste. We conclude that environmental, social, and genetic variation interact to create morphological and physiological variation among ...