Interdemic Selection Research Articles

Unexpected but welcome. Artificially selected traits may increase fitness in wild boar.

Artificial selection affects phenotypes differently by natural selection. Domestic traits, which pass into the wild, are usually negatively selected. Yet, exceptionally, this axiom may fail to apply if genes, from the domestic animals, increase fertility in the wild. We studied a rare case of a wild boar population under the framework of Wright's interdemic selection model, which could explain gene flow between wild boar and pig, both considered as demes. We analysed the MC1R gene and microsatellite neutral loci in 62 pregnant wild boars as markers of hybridization, and we correlated nucleotide mutations on MC1R (which are common in domestic breeds) to litter size, as an evaluation of fitness in wild sow. Regardless of body size and phyletic effects, wild boar sows bearing nonsynonymous MC1R mutations produced larger litters. This directly suggests that artificially selected traits reaching wild populations, through interdemic gene flow, could bypass natural selection if and only if they increase the fitness in the wild.

Macroevolution of symbiosis as self-organization of superspecies system controlled by natural selection

Mutualistic symbioses are convenient models for analyzing the ecological-genetic mechanisms of progressive evolution, which remains obscure for unitary (free-living) organisms. In the system of legume-rhizobia symbiosis, the hosting of N2-fixing bacteria within extracellular and intracellular compartments of nodules (infection threads, symbiosomes) acquired by plants during their coevolution with microbes induces in their populations, group selection is in favor of mutualistic traits (complete transfer of fixed nitrogen to hosts, differentiation of bacteria into the nonreproducible bacteroids). The colonization of infection threads by rhizobia increases the clonality in their populations that induce the interdeme selection for elevated nitrogenase activity. Its further increase may be due to colonization of symbiosomes, which induces the selection of kin in microbial populations in favor of irreversible bacteroid differentiation. The impact of these selection modes on bacteria resulted in the transition of anodular (rhizospheric, endophytic) plant-microbe associations based on the stimulation of root growth by auxins into nodular symbioses based on the effects of nitrogen fixation.

Pluralism in evolutionary controversies: styles and averaging strategies in hierarchical selection theories

Two controversies exist regarding the appropriate characterization of hierarchical and adaptive evolution in natural populations. In biology, there is the Wright–Fisher controversy over the relative roles of random genetic drift, natural selection, population structure, and interdemic selection in adaptive evolution begun by Sewall Wright and Ronald Aylmer Fisher. There is also the Units of Selection debate, spanning both the biological and the philosophical literature and including the impassioned group-selection debate. Why do these two discourses exist separately, and interact relatively little? We postulate that the reason for this schism can be found in the differing focus of each controversy, a deep difference itself determined by distinct general styles of scientific research guiding each discourse. That is, the Wright–Fisher debate focuses on adaptive process, and tends to be instructed by the mathematical modeling style, while the focus of the Units of Selection controversy is adaptive product, and is typically guided by the function style. The differences between the two discourses can be usefully tracked by examining their interpretations of two contested strategies for theorizing hierarchical selection: horizontal and vertical averaging.

PHASE III OF WRIGHT'S SHIFTING BALANCE PROCESS AND THE VARIANCE AMONG DEMES IN MIGRATION RATE

Interdemic selection by the differential migration of individuals out from demes of high fitness and into demes of low fitness (Phase III) is one of the most controversial aspects of Wright's Shifting Balance Theory. I derive a relationship between Phase III migration and the interdemic selection differential, S, and show its potential effect on FST . The relationship reveals a diversifying effect of interdemic selection by Phase III migration on the genetic structure of a metapopulation. Using experimental metapopulations, I explored the effect of Phase III migration on FST by comparing the genetic variance among demes for two different patterns of migration: (1) island model migration and (2) Wright's Phase III migration. Although mean migration rates were the same, I found that the variance among demes in migration rate was significantly higher with Phase III than with island model migration. As a result, FST for the frequency of a neutral marker locus was higher with Phase III than it was with island model migration. By increasing FST , Phase III enhanced the genetic differentiation among demes for traits not subject to interdemic selection. This feature makes Wright's process different from individual selection which, by reducing effective population size, decreases the genetic variance within demes for all other traits. I discussed this finding in relation to the efficacy of Phase III and random migration for effecting peak shifts, and the contribution of genes with indirect effects to among-deme variation.

Shift happens! Shifting balance and the evolution of diversity in warning colour and mimicry

1. At first sight, it seems most unlikely thatHeliconiuswarning colour races have evolved by means of stochastic peak shift or shifting balance.2. Phase I, random local processes (including genetic drift and idiosyncratic selection), and phase III, interdemic selection are the most controversial phases of the shifting balance. Phase II consists of ordinary natural selection to a new adaptive peak within populations, and is uncontroversial.3.Heliconiushave bold patterns of iridescent blue, black, yellow, white, and red. These are clearly warning patterns, and near‐perfect Müllerian mimicry has evolved among species, suggesting tight control by natural selection. Field experiments have also demonstrated strong selection (oftens >0.1 on single colour pattern loci), and the population structure ofHeliconiusis typically not conducive to phase I. Yet the colour patterns are clearly somewhat independent and incompatible signals of unpalatability.4. There is empirical evidence inHeliconiusfor both controversial phases. For phase I, occasional and local polymorphisms of colour pattern in a number of species go against the generally expected (and generally observed) monomorphism for Müllerian mimics.5. For phase III, one of the few colour pattern clines mapped in detail has been observed to move rapidly over a period of 20 years. There are also a number of curious ‘leapfrog’ geographical disjunctions in colour pattern races. Disjunctions are expected if successful races have spread from the centre of the range (e.g. the Amazonian rayed races) via phase III, in competition with earlier races that are now distributed in scattered places along the periphery of the range.6. Evidence from the genomes ofHeliconiusmay in the near future aid in understanding colour pattern ‘supergenes’ and to help test for origin and spread via shifting balance.

Amplified fragment length polymorphism fingerprints support limited gene flow among social spider populations

We used DNA fingerprints to determine whether the population structure and colony composition of the cooperative social spider Stegodyphus dumicola are compatible with requirements of interdemic ('group') selection: differential proliferation of demes or groups and limited gene flow among groups. To investigate gene flow among groups, spiders were collected from nests at 21 collection sites in Namibia. Analysis of molecular variance showed a small but highly significant differentiation among geographic regions (Phi(PT) = 0.23, P = 0.001). Thirty-three nests at four collection sites (6-10 spiders per nest, 292 individual spiders) were investigated in more detail to evaluate variation within and among colonies and among collection sites. In these 33 nests, an average of 15% of loci (fingerprint bands) were polymorphic among nestmates; 16% of observed variance was partitioned among collection sites, 48% among nests within a collection site, and 36% among individuals within nests. Spatial autocorrelation analyses of spiders at three collection sites showed that the maximum extent of detectable spatial autocorrelation among individuals was approximately 30 m, indicating dispersal over greater distances is not typical. These results indicate limited gene flow among nests, as well as spatial structuring at the level of regions, local populations, and nests, compatible with interdemic selection. (C) 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 97, 235-246.

Differential admixture shapes morphological variation among invasive populations of the lizardAnolis sagrei

The biological invasion of the lizard Anolis sagrei provides an opportunity to study evolutionary mechanisms that produce morphological differentiation among non-native populations. Because the A. sagrei invasion represents multiple native-range source populations, differential admixture as well as random genetic drift and natural selection, could shape morphological evolution during the invasion. Mitochondrial DNA (mtDNA) analyses reveal seven distinct native-range source populations for 10 introduced A. sagrei populations from Florida, Louisiana and Texas (USA), and Grand Cayman, with 2-5 native-range sources contributing to each non-native population. These introduced populations differ significantly in frequencies of haplotypes from different native-range sources and in body size, toepad-lamella number, and body shape. Variation among introduced populations for both lamella number and body shape is explained by differential admixture of various source populations; mean morphological values of introduced populations are correlated with the relative genetic contributions from different native-range source populations. The number of source populations contributing to an introduced population correlates with body size, which appears independent of the relative contributions of particular source populations. Thus, differential admixture of various native-range source populations explains morphological differences among introduced A. sagrei populations. Morphological differentiation among populations is compatible with the hypothesis of selective neutrality, although we are unable to test the hypothesis of interdemic selection among introductions from different native-range source populations.

Invasion and fixation of sex‐reversal genes

We simulated a meta-population with random dispersal among demes but local mating within demes to investigate conditions under which a dominant female-determining gene W, with no individual selection advantage, can invade and become fixed in females, changing the population from male to female heterogamety. Starting with one mutant W in a single deme, the interaction of sex ratio selection and random genetic drift causes W to be fixed among females more often than a comparable neutral mutation with no influence on sex determination, even when YY males have slightly reduced viability. Meta-population structure and interdeme selection can also favour the fixation of W. The reverse transition from female to male heterogamety can also occur with higher probability than for a comparable neutral mutation. These results help to explain the involvement of sex-determining genes in the evolution of sex chromosomes and in sexual selection and speciation.

Differential migration from high fitness demes in the shining fungus beetle, Phalacrus substriatus.

Using data from three years (1994-1996), I tested whether differential migration occurs from demes of high mean fitness in the shining fungus beetle, Phalacrus substriatus. The results show evidence for differential migration, thus providing evidence from a natural population for a critical demographic assumption of many interdemic selection models. To predict the evolutionary response to interdemic selection through differential migration, the genetic basis of the variation among demes in mean fitness must be known because the observed patterns could also be explained by some demes having an intrinsically favorable habitat. Thus, the importance of differential migration through interdemic selection in natural populations cannot be unequivocally answered without experiments specifically addressing the question of what causes differences in mean fitness among demes.

Design and Interpretation of Experimental Studies of Interdemic Selection: A Reply to Getty.

In this article, we reply to Getty’s (1999, in this issue) critique of laboratory studies of interdemic selection, particularly the study of Wade and Goodnight (1991). Getty (1999) raises several issues regarding the interpretation of experimental studies of group selection (reviewed in Goodnight and Stevens 1997). The first issue concerns offspring production, or demic productivity, the grouplevel trait used in several experimental studies of flour beetle metapopulations. This trait, unlike other traits, has the property that random sampling of offspring from within a deme is individual selection. The second issue is the different interpretations of hard and soft selection visa-vis group selection in Wade (1985b) and Goodnight et al. (1992). The last is the relationship between hard and soft selection and the appropriate experimental control for artificial interdemic selection on the trait, demic productivity. Getty (1999) argues that there was no group selection and only individual selection in the experimental treatments of Wade and Goodnight (1991) and that there was group selection in the controls. We address each of these issues below. Getty (1999) points out that random sampling of offspring from within demes is individual selection on offspring number. If individuals differ from one another within a deme in offspring numbers, then random sampling of offspring from a deme reflects this fitness variation

Group founding and breeding structure in the subsocial spider stegodyphus lineatus (Eresidae)

Co-operative behaviour may evolve by enhancing the genetic similarity of group members. Increased group similarity is thought to be the basis for the 'subsocial route' of social evolution in the spider family Eresidae. Two processes may promote the similarity of individuals within populations or breeding groups, namely philopatry in stable environments and founder events in a stochastic environment. We show that both processes led to genetic differentiation within and among populations of the subsocial spider Stegodyphus lineatus. Within populations we distinguished between the genetic structure caused by random mating and philopatry in old breeding groups and that caused by newly founded groups consisting of sibs. Such sib-groups suggest that new breeding groups are established primarily by single females. The different gene coancestries among breeding groups resulted in high variances among single-locus data. The results imply that sex-specific dispersal behaviour (random male mating-dispersal or female group founding) had different impacts on the population structure. This type of population structure, where within-population philopatry and founder events may lead to differential proliferation of breeding groups, is very similar to that presumed for social spiders, and is also one that could provide the conditions for interdemic selection.

KIN-STRUCTURED COLONIZATION AND SMALL-SCALE GENETIC DIFFERENTIATION IN SILENE DIOICA.

We investigated the genetic structure of a single island population of the dioecious plant Silene dioica in the Skeppsvik Archipelago, Umeå, Sweden. The population is less than 10 years old and consists of approximately 700 individuals growing within an area of about 200 m2 . Despite the small scale of the study, levels of genetic differentiation among contiguous patches are greater than or comparable to what is observed over larger scales in the archipelago. The results suggest that the small-scale structuring occurs during population expansion, soon after island colonization, and that the observed patterns of genetic differentiation can be attributed to the population being substructured into family groups. This family structure results from kin-structured dispersal processes (colonization and migration) as the population expands over the island. As plant densities increase over time, either spatial fusion or temporal fusion of patches reduce the among patch variation. These processes, however, do not completely eradicate the genetic differentiation established by the kin-structured dispersal processes. We discuss some implications of kin structuring for evolution through either kin or interdemic selection.

Design and Interpretation of Experimental Studies of Interdemic Selection: A Reply to Getty

Design and Interpretation of Experimental Studies of Interdemic Selection: A Reply to Getty

What do Experimental Studies Tell Us about Group Selection in Nature?

Previous articleNext article No AccessWhat Do Experimental Studies Tell Us about Group Selection in Nature?Thomas Getty and Associate Editor: Nicholas BartonThomas GettyKellogg Biological Station and Department of Zoology, Michigan State University, Hickory Corners, Michigan 19060*E‐mail: [email protected]. Search for more articles by this author and Associate Editor: Nicholas Barton Search for more articles by this author Kellogg Biological Station and Department of Zoology, Michigan State University, Hickory Corners, Michigan 19060PDFPDF PLUSFull Text Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by The American Naturalist Volume 154, Number 5November 1999 Published for The American Society of Naturalists Article DOIhttps://doi.org/10.1086/303257 Views: 35Total views on this site Citations: 4Citations are reported from Crossref HistoryReceived February 13, 1998Accepted June 29, 1998 Keywordsgroup selectionmultilevel selectionevolutionshifting balance© 1999 by The University of Chicago.PDF download Crossref reports the following articles citing this article:Samir Okasha Altruism, Group Selection and Correlated Interaction, The British Journal for the Philosophy of Science 56, no.44 (Nov 2020): 703–725.https://doi.org/10.1093/bjps/axi143Massimo Pigliucci On the Relationship between Science and Ethics, Zygon® 38, no.44 (Dec 2003): 871–894.https://doi.org/10.1111/j.1467-9744.2003.00544.xMassimo Pigliucci Ecology and Evolutionary Biology of Arabidopsis, The Arabidopsis Book 1 (Jan 2002): e0003.https://doi.org/10.1199/tab.0003 Michael J. Wade , Charles J. Goodnight , and Lori Stevens Design and Interpretation of Experimental Studies of Interdemic Selection: A Reply to Getty. M. J. Wade et al., The American Naturalist 154, no.55 (Jul 2015): 599–603.https://doi.org/10.1086/303259

Gulliver's further travels: the necessity and difficulty of a hierarchical theory of selection.

For principled and substantially philosophical reasons, based largely on his reform of natural history by inverting the Paleyan notion of overarching and purposeful beneficence in the construction of organisms, Darwin built his theory of selection at the single causal level of individual bodies engaged in unconscious (and metaphorical) struggle for their own reproductive success. But the central logic of the theory allows selection to work effectively on entities at several levels of a genealogical hierarchy, provided that they embody a set of requisite features for defining evolutionary individuality. Genes, cell lineages, demes, species, and clades-as well as Darwin's favoured organisms-embody these requisite features in enough cases to form important levels of selection in the history of life. R. A. Fisher explicitly recognized the unassailable logic of species selection, but denied that thsi real process could be important in evolution because, compared with the production of new organisms within a species, the origin of new species is so rare, and the number of species within most clades so low. I review this and other classical arguments against higher-level selection, and conclude (in the first part of this paper) that they are invalid in practice for interdemic selection, and false in principle for species selection. Punctuated equilibrium defines the individuality of species and refutes Fisher's classical argument based on cycle time. In the second part of the paper, I argue that we have failed to appreciate the range and power of selection at levels above and below the organismic because we falsely extrapolate the defining properties of organisms to these other levels (which are characterized by quite different distinctive features), and then regard the other levels as impotent because their effective individuals differ so much from organisms. We would better appreciate the power and generality of hierarchical models of selection if we grasped two key principles: first, that levels can interact in all modes (positively, negatively, and orthogonally), and not only in the negative style (with a higher level suppressing an opposing force of selection from the lower level) that, for heuristic and operational reasons, has received almost exclusive attention in the existing literature; and second, that each hierarchical level differs from all others in substantial and interesting ways, both in the style and frequency of patterns in change and causal modes.

The significance of relatedness and gene flow on population genetic structure in the subsocial spiderEresus cinnaberinus(Araneae: Eresidae)

Interdemic selection, inbreeding and highly structured populations have been invoked to explain the evolution of cooperative social behaviour in the otherwise solitary and cannibalistic spiders. The family Eresidae consists of species ranging from solitary and intermediate subsocial to species exhibiting fully cooperative social behaviour. In this study we, in a hierarchical analysis, investigated relatedness of putative family clusters, inbreeding and population genetic structure of the subsocial spiderEresus cinnaberinus. Five hierarchical levels of investigation ranging from large scale genetic structure (distances of 250 and 50 km level 1 and 2) over microgeographic structure (20 km2and 4 km2, level 3 and 4) to a single hill transect of 200 m (level 5) were performed. The purpose of level 5 was two-fold: (1) to investigate the relatedness of putative family groups, and (2) to evaluate the influence of both family living and sampling design on higher level estimates. Relatedness estimates of putative family groups showed an average relatedness ofR=0.26. There was no indication of inbreeding. In contrast to social spiders, genetic variation was abundant,He≈0.10. The population genetic structure was intermediate between social and asocial spiders. Genetic variance increased continually across hierarchical levels. Family structured neighbourhoods biased differentiation estimates among level 5 samples (FST=0.04) and level 3 and 4 samples (0.07<FST<0.18), and apparent inbreeding among level 3 and 4 samples,FIS>0, was caused by disjunct sampling from separate neighbourhoods. Larger scale samples were highly differentiated 0.12<FST<0.26, depending on level and sampling design. Due to a distance effect family living did not influence estimates of the higher level 1. Although the dispersing sex among social spiders and the subsocialE. cinnebarinusdiffer, females versus males, female behaviour of both sociality classes lead to high genetic variance.

The significance of relatedness and gene flow on population genetic structure in the subsocial spider Eresus cinnaberinus (Araneae: Eresidae)

Interdemic selection, inbreeding and highly structured populations have been invoked to explain the evolution of cooperative social behaviour in the otherwise solitary and cannibalistic spiders. The family Eresidae consists of species ranging from solitary and intermediate subsocial to species exhibiting fully cooperative social behaviour. In this study we, in a hierarchical analysis, investigated relatedness of putative family clusters, inbreeding and population genetic structure of the subsocial spider Eresus cinnaberinus. Five hierarchical levels of investigation ranging from large scale genetic structure (distances of 250 and 50 km level 1 and 2) over microgeographic structure (20 km2 and 4 km2, level 3 and 4) to a single hill transect of 200 m (level 5) were performed. The purpose of level 5 was two-fold: (1) to investigate the relatedness of putative family groups, and (2) to evaluate the influence of both family living and sampling design on higher level estimates. Relatedness estimates of putative family groups showed an average relatedness of R=0.26. There was no indication of inbreeding. In contrast to social spiders, genetic variation was abundant, Heapproximately0.10. The population genetic structure was intermediate between social and asocial spiders. Genetic variance increased continually across hierarchical levels. Family structured neighbourhoods biased differentiation estimates among level 5 samples (FST=0.04) and level 3 and 4 samples (0.07<FST<0.18), and apparent inbreeding among level 3 and 4 samples, FIS>0, was caused by disjunct sampling from separate neighbourhoods. Larger scale samples were highly differentiated 0.12<FST<0.26, depending on level and sampling design. Due to a distance effect family living did not influence estimates of the higher level 1. Although the dispersing sex among social spiders and the subsocial E. cinnebarinus differ, females versus males, female behaviour of both sociality classes lead to high genetic variance.Copyright 1998 The Linnean Society of London

Population structure and interdemic selection in the cooperative spider Anelosimus eximius

AbstractThe 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.

THE ROLE OF DEME SIZE, REPRODUCTIVE PATTERNS, AND DISPERSAL IN THE DYNAMICS OF t-LETHAL HAPLOTYPES.

The t-lethal haplotypes (t) found in house mouse (Mus musculus) populations are recessive lethals favored by gametic selection whereby male heterozygotes exhibit a non-Mendelian transmission ratio of about 95% t. The expected equilibrium frequency is 0.385; however, empirical values are lower, averaging close to 0.13. We examined the hypothesis that interdemic selection is the cause of the low empirical values by using a deme-structured simulation model that included overlapping generations, a realistic breeding system, differential deme productivity, and a large total population. We found that under some conditions interdemic selection could lower t frequency below 0.13 in the face of immigration rates up to 5%. Low frequencies were correlated with effective deme size (ne ), regardless of whether ne was changed through changing deme size (n) or through changing the proportion of breeding adults. Earlier workers showed how the first two phases of interdemic selection (random genetic differentiation and mass selection) interacted to reduce the haplotype frequency, but here we show the importance of the third phase (differential productivity of demes) once demes are linked by dispersal. The effect of this phase is not due to the (negative) covariation between deme productivity and haplotype frequency, but occurs when differential deme productivity generates a difference in t frequency between the population of juveniles recruited into their natal deme and the population of juvenile dispersers. This difference was maximized when the average productivity of demes was low, either because few adult females bred at any one time and/or because fecundity was low. Contrary to an earlier prediction, male-biased dispersal also reduced haplotype frequency, and this probably stems from the relative excess of wild-type genotypes among dispersers compared to the deme residents. Another unexpected finding was that the randomly generated excess of heterozygotes (FIS < 0) found in small demes favored t haplotypes; however, the effect was only seen when the more powerful influence of the third phase of interdemic selection was removed. Simulations of neutral polymorphisms showed that a deme structure giving FST ≤ 0.6 is inconsistent with a haplotype frequency below 0.13. Based on current empirical estimates of FST (about 0.2), we concluded that immigration rates in the field are too high for interdemic selection alone to cause the observed deficit of lethal haplotypes. One factor that could combine with population structure effects is the observation that the transmission ratio is lowered to around 0.6 in litters produced from postpartum estrus (PPE). Incorporating this factor, we showed that interdemic selection could be effective in lowering the frequency of t below 0.13 when FST was above 0.43 even when migration rates were up to 10%. These results suggest that if empirical haplotype and FST estimates are accurate, then additional factors such as a lowered fitness of heterozygotes may be involved.

Interdemic Selection and the Sex Ratio: A Social Spider Perspective

Computer simulations of a metapopulation model that mimics social spider populations show that highly female-biased sex ratios evolve when continuously inbreeding lineages (colonies) proliferate differentially to replace other lineages that have become extinct. When lineages of any size proliferated, that is, when the advantage to the colony of producing more females was removed, biased sex ratios did not evolve despite extreme conditions of inbreeding. Selection at the colony level is therefore necessary to counteract Fisherian selection within colonies, which here is shown to be acting regardless of the degree of population subdivision. Smaller size of the founding groups and lower migration rates resulted in more female-biased sex ratios because they reduced the within-group genetic variance and increased the variance among groups and therefore made selection among groups more effective. The outcome of the selective process, however, depended not only on the degree of population subdivision (i.e., the ratio of the variances), but also on the relative rate of turnover of the groups and the individuals within them: the lower the rate of colony turnover, the less biased the equilibrium sex ratio. The threshold size for proliferation, brood size, and conditional control over the production of at least one male also affected the equilibrium sex ratio under some of the conditions investigated