Kin Competition Research Articles

Dispersal of the Golden-mantled Ground Squirrel (Callospermophilus lateralis)

Abstract Dispersal is common in mammals and can have an important role in shaping demography, genetics, distribution, and social structure. Dispersal entails potential costs but also potential benefits, and the dispersal decision is thought to be conditional; the potential disperser assesses prospects for success at its current location and disperses to improve its fitness. However, the costs and benefits of dispersal, as well as factors influencing the dispersal decision, are not well known. We used trapping and observation to study dispersal in the Golden-mantled Ground Squirrel (Callospermophilus lateralis), a species for which dispersal is largely unknown. We characterized the dispersal process by evaluating dispersal timing and distance, assessed factors that might influence the dispersal decision, and analyzed the fitness cost of dispersal after settlement. We found that most dispersal occurred during the summer of birth, as is expected for a small-bodied sciurid. However, some squirrels delayed dispersal until early in their yearling summer. Dispersal was male-biased in dispersal tendency, and it was also male-biased in dispersal distance, but only over shorter dispersal distances. The dispersal decision for juvenile females appeared to originate as soon as 10 days after they emerged from the natal burrow, and the decision was not associated with body mass or several measures of competition. Instead, dispersal of juvenile females was associated with the number of littermate sisters, with each sister present increasing the likelihood of dispersal by 26%. Littermate sisters might be a cue foretelling the effects of kin competition the following year. We did not find a significant difference in lifetime reproductive success between philopatric and dispersing females after settlement, suggesting that for golden-mantled ground squirrels, any cost of dispersal is experienced primarily during the transience phase.

Resource Variation Within and Between Patches: Where Exploitation Competition, Local Adaptation, and Kin Selection Meet.

AbstractIn patch- or habitat-structured populations, different processes can favor adaptive polymorphism at different scales. While spatial heterogeneity can generate spatially disruptive selection favoring variation between patches, local competition can lead to locally disruptive selection promoting variation within patches. So far, almost all theory has studied these two processes in isolation. Here, we use mathematical modeling to investigate how resource variation within and between habitats influences the evolution of variation in a consumer population where individuals compete in finite patches connected by dispersal. We find that locally and spatially disruptive selection typically act in concert, favoring polymorphism under a wider range of conditions than when in isolation. But when patches are small and dispersal between them is low, kin competition inhibits the emergence of polymorphism, especially when the latter is driven by local competition for resources. We further use our model to clarify what comparisons between trait and neutral genetic differentiation ( comparisons) can tell about the nature of selection. Overall, our results help us understand the interaction between two major drivers of polymorphism: locally and spatially disruptive selection, and how this interaction is modulated by the unavoidable effects of kin selection under limited dispersal.

Flight capabilities of invasive yellowjacket Vespula germanica drones: the effect of kinship and nutrition

AbstractDispersal is a multifactorial process which may influence, among several others, population dynamics, inbreeding likelihood, and mate competition. For species that disperse by flight, many studies have suggested that life‐history traits, such as body size or nutritional condition, could promote variation in flight capabilities and, consequently, on dispersal behavior. Eusocial hymenopterans are likely to experience high densities of related reproductive individuals near their nests, thus increasing probabilities of inbred matings and kin competition. Spatial segregation resulting from differences in flight capabilities of Vespula germanica (Fabricius) (Hymenoptera: Vespidae) nestmate drones could reduce interactions with kin, thus decrease inbreeding and kin competition. Our aim was to characterize, in the laboratory, flight capabilities of sibling drones and elucidate traits that could affect it, focusing on the relevance of carbohydrate intake (diets with different sugar concentration) during early adulthood. Our results indicate that in tethered flight mill assays, V. germanica drones have highly variable flight capabilities within and between nests, with most drones likely to remain relatively close to their nest of origin. The observed flight capabilities are affected by nutrition, with those individuals better nurtured (i.e., with higher nutritional index), flying farther distances. Additionally, diets with variable carbohydrate concentration provided during early adulthood did not affect flight capabilities (only those exposed to a carbohydrate‐free diet had reduced flight distances and speeds), suggesting that nutrition during larval stages is determinant for flight. Our findings contribute to the understanding of the mechanisms underlying V. germanica drone dispersal behavior which, in turn, might influence inbreeding likelihood in the species.

Aggression and spatial positioning of kin and non-kin fish in social groups.

Group-living animals are faced with the challenge of sharing space and local resources amongst group members who may be either relatives or non-relatives. Individuals may reduce the inclusive fitness costs they incur from competing with relatives by either reducing their levels of aggression toward kin, or by maintaining physical separation between kin. In this field study, we used the group-living cichlid Neolamprologus multifasciatus to examine whether within-group aggression is reduced among group members that are kin, and whether kin occupy different regions of their group's territory to reduce kin competition over space and local resources. We determined the kinship relationships among cohabiting adults via microsatellite genotyping and then combined these with spatial and behavioral analyses of groups in the wild. We found that aggressive contests between group members declined in frequency with spatial separation between their shelters. Female kin did not engage in aggressive contests with one another, whereas non-kin females did, despite the fact these females lived at similar distances from one another on their groups' territories. Contests within male-male and male-female dyads did not clearly correlate with kinship. Non-kin male-male and male-female dyads lived at more variable distances from one another on their territories than their corresponding kin dyads. Together, our study indicates that contests among group members can be mediated by relatedness in a sex-dependent manner. We also suggest that spatial relationships can play an important role in determining the extent to which group members compete with one another.

Relatedness modulates reproductive competition among queens in ant societies with multiple queens.

Reproductive sharing in animal groups with multiple breeders, insects and vertebrates alike, contains elements of both conflict and cooperation, and depends on both relatedness between co-breeders, as well as their internal and external conditions. We studied how queens of the ant Formica fusca adjust their reproductive efforts in response to experimental manipulations of the kin competition regime in their nest. Queens respond to the presence of competitors by increasing their egg laying efforts, but only if the competitors are highly fecund and distantly related. Such a mechanism is likely to decrease harmful competition among close relatives. We demonstrate that queens of Formica fusca fine-tune their cooperative breeding behaviors in response to kinship and fecundity of others in a remarkably precise and flexible manner.

Technical comment on "sex ratios when helpers stay at the nest".

I contributed a paper to volume 60 of the journal. The paper reported on my study of sex-ratio evolution when one sex (females) is helpful but the other sex (males) suffers less from kin competition. I had based my study on a kin-selection model, and so I was dismayed to discover an error in the relatedness calculations therein. Specifically, relatedness coefficients that should have been calculated using a sampling-without-replacement scheme were instead calculated using sampling with replacement. Here, I correct my error and show how it impacts my original findings. I argue that my main conclusions are unchanged. Furthermore, only two new findings contrast with those I presented earlier. First, changing those model details unrelated to the marginal fitness benefits of help does not, in turn, impact substantially the conflict that occurs between mates over the brood sex ratio (I had previously reported some noteworthy impact was possible). Second, help can reduce sex-ratio conflict between mates more effectively when breeders occur in smaller groups (previously, I had said this occurred in larger groups).

Kinship and similarity drive coordination of breeding-group choice in male spotted hyenas.

When and where animals reproduce influences the social, demographic and genetic properties of the groups and populations they live in. We examined the extent to which male spotted hyenas (Crocuta crocuta) coordinate their breeding-group choice. We tested whether their propensity to settle in the same group is shaped by passive processes driven by similarities in their socio-ecological background and genotype or by an adaptive process driven by kin selection. We compared the choices of 148 pairs of same-cohort males that varied in similarity and kinship. We found strong support for both processes. Coordination was highest (70% of pairs) for littermates, who share most cumulative similarity, lower (36%) among peers born in the same group to different mothers, and lowest (7%) among strangers originating from different groups and mothers. Consistent with the kin selection hypothesis, the propensity to choose the same group was density dependent for full siblings and close kin, but not distant kin. Coordination increased as the number of breeding females and male competitors in social groups increased, i.e. when costs of kin competition over mates decreased and benefits of kin cooperation increased. Our results contrast with the traditional view that breeding-group choice and dispersal are predominantly solitary processes.

Co-evolution of dormancy and dispersal in spatially autocorrelated landscapes.

The evolution of dispersal can be driven by spatial processes, such as landscape structure, and temporal processes, such as disturbance. Dormancy, or dispersal in time, is generally thought to evolve in response to temporal processes. In spite of broad empirical and theoretical evidence of trade-offs between dispersal and dormancy, we lack evidence that spatial structure can drive the evolution of dormancy. Here, we develop a simulation-based model of the joint evolution of dispersal and dormancy in spatially heterogeneous landscapes. We show that dormancy and dispersal are each favored under different landscape conditions, but not simultaneously under any of the conditions we tested. We further show that, when dispersal distances are short, dormancy can evolve directly in response to landscape structure. In this case, selection is primarily driven by benefits associated with avoiding kin competition. Our results are similar in both highly simplified and realistically complexlandscapes.

A plant growth model to test for changes in plant–plant interaction over a growing season: the case of kin competition

Kin recognition and kin selection have long been known to occur in animals where they shape altruistic behavior towards relatives. More recently, studies have found that kin recognition and altered behavior towards kin can also occur in plants. However, inferring the underlying mechanism responsible for variation in plant performance in experimental studies is challenging as often, results can be explained by alternative and non‐exclusive mechanisms such as niche differences, kin competition avoidance and genetic variation in growth rate and competitive ability. Plant–plant interactions may change with the life stage of plants, and competition is often most intense towards the end of plants growing season. However, changes in plant–plant interaction intensity across plants life cycle are rarely considered in kin interaction studies. Here, we adapt a model of plant growth over time modified to specifically include effects of kin and non‐kin competition. The model decompose competitive interactions at different stages during plant growth from initial growth to the end of the growing season. It estimates genotype specific variation in growth rate, and how sensitive individual genotypes are to competition from neighbors. Furthermore, it estimates size asymmetry among plants accounting for both variation in growth rate, neighbor relatedness and resource variation (here water availability). We use this model to analyze the results from a competition experiment where plants grew in mini‐populations with neighbor plants that were either kin or non‐kin. We find that when applied to our experiments, this approach can disentangle kin effects from other effects caused by genotypic variation in growth rate and competitive response to neighbors, and thus significantly help to detect whether plants exhibit kin‐cooperative behavior.

Density-dependent dispersal promotes female-biased sex allocation in viscous populations

A surprising result emerging from the theory of sex allocation is that the optimal sex ratio is predicted to be completely independent of the rate of dispersal. This striking invariance result has stimulated a huge amount of theoretical and empirical attention in the social evolution literature. However, this sex-allocation invariant has been derived under the assumption that an individual's dispersal behaviour is not modulated by population density. Here, we investigate how density-dependent dispersal shapes patterns of sex allocation in a viscous-population setting. Specifically, we find that if individuals are able to adjust their dispersal behaviour according to local population density, then they are favoured to do so, and this drives the evolution of female-biased sex allocation. This result obtains because, whereas under density-independent dispersal, population viscosity is associated not only with higher relatedness—which promotes female bias—but also with higher kin competition—which inhibits female bias—under density-dependent dispersal, the kin-competition consequences of a female-biased sex ratio are entirely abolished. We derive analytical results for the full range of group sizes and costs of dispersal, under haploid, diploid and haplodiploid modes of inheritance. These results show that population viscosity promotes female-biased sex ratios in the context of density-dependent dispersal.

From inter-group conflict to inter-group cooperation: insights from social insects.

The conflict between social groups is widespread, often imposing significant costs across multiple groups. The social insects make an ideal system for investigating inter-group relationships, because their interaction types span the full harming-helping continuum, from aggressive conflict, to mutual tolerance, to cooperation between spatially separate groups. Here we review inter-group conflict in the social insects and the various means by which they reduce the costs of conflict, including individual or colony-level avoidance, ritualistic behaviours and even group fusion. At the opposite extreme of the harming-helping continuum, social insect groups may peacefully exchange resources and thus cooperate between groups in a manner rare outside human societies. We discuss the role of population viscosity in favouring inter-group cooperation. We present a model encompassing intra- and inter-group interactions, and local and long-distance dispersal. We show that in this multi-level population structure, the increased likelihood of cooperative partners being kin is balanced by increased kin competition, such that neither cooperation (helping) nor conflict (harming) is favoured. This model provides a baseline context in which other intra- and inter-group processes act, tipping the balance toward or away from conflict. We discuss future directions for research into the ecological factors shaping the evolution of inter-group interactions. This article is part of the theme issue 'Intergroup conflict across taxa'.

Pivotal role of O-antigenic polysaccharide display in the sensitivity against phage tail-like particles in environmental Pseudomonas kin competition

Environmental pseudomonads colonize various niches including insect and plant environments. When invading these environments, bacteria are confronted with the resident microbiota. To oppose with closely related strains, they rely on narrow-spectrum weaponry such as tailocins, i.e., phage tail-like particles. Little is known about the receptors for these tailocins especially among phylogenetically closely related species. Here, we studied the interaction between an R-tailocin from Pseudomonas protegens CHA0 and a targeted kin, Pseudomonas protegens Pf-5. Using genome-wide transposon insertion sequencing, we identified that lipopolysaccharides are involved in the sensitivity of Pf-5 towards the tailocin of CHA0. By generating Pf-5 lipopolysaccharide mutants and exposing them to extracted tailocin, we specified the two O-antigenic polysaccharides (O-PS) targeted by the tailocin. We affirmed the role of these O-PS through competition assays in vitro as well as in insects. Further, we demonstrate that O-PS are double-edge swords that are responsible for the sensitivity of P. protegens towards tailocins and phages produced by their kin, but shield bacteria from the immune system of the insect. Our results shed light on the trade-off that bacteria are confronted with, where specific O-PS decorations can both be of benefit or disadvantage depending on the host environment and its bacterial inhabitants.

Population viscosity promotes altruism under density-dependent dispersal.

A basic mechanism of kin selection is population viscosity, whereby individuals do not move far from their place of birth and hence tend to be surrounded by relatives. In such circumstances, even indiscriminate altruism among neighbours will often involve interactions between kin, which has a promoting effect on the evolution of altruism. This has the potential to explain altruistic behaviour across the whole tree of life, including in taxa for which recognition of kin is implausible. However, population viscosity may also intensify resource competition among kin, which has an inhibitory effect on altruism. Indeed, in the simplest scenario, in which individuals disperse with a fixed probability, these two effects have been shown to exactly cancel such that there is no net impact of viscosity on altruism. Here, we show that if individuals are able to disperse conditionally upon local density, they are favoured to do so, with more altruistic neighbourhoods exhibiting a higher rate of dispersal and concomitant relaxation of kin competition. Comparing across different populations or species, this leads to a negative correlation between overall levels of dispersal and altruism. We demonstrate both analytically and using individual-based simulations that population viscosity promotes the evolution of altruism under density-dependent dispersal.

Evolution under Spatially Heterogeneous Selection in Solid Tumors.

Spatial genetic and phenotypic diversity within solid tumors has been well documented. Nevertheless, how this heterogeneity affects temporal dynamics of tumorigenesis has not been rigorously examined because solid tumors do not evolve as the standard population genetic model due to the spatial constraint. We therefore, propose a neutral spatial (NS) model whereby the mutation accumulation increases toward the periphery; the genealogical relationship is spatially determined and the selection efficacy is blunted (due to kin competition). In this model, neutral mutations are accrued and spatially distributed in manners different from those of advantageous mutations. Importantly, the distinctions could be blurred in the conventional model. To test the NS model, we performed a three-dimensional multiple microsampling of two hepatocellular carcinomas. Whole-genome sequencing (WGS) revealed a 2-fold increase in mutations going from the center to the periphery. The operation of natural selection can then be tested by examining the spatially determined clonal relationships and the clonal sizes. Due to limited migration, only the expansion of highly advantageous clones can sweep through a large part of the tumor to reveal the selective advantages. Hence, even multiregional sampling can only reveal a fraction of fitness differences in solid tumors. Our results suggest that the NS patterns are crucial for testing the influence of natural selection during tumorigenesis, especially for small solid tumors.

Competition Drives Group Formation and Reduces Within Nest Relatedness in a Facultatively Social Carpenter Bee

Animals respond to competition among kin for critical breeding resources in two ways: avoidance of direct fitness costs via dispersal of siblings to breed separately, and formation of kin-based societies in which subordinates offset direct fitness costs of breeding competition via altruism and increased indirect fitness. In the facultatively social eastern carpenter bee, nests are a critical breeding resource in perpetually short supply, leading to strong competition among females. Observations of individually marked and genotyped females in conditions of high and low resource competition demonstrate that competition leads to resource sharing and group nesting. However, in contrast to almost all known animal societies, females avoid nesting with relatives, and disperse from their natal nests to join social groups of non-relatives. This is the first example of a structured insect society with cooperation nestmates, the majority of which are unrelated; thus cooperation is more likely based on selection for direct, rather than indirect fitness. By forming social groups of non-kin, females avoid the indirect fitness costs of kin competition among sisters, yet increase their chances of successful reproduction, and thus direct fitness, when forming colonies of non-relatives.

Kin discrimination in allelopathy and consequences for agricultural weed control.

Among all biotic stress types (i.e. pathogens, pests and weeds), weeds have the largest potential for yield reduction (larger than the other two combined) (Oerke, 2006). Chemical control of weeds is coming under increasing pressure due to concerns about their health- and environmental impacts and increasing herbicide resistance of weeds. As a consequence there is an increased interest in ecological weed control, of which development of weed-suppressive crops can be an important part (Bastiaans, Paolini, & Baumann, 2008). In the current issue, Xu, Cheng, Kong, and Meiners (2021) for the first time, show that kin recognition (the ability of plants to distinguish genetically related individuals from strangers) can make rice plants more competitive against weeds potentially being a new strategy in ecological weed control. This article is protected by copyright. All rights reserved.

Hamilton’s rule and kin competition in a finite kin population

Kin selection means that individuals can increase their own inclusive fitness through displaying more altruistically toward their relatives. So, Hamilton’s rule says kin selection will work if the coefficient of relatedness exceeds the cost-to-benefit ratio of the altruistic act. However, some studies have shown that the kin competition due to the altruism among relatives can reduce, and even totally negate, the kin-selected benefits of altruism toward relatives. In order to understand how the evolution of cooperation is influenced by both kin selection and kin competition under a general theoretical framework, we here consider the evolutionary dynamics of cooperation in a finite kin population, where kin competition is incorporated into a simple Prisoner’s Dilemma game between relatives. Differently from the previous studies, we emphasize that the difference between the effects of mutually and unilaterally altruistic acts on kin competition may play an important role for the evolution of cooperation. The main results not only show the conditions that Hamilton’s rule still works under the kin competition but also reveal the evolutionary biological mechanism driving the evolution of cooperation in a finite kin population.

Immune function does not trade‐off with reproductive effort in a semelparous wolf spider with parental care

AbstractTrade‐offs between negatively associated traits underlie life history evolution. Immune function is often involved in life history trade‐offs, because of the energetic and nutritional costs of mounting and maintaining immune responses. Reproductive strategies exist on a continuum between semelparity and iteroparity. While immune function is often downregulated in semelparous organisms because they do not have to account for future survival or reproduction, those organisms that also provide parental care may retain the strength of immune responses. Wolf spiders (family: Lycosidae) are semelparous yet provide parental and provide a good system to evaluate trade‐offs between immune responses and reproductive effort. We measured encapsulation response and reproductive effort of female wolf spiders from three reproductive classes: nongravid, gravid, and carrying young. To our knowledge, this is the first investigation of the immune responses of female wolf spiders carrying young. We hypothesized female T. georgicola derive the allocate resources to reproduction at the expense of immune function. However, we found reproductive effort had no relationship with encapsulation response in spiders carrying young. There was also no difference in the encapsulation response between reproductive classes. Individual differences in resource acquisition may explain the lack of a relationship between reproductive effort and encapsulation in spiders carrying young. Spiders with larger resource pools have more resources to devote to reproduction and immunity. Maintaining resources to mount immune responses across reproductive stages could also increase the fitness of female wolf spiders because they must survive to carry and disperse the young, which reduces kin competition among spiderlings.

Dispersal Alters the Nature and Scope of Sexually Antagonistic Variation.

AbstractIntralocus sexual conflict, or sexual antagonism, occurs when alleles have opposing fitness effects in the two sexes. Previous theory suggests that sexual antagonism is a driver of genetic variation by generating balancing selection. However, most of these studies assume that populations are well mixed, neglecting the effects of spatial subdivision. Here, we use mathematical modeling to show that limited dispersal changes evolution at sexually antagonistic autosomal and X-linked loci as a result of inbreeding and sex-specific kin competition. We find that if the sexes disperse at different rates, kin competition within the philopatric sex biases intralocus conflict in favor of the more dispersive sex. Furthermore, kin competition diminishes the strength of balancing selection relative to genetic drift, reducing genetic variation in small subdivided populations. Meanwhile, by decreasing heterozygosity, inbreeding reduces the scope for sexually antagonistic polymorphism due to nonadditive allelic effects, and this occurs to a greater extent on the X chromosome than autosomes. Overall, our results indicate that spatial structure is a relevant factor in predicting where sexually antagonistic alleles might be observed. We suggest that sex-specific dispersal ecology and demography can contribute to interspecific and intragenomic variation in sexual antagonism.

Intraspecific interactions in the annual legume Medicago minima are shaped by both genetic variation for competitive ability and reduced competition among kin

Documenting if plants exhibit kin competition avoidance in intraspecific plant interactions is relevant both to improve crop growth, and to understand diversity and composition in natural plant communities. However, a number of confounding mechanisms complicates detecting kin competition avoidance from experiments comparing plants growing with kin and non-kin neighbors. We conducted complementary greenhouse experiments using genotypes from four populations of the annual Medicago minima, which in a previous study showed higher survival when interacting with kin relative to non-kin. We show that genotypes vary in kin competition avoidance, and in competitive ability, but find no indication of complementary resource use. Importantly, from our first experiment of root growth behavior, we know that some genotypes exhibit kin competition avoidance. Yet, the variation in competitive ability we find in our second experiment, where plants grow in mini communities together with either kin or unrelated genotypes, can alone explain the variation we observe in growth and biomass among communities. In our case, the genotypes with highest competitive ability were also those that showed kin competition avoidance. This confounding effect obscured the disentangling of mechanisms underlying difference in growth between kin and non-kin interactions. When silencing root exudates by adding activated carbon to a subset of our genotype combinations, we found increased size asymmetry of plants grown together, and mostly in kin communities. This suggests that plants recognize the identity of neighbors via root exudates, and compete less with neighbors recognized as kin. To detect kin competition avoidance we suggest designing experiments that pair unrelated genotypes with similar competitive abilities. Such design, combined with silencing root exudates would be powerful to detect whether plants show kin competition avoidance or not.