Non-kin Groups Research Articles

Dispersal Risks and Decisions Shape How Non-kin Groups Form in a Tropical Silk-Sharing Webspinner (Insecta: Embioptera)

Relying on silk can promote sharing, especially when its presence means life and its absence, quick death. In the case of Embioptera, they construct silken tubes and coverings exposed on tree bark in humid and warm environments or in leaf litter and underground in dry habitats. These coverings protect occupants from rain and natural enemies. Of note, adult females are neotenous, wingless and must walk to disperse. Evidence is pulled together from two sources to explore mechanisms that promote the establishment of non-kin groups that typify the neotropical Antipaluria urichi (Clothodidae): (1) a review of relevant information from 40 years of research to identify potential drivers of the facultative colonial system and (2) experimental and observational data exploring how dispersal contributes to group formation. To determine risks of dispersal and decisions of where to settle, adult females were released into the field and their ability to survive in the face of likely predation was monitored. Additional captured dispersers were released onto bark containing silk galleries; their decision to join the silk or to settle was noted. An experiment tested which attributes of trees attract a disperser: vertical or horizontal boles in one test and small, medium, or large boles in another. While walking, experimentally released adult female dispersers experienced a risk of being killed of approximately 25%. Dispersers orient to large diameter trees and join silk of others if encountered. These results align with observations of natural colonies in that adults and late-stage nymphs join existing colonies of non-kin. Experiments further demonstrated that dispersing females orient to vertical and larger diameter tree-like objects, a behavior that matched the distribution of field colonies. The ultimate reason for the observed dispersion pattern is probably because large trees support more expansive epiphytic algae and lichens (the food for this species), although the impact of food resources on dispersion has not been tested. Finally, further research questions and other webspinner species (including parthenogenetic ones) that warrant a closer look are described. Given that this group of primitively social insects, with approximately 1,000 species known, has remained virtually unstudied, one hope is that this report can encourage more exploration.

Ecological Drivers of Non-kin Cooperation in the Hymenoptera

Despite the prominence of kin selection as a framework for understanding the evolution of sociality, many animal groups are comprised of unrelated individuals. These non-kin systems provide valuable models that can illuminate drivers of social evolution beyond indirect fitness benefits. Within the Hymenoptera, whose highly related eusocial groups have long been cornerstones of kin selection theory, groups may form even when indirect fitness benefits for helpers are low or absent. These non-kin groups are widespread and abundant, yet have received relatively little attention. We review the diversity and organization of non-kin sociality across the Hymenoptera, particularly among the communal bees and polygynous ants and wasps. Further, we discuss common drivers of sociality across these groups, with a particular focus on ecological factors. Ecological contexts that favor non-kin sociality include those dominated by resource scarcity or competition, climatic stressors, predation and parasitism, and/or physiological constraints associated with reproduction and resource exploitation. Finally, we situate Hymenopteran non-kin sociality within a broader biological context by extending insights from these systems across diverse taxa, especially the social vertebrates. Non-kin social groups thus provide unique demonstrations of the importance of ecological factors in mediating the evolutionary transition from solitary to group living.

Impact of genetic relatedness and food competition on female dominance hierarchies in a cichlid fish

Kin selection theory predicts that genetic relatedness between group members can reduce the asymmetry in resource partitioning between superior and inferior competitors. In social groups, access to resources is often regulated by dominance hierarchies; thus, the degree of relatedness within a group may have a substantial impact on hierarchy structure. However, evidence of such effects is scarce. This study investigated how genetic relatedness and food competition affect dominance hierarchies in adult female Pelvicachromis taeniatus , a biparental African cichlid that shows kin-directed cooperation during juvenile shoaling and parental care. We compared triads of unfamiliar females, consisting of either a sister pair and an unrelated female (‘mixed’ groups) or three unrelated females (‘nonkin’ groups), and measured food monopolization and hierarchy characteristics (linearity, hierarchy steepness and short-term stability). To determine dominance relationships, we used an automated analysis of approach–avoidance events based on video-tracking data. The females formed hierarchies that remained stable over 2 days and were linear or near linear with one clear alpha female dominating the other two group members. Higher-ranking females tended to have prior access to food and could better sustain their body mass. The steepness of these hierarchies decreased after feeding, showing that dominance behaviour changed plastically depending on the intensity of competition over limited resources. Mixed groups consumed food slower than nonkin groups, but the treatments did not differ in food monopolization or hierarchy characteristics. In conclusion, kin-biased behaviour was highly dependent on life stage and social context: Within the same species, juveniles and mating partners showed increased cooperation, whereas female–female competition and dominance remained unaffected by genetic relatedness. • Dominance hierarchies in nonkin and mixed kinship groups show similar properties. • Hunger intensifies dominance relationships. • The alpha female can better sustain her body mass than lower-ranking competitors. • Dominance behaviours can be automatically analysed using video-tracking software.

Non-kin Cooperation in Ants

Eusociality represents an extreme form of social behavior characterized by a reproductive division of labor. Eusociality necessarily evolved through kin selection, which requires interactions among related individuals. However, many eusocial taxa also show cooperation between non-kin groups, challenging the idea that cooperative actions should only occur among relatives. This review explores the causes and consequences of non-kin cooperation in ants. Ants display a diversity of behaviors that lead to non-kin cooperation within and between species. These interactions occur among both reproductive and non-reproductive individuals. The proximate and ultimate mechanisms leading to non-kin cooperative interactions differ substantially depending on the biotic and abiotic environment. We end this review with directions for future research and suggest that the investigation of non-kin cooperative actions provides insight into processes leading to social evolution.

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.

Cooperation among unrelated ant queens provides persistent growth and survival benefits during colony ontogeny

The fitness consequences of cooperation can vary across an organism’s lifespan. For non-kin groups, especially, social advantages must balance intrinsic costs of cooperating with non-relatives. In this study, we asked how challenging life history stages can promote stable, long-term alliances among unrelated ant queens. We reared single- and multi-queen colonies of the primary polygynous harvester ant, Pogonomyrmex californicus, from founding through the first ten months of colony growth, when groups face high mortality risks. We found that colonies founded by multiple, unrelated queens experienced significant survival and growth advantages that outlasted the colony founding period. Multi-queen colonies experienced lower mortality than single-queen colonies, and queens in groups experienced lower mortality than solitary queens. Further, multi-queen colonies produced workers at a faster rate than did single-queen colonies, even while experiencing lower per-queen worker production costs. Additionally, we characterized ontogenetic changes in the organization of labor, and observed increasing and decreasing task performance diversity by workers and queens, respectively, as colonies grew. This dynamic task allocation likely reflects a response to the changing role of queens as they are increasingly able to delegate risky and costly tasks to an expanding workforce. Faster worker production in multi-queen colonies may beneficially accelerate this behavioral transition from a vulnerable parent–offspring group to a stable, growing colony. These combined benefits of cooperation may facilitate the retention of multiple unrelated queens in mature colonies despite direct fitness costs, providing insight into the evolutionary drivers of stable associations between unrelated individuals.

Parrots do not show inequity aversion

Inequity aversion, the negative reaction to unequal treatment, is considered a mechanism for stabilizing cooperative interactions between non-kin group members. However, this might only be adaptive for species that switch cooperative partners. Utilizing a comparative approach, inequity aversion has been assessed in many mammalian species and recently also in corvids and one parrot species, kea, revealing mixed results. To broaden our knowledge about the phylogenetic distribution of inequity aversion, we tested four parrot species in the token exchange paradigm. We varied the quality of rewards delivered to dyads of birds, as well as the effort required to obtain a reward. Blue-headed macaws and African grey parrots showed no reaction to being rewarded unequally. The bigger macaws were less willing to exchange tokens in the “unequal” condition compared to the “equal high” condition in which both birds obtained high quality rewards, but a closer examination of the results and the findings from the control conditions reveal that inequity aversion does not account for it. None of the species responded to inequity in terms of effort. Parrots may not exhibit inequity aversion due to interdependence on their life-long partner and the high costs associated with finding a new partner.

Preferential helping to relatives: A potential mechanism responsible for lower yield of crop variety mixtures?

Variety mixtures, the cultivation of different genotypes within a field, have been proposed as a way to increase within‐crop diversity, allowing the development of more sustainable agricultural systems with reduced environmental costs. Although mixtures have often been shown to over‐yield the average of component varieties in pure stands, decreased yields in mixtures have also been documented. Kin selection may explain such pattern, whenever plants direct helping behaviors preferentially toward relatives and thus experience stronger competition when grown with less related neighbors, lowering seed production of mixtures. Using varieties of durum wheat originating from traditional Moroccan agrosystems, we designed a greenhouse experiment to address whether plants reduced competition for light by limiting stem elongation when growing with kin and whether such phenotypic response resulted in higher yield of kin groups. Seeds were sown in groups of siblings and nonkin, each group containing a focal plant surrounded by four neighbors. At the group level, mean plant height and yield did not depend upon relatedness among competing plants. At the individual level, plant height was not affected by genetic relatedness to neighbors, after accounting for direct genetic effects that might induce among‐genotype differences in the ability to capture resources that do not depend on relatedness. Moreover, in contrast to our predictions, shorter plants had lower inclusive fitness. Phenotypic plasticity in height was very limited in response to neighbor genotypes. This suggests that human selection in crops may have attenuated shade‐avoidance responses to competition for light. Future research on preferential helping to relatives in crops might thus target social traits that drive competition for other resources than light. Overall, our study illustrates the relevance of tackling agricultural issues from an evolutionary standpoint and calls for extending such approaches to a larger set of crop species.

‘Call me if you need’: Social support experiences under economic and social change

ABSTRACTSocial interactions play an important role in people’s life and people’s health but their scope and intensity tend to decrease with age, challenging social support dynamics and increasing the risk of social isolation and helplessness. In Portugal, policymakers still seem to rely on traditional social relations in eldercare, while contextual changes and trends are redefining family roles and behaviors and defying the established social support structure. In this work, we aim to examine the scope, structure and experiences of the informal social support network available in the country for stroke patients 6 months after their discharge from the acute care unit in the context of a larger study. The results seem to confirm the importance of family as a source of social support and shed light on different bonding experiences with non-kin social groups, such as neighbors and friends. A coordinated care provision, combining formal and informal support is vital and beneficial for patients, their caregivers and the care system.

Habitat quality affects stress responses and survival in a bird wintering under extremely low ambient temperatures.

Animals normally respond to stressful environmental stimuli by releasing glucocorticoid hormones. We investigated whether baseline corticosterone (CORT), handling-induced corticosterone concentration(s), and body condition indices of members of willow tit (Poecile montanus) groups differed while wintering in old growth forests and managed young forests in mild weather conditions and during cold spells. Willow tits spend the winter season in non-kin groups in which dominant individuals typically claim their priority to access resources, while subordinate individuals may experience greater levels of stress and higher mortality, especially during cold spells. We captured birds to measure baseline CORT and levels of handling-induced CORT secretion after 20min of capture. Willow tits in the young forests had higher baseline CORT and a smaller increase in CORT in response to capture than individuals in the old forests. Baseline CORT was higher in females and juvenile birds compared to adult males, whereas handling-induced CORT secretion did not differ between birds of different ages. During cold spells, baseline CORT of willow tits increased and handling-induced CORT secretion decreased, especially in birds in young forests. Willow tits' survival was higher in the old forests, with dominant individuals surviving better than subordinates. Our results show that changes in CORT secretion reflect responses to habitat quality and climate harshness, indicating young managed coniferous forests as a suboptimal habitat for the willow tit.

“Brothers” in Arms: Does Metaphorizing Kinship Increase Approval of Parochial Altruism?

Parochial altruism is manifested in the most violent of conflicts. Although it makes evolutionary sense for kin, many non-kin groups also behave parochially altruistically in response to threat from out-groups. It is possible that such non-kin groups share a sense of “fictive” kinship which encourages them to behave parochially altruistically for each other’s benefit. Our findings show that individuals not directly involved in a conflict approved of parochial altruism enacted by an in-group against an out-group more when the out-group posed a threat to the in-group; however, this effect wasgreaterwhen the in-group members expressed fictive kinship by addressing each other using kinship metaphors such as “brothers.” Furthermore, although males approved of parochial altruism more than females, as the male warrior hypothesis would suggest, the effects of threat and kinship metaphor on approval of parochial altruism applied to both genders. These findings were replicated in an honour (Lebanon) and non-honour (Australia) culture.

The role of collectivism among Latino American college students

ABSTRACTIn an attempt to explain the lower Latino college graduation rate, the current study focuses on collectivism in kin and nonkin helping situations. The sample comprised 60 students at a 4-year college in the southwestern United States. Results revealed significance between ethnicity and nonkin collectivism: Latino American college students were significantly more collectivistic toward nonkin groups compared to their non–Latino American counterparts. The use of various support systems may shed some light on the necessary remedy for Latinos’ lower college graduation rate. Implications are discussed for cultural sensitivity training and program development to foster the experience and success of Latino American college students.

Sharing Mechanisms in Corporate Groups may be More Resilient to Natural Disasters than Kin Groups in the Nicobar Islands

It has been suggested that kin groups are better predisposed to cooperatively manage essential natural resources than non-kin groups because of inclusive fitness gains. Whether these long-term genetic pay-offs sufficiently offset the immediate costs of cooperation in periods of scarcity is uncertain. We compared patterns of resource sharing across three island communities in the Nicobar Archipelago affected by the 2004 tsunami. While sharing mechanisms were similar across regions, group composition varied: Central and Southern Nicobar were organised along kinship lines, while Chowra was organised as corporate alliances of unrelated households. We documented post-tsunami losses and conflicts emerging in resource sharing after the event. While kin groups showed considerable breakdown in resource sharing arrangements, corporate communities in Chowra were much more resilient to change. Our results suggest that the more immediate reciprocity of corporate alliances may outweigh the potential benefits of inclusive fitness when faced with conditions of extreme resource scarcity.

The Genetic Relatedness in Groups of Joint-Nesting Taiwan Yuhinas: Low Genetic Relatedness with Preferences for Male Kin.

The relative importance of direct and indirect fitness and, thus, the role of kinship in the evolution of social behavior is much debated. Studying the genetic relatedness of interacting individuals is crucial to improving our understanding of these issues. Here, we used a seven-year data set to study the genetic structure of the Taiwan yuhina (Yuhina brunneciceps), a joint-nesting passerine. Ten microsatellite loci were used to investigate the pair-wised relatedness among yuhina breeding group members. We found that the average genetic relatedness between same-sex group members was very low (0.069 for male dyads and 0.016 for female dyads). There was also a low ratio of closely-related kin (r>0.25) in the cooperative breeding groups of yuhinas (21.59% and 9.68% for male and female dyads, respectively). However, the relatedness of male dyads within breeding groups was significantly higher than female dyads. Our results suggest that yuhina cooperation is maintained primarily by direct fitness benefits to individuals; however, kin selection might play a role in partner choice for male yuhinas. Our study also highlights an important, but often neglected, question: Why do animals form non-kin groups, if kin are available? We use biological market theory to propose an explanation for group formation of unrelated Taiwan yuhinas.

Reduced plant competition among kin can be explained by Jensen's inequality.

Plants often compete with closely related individuals due to limited dispersal, leading to two commonly invoked predictions on competitive outcomes. Kin selection, from evolutionary theory, predicts that competition between relatives will likely be weaker. The niche partitioning hypothesis, from ecological theory, predicts that competition between close relatives will likely be stronger. We tested for evidence consistent with either of these predictions by growing an annual legume in kin and nonkin groups in the greenhouse. We grew plant groups in treatments of symbiotic nitrogen fixing bacteria differing in strain identity and composition to determine if differences in the microbial environment can facilitate or obscure plant competition patterns consistent with kin selection or niche partitioning. Nonkin groups had lower fitness than expected, based on fitness estimates of the same genotypes grown among kin. Higher fitness among kin groups was observed in mixtures of N-fixing bacteria strains compared to single inoculations of bacteria strains present in the soil, which increased fitness differences between kin and nonkin groups. Lower fitness in nonkin groups was likely caused by increased competitive asymmetry in nonkin groups due to genetic differences in plant size combined with saturating relationships with plant size and fitness- i.e. Jensen's inequality. Our study suggests that microbial soil symbionts alter competitive dynamics among kin and nonkin. Our study also suggests that kin groups can have higher fitness, as predicted by kin selection theory, through a commonly heritable trait (plant size), without requiring kin recognition mechanisms.

Ethnographic Study of Experiences of Pakistani Women Immigrants With Pregnancy, Birthing, and Postpartum Care in the United States and Pakistan

Describe the comparative birthing experiences of Pakistani immigrant women in Pakistan and the United States. The framework was drawn from Berry's cultural adaptation, Glick-Schiller et al.'s transnationalism and Berkman's social network. Qualitative Women experienced difficulties associated with inability to observe cultural traditions and loss of extended, gendered kin support. Adaptive strategies were evident through development of social networks of weak ties with non-kin groups in the United States, maintenance of transnational ties with kin back in Pakistan, and assimilation of less gender-defined roles by women and their spouses.

Multilevel selection with kin and non-kin groups, experimental results with Japanese quail (Coturnix japonica).

An experiment was conducted comparing multilevel selection in Japanese quail for 43 days weight and survival with birds housed in either kin (K) or random (R) groups. Multilevel selection significantly reduced mortality (6.6% K vs. 8.5% R) and increased weight (1.30 g/MG K vs. 0.13 g/MG R) resulting in response an order of magnitude greater with Kin than Random. Thus, multilevel selection was effective in reducing detrimental social interactions, which contributed to improved weight gain. The observed rates of response did not differ significantly from expected, demonstrating that current theory is adequate to explain multilevel selection response. Based on estimated genetic parameters, group selection would always be superior to any other combination of multilevel selection. Further, near optimal results could be attained using multilevel selection if 20% of the weight was on the group component regardless of group composition. Thus, in nature the conditions for multilevel selection to be effective in bringing about social change maybe common. In terms of a sustainability of breeding programs, multilevel selection is easy to implement and is expected to give near optimal responses with reduced rates of inbreeding as compared to group selection, the only requirement is that animals be housed in kin groups.

Vigilance and predation of a forest-living bird species depend on large-scale habitat structure

Prey often use visual cues to detect predators, and consequently, many studies have assessed the effect of small-scale habitat structure on prey antipredator vigilance. This scale may be inappropriate to assess the link between habitat structure and vigilance, however, because visually hunting predators often detect prey from several hundred meters away. As a result, largescale habitat structure could affect both the hunting decisions of predators and antipredator behaviors of prey. Here we investigated the effect of small- and large-scale habitat structure, as well as group composition (kinship) on vigilance allocation of breeders in the Siberian jay Perisoreus infaustus. Vigilance had an antipredator function and was increased after exposure to a predator model. Small-scale habitat structure did not affect vigilance rates, however, habitat structure of the whole territory, measured as the proportion of visual cover, affected vigilance depending on group composition. Breeders with retained offspring (kin) in their group were more vigilant in managed open territories than on pristine dense territories, whereas breeders without kin in their groups did not adjust vigilance rates in relation to large-scaled habitat structure. Earlier studies have revealed that hawks, the main predators of jays, primarily kill non-kin group members living in groups inhabiting open territories. Therefore, we suggest that breeders adjusted their vigilance depending on the habitat-specific predation risk to protect their retained offspring. This demonstrates that large-scale habitat structure affects predator‐prey interactions and is crucial to understanding spatial variation in antipredator allocation and mortality. Key words: delayed dispersal, family group, goshawk Accipiter gentilis, population dynamics, predation, risk taking, sparrow hawk Accipiter nisus. [Behav Ecol]

Major histocompatibility complex and kin discrimination in Atlantic salmon and brook trout

Many species of salmonids can discriminate kin from unrelated conspecifics using olfactory cues. In this study, we determined the role of the major histocompatibility complex (MHC) in kin discrimination by juvenile Atlantic salmon (Salmo salar) and brook trout (Salvelinus fontinalis). Genetic variation at the highly polymorphic exon coding for peptide-binding region of an MHC class II gene was studied using polymerase chain reaction and denaturing gradient gel electrophoresis. Experiments compared discrimination ability based on MHC haplotypes both within and among kin and non-kin groups. Juveniles chose kin sharing both alleles over kin sharing no alleles. Juveniles also preferred non-kin sharing both alleles to non-kin sharing no alleles. These data suggest that the MHC class II gene influence kin discrimination in juvenile Atlantic salmon and brook trout. The influence of additional genes was also apparent in trials where juveniles were able to recognize kin sharing no alleles over non-kin sharing no alleles. However, the inability of juveniles to discriminate between kin sharing no alleles and non-kin sharing either one or both alleles indicates that MHC is as potent as the rest of the genome in producing distinguishable odours.

Effect of dietary cues on kin discrimination of juvenile Atlantic salmon (Salmo salar) and brook trout (Salvelinus fontinalis)

Several salmonid species can discriminate kin from non-kin using recognition cues. These are known to involve both genetic and environmental components. This study examined the effect of diet, an environmental cue, on kin discrimination in juvenile Atlantic salmon ( Salmo salar L., 1758) and brook trout ( Salvelinus fontinalis (Mitchill, 1814)). Juveniles were reared in kin and non-kin groups. Three different diets were fed to three kin groups and three non-kin groups. Juveniles were then tested for their ability to discriminate kin. We found that juveniles discriminated individuals between kin and non-kin when they shared a common diet with kin, but did not do so when kin were fed a different diet. Moreover, we predicted that diet and genotype together would provide stronger cues than sharing either dietary cues or genetic cues. When the juveniles were given a choice between kin fed the same diet and kin fed a different diet, they did not show a consistent preference for the former. However, in the absence of kinship, juveniles preferred cues from a common diet, i.e., they preferred cue water conditioned by non-kin sharing a common diet than cue water from non-kin fed a different diet. Our results show that dietary cues affect kin discrimination in juvenile Atlantic salmon and brook trout and provide the first empirical evidence for the influence of diet on kin discrimination in salmonids. The functional explanation of these results is that the preferences in kin discrimination are likely context dependent.