Kin Recognition

Our objective in this study was to evaluate whether a group of paternally related, subadult baboons (Papio cynocephalus) would preferentially interact with kin or nonkin when they had been raised apart from kin other than their mothers. Subjects and their mothers were removed from the breeding group and placed in alternate housing within 24 h after birth to ensure that the subjects would not have a social history with either their sire or their half-siblings. At 90 days of age, the 23 subjects were separated from their mothers and assigned to a peer-peer social group. Behavioral performance was measured using focal animal sampling techniques and 12 molecular behavioral criteria. Analyses of the data indicate that in dyadic interactions kin did not interact more frequently than nonkin in performance of affiliative, sociosexual, and agonistic behaviors. The hypothesis that baboons recognize kin in the absence of maternal associations was not supported by the data; moreover, we suggest that social learning and social history are the most likely mechanisms for kin recognition. Am.

Animals often spend a signifi cant portion of their lives engaged in interactions with conspecifi cs (Allee 1927 ), and engage in helping, aggression, competition, mating and cooperation, to name but a few possible exchanges. As a result, many behaviours, if not the majority, have a social facet, and even those behaviours How and when social behaviour evolves has long been a focus of study within evolutionary biology, yielding the entire subfi eld of sociobiology and behavioural ecology. Although social behaviours may be explored in the same way as any other type of phenotype, the genetics underlying social behaviours diff er from traits that do not vary depending on the social environment in which they are expressed. Social behaviour is best described as an interacting phenotype : a phenotype that depends at least in part on interactions with social partners for its expression. Models of indirect genetic eff ects provide a quantitative genetic framework for understanding the sources of variation underlying interacting phenotypes. Th ey also suggest a genetic mechanism for inheriting traits that are expressed among rather than within individual animals, and identify selection arising from the interactions (termed social selection ).

Three studies explored kin recognition through olfaction. In Study I, adults ðN ¼ 22Þ were tested for ability to identify the odors of themselves; their mother; their father; a sister; a brother; a familiar, unrelated individual; and a stranger. Acquaintances were identified as accurately as biological kin, implicating an association mechanism. However, biological kin were often confused, implicating phenotypic matching. Same-sex kin were confused more than opposite-sex kin, but mainly when same-sex kin had odors of similar intensity. Study II implicated phenotypic matching. Mothers ðN ¼ 18Þ could identify their biological children but not their stepchildren. The preadolescent children ðN ¼ 37Þ identified their full siblings but not half-siblings or stepsiblings. Thus, olfactory cues may help mediate favoritism of blood relatives. In Study III, mutual olfactory aversion occurred only in the father-daughter and brother-sister nuclear family relationships. Recognition occurred between opposite-sex siblings but not same-sex siblings. Thus, olfaction may help mediate the development of incest avoidance during childhood (the Westermarck effect).

Two lines of reasoning predict that women's preferences for people exhibiting cues to kinship will be lower in the follicular phase than in the luteal phase of the menstrual cycle. Women may avoid kinship cues during the follicular phase when they are most fertile due to the costs of inbreeding. Alternatively, women may seek kinship cues during the luteal phase as a byproduct of the benefits of associating with kin during pregnancy, which is also characterized by high progesterone. We find that preferences for facial resemblance, a putative kinship cue, follow this predicted pattern and are positively correlated with estimated progesterone levels based on cycle day. Neither estimated estrogen levels nor conception risk predicted preferences for self-resemblance, and the cyclic shift was stronger for preferences for female faces than male faces. These findings lead to the possibility that this cyclic change in preference for self-resemblance may be a byproduct of a hormonal mechanism for increasing affiliative behavior toward kin during pregnancy rather than a mechanism for preventing inbreeding during fertile periods.

Although unrelated friends are genetically equivalent to strangers, several lines of reasoning suggest that close friendship may sometimes activate processes more relevant to kinship and that this may be especially true for women. We compared responses to strangers, friends, and kin in two studies designed to address distinct domains for which kinship is known to have functional significance: incest avoidance and nepotism. Study 1 examined emotional responses to imagined sexual contact with kin, friends, and strangers. Results revealed that women, compared to men, treated friends more like kin. Study 2 examined benevolent attributions to actual kin, friends, and strangers. Results revealed that women treated friends very much like kin, whereas men treated friends very much like strangers. The current findings support a domain-specific over a domain-general approach to understanding intimate relationships and raise a number of interesting questions about the modular structure of cognitive and affective processes involved in these relationships.

Synopsis. Toads, like many amphibians, display breeding site fidelity. Individuals that return to natal ponds to breed are likely to encounter siblings as potential mates. We examined the genetic structure of Bufo americanus breeding populations at five localities within a 1 km radius. Mitochondrial DNA (mtDNA) haplotypes significantly differed among the breeding populations, but haplotype distributions did not differ from year to year within breeding sites. Natal philopatry may account for these results. Although incest is thus possible, siblings rarely mate. Comparing haplotypes of toads captured while mating, we found only 2 of 86 pairs that could possibly be siblings. We suggest that toads might recognize and actively avoid close kin as mates. Advertisement vocalizations given by males serve as potential cues by which females might recognize their kin. We recorded calls of males, in the field, and later obtained rank estimates of their relationships to one another by DNA fingerprinting of the nuclear genome. The resemblance of males' calls was positively correlated with the similarity of their fingerprints. Significant differences in call characteristics were also found among breeding populations. Temporal parameters, rather than frequency components, encode kinship information. Recently developed techniques in molecular genetics facilitate studies of the heritability of behavioral traits in natural populations.

While most spiders are solitary and opportunistically cannibalistic, a variety of social organisations has evolved in a minority of spider species. One form of social organisation is subsociality, in which siblings remain together with their parent for some period of time but disperse prior to independent reproduction. We review the literature on subsocial and maternal behaviour in spiders to highlight areas in which subsocial spiders have informed our understanding of social evolution and to identify promising areas of future research. We show that subsocial behaviour has evolved independently at least 18 times in spiders, across a wide phylogenetic distribution. Subsocial behaviour is diverse in terms of the form of care provided by the mother, the duration of care and sibling association, the degree of interaction and cooperation among siblings, and the use of vibratory and chemical communication. Subsocial spiders are useful model organisms to study various topics in ecology, such as kin recognition and the evolution of cheating and its impact on societies. Further, why social behaviour evolved in some lineages and not others is currently a topic of debate in behavioural ecology, and we argue that spiders offer an opportunity to untangle the ecological causes of parental care, which forms the basis of many other animal societies.

The costs of inbreeding depression, as well as the opportunity costs of inbreeding avoidance, determine whether and which mechanisms of inbreeding avoidance evolve. In African elephants, sex-biased dispersal does not lead to the complete separation of male and female relatives, and so individuals may experience selection to recognize kin and avoid inbreeding. However, because estrous females are rare and male-male competition for mates is intense, the opportunity costs of inbreeding avoidance may be high, particularly for males. Here we combine 28 years of behavioural and demographic data on wild elephants with genotypes from 545 adult females, adult males, and calves in Amboseli National Park, Kenya, to test the hypothesis that elephants engage in sexual behaviour and reproduction with relatives less often than expected by chance. We found support for this hypothesis: males engaged in proportionally fewer sexual behaviours and sired proportionally fewer offspring with females that were natal family members or close genetic relatives (both maternal and paternal) than they did with nonkin. We discuss the relevance of these results for understanding the evolution of inbreeding avoidance and for elephant conservation.

The ability to distinguish between members of a social group and unfamiliar individuals is a critical element of social behaviour. Social insects can differentiate between nestmates and non-nestmates via recognition cues, which in most species are cuticular hydrocarbons. Cuticular hydrocarbon patterns are altered by genotype and environmental conditions, but it is unclear whether colony social conditions can also affect nestmate interactions. Honeybee queens produce pheromones that regulate many aspects of worker behaviour, physiology and colony organization. A five-component blend, queen mandibular pheromone (QMP), produces many of the effects of a live queen. We found that QMP treatment alters how resident bees interact with intruder bees, based on standard nestmate recognition assays. However, QMP does not appear to alter the ability of bees to distinguish between nestmates and non-nestmates, or general aggression levels. Rather, QMP exposure significantly alters cuticular hydrocarbon patterns of worker bees, suggesting that QMP-treated nestmates are no longer recognized as nestmates by untreated bees, and vice versa. Thus, queen pheromone can have significant effects on nestmate recognition and interactions in honeybees, which may be important for colony cohesion. Ó

Relatedness is a cornerstone of the evolution of social behavior. In the human lineage, the existence of cooperative kin networks was likely a critical stepping stone in the evolution of modern social complexity. Here we report the results of the first experimental manipulation of a putative cue of human kinship (facial self-resemblance) among ostensible players in a variant of the "tragedy of the commons," the oneshot public goods game, in which group-level cooperation-via contributions made to the public good and the punishment of free riders-is supported at a personal cost. In accordance with theoretical predictions, contributions increased as a function of the "kin density" of the group. Moreover, the distribution of punishment was not contingent on kin density level. Our findings indicate that the presence of a subtle cue of genealogical relatedness facilitates group cooperation, supporting the hypothesis that the mechanisms fostering contemporary sociality took root in extended family networks.

Tbe importance of learning for sibling odor preference in juvenile Arctic char was analyzed in the present study. Fish were reared in the following eight conditions: (l) communally with siblings for 15 months; (2) communally with siblings for 17 months; (3) in isolation since fertilization; (4) in isolation since fertilization and exposed to sibling scent during the whole rearing period; (5) in isolation since fertilization and exposed to sibling scent from time of free swimming; (6) in isolation since fertilization and exposed to sibling scent during the whole rearing period, except two months without scent until testing; (7) in isolation since fertilization and exposed to sibling scent from time of free swimming, except two months without scent until testing; and (8) communally with siblings followed by a two-month isolation until testing. Char were followed individually in a Y-maze (fluviarium test) with a video-computer-based image analysis system for 12 hr. Sibling-scented water was supplied to one lateral half of the test area and water from nonsiblings on the opposite half. Isolated individuals without any preexposure to siblings showed no significant preference. Test fish reared with siblings and those that had been reared in isolation but exposed to sibling scent until testing preferred water conditioned by their own siblings. Isolated fish that had been exposed to sibling scent since fertilization, or since free swimming, followed by a two-month period with only pure water, showed no significant preference. Char isolated for two months after being communally reared preferred water scented by siblings. The results demonstrated that behavioral discrimination between siblings and nonsibling odors occurred after total isolation (isolated both from siblings and sibling odors) only in individuals that had been communally reared. This may suggest that social interactions are important for learning and long-term memory of sibling odors in Arctic char.

A few species of mammals produce group-specific vocalisations that are passed on by learning, but the function of learned vocal variation remains poorly understood. Resident killer whales live in stable matrilineal groups with repertoires of seven to 17 stereotyped call types. Some types are shared among matrilines, but their structure typically shows matriline-specific differences. Our objective was to analyse calls of nine killer whale matrilines in British Columbia to test whether call similarity primarily reflects social or genetic relationships. Recordings were made in 1985-1995 in the presence of focal matrilines that were either alone or with groups with non-overlapping repertoires. We used neural network discrimination performance to measure the similarity of call types produced by different matrilines and determined matriline association rates from 757 encounters with one or more focal matrilines. Relatedness was measured by comparing variation at 11 microsatellite loci for the oldest female in each group. Call similarity was positively correlated with association rates for two of the three call types analysed. Similarity of the N4 call type was also correlated with matriarch relatedness. No relationship between relatedness and association frequency was detected. These results show that call structure reflects relatedness and social affiliation, but not because related groups spend more time together. Instead, call structure appears to play a role in kin recognition and shapes the association behaviour of killer whale groups. Our results therefore support the hypothesis that increasing social complexity plays a role in the evolution of learned vocalisations in some mammalian species.

Besides its immunological function of self/non-self discrimination the major histocompatibility complex (MHC) has been recognized as a possible source of individual specific body odors. Dating back to speculations on the role of the extraordinary polymorphism of the MHC as background of an individual chemosensory identity and to early observations of MHC-dependent mate choice in inbred strains of mice, systematic experimental studies revealed a first evidence for H-2 related body odors in this species. Meanwhile a large number of animal studies with rodents and a series of field studies and experiments with humans have extended our knowledge of MHC-related odor signals and substantiated the hypothesis of immunogenetic associated odor types. These results suggest that the most prominent feature of the MHC, its extraordinary genetic diversity, seems in part to be selectively maintained by behavioral mechanisms which operate in contemporary natural populations. The high degree of heter...

Two lines of reasoning predict that highly social species will have mechanisms to influence behavior toward individuals depending on their degree of relatedness. First, inclusive fitness theory leads to the prediction that organisms will preferentially help closely related kin over more distantly related individuals. Second, evaluation of the relative costs and potential benefits of inbreeding suggests that the degree of kinship should also be considered when choosing a mate. In order to behaviorally discriminate between individuals with different levels of relatedness, organisms must be able to discriminate cues of kinship. Facial resemblance is one such potential cue in humans. Computer-graphic manipulation of face images has made it possible to experimentally test hypotheses about human kin recognition by facial phenotype matching. We review recent experimental evidence that humans respond to facial resemblance in ways consistent with inclusive fitness theory and considerations of the costs of inbreeding, namely by increasing prosocial behavior and positive attributions toward self-resembling images and selectively tempering attributions of attractiveness to other-sex faces in the context of a sexual relationship.

Kin recognition is a critical element to kin cooperation, and in vertebrates, it is primarily based on associative learning. Recognition of socially unfamiliar kin occurs rarely, and it is reported only in vertebrate species where promiscuity prevents recognition of first-order relatives. However, it is unknown whether the recognition of socially unfamiliar kin can evolve in monogamous species. Here, we investigate whether genetic relatedness modulates aggression among group members in Siberian jays (Perisoreus infaustus). This bird species is genetically and socially monogamous and lives in groups that are formed through the retention of offspring beyond independence, and the immigration of socially unfamiliar nonbreeders. Observations on feeders showed that genetic relatedness modulated aggression of breeders towards immigrants in a graded manner, in that they chased most intensely the immigrant group members that were genetically the least related. However, cross-fostering experiments showed that breeders were equally tolerant towards their own and cross-fostered young swapped as nestlings. Thus, breeders seem to use different mechanisms to recognize socially unfamiliar individuals and own offspring. As Siberian jays show a high degree of nepotism during foraging and predator encounters, inclusive fitness benefits may play a role for the evolution of fine-scale kin recognition. More generally, our results suggest that fine-graded kin recognition can evolve independently of social familiarity, highlighting the evolutionary importance of kin recognition for social species.

Cooperation and conflict are inevitable consequences whenever a group of individuals get together, be they groups of self-replicating molecules or groups of warring nations. This paper gives an overview of my research using the tropical primitively eusocial paper wasp Ropalidia marginata, aimed at understanding the factors that modulate cooperation and conflict in an insect society. Hamilton's rule provides an excellent theoretical framework not only for investigating the role of genetic relatedness in modulating the levels of cooperation and conflict, as has been done so extensively in the last 30 years, but also for focussing on other factors, when genetic relatedness may be relatively unimportant. Polyandry or multiple mating by queens of R. marginata and serial polygyny or the frequent change in queens, breakdown the genetic asymmetries created by haplodiploidy and make it genetically less advantageous to be a worker, than theoretically expected. Intra-colony kin recognition abilities appear not to be so well developed as to facilitate nepotism in the face of intra-colony genetic variability. Artificial colonies with highly elevated levels of genetic variability appear to be indistinguishable from natural colonies. We have therefore investigated the possibility that social behaviour in insect societies is at least in part mutualistic. The response of wasps to alien conspecifics in the context of their nestS and outside, suggest that factors other than genetic relatedness such as inter-individual assessments, facilitated by impressive cognitive abilities, may play a significant role in modulating the levels of cooperation and conflict.

Significant advances have been made in understanding kin recognition as it pertains to nepotism (preferential treatment of kin) and mate choice (optimization of inbreeding and outbreeding). Yet complementary knowledge about how animals discriminate conspecifics on the basis of genetic relatedness remains unclear for most species. Because of the diversity of their scent sources and highly developed olfactory systems, rodents present a unique opportunity for examining chemical communication and kin recognition as a function of sociality. I review general processes of kin recognition and summarize mechanisms of recognition used by rodents. As a case study, I also examine recognition systems of ground squirrels, relating odor production and perception to differences in patterns of nepotism. Belding's ground squirrels (Spermophilus beldingi) produce Ն2 odors (from oral and dorsal glands) that correlate with relatedness (kin labels), and they are able to use these odors to make precise discriminations among their unfamiliar relatives. Thus, S. beldingi can recognize their distant female kin and male kin, even though these kin are not treated nepotistically (e.g., through cooperative territory defense or alarm call production). Furthermore, S. beldingi use these kin labels and recognition abilities to interact differentially with conspecifics as a function of relatedness. In ground squirrels and in other rodents, components of the kin recognition process (production of recognition cues, discrimination of these cues, and differential treatment of conspecifics) have evolved differentially among even closely related species. Kin recognition abilities in the absence of nepotism might reflect selection for inbreeding avoidance mechanisms, in addition to sex-biased natal dispersal. Together, data and the review demonstrate that recognition abilities cannot be predicted on the basis of sociality alone and suggest that comparative analyses, by multiple assays of discrimination, might be necessary to understand variation in the function of kin recognition within and across species.

Colonial identity in social insects is based on nestmate recognition which is mediated through cuticular substances. Although this is considered to be distinct from kin recognition, it is possible that through evolution the signal mediating kinship was replaced by the signal mediating "nestmateship". Cuticular hydrocarbons in Cataglyphis niger are responsible for modifying the ant's aggressive behavior and are considered to

The ability to discriminate nestmates from non-nestmates is critical to the maintenance of the integrity of social insect colonies. Guard workers compare the chemical cues of an incoming individual with their internal template to determine whether the entrant belongs to their colony. In contrast to honeybees, Apis mellifera, stingless bees have singly mated queens and, therefore, are expected to have a higher chemical homogeneity in their colonies. We tested whether aggressive behaviour of Frieseomelitta varia guards towards nestmate and non-nestmate foragers reflects chemical similarities and dissimilarities, respectively, of cuticular hydrocarbon profiles. We also introduced individuals of Lestrimelitta limao, an obligatory robber species, to test the ability of guards to react effectively to intruders from other taxa. We verified that foraging nestmates were almost invariably accepted, while heterospecific and conspecific non-nestmates were rejected at relatively high rates. However, non-nestmate individuals with higher chemical profile similarity were likely to be accepted by guards. We conclude that guards compare the chemical cuticular blend of incoming individuals and make acceptance decisions according to the similarity of the compounds between the colonies.

Humans possess explicit, rule-based, and culturally determined systems for identifying kin, but kinship inferences are also influenced implicitly by cue-based mechanisms found commonly across the animal kingdom. These mechanisms are fallible. An evolutionarily informed signal-detection analysis suggests that (a) cue-based kin recognition may sometimes be biased in favor of false-positive errors, resulting in implicit kinship inferences even in the presence of nonkin, and (b) the tendency toward this inferential error may vary predictably in response to specific developmental and contextual circumstances. This analysis has important implications for a wide variety of psychological phenomena (especially in the realms of person perception, interpersonal attraction, and prosocial behavior) and leads to the deduction of many novel hypotheses.

One day old honeybee workers (Apis mellifera) were observed in small experimental groups (10 workers per group). These groups were either composed of offspring workers of singly inseminated queens (super-sister groups) or multiply inseminated queens (mixed groups). The groups thus consisted of either super-sisters or a mix of super-and halfsisters. The positions of the individually labelled workers were observed with infrared sensitive video equipment over a 24 h period and analysed with digital image analysis. The spatial distribution of workers in super-sister and mixed groups differed significantly. The distance between supersister workers was significantly less than in mixed groups (n = 339; p < 0.01). Also the distance of the workers from the group centre was significantly less in super-sister groups as compared to mixed groups (n = 3440, p<0.05). The super-sisters thus formed tighter groups than the groups including half-sisters. A genotypic analysis of the mixed groups with microsatellite DNA markers revealed that workers were significantly more frequently observed next to a super-sister rather than a half-sister (p < 0.001). Irrespective whether this results from kin recognition or not, we expect clique formation to be an important factor for the development of task specialisation among worker bees.

We tested the hypothesis that sex-biased natal dispersal reduces close inbreeding in American black bears, a solitary species that exhibits nearly complete male dispersal and female philopatry. Using microsatellite DNA and spatial data from reproductively mature bears (³ 4 years old), we examined the spatial genetic structure of two distinct populations in New Mexico from 1993 to 2000. As predicted, relatedness (r) and the frequency of close relationships (parent-offspring or full siblings) decreased with distance among female dyads, but little change was observed among male or opposite-sex dyads. Neighbouring females were more closely related than neighbouring males. The potential for inbreeding was low. Most opposite-sex pairs that lived sufficiently close to facilitate mating were unrelated, and few were close relatives. We found no evidence that bears actively avoided inbreeding in their selection of mates from this nearby pool, as mean r and relationship frequencies did not differ between potential and actual mating pairs (determined by parentage analysis). These basic patterns were apparent in both study areas despite a nearly two-fold difference in density. However, the sex bias in dispersal was less pronounced in the lower-density area, based on proportions of bears with male and female relatives residing nearby. This result suggests that male bears may respond to reduced competition by decreasing their rate or distance of dispersal. Evidence supports the hypothesis that inbreeding avoidance is achieved by means of male-biased dispersal but also indicates that competition (for mates or resources) modifies dispersal patterns.

ated tap) water showed no tendencies to discriminate between these stimuli. When individuals were exposed both to water from non-siblings and to blank water, however, they oriented significantly toward the blank water. Kin association may thus result in part from negative klinokinetic responses induced by contact with factors released by nonkin.

Experiments simulating spring emergence and partial second generation emergence of the alfalfa leafcutting bee were conducted to determine if emerging bees distinguish full sibs from non-kin and the conditions under which fratricide occurs. Using glass tubes and different incubation treatments, bees were forced to emerge behind sibs or non-sibs whose development had been delayed by 4 or 17 days. Under these conditions, emerging bees had three choices: (1)to destroy their nest mate to exit the tube; (2) to circumvent their nest mate to exit; and (3)to return to their own cells and await the emergence of their nest mate. Emerging bees made no distinction between sibs and nonsibs: non-sibs were not destroyed more often than sibs. This suggests that nest mates are routinely treated as sibs. The emergence behavior of bees was governed by the developmental stage of their nest mates: when development of nest mates was delayed by 4 days, emerging bees most often returned to their cells and waited. Conversely, when development of nest mates was delayed by 17 days, emerging bees either destroyed or circumvented them. Due to their small size, males circumvented nest mates more often than females did. Thus, emerging bees avoided killing their nest mates, except in situations where suicide was the only other option. These results seem consistent with models predicting the conditions under which extreme selfish behavior and kin recognition will occur.

"Social behaviour in spiders is rare: of the 39 000 species of spiders known, only 23 are considered to be cooperatively social. Delena cancerides is a social species of the huntsman spider that is endemic to Australia. This species is virtually unique among social spiders, having evolved social behaviour in the absence of a snare web. It is thought that this form of social behaviour in D. cancerides has evolved via the sub-social route, that is, the extension of an ancestrally occurring period of maternal care and the delayed dispersal of juveniles. Most social spiders show no aggression towards non-kin conspecifics, prompting suggestions that spiders cannot recognize kin; however, D. cancerides individuals are highly aggressive towards conspecifics introduced from outside their own colony. In order to determine whether selective aggression in D. cancerides has its basis in kin recognition, tolerance behaviour was assessed in the context of kinship and size. We observed that, in general, juveniles preferred to starve than engage in cannibalism of any conspecifics, related or not. However, where cannibalism did occur, non-kin were preferentially eaten, indicating that this species is clearly capable of kin recognition. Size thresholds were also established, below which juveniles are tolerated by adults and above which aggressive interactions leading to death occur. We conclude that kin recognition and juvenile dispersal explain the
uncharacteristically high levels of genetic polymorphism in this species."

Kin-recognition systems have been hypothesized to exist in humans, and adaptively to regulate altruism and incest avoidance among close genetic kin. This latter function allows the architecture of the kin recognition system to be mapped by quantitatively matching individual variation in opposition to incest to individual variation in developmental parameters, such as family structure and co-residence patterns. Methodological difficulties that appear when subjects are asked to disclose incestuous inclinations can be circumvented by measuring their opposition to incest in third parties, i.e. morality. This method allows a direct test of Westermarck's original hypothesis that childhood co-residence with an opposite-sex individual predicts the strength of moral sentiments regarding third-party sibling incest. Results support Westermarck's hypothesis and the model of kin recognition that it implies. Co-residence duration objectively predicts genetic relatedness, making it a reliable cue to kinship. Co-residence duration predicts the strength of opposition to incest, even after controlling for relatedness and even when co-residing individuals are genetically unrelated. This undercuts kin-recognition models requiring matching to self (through, for example, major histocompatibility complex or phenotypic markers). Subjects' beliefs about relatedness had no effect after controlling for co-residence, indicating that systems regulating kin-relevant behaviours are non-conscious, and calibrated by co-residence, not belief.

Kin recognition in social insects In two very well known papers in 1964, W. D. Hamilton proposed a genetical theory for the evolution of altruistic and other social behaviour, a theory which is now known as kin selection. Hamilton's ideas were rapidly appreciated and widely applied (Wilson, 1971). Yet, at least for the next 15 year~:; we had no clue as to how animals assessed kinship or genetic relatedness amongst themselves. This situation has now changed and the ability to discriminate kin from non-kin has been reported not only in ants, bees and wasps but also in marine invertebrates. isopods, fishes, frogs, toads, birds and a variety of mammalian species (Gadagkar, 1985).

Theories of parental care evolution predict that genetic relatedness will be an important variable in the amount of care a parent provides. However, current inferences of relatedness-based parental investment from studies in humans and birds remain challenged. No study has yet demonstrated parental care adjustment in a manner uncomplicated by life-history correlates or experimental design. We now present a unique test that controls for individual life histories and demonstrates paternity-related dynamic adjustments in parental care. Brood-rearing male bluegill sun¢sh (Lepomis macrochirus) that are cuckolded to a varying degree will either increase or decrease their parental investment in response to changing information on paternity during brood development. Speci¢cally, as parental males detect paternity lost to cuckolders and, hence, a reduction in the value of their brood, they adaptively lower their level of parental care. Conversely, if they detect that their paternity is higher than previously assessed, they adaptively raise their level of parental care. This dynamic adjustment during brood rearing indicates the importance of genetic relatedness in parental investment decisions and provides needed empirical support for theoretical predictions.

A central question in social evolution is what processes regulate the number of breeders in each social group. Here, we tested whether differences in the rate of acceptance of new queens by resident workers could be a proximate cause explaining the coexistence of single-and multiple-queen colonies in an ant population. We found that Formica selysi workers discriminated against foreign (non-nestmate) queens, which contributes to maintaining the genetic integrity of the social group essential to kin selection. All the young and newly mated foreign queens introduced into experimental groups of workers died within 48 h. In contrast, workers frequently accepted young newly mated nestmate queens. The survival of nestmate queens was not significantly lower in groups of workers originating from single-queen colonies than in groups of workers originating from multiple-queen colonies. Finally, virgin queens had significantly higher survival than mated queens. Together, these results show that the maintenance of singlequeen and multiple-queen colonies in the same population is unlikely to be caused by strong differences between the two types of colonies in their rate of acceptance of new queens by workers. They also suggest that the discrimination of queens by resident workers restricts the dispersal of foreign queens among colonies, but not the acceptance of additional nestmate queens. Ó

In cooperatively breeding species, helpers typically provide food to offspring, and distribute food throughout the brood or litter. However, in the communal breeding banded mongoose (Mungos mungo), some group members escort individual pups during their period of dependence, and escorts consistently associate with the same pup, although not all pups have an escort. The aim of the present study was to determine whether group members actively care for pups, pups benefit from association, and escorts or pups maintain association. Adult banded mongooses provision, protect, carry, groom, and play with pups. Although escorts fed pups more than did nonescorts, escorted pups were neither larger nor in better condition than were nonescorted pups at the end of the association period. Nevertheless, escorted pups were more likely to survive the association period than were nonescorted pups, providing evidence that carers confer beneficial effects on their recipients. However, the recipients are unlikely to be the genetic offspring of the escort because it is the pup that maintains the pup-escort association, and escorts, rather than showing a preference for provisioning their paired pup, follow a ''feed the closest pup'' rule. Although carers gain indirect fitness benefits through increasing survival of related pups, the lack of kin discrimination means carers are unable to maximize their fitness by preferentially escorting their own offspring or the offspring of closer relatives.

The life of a colony of subterranean termites, such as Coptotermes formosanus Shiraki (Isoptera: Rhinotermitidae), has natural inbreeding and outbreeding cycles. Reproductives of mature colonies can be replaced by their offspring, which increases the degree of inbreeding in each generation. High degrees of inbreeding may lead to inbreeding depression. In this study we focused on mechanisms for inbreeding avoidance during swarming that do not require kin recognition. We investigated genetic differentiation between swarm aggregations (isolation by distance), genetic diversity within swarm aggregations (multiple colony origin) and genetic differentiation between sexes. Alates were collected from fi ve swarm aggregations in New Orleans, La. The genetic make-up of each swarm aggregation was then described by microsatellite genotyping. Alates from the different swarm aggregations were genetically differentiated; however, no isolation by distance up to at least 1000 m was detected. The dispersal distance of alates was suffi cient to guarantee mixing of an average of 13 colonies within swarm aggregations. On average, eleven percent of all possible pairs of alates in each swarm aggregation were putative full siblings. Genotypic frequencies differed signifi cantly between males and females. This could not be explained by sex-biased dispersal. We hypothesize sex-biased investment at the colony level to account for this difference. Genetic differentiation between the sexes and dispersal distances suffi cient to promote high genetic diversity within swarm aggregations each facilitate inbreeding avoidance. These observations are consistent with the results of previous studies demonstrating that the majority of simple family colonies in Louisiana populations are headed by unrelated and outbred pairs of reproductives.

Honeybee colonies reproduce by colony fission and swarming. The primary swarm leaves the nest with the mated mother queen. Further ''after-swarms'' can leave the nest. These are composed of virgin queens and sister workers. Since all workers in the primary swarm have the same relationship to the mother queen, kin recognition cannot have any effect on the worker distribution in the swarm. Because of polyandry of the mother queen, the after-swarm is composed of superand halfsister workers of the virgin queen. In this case kin recognition might affect swarm composition if workers increase their inclusive fitness by preferentially investing in a supersister queen. The distribution of workers in the mother colony, the primary and the afterswarm was analyzed using single-locus DNA fingerprinting in two colonies of the honeybee (Apis mellifera). The colonies were composed of 21 and 24 worker subfamilies because of multiple mating of the queen. The subfamily distribution in the mother colonies before swarming was significantly different from the subfamily frequencies in the primary swarm. This indicates different propensities for swarming in the various subfamilies. The subfamily distribution was also significantly different between the mother colony and the after-swarm. There was however no significant difference between the subfamily composition of the primary and the afterswarm. The average effects of kin recognition on the distribution of the subfamilies in the two after-swarms were less than 2%. We conclude that colony-level selection sets the evolutionary framework for swarming behaviour.

Responding differentially to kin and non-kin is known to be adaptive in many species. One example is the inclusive fitness benefits of reducing aggression toward closer relatives. Little is known, however, about the ability of animals to assess differential degrees of genetic relatedness and to respond accordingly with differential levels of aggression. In the present study, we tested whether aggressiveness between body mass-matched pairs of fire salamander (Salamandra infraimmaculata) larvae covaried with the genetic similarity between them. We quantified aggressiveness at three levels of genetic similarity by selecting pairs within and across pools from recently genotyped populations. We also assessed aggression between pairs of siblings. Aggression and associated injuries decreased as genetic similarity increased across the groups. These findings suggest that cannibalistic salamanders can assess their degree of genetic relatedness to conspecifics and vary their behavioral responses depending on the degree of similarity between them along a genetic relatedness continuum.

Kin recognition requires the ability to discriminate between one’sowngenetic relatives and non-relatives.
There are two mechanisms that aid in kin discrimination: phenotype matching and familiarity. Dogs
may be a good model for assessing these mechanisms as dogs are a promiscuous social species with a
keen sense of smell. Domestic dogs of both sexes were presented with two scents (close kin, distantkin)
and preference was assessed through three measures (latency to approach, number of visits, time
spent). Experiment 1 explored the possibility of phenotype matching as subjects had no contact with
sires, whose scent was presented alongside a control male’s scent. Experiment 2 explored recognition
of siblings raised with the subjects and then separated at seven weeks of age. Whereas female dogs in
this experiment did not show a statistically significant preference, male dogs showed a preference for
distant-kin when presented with sire and female sibling samples.