Genetic evidence for kin-based female social structure in common eiders (Somateria mollissima)

Kin-based social groups are commonly studied among cooperativelybreeding species but have been less studied in "nontraditional"group breeding systems. We investigated the presence of kin-basedsociality among females in the common eider (Somateria mollisima),a colonial nesting sea duck that exhibits high levels of natalphilopatry in females. Previous studies of female socialityin common eiders have been restricted to observations duringbrood rearing. However, aggregations of female common eidersare also observed during other periods of the life cycle suchas colony arrival and nesting. Here we apply a novel, empiricalframework using molecular markers and field sampling to geneticallycharacterize female social groups at several stages of the commoneider life cycle. When compared with mean estimates of interindividualrelatedness for the entire colony, significantly higher levelsof relatedness were found between females within groups arrivingto the colony in flight, between females and nearest neighborsat the time of nest site selection, and between groups of femalesdeparting the colony with ducklings. Both full-sibling and half-siblingequivalent relationships were also found within these groups.Therefore, throughout each of several stages including in-flightcolony arrival, nesting, and brood rearing, we provide the firstgenetically confirmed evidence of female kin-based social groupsin common eiders and anseriformes in general.     

Kin recognition by the predatory mite Iphiseius degenerans: discrimination among own, conspecific, and heterospecific eggs

1. Kin recognition is important in many social insects, but has also been found in several nonsocial insects such as parasitoids, where it plays an important role in oviposition behaviour. In nonparasitic arthropods, however, the fitness of ovipositing females also depends on the oviposition behaviour of related and unrelated females, especially when eggs are oviposited in clusters by several females. 2. In this paper, kin recognition in a predatory mite, Iphiseius degenerans, is studied. Mothers are capable of determining offspring sex ratio, and cannibalism on juvenile stages is a common phenomenon. Therefore, kin recognition is expected to occur in this predator. 3. Oviposition behaviour of this species is particularly interesting because it alternates foraging bouts in flowers with deposition of a single egg at a time on a leaf, where predation risk is lower. The eggs are not scattered but are deposited in clusters. After feeding in a flower, females therefore have to locate clusters of eggs. 4. Experiments on two‐choice arenas showed that females prefer to oviposit close to conspecific eggs rather than close to heterospecific eggs. Females also showed a preference for ovipositing near closely related conspecific eggs rather than more distantly related eggs. 5. Females tended to displace eggs of heterospecifics more frequently than eggs of conspecifics. 6. These behavioural observations show that females can discriminate not only between conspecific and heterospecific eggs but also between eggs that vary in degree of relatedness. This enables females to oviposit in clusters containing related eggs and thus avoid cannibalism by non‐kin and/or produce adaptive sex ratios despite the fact that the adults commute between flowers and leaves.     

Kin discrimination and sex ratios in a parasitoid wasp

Sex ratio theory provides a clear and simple way to test if nonsocial haplodiploid wasps can discriminate between kin and nonkin. Specifically, if females can discriminate siblings from nonrelatives, then they are expected to produce a higher proportion of daughters if they mate with a sibling. This prediction arises because in haplodiploids, inbreeding (sib-mating) causes a mother to be relatively more related to her daughters than her sons. Here we formally model this prediction for when multiple females lay eggs in a patch, and test it with the parasitoid wasp Nasonia vitripennis. Our results show that females do not adjust their sex ratio behaviour dependent upon whether they mate with a sibling or nonrelative, in response to either direct genetic or a range of indirect environmental cues. This suggests that females of N. vitripennis cannot discriminate between kin and nonkin. The implications of our results for the understanding of sex ratio and social evolution are discussed.     

Isospora viridanae N. Sp., an Intranuclear Coccidian Parasite from the Canarian Skink, Chalcides viridanus (Lacertilia: Scincidae)

A caryotropic species of coccidium, Isospora viridanae n. sp. (Apicomplexa: Eimeriidae). has been found as a parasite in the Canarian skink, Chalcides viridanus Gravenhorst, 1851, from Tenerife, Spain, and is described here as a new species. Fully sporulaled oocysts of Isospora viridanae are spherical and measure 21.6 (1 7.6–23.4) nm in diameter. Mtcropyle, oocyst residuum and polar granule are ali absent. Oocysts of this coccidian, with a smooth bilayered wall, contain 2 ovoid sporocysts 13.2 (11.7–14.0) by 9.5 8.2–10 5) μm. A sporocyst residuum is present as well as a Stieda body and a substieda body. Most oocysts are found to be at the beginning of sporulanon when excreted and show 2 spherical sporoblasts. Sporulation is completed within 24 to 48 h at 23 × 2°C Sporozoites are 13–14 μm long and are about 2.5–3 μ m wide. Endogenous stages of schizogony and gamogony develop in the nuclei of epithelial cells from the small intestine of the skink. Comparisons with other species of the genus found in lacertilian hosts indicate that it is a new species.     

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.     

Kin structure provides no explanation for intruders in social aphids

Nontraditional social organisms have received increasing attention in recent years, because they present opportunities to study the convergent properties of social evolution. Some aphid species are social, occurring in dense clones with specialized morphs that attack predators and parasites. Little is known about how social aphid colonies resolve conflicts of interest when clonal barriers break down. Pemphigus obesinymphae is a North American gall-forming social aphid that produces both nymphal defenders that protect natal clones, and specialized intruders that invade other nearby clones on their host plants. We tested the hypothesis that clones are arranged on their host plants in spatial clusters of related family groups, such that intruders would be biased towards movement within kin groups. Movement within and not between kin groups would then provide insight into the nature of conflict in this social aphid. We sampled eight sites in the eastern United States and in Arizona, and used eight microsatellite markers to estimate pairwise relatedness between spatial groups. We found little evidence of deviation from random distributions of genotypes on their host plants. Evidently, Pem. obesinymphae intruders typically exploit unrelated clones, and spatial orientation provides no solution to the problem of 'polyclonality' in this species. We discuss implications of this result for our understanding of cooperation and conflict in social aphids.     

Competition and kin discrimination in colony founding by social Hymenoptera

Summary After mating, queens of social wasp and ant species sometimes band together to start a new colony cooperatively. I assume these queens sequentially encounter potential nest sites that may or may not already contain a queen. Whether to remain at a given site or to leave in hopes of finding a better site is modelled using dynamic programming. The results suggest that discriminating competitive ability is more valuable than discriminating kinship. Wasps, which have a high survival rate in transitions between nest site encounters and in which pleometrosis seems to have a consistently high benefit, are predicted to discriminate both competitive ability and kinship of potential partners. Ants, which have lower survivorship and variable benefits, are predicted to show conditional joining behavior (sometimes based on discriminating competitive ability, but almost never based on discriminating kinship). A survey of the literature supports the model with respect to the predictions on kin discrimination in both groups and on conditional joining behavior in ants. However, whether partners are joined based on perceptions of competitive ability needs more tests.     

Cannibalism and kin recognition in Delena cancerides (Araneae: Sparassidae), a social huntsman spider

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.     

Brood discrimination, nest mate discrimination, and determinants of social behavior in facultatively quasisocial beetles (Nicrophorus spp.)

In this study we investigated ecological determinants of socialityin burying beetles (Nicrophorus spp.), potential conflicts ofinterest among reproductive females, and the effects of nestingfailure and costs of fighting on cooperation. Burying beetlesare known to form monogamous pairs when exploiting small vertebratecarcasses. More complex social behavior in this group is poorlyunderstood. We conducted experiments in which one or two females(N. defodiens, N. orbicollis) were provided small or large carcasseson which to breed. On large but not on small carcasses, twofemales often formed cooperative breeding associations (jointlyprepared a carcass and fed young). In N. defodiens, but notN. orbicollis, two females produced a larger brood than singlefemales on large carcasses. In both species, the reproductiveoutput per female was less for two than for one female. Thepresence of a second female did not decrease the preparationtime of a carcass (discovery of resource to egg hatch). Conflictwas evident between females. Trials employing females of similarsize were more likely to result in injury than trials usingfemales of dissimilar size (N. tomentosus, N. defodiens, N.orbicollis). In N. tomentosus, those associations that persistedthe longest resulted in the fewest injuries. After care of youngwas initiated, conflict among familiar nest mates was not observed.There was no evidence that breeding females could discriminatebetween brood; use of a genetic marker (N. orbicollis) demonstratedthat females fed related and unrelated young alike. Femalesof similar size (high potential cost of fighting for the dominantindividual) were not more likely to form cooperative breedingassociations than females of dissimilar size (low cost of fightingfor dominant). Females of a species subject to a high rate ofnest failure (N. defodiens) were more likely to cooperate thanfemales of a species with a low rate of nest failure (N. orbicollis).It is argued that limited reproductive opportunities, difficultyin controlling rivals' access to a large carcass, and the superabundantlarval food supply represented by a large carcass, but not kinselection, have contributed to the evolution of cooperativebehavior in this group. In addition, we hypothesize that beetlesmight initially tolerate consexual rivals on large carcasseswhen there is a high likelihood of nesting failure, therebyavoiding potentially costly conflicts.     

Kin distribution of amphibian larvae in the wild

According to kin selection theory, the location of an individual with respect to its relatives can have important ramifications for its fitness. Perhaps more than any other vertebrate group, anuran amphibian larvae have been the subject of many experiments on this topic. Some anuran species have been shown in the laboratory to recognize and associate with their siblings and half-siblings. However, due to the difficulty of identifying sibships, no kinship studies with anuran larvae have been conducted in the wild. Here, we use microsatellite analysis to show that wood frog (Rana sylvatica) tadpoles were nonrandomly distributed in two ponds with respect to their relatives. In one pond, the tadpoles were significantly clumped with their siblings or half-siblings as expected from other published laboratory studies on this species. However, in another pond, the tadpoles were significantly nonrandomly dispersed from their siblings or half-siblings. This is the first example of kin repulsion of nonreproductive animals in the wild and the first time a species has been shown to display both aggregation and repulsion under different circumstances. These results suggest that kin distribution is context dependent and demonstrate the importance of testing kin selection hypotheses under natural conditions.     

Convergent evolution of kin-based sociality in a lizard

Studies of social birds and mammals have produced extensive theory regarding the formation and dynamics of kin-based social groups in vertebrates. However, comparing kin dynamics in birds and mammals to social reptiles provides the opportunity to identify selective factors that promote independent origins of kin sociality across vertebrates. We combined a 5-year mark-recapture study with a DNA microsatellite analysis of relatedness in a social lizard (Xantusia vigilis) to examine the formation and stability of kin groups. We found that these lizards are highly sedentary and that groups often form through the delayed dispersal of offspring. Groups containing juveniles had higher relatedness than adult-only groups, as juveniles were commonly found in aggregations with at least one parent and/or sibling. Groups containing nuclear family members were more stable than groups of less-related lizards, as predicted by social theory. We conclude that X. vigilis aggregations conform to patterns of kin sociality observed in avian and mammalian systems and represent an example of convergent evolution in social systems. We suggest that kin-based sociality in this and other lizards may be a by-product of viviparity, which can promote delayed juvenile dispersal by allowing prolonged interaction between a neonate and its mother.     

Evolutionary diversification of the lizard genus Bassiana (Scincidae) across Southern Australia

Background

Relatively recent (Plio-Pleistocene) climatic variations had strong impacts on the fauna and flora of temperate-zone North America and Europe; genetic analyses suggest that many lineages were restricted to unglaciated refuges during this time, and have expanded their ranges since then. Temperate-zone Australia experienced less severe glaciation, suggesting that patterns of genetic structure among species may reflect older (aridity-driven) divergence events rather than Plio-Pleistocene (thermally-mediated) divergences. The lizard genus Bassiana (Squamata, Scincidae) contains three species that occur across a wide area of southern Australia (including Tasmania), rendering them ideally-suited to studies on the impact of past climatic fluctuations.

Methodology/Principal Findings

We performed molecular phylogenetic and dating analyses using two partial mitochondrial genes (ND2 and ND4) of 97 samples of Bassiana spp. Our results reveal a pattern of diversification beginning in the Middle Miocene, with intraspecific diversification arising from 5.7 to 1.7 million years ago in the Upper Miocene-Lower Pleistocene.

Conclusions/Significance

In contrast to the temperate-zone Northern Hemisphere biota, patterns of evolutionary diversification within southern Australian taxa appear to reflect geologically ancient events, mostly relating to east-west discontinuities imposed by aridity rather than (as is the case in Europe and North America) relatively recent recolonisation of northern regions from unglaciated refugia to the south.     

Kin cohesiveness and possible inbreeding in the mouthbrooding tilapia Sarotherodon melanotheron (Pisces Cichlidae)

Four microsatellite markers were used to study genetic variation among individuals of the mouthbrooding tilapia Sarotherodon melanotheron (Rüppel 1852) caught in separate but adjacent shoals. A comparison was also made with fish from six other localities. Populations originating from riverine environments appear to be panmictic, while samples from open waters such as lagoons showed highly significant heterozygote deficiencies. For instance, at the 33-allele locus SMEL4, 32 homozygous individuals were observed among the 82 individuals from the same lagoon location instead of only five homozygotes expected if random mating occurred. A further assessment of the genetic similarity of individuals within each shoal, validated by robust permutation techniques requiring no precise knowledge of gene frequencies, showed that related individuals tend to aggregate, and suggested that mating occurs preferentially within small groups of kin. Cichlids are often presented as a group of fish where microallopatric speciation takes place. The possible link between kin aggregation, inbreeding and shoaling behaviour we propose here may have important consequences for our understanding of the mechanisms involved in this fast speciation process.     

Kin recognition in a semi-natural context: Behaviour towards foreign conspecifics in the social waspRopalidia marginata (Lep.) (Hymenoptera: Vespidae)

Summary Female wasps of the tropical primitively eusocial speciesRopalidia marginata are known to discriminate unfamiliar nestmates from unfamiliar non-nestmates outside the context of their nests. Here, we show that when foreign conspecifics are introduced in the context of a nest in laboratory cages, genetic relatives among them are treated by nest inhabitants more tolerantly than non-relatives, but that no foreign conspecifics are accepted into the nests. However, some wasps may leave their nest and join the foreign relatives and non-relatives to found new colonies cooperatively. Very few of the introduced animals are severely attacked or killed; most are allowed to remain in parts of the cage away from the nest. These results suggest that factors other than genetic relatedness may be involved in regulating tolerance and acceptance of foreign conspecifics on a nest and its vicinity. Our results are different from those of similar experiments with ants, which have demonstrated that former nestmates that are removed as pupae and later introduced as adults are either accepted into the nest or attacked and killed. We attribute this difference to the fact that in a primitively eusocial species such asR. marginata, the rules governing tolerance and acceptance of foreign conspecifics must be quite different from those in highly eusocial species. We also attempt to test some predictions of the conspecific acceptance threshold models of Reeve (Am. Nat. 133:407–435, 1989). Our results uphold the predictions of his fitness consequence submodel but do not support those of his interaction frequency sub-model.     

Phylogenetic relationships and limb loss in sub-Saharan African scincine lizards (Squamata: Scincidae)

Skinks are the largest family of lizards and are found worldwide in a diversity of habitats. One of the larger and more poorly studied groups of skinks includes members of the subfamily Scincinae distributed in sub-Saharan Africa. Sub-Saharan African scincines are one of the many groups of lizards that show limb reduction and loss, and the genus Scelotes offers an excellent opportunity to look at limb loss in a phylogenetic context. Phylogenetic relationships were reconstructed for a total of 52 taxa representing all subfamilies of skinks as well as other Autarchoglossan families using sequence from six gene regions including; 12S, 16S, and cytochrome b (mitochondrial), as well as alpha-Enolase, 18S, and C-mos (nuclear). The family Scincidae is recovered as monophyletic and is the sister taxon to a (Cordylidae+Xantusiidae) clade. Within skinks the subfamily Acontinae is monophyletic and sister group to all remaining skinks. There is no support for the monophyly of the subfamilies Lygosominae and Scincinae, but sub-Saharan African scincines+Feylinia form a well supported monophyletic group. The monophyly of Scelotes is confirmed, and support is found for two geographic groups within the genus. Reconstructions of ancestral states for limb and digital characters show limited support for the reversal or gain of both digits and limbs, but conservative interpretation of the results suggest that limb loss is common, occurring multiple times throughout evolutionary history, and is most likely not reversible.