Dominance hierarchy and social grooming in female lion- tailed macaques (Macaca silenus) in the Western Ghats, India

This article reports the structure of dominance and its relationship with social grooming in wild lion-tailed macaque females. The strength of dominance hierarchy was 0.79 on a scale of 0 to 1 indicating a moderate linearity in the ranking system. Dominance scores were converted into an ordinal as well as an interval scale. Grooming scores were also converted into interval scales using standard scores. Grooming received and grooming given correlated positively and negatively respectively with dominance ranks indicating that high ranking females received more and gave less grooming. Grooming was also positively related to encounter rates for dyads of females. More grooming among adjacent ranks, and grooming being more reciprocal, occurred only in the case of dominant females. The grooming patterns, therefore, appeared to be more of despotic than egalitarian nature. While ranking macaques into different Grades of social systems ranging from despotic to egalitarian, Thierry (2004) has placed lion-tailed macaques in Grade 3 corresponding to the ‘relaxed’ social system. Our results indicate that the grooming and dominance relationships in this species are more despotic, and hence, the Grade for this species requires to be shifted toward 2 or 1.     

Breeding suppression between two unrelated and initially unfamiliar females occurs with or without social tolerance in common voles (<Emphasis Type="Italic">Microtus arvalis</Emphasis>)

Female common voles can breed in small groups or in isolation. Given the option, will isolated females opt for communal breeding with unrelated females and a probable low reproductive bias, or will they remain isolated, forgoing the advantages of group living? This laboratory work examined the response of two unrelated females to a foreign male in order to determine their social and breeding strategies. Before encountering a male, 70% of the females lived communally and 30% were solitary with a dominance hierarchy. In the presence of the male, only 33% of the females were still associated and lived with the male in a communal nest. In the other triads, only the oldest female lived with the male and she dominated the younger female. Although all animals were then experimentally separated to avoid late abortion due to social stress or infanticide, in 89% of the dyads only one female littered. This breeding suppression happened in hierarchic dyads but also in tolerant ones. This laboratory study on the social influence on reproduction showed that breeding suppression can occur in unrelated female common voles even when they are not closely grouped. It suggests that cooperative breeding between unrelated females should remain rare.     

The social function of tail up in the domestic cat (Felis silvestris catus)

We investigated the social function of tail up in order to verify its possible relationship with the hierarchical organization of a social group. Domestic cats live at higher densities than their ancestor which is a solitary species. Since the signals needed by solitary animals have different properties than those needed by group-living individuals, signalling pattern utilised by the domestic cat has inevitably changed. Kittens displayed the tail up when greeting their mother; this behaviour can also be observed in wild species. But, in domestic cat the tail up can be also observed when an adult individual meets another one and it signals the intention to interact amicably. Rank order affected the display of tail up posture: it was more frequently displayed by low-ranking cats, and high-ranking individuals received it more often than other members of the social group. Then, tail up seems to be a signal by means of which a cat shows the recognition of the higher social status of the individual to whom is directed. We confirmed the association between tail up and other affiliative behavioural patterns and the individual variability in displaying them. Considerations on the evolution of the tail up as a visual signal will be discussed.     

Quantifying the genetic component of phenotypic variation in unpedigreed wild plants: tailoring genomic scan for within-population use

The study of adaptive genetic variation in natural populations is central to evolutionary biology. Quantitative genetics methods, however, are hardly applicable to long-lived organisms, and current knowledge on adaptive genetic variation in wild plants mostly refers to annuals and short-lived perennials. Studies on long-lived species are essential to explore possible life-history correlates of genetic variation, selection, and trait heritability. In this paper, we propose a method based on molecular markers to quantify the genetic basis of individual phenotypic differences in wild plants under natural conditions. Rather than focusing on inferring individual relatedness to estimate the heritability of phenotypic traits, we directly estimate the proportion of observed phenotypic variance that is statistically accounted for by genotypic differences between individuals. This is achieved by (i) identifying loci that are correlated across individuals with the phenotypic trait of interest by means of an amplified fragment length polymorphism (AFLP)-based explorative genomic scan, and (ii) fitting multiple regression and linear random effect models to estimate the effects of genotype, environment and genotype × environment on phenotypes. We apply this method to estimate genotypic and environmental effects on cumulative maternal fecundity in a wild population of the long-lived Viola cazorlensis monitored for 20 years. Results show that between 56–63% (depending on estimation method) of phenotypic variance in fecundity is accounted for by genotypic differences in 11 AFLP loci that are significantly related to fecundity. Genotype × environment effects accounted for 38% of fecundity variance, which may help to explain the unexpectedly high levels of genetic variance for fecundity found.     

EVOLUTION OF IDENTITY SIGNALS: FREQUENCY‐DEPENDENT BENEFITS OF DISTINCTIVE PHENOTYPES USED FOR INDIVIDUAL RECOGNITION

Identifying broad‐scale evolutionary processes that maintain phenotypic polymorphisms has been a major goal of modern evolutionary biology. There are numerous mechanisms, such as negative frequency‐dependent selection, that may maintain polymorphisms, although it is unknown which mechanisms are prominent in nature. Traits used for individual recognition are strikingly variable and have evolved independently in numerous lineages, providing an excellent model to investigate which factors maintain ecologically relevant phenotypic polymorphisms. Theoretical models suggest that individuals may benefit by advertising their identities with distinctive, recognizable phenotypes. Here, we test the benefits of advertising one's identity with a distinctive phenotype. We manipulated the appearance of Polistes fuscatus paper wasp groups so that three individuals had the same appearance and one individual had a unique, easily recognizable appearance. We found that individuals with distinctive appearances received less aggression than individuals with nondistinctive appearances. Therefore, individuals benefit by advertising their identity with a unique phenotype. Our results provide a potential mechanism through which negative frequency‐dependent selection may maintain the polymorphic identity signals in P. fuscatus. Given that recognition is important for many social interactions, selection for distinctive identity signals may be an underappreciated and widespread mechanism underlying the evolution of phenotypic polymorphisms in social taxa.     

Tolerant food sharing and reciprocity is precluded by despotism among bonobos but not chimpanzees

Tolerant food sharing among human foragers can largely be explained by reciprocity. In contrast, food sharing among chimpanzees and bonobos may not always reflect reciprocity, which could be explained by different dominance styles: in egalitarian societies reciprocity is expressed freely, while in more despotic groups dominants may hinder reciprocity. We tested the degree of reciprocity and the influence of dominance on food sharing among chimpanzees and bonobos in two captive groups. First, we found that chimpanzees shared more frequently, more tolerantly, and more actively than bonobos. Second, among chimpanzees, food received was the best predictor of food shared, indicating reciprocal exchange, whereas among bonobos transfers were mostly unidirectional. Third, chimpanzees had a shallower and less linear dominance hierarchy, indicating that they were less despotic than bonobos. This suggests that the tolerant and reciprocal sharing found in chimpanzees, but not bonobos, was made possible by the absence of despotism. To investigate this further, we tested the relationship between despotism and reciprocity in grooming using data from an additional five groups and five different study periods on the main groups. The results showed that i) all chimpanzee groups were less despotic and groomed more reciprocally than bonobo groups, and ii) there was a general negative correlation between despotism and grooming reciprocity across species. This indicates that an egalitarian hierarchy may be more common in chimpanzees, at least in captivity, thus fostering reciprocal exchange. We conclude that a shallow dominance hierarchy was a necessary precondition for the evolution of human‐like reciprocal food sharing. Am J Phys Anthropol 143:41–51, 2010. © 2010 Wiley‐Liss, Inc.     

Examining the hierarchy threshold model in a no-choice feeding assay

The hierarchy threshold model of individual insect diet predicts the acceptance or rejection of individual hosts when encountered by insects. One assumption of the hierarchy threshold model is that post-discrimination phase insects which accept lower ranked hosts will also accept hosts that are ranked higher. This assumption does not however suggest whether or not such insects behave differently when encountering these two hosts. This question is explored using Zygogramma bicolorata Pallister (Coleoptera: Chrysomelidae). Adult beetles that had just fed, or were one inter-meal interval after feeding, or were deprived for three or six days after feeding, were individually observed on a plant that either ranked high, Parthenium hysterophorus L., or low Xanthium occidentale Bertol. (Heliantheae: Ambrosiinae) in choice tests. Just-fed beetles were generally unresponsive to either host plant and did not feed. Beetles held for one inter-meal interval showed more feeding responses (shorter lag time between sampling and feeding, higher proportions of individuals feeding, and more time feeding) towards the higher ranked plant. As the beetles approached six days deprivation, behaviours of sampling, feeding and locomotion differed less between the two plants, but were still apparent. I conclude that food deprived Z. bicolorata beetles do still discriminate between the two plants. This result partially supports the hierarchy threshold model.     

Targeted reduction of complex models with time scale hierarchy--a case study

With the increasing flow of biological data there is a growing demand for mathematical tools whereby essential aspects of complex causal dynamic models can be captured and detected by simpler mathematical models without sacrificing too much of the realism provided by the original ones. Given the presence of a time scale hierarchy, singular perturbation techniques represent an elegant method for making such minimised mathematical representations. Any reduction of a complex model by singular perturbation methods is a targeted reduction by the fact that one has to pick certain mechanisms, processes or aspects thought to be essential in a given explanatory context. Here we illustrate how such a targeted reduction of a complex model of melanogenesis in mammals recently developed by the authors provides a way to improve the understanding of how the melanogenic system may behave in a switch-like manner between production of the two major types of melanins. The reduced model is shown by numerical means to be in good quantitative agreement with the original model. Furthermore, it is shown how the reduced model discloses hidden robustness features of the full model, and how the making of a reduced model represents an efficient analytical sensitivity analysis. In addition to yielding new insights concerning the melanogenic system, the paper provides an illustration of a protocol that could be followed to make validated simplifications of complex biological models possessing time scale hierarchies.     

Fluorescence activated cell sorting reveals heterogeneous and cell non-autonomous osteoprogenitor differentiation in fetal rat calvaria cell populations

Identification of osteoblast progenitors, with defined developmental capacity, would facilitate studies on a variety of parameters of bone development. We used expression of alkaline phosphatase (ALP) and the parathyroid hormone/parathyroid hormone-related protein receptor (PTH1R) as osteoblast markers in dual-color fluorescence activated cell sorting (FACS) to fractionate rat calvaria (RC) cells into ALP(-)PTH1R(-), ALP(+)PTH1R(-), ALP(-)PTH1R(+), and ALP(+)PTH1R(+) populations. These fractionated populations were seeded clonally (n = 96) or over a range of cell densities ( approximately 150-8,500 cell/cm(2); n = 3). Our results indicate that colony forming unit-osteoblast (CFU-O)/bone nodule-forming cells are found in all fractions, but the frequency of CFU-O and total mineralized area is different across fractions. Analysis of these differences suggests that ALP(-)PTH1R(-), ALP(-)PTH1R(+), ALP(+)PTH1R(-), and ALP(+)PTH1R(+) cell populations are separated in order of increasing bone formation capacity. Dexamethasone (dex) differentially increased the CFU-O number in the four fractions, with the largest stimulation in the ALP(-) cell populations. However, there was no significant difference in the number or size distribution of CFU-F (fibroblast) colonies that formed in vehicle versus dex. Finally, both cell autonomous and cell non-autonomous (i.e., inhibitory/stimulatory effects of cell neighbors) differentiation of osteoprogenitors was seen. Only the ALP(-)PTH1R(-) population was capable of forming nodules at the clonal level, at approximately 3- or 12-times the predicted frequency of unfractionated populations in dex or vehicle, respectively. These data suggest that osteoprogenitors can be significantly enriched by fractionation of RC populations, that assay conditions modify the osteoprogenitor frequencies observed and that fractionation of osteogenic populations is useful for interrogation of their developmental status and osteogenic capacity.