'Friendship' for fitness in chimpanzees?

It has been repeatedly suggested that primates trade social services for fitness benefits in their relationships with the opposite sex. We tested this proposal in a colony of captive chimpanzees, Pan troglodytes, by examining behavioural data on grooming, agonistic support and food sharing in relation to genetically established paternity. We found no support for the notion of trade. First, males did not sire more offspring with females that they actively groomed more frequently, that they supported more often or with which they shared food more frequently. Correspondingly, females did not give birth to more offspring sired by males from which they received more services. Second, males that showed more affiliative behaviour towards females in general did not sire more progeny. Furthermore, females did not bear more offspring sired by males to which they themselves directed more sociopositive behaviour. Results from this captive colony are compatible with those reported for chimpanzees under natural conditions. Copyright 1999 The Association for the Study of Animal Behaviour.     

Evidence for Fisher's dominance theory: how many 'special cases'?

Dominance, its genetic basis and evolution has been at the heart of one of the most intense controversies in the history of genetics. For more than eighty years the existence of dominance modifiers, genetic elements controlling dominance-recessivity interactions, has been suggested as a theoretical possibility, but the modifier elements themselves have remained elusive. A recent study of the self-incompatibility locus in flowering plants provided the first empirical evidence for such genetic elements: small non-coding RNAs that control dominance-recessivity by mediating methylation of the promoter of the recessive allele. Theory has shown that several biological situations are favorable for the evolution of dominance modifiers. We argue that the elucidation of this mechanism of dominance opens up new research avenues that could lead to uncovering dominance modifiers in other genetic systems, such as genes controlling Batesian and Müllerian mimicry or host-parasite interactions, thereby shedding light on the generality of the proposed mechanism.     

Shift in Black Rhinoceros Diet in the Presence of Elephant: Evidence for Competition?

In African large herbivore assemblages, megaherbivores dominate the biomass and utilise the greatest share of available resources. Consequently, they are considered a separate trophic guild that structures the food niches of coexisting large herbivores. However, there exists little empirical evidence on how food resources are shared within this guild, and none for direct competition for food between megaherbivores. Using the histological analysis of faeces, we explore this phenomenon for African elephant Loxodonta africana and black rhinoceros Diceros bicornis in the Addo Elephant National Park, South Africa, where the accumulated impacts of elephant have reduced browse availability. Despite being unable to generalise beyond our study sites, our observations support the predictions of competition theory (as opposed to optimality theory) by showing (1) a clear seasonal separation in resource use between these megaherbivores that increased as resource availability declined, and (2) rhinoceros changed their selectivity in the absence of elephant (using an adjacent site) by expanding and shifting their diet along the grass-browse continuum, and in relation to availability. Although black rhinoceros are generally considered strict browsers, the most significant shift in diet occurred as rhinoceros increased their preferences for grasses in the presence of elephant. We speculate that the lack of specialised grazing adaptations may increase foraging costs in rhinoceros, through reduced harvest- and handling-efficiencies of grasses. In the short-term, this may be off-set by an enhanced tolerance for low quality food and by seasonally mobilising fat reserves; however, the long-term fitness consequences require further study. Our data suggest that managing elephant at high densities may compromise the foraging opportunities of coexisting browsers. This may be particularly important in small, fenced areas and overlapping preferred habitats where impacts intensify.     

Behavioral diversity in populations of free-ranging chimpanzees in Africa: is it culture?

Behavioral differences exist among populations of wild chimpanzees (Pan troglodytes, Hominoidea) across Africa. Deciding if these are cross-cultural differences demands careful interpretation and rigorous scrutiny. Even standard patterns like social grooming may show variation in detail between neighboring populations. Some patterns of tool use, such as using hammers to crack nuts, also vary across far western Africa. At least 37 populations of free-ranging chimpanzees show tool use, and 14 show at least one habitual pattern of tool use. Regional differences exist among the three subspecies or geographical races of chimpanzees. Convincing empirical demonstration of social customs and traditions in non-human species is problematical, and even something so simple in principle as innovation is hard to show in practice. However, culture need not depend on imitation, teaching, or language, either in humans or in other species.     

Evidence for pollinator sharing in Mediterranean nectar-mimic orchids: absence of premating barriers?

Pollinator specificity has traditionally been considered the main reproductive isolation mechanism in orchids. Among Mediterranean orchids, however, many species attract and deceive pollinators by mimicking nectar-rewarding plants. To test the extent to which deceptive orchid species share pollinators, we collected and identified hemipollinaria-carrying insects, and used ribosomal sequences to identify the orchid species from which hemipollinaria were removed. We found that social and solitary bees, and also flies, carried hemipollinaria belonging to nine orchid species with different degrees of specialization. In particular, Anacamptis morio, Dactylorhiza romana and Orchis mascula used a large set of pollinator species, whereas others such as Orchis quadripunctata seemed to be pollinated by one pollinator species only. Out of the insects with hemipollinaria, 19% were found to carry hemipollinaria from more than one orchid species, indicating that sympatric food-deceptive orchids can share pollinators. This sharing was apparent even among orchid sister-species, thus revealing an effective overlap in pollinator sets among closely related species. These results suggest varying degrees of pollinator specificity in these orchids, and indicate that pollinator specificity cannot always act as the main isolation mechanism in food-deceptive temperate orchids.     

Symbolic communication in wild chimpanzees?

The language abilities of captive chimpanzees give rise to the question of the existence and use of similar capabilities in wild chimpanzees. In Taï forest, wild chimpanzees seem to use drumming on buttressed trees to convey information an changes of travel direction, resting periods or both information combined. This communication system is iconic and relies on some arbitrariness. Emergence of symbol-like communication in wild chimpanzees seems mainly dependent on a low visibility environment, a high predation pressure and a large group of males.     

What's in it for me? Self-regard precludes altruism and spite in chimpanzees

Sensitivity to fairness may influence whether individuals choose to engage in acts that are mutually beneficial, selfish, altruistic, or spiteful. In a series of three experiments, chimpanzees (Pan troglodytes) could pull a rope to access out-of-reach food while concomitantly pulling another piece of food further away. In the first study, they could make a choice that solely benefited themselves (selfishness), or both themselves and another chimpanzee (mutualism). In the next two experiments, they could choose between providing food solely for another chimpanzee (altruism), or for neither while preventing the other chimpanzee from receiving a benefit (spite). The main result across all studies was that chimpanzees made their choices based solely on personal gain, with no regard for the outcomes of a conspecific. These results raise questions about the origins of human cooperative behaviour.     

Masting in a temperate tree: Evidence for environmental prediction?

Many plant species produce large fruit crops in some years and then produce few or no fruits in others. Synchronous, inter‐annual variation in plant reproduction is known as ‘masting’ and its adaptive significance has yet to be fully resolved. For 8 consecutive years, I quantified every fruit produced by 22 females of a New Zealand tree species (Dysoxylum spectabile), which has an unusual habit of taking a full calendar year to mature fruits after flowering. Fruit production varied strongly among years and was tightly synchronized among trees. Annual variability in fruit production declined with total reproductive output, indicating trees with lower fecundity exhibited a stronger tendency to mast. Although unrelated to temperature, annual fruit production was positively related to precipitation during annual periods of fruit development, and negatively related to fruit production in the previous year. Seedlings had higher rates of survivorship in a wet, high‐seed year than in a dry, low‐seed year, suggesting that seedlings might be drought sensitive. Therefore, D. spectabile produced large fruit crops during periods of high rainfall prior to fruit maturation, which may enhance survivorship of drought‐intolerant seeds. Results were inconsistent with several hypotheses that are widely believed to be the most likely explanations for masting. Instead, results were consistent with the environmental prediction hypothesis, suggesting that this hypothesis may be more important than previously appreciated.     

Evidence for scent marking in vervet monkeys?

We used data from two troops of free-ranging vervet monkeys (Chlorocebus aethiops) to assess the proposition that the conspicuous chest rubbing observed in this species constitutes scent-marking behavior. Our data indicate that chest-rubbing behavior is associated with higher-ranking males who are more likely to do so during the breeding season in areas where territorial encounters occur. We found no indication that chest rubbing was triggered directly by encounters between troops. We conclude that these data, in conjunction with reports of chest rubbing from other Old World monkeys, are sufficiently suggestive of scent marking to warrant further, directed research and support the suspicion that olfactory cues remain important to catarrhines in a number of domains.     

Magnetic maps in animals: a theory comes of age?

The magnetic map hypothesis proposes that animals can use spatial gradients in the Earth's magnetic field to help determine geographic location. This ability would permit true navigation--reaching a goal from an entirely unfamiliar site with no goal-emanating cues to assist. It is a highly contentious hypothesis since the geomagnetic field fluctuates in time and spatial gradients may be disturbed by geological anomalies. Nevertheless, a substantial body of evidence offers support for the hypothesis. Much of the evidence has been indirect in nature, such as the identification of avian magnetoreceptor mechanisms with functional properties that are consistent with those of a putative map detector or the patterns of orientation of animals exposed to temporal and/or spatial geomagnetic anomalies. However; the most important advances have been made in conducting direct tests of the magnetic map hypothesis by exposing experienced migrants to specific geomagnetic values representing simulated displacements. Appropriate shifts in the direction of orientation, which compensate for the simulated displacements, have been observed in newts, birds, sea turtles, and lobsters, and provide the strongest evidence to date for magnetic map navigation. Careful experimental design and interpretation of orientation data will be essential in the future to determine which components of the magnetic field are used to derive geographic position.     

Different Expression of Helicobacter pylori Gastritis in Children: Evidence for a Specific Pediatric Disease?

Background Infection with Helicobacter pylori causes active chronic gastritis. Once the infection is acquired, gastritis will persist for almost the rest of one's life. To date, very few data are available on H. pylori gastritis in relation to age. Therefore, we attempted to inestigate whether H. pylori gastritis in children exhibits features different from H. pylori gastritis in adults of two different age groups. Materials and Methods. Fifty consecutive children with a median age of 11 years (range, 3–18 years) were compared with two groups of 50 adult patients, one group with a median age of 43 (range, 19–56 years) and another group with a median age of 70 years (range, 59–86 years). All patients had H. pylori gastritis unrelated to active peptic ulcer disease. Two biopsy specimens were taken from the antrum and two from the corpus, and the following gastritis parameters were evaluated: degree and activity of gastritis, H. pylori colonization, replacement of foveolar epithelium by regenerative epithelium, mucous depletion, presence of atrophic gastritis with intestinal metaplasia, and presence of lymphoid follicles. Results. Degree and activity of gastritis, extent of H. pylori colonization, degree of replacement by regenerative epithelium, extent of mucous depletion, degree of atrophic gastritis with intestinal metaplasia, and the presence of lymphoid follicles in the antrum, as well as the presence of lymphoid follicles in the corpus differed significantly (chi-square test: p < .05). All these differences—except the once frequent occurrence of atrophic gastritis with intestinal metaplasia in adults—were attributable to a higher expression of these gastritis parameters in children. Conclusions. We conclude that H. pylori gastritis, particularly in the antrum, is more severely expressed in childhood. One reason for this might be a child-specific immune response to an infection with H. pylori. Alternatively, infection may represent a pediatric disease characterized by a nonatrophic, highly expressed form of gastritis, which changes its appearance once the host becomes adapted over time.     

Connexon rearrangement in cardiac gap junctions: Evidence for cytoskeletal control?

Summary Using ultrarapid-freezing techniques and freezefracture electron microscopy, we report here a close association between cardiac gap junctions and specialized membrane domains containing regularly-spaced furrows. These specialized furrowed domains are observed only during periods of gap junction re-organisation (i.e., connexon redistribution) and may reflect the presence of underlying cytoskeletal elements controlling the position of connexons in the membrane.     

Use of leaves to inspect ectoparasites in wild chimpanzees: a third cultural variant?

We report 26 cases of using leaves as tools with which wild chimpanzees (Pan troglodytes schweinfurthii) in the Sonso community, Budongo Forest, Uganda, appeared to inspect objects removed during grooming. Careful removal of potential ectoparasites and delicate lip or manual placement on leaves followed by intense visual examination characterised this behaviour. It appears to be done to judge whether either ingestion or discarding is most appropriate, the former occurring in most cases. This behaviour may represent a third variant of ectoparasite handling, different from those described at Taï and Gombe, yet sharing features with the latter. These two East African techniques may thus have evolved from leaf grooming.     

New insights into the role of mast cells in autoimmunity: Evidence for a common mechanism of action?

Mast cells are classically considered innate immune cells that act as first responders in many microbial infections and have long been appreciated as potent contributors to allergic reactions. However, recent advances in the realm of autoimmunity have made it clear that these cells are also involved in the pathogenic responses that exacerbate disease. In the murine models of multiple sclerosis, rheumatoid arthritis and bullous pemphigoid, both the pathogenic role of mast cells and some of their mechanisms of action are shared. Similar to their role in infection and a subset of allergic responses, mast cells are required for the efficient recruitment of neutrophils to sites of inflammation. Although this mast cell-dependent neutrophil response is protective in infection settings, it is postulated that neutrophils promote local vascular permeability and facilitate the entry of inflammatory cells that enhance tissue destruction at target sites. However, there is still much to learn. There is little information regarding mechanisms of mast cell activation in disease. Nor is it known how many mast cell-derived mediators are relevant and whether interactions with other cells are implicated in these diseases including T cells, B cells and astrocytes. Here we review the current state of knowledge about mast cells in autoimmune disease. We also discuss findings regarding newly discovered mast cell actions and factors that modulate mast cell function. We speculate that much of this new information will ultimately contribute to a greater understanding of the full range of mast cell actions in autoimmunity. This article is part of a Special Issue entitled: Mast cells in inflammation.     

Evidence for dynamic alteration in histone gene clusters of Caenorhabditis elegans: a topoisomerase II connection?

Chromatin integrity is maintained throughout the cell cycle through repair mechanisms and intrinsically by the ordered packaging of DNA in association with histone proteins; however, aberrant rearrangements within and between chromosomes do occur. The role of the nuclear matrix protein topoisomerase II (TopoII) in generating chromosome breakpoints has been a focus of recent investigations. TopoII preferentially binds in vitro to scaffold-associated regions (SARs) and is involved in many DNA processing activities that require chromosome untangling. SARs, biochemically defined DNA elements rich in A + T, have been proposed to serve as structural boundaries for chromatin loops and to delineate functional domains. In our investigation of gene compartmentalization in a eukaryotic genome, SAR-associated nucleotide motifs from Drosophila were mapped in the regions of three histone gene clusters in an in silico analysis of the genome of Caenorhabditis elegans. Sites with similarity to the 15 bp consensus for TopoII cleavage were found predominantly in A + T enriched intergenic regions. Reiteration of sites matching the TopoII core consensus led to the identification of a novel core histone gene on chromosome IV and provided evidence for duplication and inversion in each of the three histone gene clusters. Breakpoint analysis of DNA flanking reiterated regions revealed potential sites for TopoII cleavage and a base composition phenomenon suggestive of a trigger for inversion events.