The evolution of primate communities and societies in Madagascar

During their 120 to 165 million years of isolation, the flora and fauna of Madagascar evolved, to a large extent, independently of the African mainland.¹ In contrast to other oceanic islands, Madagascar is large enough to house the major components of tropical ecosystems, allowing tests of evolutionary hypotheses on the level of complete communities. Taking lemurs, the primates of Madagascar, as an example, evolutionary hypotheses correctly predict the organization of their community structure with respect to ecological correlates. Lemur social systems and their morphological correlates, on the other hand, deviate in some respects from those of other primates. Apparently, lemur social systems are influenced by several selection pressures that are weak or rare in other primates. These include variable activity patterns and avoidance of infanticide. The interspecific variation in lemur social systems therefore offers a unique opportunity for a comprehensive study of the determinants of primate social systems.     

Investigation on rate — Determining factors in the microbial reduction of azo dyes

Summary Investigations on the effects of pH, temperature, type and concentration of respiration substrates and oxygen tension on the reduction rate of derivatives of 1-phenylazo-2-naphthol and of a variety of textile dyes served as a basis for establishing a bioassay for strictly reproducible measurements of the microbial reduction rate of azo dyes. Standard organism was a strain of Bacillus cereus isolated from soil. Dye reduction occurred with the standard organism and other facultatively or obligatory aerobic bacteria in exclusively anoxic conditions. In principle, first order kinetics of decolorization were found. Reduction products may however inhibit the reaction. All dyes not measurably reduced by living cells of B. cereus were decolorized by cell extracts of the same species. Dyes adsorbed by the cell walls were in most cases reduced at slow rates and did not influence the simultaneous reduction of non-adsorbable dyes in the medium. The observations confirm the hypothesis advanced by Gingell and Walker (1971) of an intracellular, non-enzymatic reduction of azo compounds by reduced flavin nucleotides. The rate of permeation of the dyes through the cell membrane is the primordial ratelimiting step in the microbial decolorization of azo dyes. Sulfonic acid substitution seems to be an effective inhibitor of permeation.     

Genetic population structure and relatedness in the narrow‐striped mongoose (Mungotictis decemlineata), a social Malagasy carnivore with sexual segregation

Information on the genetic structure of animal populations can allow inferences about mechanisms shaping their social organization, dispersal, and mating system. The mongooses (Herpestidae) include some of the best‐studied mammalian systems in this respect, but much less is known about their closest relatives, the Malagasy carnivores (Eupleridae), even though some of them exhibit unusual association patterns. We investigated the genetic structure of the Malagasy narrow‐striped mongoose (Mungotictis decemlineata), a small forest‐dwelling gregarious carnivore exhibiting sexual segregation. Based on mtDNA and microsatellite analyses, we determined population‐wide haplotype structure and sex‐specific and within‐group relatedness. Furthermore, we analyzed parentage and sibship relationships and the level of reproductive skew. We found a matrilinear population structure, with several neighboring female units sharing identical haplotypes. Within‐group female relatedness was significantly higher than expected by chance in the majority of units. Haplotype diversity of males was significantly higher than in females, indicating male‐biased dispersal. Relatedness within the majority of male associations did not differ from random, not proving any kin‐directed benefits of male sociality in this case. We found indications for a mildly promiscuous mating system without monopolization of females by males, and low levels of reproductive skew in both sexes based on parentages of emergent young. Low relatedness within breeding pairs confirmed immigration by males and suggested similarities with patterns in social mongooses, providing a starting point for further investigations of mate choice and female control of reproduction and the connected behavioral mechanisms. Our study contributes to the understanding of the determinants of male sociality in carnivores as well as the mechanisms of female competition in species with small social units.     

OntoGene in BioCreative II

Background:

Research scientists and companies working in the domains of biomedicine and genomics are increasingly faced with the problem of efficiently locating, within the vast body of published scientific findings, the critical pieces of information that are needed to direct current and future research investment.

Results:

In this report we describe approaches taken within the scope of the second BioCreative competition in order to solve two aspects of this problem: detection of novel protein interactions reported in scientific articles, and detection of the experimental method that was used to confirm the interaction. Our approach to the former problem is based on a high-recall protein annotation step, followed by two strict disambiguation steps. The remaining proteins are then combined according to a number of lexico-syntactic filters, which deliver high-precision results while maintaining reasonable recall. The detection of the experimental methods is tackled by a pattern matching approach, which has delivered the best results in the official BioCreative evaluation.

Conclusion:

Although the results of BioCreative clearly show that no tool is sufficiently reliable for fully automated annotations, a few of the proposed approaches (including our own) already perform at a competitive level. This makes them interesting either as standalone tools for preliminary document inspection, or as modules within an environment aimed at supporting the process of curation of biomedical literature.

     

Host intrinsic determinants and potential consequences of parasite infection in free‐ranging red‐fronted lemurs (Eulemur fulvus rufus)

Parasites and infectious diseases represent ecological forces shaping animal social evolution. Although empirical studies supporting this link abound in various vertebrate orders, both the study of the dynamics and impact of parasite infections and infectious diseases in strepsirrhine primates have received little empirical attention. We conducted a longitudinal parasitological study on four groups of wild red‐fronted lemurs (Eulemur fulvus rufus) at Kirindy Forest, Madagascar, during two field seasons in consecutive years to investigate i) the degree of gastrointestinal parasite infection on population and individual levels and ii) factors potentially determining individual infection risk. Using a comprehensive dataset with multiple individually assignable parasite samples as well as information on age, sex, group size, social rank, and endocrine status (fecal androgen and glucocorticoid), we examined parasite infection patterns and host traits that may affect individual infection risk. In addition, we examined whether parasite infection affects mating and reproductive success. Our results indicated high variability in parasite infection on individual and population levels. Time of year and group size was important determinants of variability in parasite infection. Variation in hormone levels was also associated with parasite species richness and parasite infection intensity. Differences in parasite infection between years indicate a potential immune‐enhancing function of steroid hormones on nematode infections, which has not been reported before from other vertebrates studied under natural conditions. Male mating and reproductive success were not correlated to any measure of parasite infection, which suggests a nonfunctional role of the parasites we examined in primate sexual selection. Am J Phys Anthropol, 2010. © 2010 Wiley‐Liss, Inc.     

MHC‐disassortative mate choice and inbreeding avoidance in a solitary primate

Sexual selection theory suggests that choice for partners carrying dissimilar genes at the major histocompatibility complex (MHC) may play a role in maintaining genetic variation in animal populations by limiting inbreeding or improving the immunity of future offspring. However, it is often difficult to establish whether the observed MHC dissimilarity among mates drives mate choice or represents a by‐product of inbreeding avoidance based on MHC‐independent cues. Here, we used 454‐sequencing and a 10‐year study of wild grey mouse lemurs (Microcebus murinus), small, solitary primates from western Madagascar, to compare the relative importance on the mate choice of two MHC class II genes, DRB and DQB, that are equally variable but display contrasting patterns of selection at the molecular level, with DRB under stronger diversifying selection. We further assessed the effect of the genetic relatedness and of the spatial distance among candidate mates on the detection of MHC‐dependent mate choice. Our results reveal inbreeding avoidance, along with disassortative mate choice at DRB, but not at DQB. DRB‐disassortative mate choice remains detectable after excluding all related dyads (characterized by a relatedness coefficient r > 0), but varies slightly with the spatial distance among candidate mates. These findings suggest that the observed deviations from random mate choice at MHC are driven by functionally important MHC genes (like DRB) rather than passively resulting from inbreeding avoidance and further emphasize the need for taking into account the spatial and genetic structure of the population in correlative tests of MHC‐dependent mate choice.     

Ageing, genetics and the somatotropic axis

Research on ageing made a big leap forward when genes regulating lifespan were discovered about a decade ago. First isolated by screening the genome of the nematode Caenorhabditis elegans, most of these genes belong to an essential signalling pathway that is highly conserved during animal evolution. Orthologous genes in vertebrate species are the families of genes coding for insulin, insulin-like growth factors (IGF) and related proteins. Intensively studied and well-known for their pivotal roles in proliferation, differentiation, survival and metabolism of most cells, we now discover their multiples functions with respect to the control of longevity and their ability to modulate the cell's responses to oxidative stress, a major cause of cellular and organismal ageing. The activity of IGF signalling in mammals depends on a complex interplay of endocrine signals that together constitute the somatotropic axis. Accordingly, several components of this hormone axis, like growth hormone or growth hormone releasing hormone receptors, regulate efficiently animal longevity, which has been elegantly demonstrated by studies performed in genetically modified mouse models. From this and other work, it becomes increasingly clear that the control of ageing is a question of hormonal regulations. We here present several of these models and discuss the respective contributions of insulin and IGF signalling to the regulation of lifespan. We review data on the Klotho gene that acts on lifespan via surprising and not yet fully understood molecular mechanisms, connecting this new, hormone-like substance to IGF and insulin signalling. We further report recent evidence showing that human lifespan might be controlled in similar ways. Finally, we shed some light on clinical GH treatment in humans, from an endocrinologist's point of view.     

Distinct roles of doublecortin modulating the microtubule cytoskeleton

Doublecortin is a neuronal microtubule-stabilising protein, mutations of which cause mental retardation and epilepsy in humans. How doublecortin influences microtubule dynamics, and thereby brain development, is unclear. We show here by video microscopy that purified doublecortin has no effect on the growth rate of microtubules. However, it is a potent anti-catastrophe factor that stabilises microtubules by linking adjacent protofilaments and counteracting their outward bending in depolymerising microtubules. We show that doublecortin-stabilised microtubules are substrates for kinesin translocase motors and for depolymerase kinesins. In addition, doublecortin does not itself oligomerise and does not bind to tubulin heterodimers but does nucleate microtubules. In cells, doublecortin is enriched at the distal ends of neuronal processes and our data raise the possibility that the function of doublecortin in neurons is to drive assembly and stabilisation of non-centrosomal microtubules in these doublecortin-enriched distal zones. These distinct properties combine to give doublecortin a unique function in microtubule regulation, a role that cannot be compensated for by other microtubule-stabilising proteins and nucleating factors.     

Large-scale MHC class II genotyping of a wild lemur population by next generation sequencing

The critical role of major histocompatibility complex (MHC) genes in disease resistance, along with their putative function in sexual selection, reproduction and chemical ecology, make them an important genetic system in evolutionary ecology. Studying selective pressures acting on MHC genes in the wild nevertheless requires population-wide genotyping, which has long been challenging because of their extensive polymorphism. Here, we report on large-scale genotyping of the MHC class II loci of the grey mouse lemur (Microcebus murinus) from a wild population in western Madagascar. The second exons from MHC-DRB and -DQB of 772 and 672 individuals were sequenced, respectively, using a 454 sequencing platform, generating more than 800,000 reads. Sequence analysis, through a stepwise variant validation procedure, allowed reliable typing of more than 600 individuals. The quality of our genotyping was evaluated through three independent methods, namely genotyping the same individuals by both cloning and 454 sequencing, running duplicates, and comparing parent–offspring dyads; each displaying very high accuracy. A total of 61 (including 20 new) and 60 (including 53 new) alleles were detected at DRB and DQB genes, respectively. Both loci were non-duplicated, in tight linkage disequilibrium and in Hardy–Weinberg equilibrium, despite the fact that sequence analysis revealed clear evidence of historical selection. Our results highlight the potential of 454 sequencing technology in attempts to investigate patterns of selection shaping MHC variation in contemporary populations. The power of this approach will nevertheless be conditional upon strict quality control of the genotyping data.     

Mutualism,reciprocity, or kin selection? Cooperative rescue of a conspecific from a boa in a nocturnal solitary forager the gray mouse lemur

Predator mobbing is a widespread phenomenon in many taxa but the evolution of cooperative mobbing as an adaptive behavior is still subject to debate. Here, we report evidence for cooperative predator defense in a nocturnal solitarily foraging primate, the gray mouse lemur (Microcebus murinus). Several mouse lemurs mobbed a snake that held a non-related male conspecific until he could escape. Evolutionary hypotheses to explain cooperative mobbing include (1) by-product mutualism, when individuals defend others in the process of defending themselves; (2) reciprocity, where animals achieve a higher fitness when helping each other than when they do not cooperate; and (3) kin selection where animals help each other only if they share genes by common descent. Owing to the solitary activity of this species, reciprocity seems to be least likely to explain our observations. By-product mutualism cannot be ruled out entirely but, if costs of snake mobbing are relatively low, the available detailed socio-genetic information indicates that kin selection, rather than any of the other proposed mechanisms, is the primary evolutionary force behind the observed cooperative rescue.