Functional host-specific adaptation of the intestinal microbiome in hominids

Fine-scale knowledge of the changes in composition and function of the human gut microbiome compared that of our closest relatives is critical for understanding the evolutionary processes underlying its developmental trajectory. To infer taxonomic and functional changes in the gut microbiome across hominids at different timescales, we perform high-resolution metagenomic-based analyzes of the fecal microbiome from over two hundred samples including diverse human populations, as well as wild-living chimpanzees, bonobos, and gorillas. We find human-associated taxa depleted within non-human apes and patterns of host-specific gut microbiota, suggesting the widespread acquisition of novel microbial clades along the evolutionary divergence of hosts. In contrast, we reveal multiple lines of evidence for a pervasive loss of diversity in human populations in correlation with a high Human Development Index, including evolutionarily conserved clades. Similarly, patterns of co-phylogeny between microbes and hosts are found to be disrupted in humans. Together with identifying individual microbial taxa and functional adaptations that correlate to host phylogeny, these findings offer insights into specific candidates playing a role in the diverging trajectories of the gut microbiome of hominids. We find that repeated horizontal gene transfer and gene loss, as well as the adaptation to transient microaerobic conditions appear to have played a role in the evolution of the human gut microbiome.

Genetic inference of group dynamics and female kin structure in a western lowland gorilla population (<i>Gorilla gorilla gorilla</i>)

Abstract. Dispersal and grouping patterns form the foundations of social interactions in group-living mammals and are the outcomes of a complex interplay between inbreeding avoidance, kin cooperation and competition, predation pressure and food resource distribution. In species where both sexes disperse, the potential for kin-biased associations would seem limited. In one such species, the western lowland gorilla (WLG), short-term data suggest that female kin associations may be present due to directed local dispersal decisions, but monitoring of groups over longer timescales is needed to better elucidate this pattern. Using autosomal genotyping of 419 faecal samples representing 85 unhabituated gorillas collected non-invasively over 5 years in a 132 km2 section of Loango National Park, Gabon, we investigated the dynamics of WLG group composition, social structure and patterns of dispersal. By revealing two group dissolutions, one group formation and the movement of 13 gorillas between groups, this study demonstrates the utility of genetic analysis as a way to track individuals, groups and population dynamics on a larger scale than when monitoring the behaviour of a limited number of habituated groups or through one-time genetic sampling. Furthermore, we find that females are found in groups containing their female kin more often than expected by chance, suggesting that dispersal may not impede female kin associations in WLGs.

Major histocompatibility complex and microsatellite variation in two populations of wild gorillas

In comparison to their close relatives the chimpanzees and humans, very little is known concerning the amount and structure of genetic variation in gorillas. Two species of gorillas are recognized and while the western gorillas number in the tens of thousands, only several hundred representatives of the mountain gorilla subspecies of eastern gorillas survive. To analyse the possible effects of these different population sizes, this study compares the variation observed at microsatellite and major histocompatibility complex (MHC) loci in samples of wild western and mountain gorillas, collected using a sampling scheme that targeted multiple social groups within defined geographical areas. Noninvasive samples proved a viable source of DNA for sequence analysis of the second exon of the DRB loci of the MHC. Observed levels of variation at the MHC locus were similar between the two gorilla species and were comparable to those in other primates. Comparison of results from analysis of variation at multiple microsatellite loci found only a slight reduction in heterozygosity for the mountain gorillas despite the relatively smaller population size.

Factors affecting the amount of genomic DNA extracted from ape faeces and the identification of an improved sample storage method

Abstract Genetic analysis using noninvasively collected samples such as faeces continues to pose a formidable challenge because of unpredictable variation in the extent to which usable DNA is obtained. We investigated the influence of multiple variables on the quantity of DNA extracted from faecal samples from wild mountain gorillas and chimpanzees. There was a small negative correlation between temperature at time of collection and the amount of DNA obtained. Storage of samples either in RNAlater solution or dried using silica gel beads produced similar results, but significantly higher amounts of DNA were obtained using a novel protocol that combines a short period of storage in ethanol with subsequent desiccation using silica.

A preliminary investigation of urinary testosterone and cortisol levels in wild male mountain gorillas

Urinary steroid hormone levels were measured in wild male mountain gorillas (Gorilla gorilla beringei) to determine how levels of testosterone and cortisol corresponded with age and social rank. Urine samples were collected noninvasively from 18 males, ranging in age from 3-26 years, in three groups of wild mountain gorillas at the Karisoke Research Center, Rwanda, Africa, and samples were analyzed using radioimmunoassay procedures. Males were classified as being immature (< 7 years), maturing (10-13 years), or adult (+13 years of age). Immature males had significantly lower levels of testosterone and higher levels of cortisol than both maturing and adult males. No differences in testosterone or cortisol levels were found between maturing and adult males. Dominant males exhibited a trend toward significantly higher levels of testosterone than subordinate males, but no difference was found between cortisol levels of dominant and subordinate males. These results suggest that the increase in testosterone associated with puberty occurs prior to any outward sign of development of secondary sexual characteristics. Within-group male-male competition may affect testosterone levels, but the lack of difference in cortisol levels between dominant and subordinate males suggests that subordinate males are not socially stressed, at least as measured by cortisol.

Male mating patterns in wild multimale mountain gorilla groups

Although mountain gorillas, Gorilla gorilla beringei, are classified as having a one-male mating system, approximately 40% of the social units are multimale groups. I observed two multimale groups of mountain gorillas at the Karisoke Research Center, Rwanda, Africa, for 17 months to determine male mating patterns and male-male mating harassment in relation to both male dominance rank and female reproductive status. Dominant males mated significantly more than did individual subordinate males, and dominant males mated more with cycling adult and pregnant females. The dominant males participated in 47 and 83% of observed matings in the two groups. Subordinate males were more likely than dominant males to mate with subadult females. Eleven of 14 females were observed to mate with more than one male, and multiple males mated with three of the five females observed at the probable time of conception. Mating harassment was initiated and received by both dominant and subordinate males. Mating harassment occurred infrequently (during 30 and 22% of matings in each group), usually consisted of mild aggression, and usually terminated copulations by subordinate males, but not those by dominant males. These results suggest that multimale mountain gorilla groups can be favourable environments for subordinate males to obtain mating opportunities. Dominant males may be unable or unwilling to prevent subordinate males from mating. Based on behavioural observations, mountain gorillas can have a multimale mating system but further research on the role of females in male mating success and paternity determination is needed to understand fully this species' mating system. Copyright 1999 The Association for the Study of Animal Behaviour.

Lining up their shots. Exclusive new Hay survey shows the impact of integration on MD compensation

Managed care and systems integration are having a major impact on physician compensation, says a new survey by the Hay Group. The survey of physician compensation across hospital, group practice and managed care settings shows a slowing in pay growth, a shift in emphasis toward primary care, and increased emphasis on variable compensation strategies. At the same time, demand for physician executives is rising dramatically.

Transformational leadership. Leadership competencies for physicians

Physician leaders accustomed to operating as "captain of the ship" must now employ group leadership skills to inspire a shared vision, facilitate consensus and ease the transition to integrated systems.