雄性短尾猴的等级顺位、睾酮水平与肠道寄生虫感染强度的关系

在等级森严的非人灵长类群体中,睾酮对雄性顺位维持有着重要作用,且影响着体内寄生虫种类和荷虫量。本研究以栖息于安徽黄山的雄性短尾猴为研究对象,通过计算成年雄性的等级顺位,测定其粪便中睾酮含量以及寄生虫的荷虫量,探讨雄性等级顺位、睾酮水平与健康间的平衡关系。结果表明：共检测出10种肠道寄生虫,包括4种蠕虫、5种原虫和1种螨虫;其中雄性短尾猴个体间睾酮水平（1.00±0.42） ng/g和肠道寄生虫荷虫量（112.44±83.62）EPG均存在显著差异（Kruskal-Wallis H,P<0.05）;等级顺位与睾酮水平呈正相关（Spearman, N=8,ρ= 0.326, P<0.05）,与肠道原虫类的荷虫量呈负相关（Spearman, N=8,ρ= - 0.345, P<0.05）,与肠道蠕虫类的荷虫量无相关性（Spearman, N=8,ρ= 0.065, P>0.05）;睾酮水平与肠道原虫类寄生虫的荷虫量呈负相关（Spearman, N=8,ρ= -0.546, P<0.05）,与肠道蠕虫类的荷虫量无相关性（Spearman, N=8,ρ= -0.013, P>0.05）。本研究表明高顺位雄性拥有更高的睾酮水平,这不仅对其顺位的维持具有重要作用,对原虫类寄生虫也具有明显的抑制作用。     

COMT Val158Met moderates the link between rank and aggression in a non‐human primate

The COMT Val¹⁵⁸Met polymorphism is one of the most widely studied genetic polymorphisms in humans implicated in aggression and the moderation of stressful life event effects. We screened a wild primate population for polymorphisms at the COMT Val¹⁵⁸Met site and phenotyped them for aggression to test whether the human polymorphism exists and is associated with variation in aggressive behavior. Subjects were all adults from 4 study groups (37 males, 40 females) of Assamese macaques (Macaca assamensis) in their natural habitat (Phu Khieo Wildlife Sanctuary, Thailand). We collected focal animal behavioral data (27 males, 36 females, 5964 focal hours) and fecal samples for non‐invasive DNA analysis. We identified the human COMT Val¹⁵⁸Met polymorphism (14 Met/Met, 41 Val/Met and 22 Val/Val). Preliminary results suggest that COMT genotype and dominance rank interact to influence aggression rates. Aggression rates increased with rank in Val/Val, but decreased in Met/Met and Val/Met individuals, with no significant main effect of COMT genotype on aggression. Further support for the interaction effect comes from time series analyses revealing that when changing from lower to higher rank position Val/Val individuals decreased, whereas Met/Met individuals increased their aggression rate. Contradicting the interpretation of earlier studies, we show that the widely studied Val¹⁵⁸Met polymorphism in COMT is not unique to humans and yields similar behavioral phenotypes in a non‐human primate. This study represents an important step towards understanding individual variation in aggression in a wild primate population and may inform human behavioral geneticists about the evolutionary roots of inter‐individual variation in aggression.     

Social Relationships Among Ring-Tailed Lemurs (Lemur catta) in Two Free-Ranging Troops at Berenty Reserve, Madagascar

We observed two free-ranging troops of ring-tailed lemurs at the Berenty Reserve, Madagascar. Kinship affinities in these troops are known only for mothers and their offspring 4 years of age. We attempted to quantify social relationships. Almost all agonistic interactions were dyadic, and triadic agonistic interactions, such as alliances, were very rare. Dominance hierarchies in both sexes in the two troops were not linear. As in cercopithecine monkeys, mothers were dominant over their adult daughters. However, the daughters were not ranked immediately below their mothers. Close proximity and social grooming occurred more frequently between closely related females, such as mother–daughter and sister–sister dyads, than between unrelated females. Frequent-proximity relations also occurred between adult males that had emigrated from another troop and entered the present troop together, even though they did not rank closely to one another. Subordinates were likely to groom and to greet dominants more frequently than vice versa. During group encounters, particular females were involved in agonistic interactions with animals of other troops, regardless of dominance rank. Adult males, regardless of their dominance rank, but not adult females, constantly tried to drive solitary males away.     

Agonistic Interactions and Matrifocal Dominance Rank of Wild Bonobos (Pan paniscus) at Wamba

I studied dominance relations in a wild group of bonobos at Wamba, Democratic Republic of Congo. Although agonistic interactions between males occurred frequently, most of them consisted only of display, and physical attacks were infrequent. Dominance rank order seemed to exist among males, but its linearity is unclear. Dominant males rarely disturbed copulatory behavior by subordinate males. However, high-ranking males usually stayed in the central position of the mixed party and, so, would have more chance of access to estrous females. Among females, older individuals tended to be dominant over younger individuals. However, agonistic interactions between females occurred rather infrequently, and most consisted of displacement without any overt aggressive behavior. Dominance between males and females is unclear, but females tended to have priority of access to food. The close social status between males and females may be related to the prolonged estrus of females and their close aggregation during ranging. Existence of a male's mother in the group and her dominance status among females seemed to influence his dominance rank among males. Young adult males whose mothers were alive in the group tended to have high status. In some cases, change in dominance between high-ranking males was preceded by a corresponding change in dominance between their mothers. As the dominance status of females is similar to that of males, mothers may be able to support their sons to achieve high status, stay in the center of the mixed party, and so have greater access to females, which may maximize the number of descendants of the mothers.     

Intestinal Parasites of the Free-Ranging Cayo Santiago Rhesus Monkeys (Macaca mulatto)

Free-ranging rhesus macaques on the island of Cayo Santiago, Puerto Rico, were surveyed for intestinal parasites for the first time in over 40 years. Results were compared with the only previous study [10], and the relationships between the prevalence of Strongyloides and dominance rank, body weight, age, and matriline examined in the sampled population.     

A method for analysing spatial scales of variation in composition of assemblages

In several areas of research on ecological assemblages, it is useful to be able to analyse patterns of spatial variation at various scales. Multivariate analyses of dissimilarity or similarity in assemblages of species are limited by problems of non-independence caused by repeated use of the sample-units. Where rank-order procedures are used, no comparative quantitative measurements of dissimilarity at different scales are produced. An alternative method is described that uses the sample's average assemblage (or centroid). These estimates are themselves averaged to give centroids for larger spatial scales. Dissimilarities from the centroids at each scale are then calculated using independent replicates for each scale from those in each sample. The dissimilarity measures can then be examined by analysis of variance to detect spatial scales of differences for each sample at every level of a hierarchy of scales. The method is illustrated using data from mangrove forests and rocky shores, involving up to 97 taxonomic groups (species, other taxa). Differences among assemblages at the scales of sites (tens of meters apart) or locations at shores (hundreds of meters apart) were identified. Consequences of different numbers of replicates are discussed, with some potential problems (and their solutions) in application. Received: 14 November 1997 / Accepted: 14 September 1998     

Sequential monitoring of randomization tests: stratified randomization

In many clinical trials, it is desirable to establish a sequential monitoring plan, whereby the test statistic is computed at an interim point or points in the trial and a decision is made whether to stop early due to evidence of treatment efficacy. In this article, we will set up a sequential monitoring plan for randomization-based inference under the permuted block design, stratified block design, and stratified urn design. We will also propose a definition of information fraction in these settings and discuss its calculation under these different designs.     

A four-year study of the association between male dominance rank, residency status, and reproductive activity in rhesus macaques (Macaca mulatta)

Considerable controversy exists on the nature of the relationship between male dominance rank and reproductive activity. The nature of this relationship has important implications for understanding the manner in which males compete for access to limited resources. Behavioral data on mating patterns were collected over a four-year period from one social group of rhesus macaques on Cayo Santiago. Correlations between dominance rank and reproductive activity were not stable over a four-year period, but changed yearly. Positive, significant correlations were present in the first two years of the study while non-significant correlations were found in the second two years. The variation found in the correlations between rank and mating activity could be accounted for by changes in the mating frequencies of different classes of males. The long-term resident males had declines in ejaculation frequencies over the duration of the study. Males who immigrated into the group had yearly increases in reproductive behavior over three consecutive years. Maturing natal males also increased their levels of reproductive activity from year-to-year. Combining these mating patterns over time resulted in shifting the proportions of matings away from the long-term residents and in favor of the new males. High-ranking males had an advantage in reproductive activity over the first two years of the study, as measured by both the total number of ejaculations and the mean number of ejaculation per male. New males, comprised of recent immigrants and maturing natal males, had a greater level of reproductive activity over the last two years. These results suggest that the effect of rank on reproductive activity is variable and that males utilize alternative tactics to attain access to limited resources. Simple one-factor models explaining the relationship between rank and reproductive activity must be replaced with models explaining how alternate strategies affect male competition and reproductive success in primates.     

A Note on the Log‐Rank Test in Life Table Analysis with Correlated Observations

Survival data consisting of independent sets of correlated failure times may arise in many situations. For example, we may take repeated observations of the failure time of interest from each patient or observations of the failure time on siblings, or consider the failure times on littermates in toxicological experiments. Because the failure times taken on the same patient or related family members or from the same litter are likely correlated, use of the classical log‐rank test in these situations can be quite misleading with respect to type I error. To avoid this concern, this paper develops two closed‐form asymptotic summary tests, that account for the intraclass correlation between the failure times within patients or units. In fact, one of these two test includes the classical log‐rank test as a special case when the intraclass correlation equals 0. Furthermore, to evaluate the finite‐sample performance of the two tests developed here, this paper applies Monte Carlo simulation and notes that they can actually perform quite well in a variety of situations considered here.