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Linda Vigilant

Publications and source records attributed to Linda Vigilant.

15 recordsLinked to original sources
PubMed2007

Plant DNA sequences from feces: potential means for assessing diets of wild primates.

Analyses of plant DNA in feces provides a promising, yet largely unexplored, means of documenting the diets of elusive primates. Here we demonstrate the promise and pitfalls of this approach using DNA extracted from fecal samples of wild western gorillas (Gorilla gorilla) and black and white colobus monkeys (Colobus guereza). From these DNA extracts we amplified, cloned, and sequenced small segments of chloroplast DNA (part of the rbcL gene) and plant nuclear DNA (ITS-2). The obtained sequences were compared to sequences generated from known plant samples and to those in GenBank to identify plant taxa in the feces. With further optimization, this method could provide a basic evaluation of minimum primate dietary diversity even when knowledge of local flora is limited. This approach may find application in studies characterizing the diets of poorly-known, unhabituated primate species or assaying consumer-resource relationships in an ecosystem.

Animals↗
PubMed2006

Male competition and paternity in wild chimpanzees of the Taï forest.

In social animals, competition among males for mates affects individual reproductive success. The priority-of-access model attempts to account for the influence of demographic conditions within groups upon male reproductive success, but empirical data for testing this model are scarce. Our long-term study of chimpanzees in the Taï National Park, Côte d'Ivoire, encompasses a period of steady decrease in community size and fluctuating numbers of competing males and sexually receptive females. These demographic changes, in combination with genetic assessment of paternity for 48 offspring from three communities, allowed us to quantify the effects of varying levels of competition upon male reproductive success. On average, the highest-ranking male sired 50% of all analyzed offspring during a 14-year period from 1987-2000. Competition among males strongly decreased the relative reproductive success of the alpha male, such that the alpha male's rate of success decreased from 67% with few competitors to only 38% with four or more competitors. The increasing number of synchronously receptive females in large groups also reduced the proportion of paternities by the alpha male. Thus, patterns of paternity in Taï chimpanzees fit well the predictions of the priority-of-access model. We also found that despite the inability of dominants to monopolize reproduction, they achieved a higher reproductive rate in large multimale groups, because these have more females and a higher infant survival rate. Varied levels of male competition within communities seem to explain differences in the reproductive success of alpha males observed in different chimpanzee populations, and in other primate species.

Age Factors↗
PubMed2006

Y-chromosome analysis confirms highly sex-biased dispersal and suggests a low male effective population size in bonobos (Pan paniscus).

Dispersal is a rare event that is difficult to observe in slowly maturing, long-lived wild animal species such as the bonobo. In this study we used sex-linked (mitochondrial DNA sequence and Y-chromosome microsatellite) markers from the same set of individuals to estimate the magnitude of difference in effective dispersal between the sexes and to investigate the long-term demographic history of bonobos. We sampled 34 males from four distinct geographical areas across the bonobo distribution range. As predicted for a female-dispersing species, we found much higher levels of differentiation among local bonobo populations based upon Y-chromosomal than mtDNA genetic variation. Specifically, almost all of the Y-chromosomal variation distinguished populations, while nearly all of the mtDNA variation was shared between populations. Furthermore, genetic distance correlated with geographical distance for mtDNA but not for the Y chromosome. Female bonobos have a much higher migration rate and/or effective population size as compared to males, and the estimate for the mitochondrial TMRCA (time to most recent common ancestor) was approximately 10 times greater than the estimate for the Y chromosome (410,000 vs. 40,000-45,000). For humans the difference is merely a factor of two, suggesting a more stable demographic history in bonobos in comparison to humans.

Analysis of Variance↗
PubMed2005

Mountain gorilla tug-of-war: silverbacks have limited control over reproduction in multimale groups.

To determine who fathers the offspring in wild mountain gorilla groups containing more than one adult male silverback, we genotyped nearly one-fourth (n = 92) of the mountain gorillas (Gorilla beringei beringei) living in the Virunga Volcanoes region of Africa. Paternity analysis of 48 offspring born into four groups between 1985 and 1999 revealed that, although all infants were sired by within-group males, the socially dominant silverback did not always monopolize reproduction within his group. Instead, the second-ranking male sired an average of 15% of group offspring. This result, in combination with previous findings that second-ranking males fare best by not leaving the group but by staying and waiting to assume dominance even if no reproduction is possible while waiting, is not consistent with expectations from a reproductive skew model in which the silverback concedes controllable reproduction to the second-ranking male. Instead, the data suggest a "tug-of-war" scenario in which neither the dominant nor the second-ranking male has full control over his relative reproductive share. The two top-ranked males were typically unrelated and this, in combination with the mixed paternity of group offspring, means that multimale gorilla groups do not approximate family groups. Instead, as long-term assemblages of related and unrelated individuals, gorilla groups are similar to chimpanzee groups and so offer interesting possibilities for kin-biased interactions among individuals.

Animals↗
PubMed2004

Gorillas.

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Africa↗
PubMed2004

Anthrax kills wild chimpanzees in a tropical rainforest.

Infectious disease has joined habitat loss and hunting as threats to the survival of the remaining wild populations of great apes. Nevertheless, relatively little is known about the causative agents. We investigated an unusually high number of sudden deaths observed over nine months in three communities of wild chimpanzees (Pan troglodytes verus) in the Taï National Park, Ivory Coast. Here we report combined pathological, cytological and molecular investigations that identified Bacillus anthracis as the cause of death for at least six individuals. We show that anthrax can be found in wild non-human primates living in a tropical rainforest, a habitat not previously known to harbour B. anthracis. Anthrax is an acute disease that infects ruminants, but other mammals, including humans, can be infected through contacting or inhaling high doses of spores or by consuming meat from infected animals. Respiratory and gastrointestinal anthrax are characterized by rapid onset, fever, septicaemia and a high fatality rate without early antibiotic treatment. Our results suggest that epidemic diseases represent substantial threats to wild ape populations, and through bushmeat consumption also pose a hazard to human health.

Animals↗
PubMed2004

Chimpanzees.

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Animals↗
PubMed2004

Dispersed male networks in western gorillas.

Although kin-selection theory has been widely used to explain the tendency of individuals to bias beneficial behaviors towards relatives living within the same social group, less attention has focused on kin-biased interactions between groups. For animal societies in which females emigrate, as is the case for mountain gorillas (Gorilla beringei beringei), encounters between males in different groups often involve aggressive displays that can escalate to physical violence and fatal injuries. However, recent findings on the little-studied western gorilla (Gorilla gorilla) indicate that interactions between social groups occur more frequently than they do in mountain gorillas and are often, although not always, surprisingly nonaggressive. We investigated the pattern of genetic relationships between individuals of different groups and found evidence suggesting a previously unrecognized "dispersed male network" social structure in western gorillas in which the single males leading social groups were usually related to one or more nearby males. We propose that this provides a basis for extra-group, kin-biased behaviors and may explain the reported peaceful intergroup interactions. Furthermore, these results suggest that a patrilocal social structure, in which males remain in their natal region and potentially benefit from kin associations, is a feature unifying African apes and humans.

Animals↗
PubMed2004

Cross-species amplification of human microsatellite markers using noninvasive samples from white-handed gibbons (Hylobates lar).

Analysis of the population genetic structure and reproductive strategies of various primate species has been facilitated by cross-species amplification (i.e., the use of microsatellite markers developed in one species for analysis of another). In this study we screened 47 human-derived markers to assess their utility in the white-handed gibbon (Hylobates lar). Only eight produced accurate, reliable results, and exhibited levels of polymorphism that were adequate for individual identification. This low success rate was surprising given that human microsatellite markers typically work well in species (such as macaques) that are evolutionarily more distant from humans than are gibbons. In addition, we experienced limited success in using a set of microsatellite markers that have been reported to be useful in the closely-related H. muelleri, and applying our set of microsatellite markers to samples obtained from one H. pileatus individual. Our results emphasize the importance of extensively screening potential markers in representatives of the population of interest.

Animals↗
PubMed2004

Genetic variation in gorillas.

This review summarizes what is currently known concerning genetic variation in gorillas, on both inter- and intraspecific levels. Compared to the human species, gorillas, along with the other great apes, possess greater genetic variation as a consequence of a demographic history of rather constant population size. Data and hence conclusions from analysis of mitochondrial DNA (mtDNA), the usual means of describing intraspecific patterns of genetic diversity, are limited at this time. An important task for future studies is to determine the degree of confidence with which gorilla mtDNA can be analyzed, in view of the risk that one will inadvertently analyze artifactual rather than genuine sequences. The limited information available from sequences of nuclear genomic segments does not distinguish western from eastern gorillas, and, in comparison with results from the two chimpanzee species, suggests a relatively recent common ancestry for all gorillas. In the near future, the greatest insights are likely to come from studies aimed at genetic characterization of all individual members of social groups. Such studies, addressing topics such as behavior of individuals with kin and non-kin, and the actual success of male reproductive strategies, will provide a link between behavioral and genetic studies of gorillas.

Animals↗
PubMed2004

Genetic analyses from ancient DNA.

About 20 years ago, DNA sequences were separately described from the quagga (a type of zebra) and an ancient Egyptian individual. What made these DNA sequences exceptional was that they were derived from 140- and 2400-year-old specimens. However, ancient DNA research, defined broadly as the retrieval of DNA sequences from museum specimens, archaeological finds, fossil remains, and other unusual sources of DNA, only really became feasible with the advent of techniques for the enzymatic amplification of specific DNA sequences. Today, reports of analyses of specimens hundreds, thousands, and even millions of years old are almost commonplace. But can all these results be believed? In this paper, we critically assess the state of ancient DNA research. In particular, we discuss the precautions and criteria necessary to ascertain to the greatest extent possible that results represent authentic ancient DNA sequences. We also highlight some significant results and areas of promising future research.

Animals↗
PubMed2003

Mitochondrial DNA sequence from an enigmatic gorilla population (Gorilla gorilla uellensis).

Although today gorillas are found in only two widely separate, discontinuous western and eastern African populations, rumors of the existence of an additional gorilla population in central Africa have inspired recent unsuccessful field expeditions in search of the "mystery ape" termed Gorilla gorilla uellensis. Such a gorilla population would have considerable conservation and scientific interest, and would presumably have descended from a population of gorillas that was thought to exist until the end of the 19th century on the Uele River in the current-day Democratic Republic of Congo. However, the sole evidence for the existence of these gorillas is three skulls and one mandible brought to the Royal Museum for Central Africa (Tervuren, Belgium) in 1898. We determined a mitochondrial DNA sequence from one of these specimens and compared it to sequences from other gorillas. Contrary to expectations, the sequence obtained did not exhibit the phylogenetic distinctiveness typical of a representative of a peripheral isolated population. Rather, the results suggest a scenario in which the museum specimens did not originally derive from the northern Congo, but were brought from the area of current distribution of western gorillas to that location; the subsequent discovery and collection of the specimens there gave rise to the false inference of a local gorilla population.

Africa, Central↗
PubMed2002

The effects of sequence length and oligonucleotide mismatches on 5' exonuclease assay efficiency.

Although increasingly used for DNA quantification, little is known of the dynamics of the 5' exonuclease assay, particularly in relation to amplicon length and mismatches at oligonucleotide binding sites. In this study we used seven assays targeting the c-myc proto-oncogene to examine the effects of sequence length, and report a marked reduction in efficiency with increasing fragment length. Three of the assays were further tested on 15 mammalian species to gauge the effect of sequence differences on performance. We show that the effects of probe and primer binding site mismatches are complex, with single point mutations often having little effect on assay performance, while multiple mismatches to the probe caused the greatest reduction in efficiency. The usefulness of the assays in predicting rates of 'allelic dropout' and successful polymerase chain reactions (PCRs) in microsatellite genotyping studies is supported, and we demonstrate that the use of a fragment more similar in size to typical microsatellites (190 bp) is no more informative than a shorter (81 bp) fragment. The assays designed for this study can be used directly for quantification of DNA from many mammalian species or, alternatively, information provided here can be used to design unique sequence-specific assays to maximise assay efficiency.

Animals↗