Comparing primate communities: a multivariate approach

Although there have been many studies of the ecology of primates in communities throughout the world, there have been few attempts to compare community ecology within and among continents. In this study the ecological characteristics of the sympatric primate species at eight localities—two from each of the major biogeographic areas inhabited by primates today—South America, Africa, Madagascar, and Asia—were compared using a multivariate technique (principal components analysis of the correlation matrix) to summarize the ten dimensional ecological niche space. The most striking clustering of species in ecological multivariate space is according to phylogeny with closely related species showing similar ecological features. Likewise, the ecological characteristics of individual communities are determined by phylogenetic groups present at each locality or biogeographic region. As a result, communities within any biogeographical region are more similar ecologically to one another than to communities from other continental areas. In several measures of ecological diversity among the species comprising each community, the neotropical communities show lower overall diversity than do communities from other continents.     

Surveys of sympatric lemurs at Anjamena, north-west Madagascar

In order to assess the status of lemurs along the lower reaches of the Mahavavy in north-west Madagascar, we carried out transect line sampling at Anjamena between April and August 1995. These data were complemented by additional absence–presence surveys conducted in 1994 and 1995 in many of the remaining forested areas of the region. This is the first study of lemur population density estimates for the faunal subregion between the rivers Mahavavy and Betisboka. Six sympatric lemurs are found at Anjamena: Cheirogaleus medius, Eulemur fulvus rufus, E. mongoz, Lepilemur sp., Microcebus murinus and Propithecus verreauxi coronatus. Data suggest that in some parts of the region large numbers of lemurs may still be found (E. f. rufus 121 individuals per km², E. mongoz (45), Lepilemur sp. (110), M. murinus (85) and P. v. coronatus (173)). No density data are provided for C. medius. In conclusion, as high lemur population densities may still be found and, in particular, P. v. coronatus is not known to exist in any protected area, Anjamena could serve as an important addition to the protected area system of north-west Madagascar.     

Habitat Characteristics and Lemur Species Richness in Madagascar1

In the extant lemur communities of Madagascar the number of lemur species increases with increasing number of tree species. In forests with few tree species lemurs use patches with higher number of tree species than average. However, in forest plots with high number of tree species, lemurs stay in places with lower number of tree species than average. At low tree species diversity a minimum number of different tree species seems to be required within the animals' home range to assure year-round food availability. At high tree species diversity tree species essential for survival might be diluted by resources which are of no use for lemurs, thus increasing energetic expenses for traveling between suitable patches. According to the present analyses, structural diversity is of subordinate importance to the number of tree species as a correlate of lemur species richness. Within limits of disturbance intensity and on a small geographic scale, disturbances increase forest productivity. Lemurs reach higher species numbers and population densities in slightly disturbed areas compared with undisturbed sites. This peaked curve of the number of lemur species over disturbance, however, may not only be a consequence of “resource dilution” in undisturbed sites and higher food abundance in slightly disturbed areas, but also a consequence of selective extinction of lemur species which were unable to cope with the disturbance regime exaggerated by human interference over the last few hundred or thousand years.     

Pair-specific usage of sleeping sites and their implications for social organization in a nocturnal Malagasy primate, the Milne Edwards' sportive lemur (Lepilemur edwardsi)

Safe sleeping sites may be a limited resource crucial for survival. In order to investigate their potential significance for social organization in nocturnal primates, we analyzed the spatial distribution of daily sleeping sites, their characteristics, their usage, and sleeping group compositions in the nocturnal Milne Edwards' sportive lemur during a 6-month field study in the dry deciduous forest of northwestern Madagascar. Sexes did not differ either in body size or in body mass. Sleeping sites were used almost exclusively by adult male-female pairs. Individuals showed a high sleeping-site fidelity limited to 2-3 different sleeping sites in close vicinity during the whole study period. Most females showed a higher fidelity to one distinct sleeping site than their male partners. Sleeping groups consisted of one adult male and one adult female and remained stable in composition over the whole study period. Exclusive pair-specific usage of sleeping sites suggests sleeping site related territoriality of male-female pairs, perhaps influenced by inter- and intrasexual resource competition. Results give first insights into the distribution patterns and social organization of this species. They imply dispersed monogamy for the Milne Edwards' sportive lemur, with sleeping sites as a potentially restricted and defendable resource.     

A possible role of plantations for primate conservation in Madagascar

The utilization of eucalyptus plantations by seven sympatric species of prosimians was studied in the eastern rainforest of Madagascar. The species were Avahi laniger, Cheirogaleus major, Hapalemur griseus, Indri indri, Lemur fulvus, Lepilemur mustelinus, and Microcebus rufus. None of the lemurs was ever found in young eucalyptus plantations with little undergrowth. This was mainly due to the lack of travel opportunities within the shrub layer and between the shrubs and the canopy. Food (mainly berries) is seasonally available in the shrub layer but cannot be exploited because frugivorous lemurs cannot reach it. Old eucalyptus plantations with dense undergrowth are used by all prosimian species. They provide food as well as travel and resting facilities. Mixed tree plantations in the western part of Madagascar were used by groups of Lemur fulvus, Lepilemur mustelinus, and Propithecus verreauxi. According to these results, old eucalyptus plantations and mixed tree species plantations could be used to provide firewood and construction wood for the human population. They also might extend the habitat for lemurs and serve as buffers against human disturbance.     

The evolution of primate general and cultural intelligence

There are consistent individual differences in human intelligence, attributable to a single 'general intelligence' factor, g. The evolutionary basis of g and its links to social learning and culture remain controversial. Conflicting hypotheses regard primate cognition as divided into specialized, independently evolving modules versus a single general process. To assess how processes underlying culture relate to one another and other cognitive capacities, we compiled ecologically relevant cognitive measures from multiple domains, namely reported incidences of behavioural innovation, social learning, tool use, extractive foraging and tactical deception, in 62 primate species. All exhibited strong positive associations in principal component and factor analyses, after statistically controlling for multiple potential confounds. This highly correlated composite of cognitive traits suggests social, technical and ecological abilities have coevolved in primates, indicative of an across-species general intelligence that includes elements of cultural intelligence. Our composite species-level measure of general intelligence, 'primate g(S)', covaried with both brain volume and captive learning performance measures. Our findings question the independence of cognitive traits and do not support 'massive modularity' in primate cognition, nor an exclusively social model of primate intelligence. High general intelligence has independently evolved at least four times, with convergent evolution in capuchins, baboons, macaques and great apes.     

雌性偏好促进象型类的性别异时进化（英文）

性双型的特征通常被认为产生于种内争夺交配优先权的斗争。例如,现生和化石的雄性长鼻类动物具有较大的体型和较粗壮的上门齿。本研究阐释了如下现象:化石象型类动物(Elephantiformes,长鼻类的主要类群)一些性双型特征与其进化历史具有相关性,而与性别竞争并非直接相关。在中新世的葛氏铲齿象(Platybelodon grangeri)和狭齿嵌齿象(Gomphotherium angustidens)中,雄性比雌性倾向于具有进化中更进步的特征,如同雄性在进化中领先雌性一步。这种现象可能与雌性偏好的机制相耦合。在象型类动物进化的早期(繁荣期),性别选择压促使雄性比雌性产生更加显著的进步特征;然而,在它们进化的晚期(衰退期),性别选择压似乎减弱,性别的异时进化也减少。这种新的发现或许在大型有蹄类的演化过程中有一定的普遍意义,因为那些繁荣的类群中通常性双型显著,如鹿科和牛科;而衰落的类群中通常性双型不显著。     

Testing some hypotheses on human evolution and sexual dimorphism

Research on human evolution and sexual dimorphism motivates an interesting test problem. In studying hominid phylogeny it is of interest to test whether parallel evolution plays a role. With regard to sexual dimorphism it is of interest to known whether the directions of sexual dimorphism in the populations being compared are the same. We show that testing these two problems gives rise to the same type of hypothesis testing, viz. the problem of testing the hypothesis that the means of independent, normally distributed random vectors with unit covariance matrices are situated on a straight line through the origin. A test is proposed and applied to study the sexual dimorphism of 20 recent skull populations. In this example the hypothesis of equal directions of sexual dimorphism is rejected. The classical theory of constructing multiple discriminant functions (canonical variates) is adapted to the problem of comparing sexual dimorphisms.     

The primate palette: The evolution of primate coloration

Flip through The Pictorial Guide to the Living Primates¹ and you will notice a striking yet generally underappreciated aspect of primate biology: primates are extremely colorful. Primate skin and pelage coloration were highlighted examples in Darwin's² original discussions of sexual selection but, surprisingly, the topic has received little research attention since. Here we summarize the patterns of color variation observed across the primate order and examine the selective forces that might drive and maintain this aspect of primate phenotypic diversity. We discuss how primate color patterns might be adaptive for physiological function, crypsis, and communication. We also briefly summarize what is known about the genetic basis of primate pigmentation and argue that understanding the proximate mechanisms of primate coloration will be essential, not only for understanding the evolutionary forces shaping phenotypic variation, but also for clarifying primate taxonomies and conservation priorities.     

Understanding primate brain evolution

We present a detailed reanalysis of the comparative brain data for primates, and develop a model using path analysis that seeks to present the coevolution of primate brain (neocortex) and sociality within a broader ecological and life-history framework. We show that body size, basal metabolic rate and life history act as constraints on brain evolution and through this influence the coevolution of neocortex size and group size. However, they do not determine either of these variables, which appear to be locked in a tight coevolutionary system. We show that, within primates, this relationship is specific to the neocortex. Nonetheless, there are important constraints on brain evolution; we use path analysis to show that, in order to evolve a large neocortex, a species must first evolve a large brain to support that neocortex and this in turn requires adjustments in diet (to provide the energy needed) and life history (to allow sufficient time both for brain growth and for 'software' programming). We review a wider literature demonstrating a tight coevolutionary relationship between brain size and sociality in a range of mammalian taxa, but emphasize that the social brain hypothesis is not about the relationship between brain/neocortex size and group size per se; rather, it is about social complexity and we adduce evidence to support this. Finally, we consider the wider issue of how mammalian (and primate) brains evolve in order to localize the social effects.     

The evolution of extinction risk: past and present anthropogenic impacts on the primate communities of Madagascar

There are two possible approaches to understanding natural and human-induced changes in the primate communities of Madagascar. One is to begin with present-day and recent historic interactions and work backwards. A second is to begin with paleoecological records of Malagasy primate communities before and immediately following human arrival, and the associated evidence of human and nonhuman primate interactions, and work forwards. On the basis of biological and climatic studies, as well as historic and ethnohistoric records, we are beginning to understand the abiotic and biotic characteristics of Madagascar's habitats, the lemurs' ecological adaptations to these unique habitats, the extent of forest loss, fragmentation and hunting, and the differential vulnerability of extant lemur species to these pressures. On the basis of integrated paleoecological, archaeological and paleontological research, we have begun to construct a detailed chronology for late prehistoric Madagascar. We are beginning to understand the complex sequence of events that led to one of the most dramatic recent megafaunal extinction/extirpation events. Combining the perspectives of the past and the present, we see a complex set of interactions affecting an initially rich but vulnerable fauna. The total evidence refutes any simple, unicausal (e.g. hunting/habitat destruction/climate change) explanation of megafaunal extinctions, yet unequivocally supports a major role--both direct and indirect--for humans as the trigger of the extinction process. It also supports a change over time in the relative importance of hunting versus habitat loss, and in the trophic characteristics of the primate communities in Madagascar.     

Cultural evolution of systematically structured behaviour in a non-human primate

Culture pervades human life and is at the origin of the success of our species. A wide range of other animals have culture too, but often in a limited form that does not complexify through the gradual accumulation of innovations. We developed a new paradigm to study cultural evolution in primates in order to better evaluate our closest relatives'' cultural capacities. Previous studies using transmission chain experimental paradigms, in which the behavioural output of one individual becomes the target behaviour for the next individual in the chain, show that cultural transmission can lead to the progressive emergence of systematically structured behaviours in humans. Inspired by this work, we combined a pattern reproduction task on touch screens with an iterated learning procedure to develop transmission chains of baboons (Papio papio). Using this procedure, we show that baboons can exhibit three fundamental aspects of human cultural evolution: a progressive increase in performance, the emergence of systematic structure and the presence of lineage specificity. Our results shed new light on human uniqueness: we share with our closest relatives essential capacities to produce human-like cultural evolution.     

Social molecular pathways and the evolution of bee societies

Bees provide an excellent model with which to study the neuronal and molecular modifications associated with the evolution of sociality because relatively closely related species differ profoundly in social behaviour, from solitary to highly social. The recent development of powerful genomic tools and resources has set the stage for studying the social behaviour of bees in molecular terms. We review 'ground plan' and 'genetic toolkit' models which hypothesize that discrete pathways or sets of genes that regulate fundamental behavioural and physiological processes in solitary species have been co-opted to regulate complex social behaviours in social species. We further develop these models and propose that these conserved pathways and genes may be incorporated into 'social pathways', which consist of relatively independent modules involved in social signal detection, integration and processing within the nervous and endocrine systems, and subsequent behavioural outputs. Modifications within modules or in their connections result in the evolution of novel behavioural patterns. We describe how the evolution of pheromonal regulation of social pathways may lead to the expression of behaviour under new social contexts, and review plasticity in circadian rhythms as an example for a social pathway with a modular structure.     

Introduction: Current studies on primate socioecology and evolution

Primate socioecology is being dramatically transformed as new studies are undertaken in Madagascar and the New World. Simultaneously, the incorporation of primate studies in a broader framework of theory in behavioral ecology promises to more intelligently inform anthropology's traditional concerns with primate and hominid evolution.     

Rates of phenotypic evolution of ecological characters and sexual traits during the Tanganyikan cichlid adaptive radiation

Theory suggests that sexual traits evolve faster than ecological characters. However, characteristics of a species niche may also influence evolution of sexual traits. Hence, a pending question is whether ecological characters and sexual traits present similar tempo and mode of evolution during periods of rapid ecological divergence, such as adaptive radiation. Here, we use recently developed phylogenetic comparative methods to analyse the temporal dynamics of evolution for ecological and sexual traits in Tanganyikan cichlids. Our results indicate that whereas disparity in ecological characters was concentrated early in the radiation, disparity in sexual traits remained high throughout the radiation. Thus, closely related Tanganyikan cichlids presented higher disparity in sexual traits than ecological characters. Sexual traits were also under stronger selection than ecological characters. In sum, our results suggest that ecological characters and sexual traits present distinct evolutionary patterns, and that sexual traits can evolve faster than ecological characters, even during adaptive radiation.     

Migration and the evolution of sexual dichromatism: evolutionary loss of female coloration with migration among wood-warblers

The mechanisms underlying evolutionary changes in sexual dimorphism have long been of interest to biologists. A striking gradient in sexual dichromatism exists among songbirds in North America, including the wood-warblers (Parulidae): males are generally more colourful than females at northern latitudes, while the sexes are similarly ornamented at lower latitudes. We use phylogenetically controlled comparative analysis to test three non-mutually exclusive hypotheses for the evolution of sexual dichromatism among wood-warblers. The first two hypotheses focus on the loss of female coloration with the evolution of migration, either owing to the costs imposed by visual predators during migration, or owing to the relaxation of selection for female social signalling at higher latitudes. The third hypothesis focuses on whether sexual dichromatism evolved owing to changes in male ornamentation as the strength of sexual selection increases with breeding latitude. To test these hypotheses, we compared sexual dichromatism to three variables: the presence of migration, migration distance, and breeding latitude. We found that the presence of migration and migration distance were both positively correlated with sexual dichromatism, but models including breeding latitude alone were not strongly supported. Ancestral state reconstruction supports the hypothesis that the ancestral wood-warblers were monochromatic, with both colourful males and females. Combined, these results are consistent with the hypotheses that the evolution of migration is associated with the relaxation of selection for social signalling among females and that there are increased predatory costs along longer migratory routes for colourful females. These results suggest that loss of female ornamentation can be a driver of sexual dichromatism and that social or natural selection may be a stronger contributor to variation in dichromatism than sexual selection.     

Role of sexual and natural selection in evolution of body size and shape: a phylogenetic study of morphological radiation in grouse

We use standardized independent contrasts (SICs) to elucidate the effect of ecology and mating systems on morphological radiation in grouse. The analysis of SICs for 38 skeletal measurements from 20 taxa, showed that changes in mating system had a significant effect on body size of both sexes. Sexual size dimorphism in grouse is consistent with Rensch's rule; the slope of the regression of male vs. female size SICs was 1.4, significantly >1. Changes in habitat were associated with accelerated rates of evolution of body proportions. SICs for male and female scores of size independent factors were directly proportional to each other (slope = 1), indicating extreme similarities between male and female ecology. Females, however, were better adapted to longer, more energy efficient flight than males. Size independent morphological differences among grouse are adaptive and are related to the differences in habitat and foraging behaviour among the species.