Evolutionary insight gained from the comparative phylogenetics of cercopithecine monkeys

Anthony J. Tosi
Anthropology Department
New York University

In cercopithecine monkeys, Y-chromosomal, mitochondrial, and autosomal DNA differ in numerous evolutionarily significant parameters: effective population size, uniparental vs. biparental inheritance, and dispersal level. Consequently, gene trees inferred from these various classes of DNA occasionally differ in divergence patterns and/or divergence times. Rather than being confounding factors in phylogenetic research, such cases of incongruence can reveal rich details in the history of closely-related taxa. Previous studies of Macaca show that comparison of tree patterns can distinguish introgression from lineage sorting, and that comparison of branch lengths can discern time of initial separation from time of last genetic contact. Ongoing studies of the (arboreal) Cercopithecus radiation are similarly useful. Though numerous molecular analyses agree that the Cercopithecus species groups are reciprocally monophyletic, members of different species groups occasionally hybridize and thereby open a conduit for genetic exchange. Thus, future gene trees which link members of different species groups as sister-taxa will provide strong evidence for interspecific exchange of (adaptive?) alleles.
Incongruence among cercopithecine gene trees reminds us that evolution does not always follow a strictly bifurcating pattern, as depicted by most phylogenies. Significant levels of reticulate gene flow can occur long after the initial separation of populations and species.

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Stress and hippocampal plasticity

Eberhard Fuchs
Department of Neurology
Medical School, University of Göttingen
and Clinical Neurobiology, German Primate Center

Neural plasticity is absolutely necessary for adequate functioning of an　individual in the continuously changing environment. However, not all neural　plasticity is beneficial, as demonstrated by the altered structure and　function e.g. in the brains of patients with mood disorders. There is　increasing evidence that psychiatric disorders not only have a neurochemical　basis but are also associated with morphological alterations the CNS. One of the brain structures that has been extensively studied with regard to the actions of stress is the hippocampal formation. Within the hippocampal formation, the dentate gyrus is one of the few brain structures where production of new neurons occurs even in the adult mammalian brain and stress was identified as one factor that suppresses the formation of new cells. Stress-induced structural remodeling in the adult hippocampus may provide a cellular basis for understanding the impairment of neural plasticity in depressive illness. Accordingly, reversal of structural remodeling may be a desirable goal for antidepressant therapy. This presentation summarizes data showing that stress-induced anatomical changes in the hippocampus could be counteracted by treatment with different antidepressants providing experimental evidence for recent concepts of pharmacological modification of neuronal viability and neuronal remodeling in the treatment of mood disorders. Although these concepts are still in their infancy they have increasingly attracted research efforts which may result in new treatment strategies of neural resilience responsible for the etiopathophysiology of psychiatric disorders, such as major depression.

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Learning tool use for nut cracking in captive chimpanzees

Satoshi Hirata
Great Ape Research Institute
Hayashibara Biochemical Laboratories, Inc.

Wild chimpanzees perform a variety of tool-using behaviors. Such behaviors have been viewed as cultural behaviors, as different repertoires of tool use are seen in different locations. For example, tool use for cracking nuts is specific to an area of West Africa and is never observed in Central or East Africa. Therefore, naive infant chimpanzees acquire the skill necessary for nut cracking after observing their mothers or other adult group members. Nut-cracking behavior requires relating three objects: a nut, an 'anvil', and a 'hammer'. Therefore, it is one of the most complex tool-use behaviors seen in chimpanzees. We investigated how naive chimpanzees learn nut-cracking behavior in captivity and recorded the entire process up to their first success. Several features characterized their learning processes. First, the manipulation of a single object and the combined manipulation of two objects, such as putting a nut on an anvil stone, were observed relatively frequently from the first session, while the combined manipulation of three objects was never or rarely observed initially. Second, stepping on the nut was observed in the early stages, but ceased in subsequent sessions, and was replaced by hitting the nut. Third, when the hitting action emerged, chimpanzees tended not to use a hammer stone as a hitting tool initially, but hit the nut with a hand directly. The frequency of hitting the nut with a hammer stone increased gradually. Fourth, when the hitting action emerged, the target of the hitting action was not always a nut; hitting a stone with another stone was also observed. The learning process was apparently affected by observing other skilled chimpanzee successfully cracking nuts using stone tools. Overall, the learning process could be divided into three stages. The first stage consisted of understanding the goal or function only, but not the other parts of tool use, as exemplified by stepping on a nut. The second stage was the emergence of the hitting action. During this stage, the chimpanzees did not understand the necessity of using hammer stones. The last stage consisted of understanding hammer stones. During this stage, the chimpanzees became able to crack nuts successfully. Therefore, this study clearly shows that understanding of the goal, action, and method (i.e., the use of tools) takes place at different stages when chimpanzees learn nut-cracking behavior. In addition, social tolerance is a key factor in the social learning of tool use.

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Multiscale biogeography of western chimpanzees
in the Bafing area, Mali

Chris S. Duvall
Department of Geography
University of Wisconsin, Madison

Chimpanzees in semi-arid southwestern Mali occupy an edge of the species' range, which centers on the African rainforest biome. Analysis of chimpanzee distribution in Mali's Bafing area provides insight on how the ape has adapted to an environment that is extremely arid and has little forest vegetation relative to most of its range. During January-December 2004, systematic surveys of chimpanzee abundance were conducted in an area of 183 km2, in which surface water, certain vegetation characteristics, and human settlements were mapped. Based on these data, the distribution of chimpanzee and nest observations shows that the ape uses habitat patches in which plant food items are abundant more frequently than habitat patches in which only surface water is present. The abundance of food patches and water sources varies relative to physical geographic features, and this variation correlates to differences in chimpanzee nesting behavior. The differences in nesting behavior suggest that the study area includes parts of the ranges of two chimpanzee groups, while the differences in food-patch and water-source abundance suggests that the northernmost part of chimpanzee range in Mali is linked to bedrock geology. Sandstone outcrops in this area have high biodiversity because the bedrock's physical structure creates stable ecological and hydrogeological conditions; chimpanzees are a component of this diverse biota. Thus, the ape's presence in part of Mali, and probably elsewhere on the periphery of its range, depends upon long-term climate conditions that maintain specific microhabitats in which chimpanzee food plants and surface water are abundant.

Keywords: diet; nesting behavior; Pan troglodytes verus; distribution; habitat

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Determining fecal glucocorticoid metabolites in wild chimpanzees from Mahale Mountains National Park, Tanzania

Taranjit Kaur
Virginia-Maryland Regional College of Veterinary Medicine
Virginia Polytechnic Institute and State University

Assessing stress in wild chimpanzees is essential to understanding and monitoring their health and well-being. In wild animals, determining fecal glucocorticoid levels is a preferred method to assess stress levels, because samples can be collected non-invasively. This study was aimed at 1) developing a reliable method for extracting fecal cortisol metabolites (FGM) from wild chimpanzee in the field, and 2) comparing FGM levels measured by different enzyme immunoassays (EIA) using antibodies raised against cortisol, corticosterone and a 11 β-hydroxyetiocholanolone. The results indicate that this modified protocol yields improved recovery of CM from the feces of wild chimpanzees. FGM measured with the 11 β-hydroxyetiocholanolone were highest among the three EIAs tested. The levels of metabolites measured with the cortisol and corticosterone EIA were below the detection limit. Preliminary results suggest that the 11β-hydroxyetiocholonolone-EIA may be used to monitor fecal glucocorticoid metabolites in wild chimpanzees.

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Modularity, ontogeny, and the morphological diversity of
the mammalian skull

Anjali Goswami
Department of Palaeontology
The Natural History Museum
and School of Biological Sciences Queen Mary College, University of London

Variation is the raw material of evolution, but there is little understanding of how variation on a microevolutionary scale relates to large-scale evolutionary patterns. In particular, trait correlations have often been invoked as a possible constraint on variation, and thus a major influence on evolutionary change, but there are few empirical studies of the relationship between trait correlations and morphological evolution. The study of modules, autonomous sets of highly-correlated traits, allows for broad comparisons of trait correlations across large clades and across scales of evolutionary study, from genetics to paleontology.
I have use a quantitative framework, 3-D morphometrics, to assess modularity in crania of fossil and Recent mammals, including monotremes, marsupials, and placentals. This work has demonstrated that monotremes and placentals differ markedly in their patterns of cranial modularity. Monotremes display only two cranial modules, while therians (marsupials and placentals) display six. Within therians, there are significant differences among modules and across taxa in the strength of within-module correlations. These patterns correlate significantly with both functional and developmental theoretical models, but may better reflect development.
Lastly, I address the question: "What is the evolutionary significance of modularity?" I will present results from two approaches to addressing this fundamental question. First, do modules show significant differences in morphological disparity? As mentioned above, some modules are highly integrated (high trait correlations), and others are more weakly integrated. If trait correlations constrain variation, it may be expected that less integrated modules show higher disparity. I use data from over 100 species from the therian orders Primates, Carnivora, Dasyuromorphia, Peramelia, and Diprotodontia to compare disparity, measured as Procrustes distance, in each of the six modules observed in therians. Second, I conduct stochastic computer simulations of cranial shape evolution using different empirically-derived covariance matrices to demonstrate how different patterns of cranial modularity may influence long-term patterns of morphological diversity.

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Biology of giant flying squirrels:
 adaptive characteristics and phylogeography of an arboreal small mammal

Tatsuo Oshida
Obihiro University of Agriculture and Veterinary Medicine

Giant flying squirrels (genus Petaurista) are ubiquitous throughout South and Southeast Asia, southern China, Taiwan, and Japan. They are nocturnal, arboreal, and well adapted to temperate mixed deciduous forest and evergreen broadleaf forest. Even though there are studies on the systematics, phylogeny, and ecology of some Petaurista species, the general biology of this genus is still unclear. Petaurista species depend on the resources of biologically rich forests. They feed on the leaves, fruit, seeds, cones, flowers, buds, and shoots of many tree species. They nest in cavities of huge trees. Therefore, the phylogeographical structure of Petaurista probably results from variation in forest dynamics during the Pleistocene's drastic climatic changes.
Here, I show how studies of arboreal small mammals, such as Petaurista species, can help resolve phylogeographical events. First, I describe the feeding behavior of some Petaurista species and explain their adaptations to Asian temperate forests. Second, I give a concrete example by introducing a recent study of the association between the phylogeographical structure of the Japanese giant flying squirrel (P. leucogenys) and forest dynamics of Japan.　This squirrel is endemic species to the Kyushu, Shikoku, and Honshu islands of Japan. To investigate the phylogeographical pattern, I analyzed complete mitochondrial cytochrome b sequences (1140 bases). There were four mitochondrial DNA phylogroups of P. leucogenys. The main phylogroup, most widely distributed from northern Honshu to southern Honshu and Shikoku, showed unclear phylogeographical structure, suggesting recent expansion of the ancestral population in a short time. This suggested the presence of P. leucogenys glacial refigia in the southern parts of Japan.

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