Biology subjects

Wittig, R. M.

Publications and source records attributed to Wittig, R. M..

11 recordsLinked to original sources

bioRxiv2026

Wild chimpanzee groups increase social connectivity prior to risky collective action

Cooperation is foundational to complex sociality, yet presents profound evolutionary dilemmas - costs and benefits are rarely distributed evenly and the decision to collaborate or defect can involve a complex contextual calculus. These challenges are compounded when cooperation scales from pairs to groups. Group-level cooperation is fundamental to many species success, but how is it sustained and regulated in nature? One promising route to addressing this question is to examine how individuals reorganise their affiliative interactions in anticipation of group-level cooperation. We examine such pre-cooperative reorganisation using long-term data (2013-2018) from three neighbouring groups of wild chimpanzees at the Tai National Park, Cote dIvoire, who routinely cooperate as a collective to defend their territory against other groups. We found that chimpanzees adjusted the distribution of their social contacts in anticipation of risky and proactive territorial defence by forming more broadly connected, yet more diffuse, affiliative networks. Specifically, adult chimpanzees groomed and played with more group members on days of proactive territorial defence, and this pattern was temporally-sensitive, with increased affiliation occurring before, rather than after, the cooperative act. Chimpanzees accessed a broader range of partners through increased interaction efficiency by switching between more partners with shorter interactions per partner. This pattern suggests a shared evolutionary basis of dynamic social readjustment in preparation for group-level social dilemmas in hominids, potentially providing the foundation for the formalized systems of affiliation found in human societies.

animal behavior and cognition↗

bioRxiv2025

Rule-based sequences in sooty mangabey vocal communication

Investigating how non-human animals produce call sequences provides key insights into the evolutionary origins of meaning in vocal communication, including syntax. Many species combine calls into structured sequences, often following specific rules, yet most studies focus on only a few sequences per species. This limits our understanding of their ability to combine calls and convey meaning through sequences. Our study addresses this gap by documenting the vocal sequence repertoire and underlying rules of sooty mangabeys (Cercocebus atys), a West African monkey species. We collected and analysed 1,672 recordings from two wild groups in the Tai National Park, Ivory Coast. Sooty mangabeys frequently combine calls but rely on a limited set of sequences. Within these, we identified rules of call ordering, recurrence and hierarchical structuring. Notably, they produced hierarchically structured sequences using only two call types, a previously unreported system in animal communication. Our findings suggest that sooty mangabeys use both structured and unstructured sequences, likely encoding different types of information. While context of production remains essential for determining meaning, our results highlight how a whole-repertoire approach reveals the full range of rule-based sequences and their potential for meaning expansion beyond the number of individual calls available in the repertoire.

animal behavior and cognition↗

bioRxiv2025

Spatial and single-nucleus transcriptomic profile of a chimpanzee frontal pole

Chimpanzees, our closest living relatives, share a vast amount of our genetic code, with the majority of differences found in non-coding regions of the genome. Functional and gene regulatory differences drive phenotypic divergence, including the distinctive brain anatomy of humans compared to chimpanzees and other apes. However, little is known about species differences in gene expression, and how they relate to the evolution of neuroanatomy and cognition. This is primarily due to the limited availability of great ape brain samples and challenges in comparative spatial transcriptomic studies. Here, we present the first spatial transcriptomic data from a chimpanzee brain based on post mortem tissue from an adult female, who was euthanised due to poor health. We focus on the frontal pole, a brain region that has undergone significant evolutionary changes in size and organisation since the last common ancestor of humans and chimpanzees, and is considered critical for cognitive evolution. We examined the gene expression profiles and cell-type composition of the frontal pole on the left hemisphere, including both neuronal and non-neuronal cell types across cortical layers and white matter. By integrating our spatial transcriptomic data with a publicly available single-nucleus transcriptomic dataset of the chimpanzee dorsolateral prefrontal cortex, we mapped the spatial distribution of 29 chimpanzee brain cell types. This study represents a first step towards characterisation of spatial gene regulatory differences between the brains of non-human great apes and humans. Significance statementRecent advances in spatial transcriptomics technologies provided important insights into the spatial organisation of gene expression and cell types in human and mouse brains, yet applications in non-model organisms remain limited. Here, we present the first-ever spatial transcriptomics dataset from a chimpanzee brain. We demonstrate i) the applicability of a widely used spatial transcriptomics technique to chimpanzee brain samples freshly frozen in isopentane, and ii) an end-to-end pipeline for generating good-quality spatial transcriptomics data from chimpanzee brains. Our work paves the way for future comparative spatial transcriptomics studies across human and non-human primate brains, and marks a step toward applying spatial omics methods to great ape brains.

evolutionary biology↗

bioRxiv2024

Lifespan trajectory of chimpanzee brains characterized by magnetic resonance imaging histology

Chimpanzee brain maturation provides an invaluable framework for understanding the evolution of the human brain. We performed ultra-high resolution quantitative magnetic resonance imaging (qMRI) with histological validation on post mortem brains from captive and wild chimpanzees with a broad age range. We mapped developmental myelination and age-related iron accumulation across regions and layers of the neocortex. Compared to humans, chimpanzees showed more myelination and iron deposition in motor and premotor cortices, while the auditory cortex was more strongly myelinated in humans. Our model suggests that chimpanzees cortical myelination was largely completed by the age of nine years, while iron accumulation continued throughout the lifespan. The regions with highest adult levels of myelin and iron took the longest to mature, challenging the widespread assumption that highly myelinated regions complete their development first. The reported maps and developmental curves provide a foundation for comparative neuroscience research and understanding of human brain evolution.

neuroscience↗

bioRxiv2023

Neuroinfectiology of an atypical anthrax-causing pathogen in wild chimpanzees

Bacillus cereus biovar anthracis (Bcbva) is an atypical anthrax-causing bacterium, inflicting wildlife fatalities across African rainforest ecosystems. The pathogens virulence in one of our closest living relatives, the chimpanzee, together with human serological evidence, suggests Bcbva is zoonotic. While classical B. anthracis-induced anthrax has been described to affect the central nervous system at a progressive disease-state, the neuroinfectiology of Bcbva is yet unknown. Here we characterised the pathogens neuro-invasiveness via gross pathological assessment, ultra-high resolution quantitative Magnetic Resonance Imaging and histological analysis on four brains, which were extracted from naturally deceased wild chimpanzees in Tai National Park, Cote dIvoire. Based on macroscopically evident pial vessel congestion and haemorrhages as well as cortical siderosis detected via MRI, we concluded that Bcbva induced meningitis analogous to B. anthracis. Further, histological visualisation of bacteria and leukocytes in the subarachnoid space evidenced the bacteriums capability to breach the arachnoid barrier. Bcbva was detected in the brain parenchyma of all four cases. This indicates a higher ability to transgress the glia limitans and therefore exhibits a higher neuroinvasiveness compared to B. anthracis that predominantly stays confined to the meninges. Heightened glial fibrillary acidic protein (GFAP) expression but little morphological gliosis suggest a rapid disease progression leading to host-death within hours to a few days after central nervous system invasion. Overall our results reveal Bcbvas ability to breach blood-brain barriers which results in a pronounced neuropathogenicity. Bcbva causes extensive damage to the meninges and the brain parenchyma, as well as rapid and massive digestion of brain extracellular matrix in chimpanzees and potentially so in humans in case of zoonotic spillover.

neuroscience↗

bioRxiv2021

Non-genetic maternal effects shape individual differences in cortisol phenotypes in wild chimpanzees

Glucocorticoids, such as cortisol, mediate homeostatic processes, allowing individuals to adjust to fluctuating environments. The regulation of circadian cortisol responses, a key homeostatic function, has been shown to be heritable. However, to understand better the role of parental care in shaping physiological functioning in long-lived mammals with protracted parental care, there is a need to disentangle genetic and non-genetic parental contributions to variation in glucocorticoid phenotypes. We used a dataset of 6,123 cortisol measures from urine samples from 170 wild chimpanzees spanning 18 years of data collection. We found consistent inter-individual differences in circadian cortisol phenotypes, with differences most apparent when considering average cortisol levels given the effect of time of day. Maternal effects explained around 10% (2-18%) variation in these average cortisol levels, while variation attributable to genetic factors was not distinguishable from zero. Our results indicate, relative to genetic effects, a qualitatively stronger influence of mothers, whether via epigenetic processes or via behavioral priming for coping with stressors, in shaping cortisol phenotypes in this species. This provides novel insight into the vital role of mothers in the developmental plasticity of long-lived mammals and, more generally, the selective pressures shaping physiological plasticity.

zoology↗

bioRxiv2021

Chimpanzees use numerous flexible vocal sequences with more than two vocal units: A step towards language?

A major question in evolutionary science is how did language evolve? Syntax, as the core of language, combines meaning-bearing units (words) into hierarchical structures, thereby creating new meanings. Some other mammals and birds combine meaning-bearing vocalisations, but no documented examples exist of non-human animals combining more than two meaning-bearing vocalisations. Was the two-unit threshold only surpassed in the hominid lineage? Here, we examine the positional patterning of vocal sequences of chimpanzees. We analysed 4826 vocal utterances of 46 wild adult female and male chimpanzees. We found a flexible system with 390 multi-unit vocal sequences, some showing positional or transitional regularities. Two-unit pairs embedded in three-unit sequences predictably occurred either in head or tail positions, and co-occurred with specific other elements. The capacity to organise vocal output beyond the two-unit level may thus exist in species other than humans and could be viewed as an important evolutionary step towards language.

animal behavior and cognition↗

bioRxiv2020

Primate phageomes are structured by superhost phylogeny and environment

The evolutionary origins of human-associated bacteriophage communities are poorly understood. To address this question, we examined fecal phageomes of 23 wild non-human primate taxa, including multiple representatives of all the major primate radiations, and find relatives of the majority of human-associated phages. Primate taxa have distinct phageome compositions that exhibit a clear phylosymbiotic signal, and phage-superhost co-divergence is detected for 44 individual phages. Within species, neighboring social groups harbor evolutionarily and compositionally distinct phageomes, structured by superhost social behavior. However, captive non-human primate phageomes are more similar to humans than their wild counterparts, revealing replacement of wild-associated phages with human-associated ones. Together, our results suggest that potentially labile primate-phage associations persisted across millions of years of evolution, potentially facilitated by transmission between groupmates. One Sentence SummaryRelatives of human-associated phages in wild primates reveal ancient but dynamic superhost-phage associations shaped by social transmission.

microbiology↗

bioRxiv2020

Increased Sensitivity and Signal-to-Noise Ratio in Diffusion-Weighted MRI using Multi-Echo Acquisitions

Post-mortem diffusion MRI (dMRI) enables acquisitions of structural imaging data with otherwise unreachable resolutions - at the expense of longer scanning times. These data are typically acquired using highly segmented image acquisition strategies, thereby resulting in an incomplete signal decay before the MRI encoding continues. Especially in dMRI, with low signal intensities and lengthy contrast encoding, such temporal inefficiency translates into reduced image quality and longer scanning times. This study introduces Multi Echo (ME) acquisitions to dMRI on a human MRI system - a time-efficient approach, which increases SNR (Signal-to-Noise Ratio) and reduces noise bias for dMRI images. The benefit of the introduced ME dMRI method was validated using numerical Monte Carlo simulations and showcased on a post-mortem brain of a wild chimpanzee. The proposed Maximum Likelihood Estimation echo combination results in an optimal SNR without detectable signal bias. The combined strategy comes at a small price in scanning time (here 30% additional) and leads to a substantial SNR increase (here up to 1.9x which is equivalent to 3.6 averages) and a general reduction of the noise bias.

neuroscience↗

bioRxiv2019

Geographically structured genomic diversity of non-human primate-infecting Treponema pallidum subsp. pertenue

BackgroundIncreasing evidence suggests many non-human primate (NHP) species in sub-Saharan Africa are infected with Treponema pallidum subsp. pertenue (TPE), the bacterium causing yaws in humans. In humans, yaws is characterized by lesions of the extremities and face, while Treponema pallidum subsp. pallidum (TPA) causes venereal syphilis and is characterized by primary lesions on the genital, anal or oral mucosae, and has not been detected in NHPs. Due to a paucity of genetic data, it remains unclear whether other Treponema pallidum (TP) subspecies found in humans also occur in NHP and how the genomic diversity of TPE lineages that do occur in NHPs is distributed across hosts and space. MethodologyWe observed a combination of yaws- and syphilis-like symptoms in sooty mangabeys (Cercocebus atys atys) in Tai National Park (TNP), Cote dIvoire and collected swabs and biopsies from symptomatic animals. We also collected NHP bones from eight species from TNP, as well as from 19 species at 12 field sites across sub-Saharan Africa. Samples were screened for TP DNA using PCRs. In-solution hybridization capture coupled with high throughput sequencing was used to sequence TP genomes from positive samples. Principal findingsWe generated four nearly complete TP genomes from biopsies and swabs and five partial genomes from bones. Phylogenomic analyses revealed that both syphilis- and yaws-like lesions of sooty mangabeys within a single social group in TNP were caused by TPE. All TPE genomes determined from these sooty mangabeys were different and exhibited divergence levels not observed in TPE from a single species at any other field site where the disease seems to be epizootic. In general, simian TPE isolates did not form monophyletic clades based on host species or the type of symptoms caused by an isolate, but rather clustered based on geography. ConclusionsThere is a large diversity of TPE strains infecting NHPs in TNP. Our observations within a single social group of sooty mangabeys do not support the epizootic spread of a single clone, but rather points towards frequent independent introductions of the bacterium, which can cause syphilis- and yaws-like lesions. On a larger scale, the geographic clustering of TPE genomes might be compatible with cross-species transmission of TPE within ecosystems or environmental exposure leading to acquisition of closely related strains. Authors summaryIndividuals in several populations of wild non-human primates (NHP) in sub-Saharan Africa are infected with Treponema pallidum subsp. pertenue (TPE), a pathogen causing yaws disease in humans. In humans, yaws is characterized by skin lesions of the extremities and face. In contrast, Treponema pallidum subsp. pallidum, which causes venereal syphilis in humans, has not been observed in NHPs. We describe a combination of yaws- and syphilis-like symptoms in a sooty mangabey (Cercocebus atys atys) social group in Tai National Park (TNP), Cote dIvoire. We sampled lesioned animals and collected and tested NHP bones from field sites across sub-Saharan Africa. We were able to reconstruct four genomes from swabs/biopsies and five partial genomes from bone samples. Phylogenomic analyses revealed that syphilis-like lesions and yaws-like lesions in TNP were caused by a large diversity of TPE strains. Additionally, simian TPE isolates did not form monophyletic clades based on the host species or the types of symptoms caused by an isolate, but rather clustered by geographic origin. This is suggestive of cross-species transmission of TPE within ecosystems or environmental exposure leading to acquisition of closely related strains.

genomics↗

bioRxiv2017

African Nonhuman Primates Are Infected With The Yaws Bacterium Treponema pallidum subsp. pertenue

Treponema pallidum subsp. pertenue (TPE) is the causative agent of yaws. The disease was subject to global eradication efforts in the mid 20th century but reemerged in West Africa, Southern Asia, and the Pacific region. Despite its importance for eradication, detailed data on possible nonhuman disease reservoirs are missing. A number of African nonhuman primates (NHPs) have been reported to show skin ulcerations suggestive of treponemal infection in humans. Furthermore antibodies against Treponema pallidum (TP) have been repeatedly detected in wild NHP populations. While genetic studies confirmed that NHPs are infected with TP strains, subspecies identification was only possible once for a strain isolated in 1966, pinpointing the involvement of TPE. We therefore collected a number of recently isolated simian TP strains and determined eight whole genome sequences using hybridization capture or long-range PCR combined with next-generation sequencing. These new genomes were compared with those of known human TP isolates. Our results show that naturally occurring simian TP strains circulating in three African NHP species all cluster with human TPE strains and show the same genomic structure as human TPE strains. These data indicate that humans are not the exclusive host for the yaws bacterium and that a One Health approach is required to achieve sustainable eradication of human yaws.

microbiology↗