Volker Sommer’s research while affiliated with University College London and other places

Ongoing ecosystem change and biodiversity decline across the Afrotropics call for tools to monitor the state of biodiversity or ecosystem elements across extensive spatial and temporal scales. We assessed relationships in the co‐occurrence patterns between great apes and other medium to large‐bodied mammals to evaluate whether ape abundance serves as a proxy for mammal diversity across broad spatial scales. We used camera trap footage recorded at 22 research sites, each known to harbor a population of chimpanzees, and some additionally a population of gorillas, across 12 sub‐Saharan African countries. From ~350,000 1‐min camera trap videos recorded between 2010 and 2016, we estimated mammalian community metrics, including species richness, Shannon diversity, and mean animal mass. We then fitted Bayesian Regression Models to assess potential relationships between ape detection rates (as proxy for ape abundance) and these metrics. We included site‐level protection status, human footprint, and precipitation variance as control variables. We found that relationships between detection rates of great apes and other mammal species, as well as animal mass were largely positive. In contrast, relationships between ape detection rate and mammal species richness were less clear and differed according to site protection and human impact context. We found no clear association between ape detection rate and mammal diversity. Our findings suggest that chimpanzees hold potential as indicators of specific elements of mammalian communities, especially population‐level and composition‐related characteristics. Declines in chimpanzee populations may indicate associated declines of sympatric medium to large‐bodied mammal species and highlight the need for improved conservation interventions.Changes in chimpanzee abundance likely precede extirpation of sympatric mammals.

How populations adapt to their environment is a fundamental question in biology. Yet, we know surprisingly little about this process, especially for endangered species, such as nonhuman great apes. Chimpanzees, our closest living relatives, are particularly notable because they inhabit diverse habitats, from rainforest to woodland-savannah. Whether genetic adaptation facilitates such habitat diversity remains unknown, despite it having wide implications for evolutionary biology and conservation. By using newly sequenced exomes from 828 wild chimpanzees (388 postfiltering), we found evidence of fine-scale genetic adaptation to habitat, with signatures of positive selection in forest chimpanzees in the same genes underlying adaptation to malaria in humans. This work demonstrates the power of noninvasive samples to reveal genetic adaptations in endangered populations and highlights the importance of adaptive genetic diversity for chimpanzees.

Strontium isotope (⁸⁷Sr/⁸⁶Sr) analysis with reference to strontium isotope landscapes (Sr isoscapes) allows reconstructing mobility and migration in archaeology, ecology, and forensics. However, despite the vast potential of research involving ⁸⁷Sr/⁸⁶Sr analysis particularly in Africa, Sr isoscapes remain unavailable for the largest parts of the continent. Here, we measure the ⁸⁷Sr/⁸⁶Sr ratios in 778 environmental samples from 24 African countries and combine this data with published data to model a bioavailable Sr isoscape for sub-Saharan Africa using random forest regression. We demonstrate the efficacy of this Sr isoscape, in combination with other lines of evidence, to trace the African roots of individuals from historic slavery contexts, particularly those with highly radiogenic ⁸⁷Sr/⁸⁶Sr ratios uncommon in the African Diaspora. Our study provides an extensive African ⁸⁷Sr/⁸⁶Sr dataset which includes scientifically marginalized regions of Africa, with significant implications for the archaeology of the transatlantic slave trade, wildlife ecology, conservation, and forensics.

How populations adapt to their environment is a fundamental question in biology. Yet we know surprisingly little about this process, especially for endangered species such as non-human great apes. Chimpanzees, our closest living relatives, are particularly interesting because they inhabit diverse habitats, from rainforest to woodland-savannah. Whether genetic adaptation facilitates such habitat diversity remains unknown, despite having wide implications for evolutionary biology and conservation. Using 828 newly generated exomes from wild chimpanzees, we find evidence of fine-scale genetic adaptation to habitat. Notably, adaptation to malaria in forest chimpanzees is mediated by the same genes underlying adaptation to malaria in humans. This work demonstrates the power of non-invasive samples to reveal genetic adaptations in endangered populations and highlights the importance of adaptive genetic diversity for chimpanzees. One-Sentence Summary Chimpanzees show evidence of local genetic adaptation to habitat, particularly to pathogens, such as malaria, in forests.

West-African populations of the African subspecies of leopards (Panthera pardus pardus) are very fragmented, particularly so in Nigeria, Africa’s most populous nation. We compile historical and recent information about the occurrence of these big cats in what is likely their last remaining stronghold: Gashaka Gumti National Park (GGNP) in Adamawa and Taraba States along the border with Cameroon. Leopards in GGNP’s northern Gumti sector are close to extinction, given that its open plains of savannah are heavily encroached upon by illegal cattle grazing. However, in GGNP’s southern Gashaka sector, leopards are better protected, given its often mountainous and densely forested landscape. We present specific data for a 30 km2 forest-savannah area around a research station at Kwano, which harbours sizeable populations of 35 species of prey species leopards target elsewhere. Here, direct evidence for leopard presence (e.g., footprints, scratchmarks, predation incidences, vocalizations, sightings, cameratrap images) amounts to 1 per year. Albeit this encounter rate is very low, it is relatively steady throughout the last 30 years and into the present. We assume that GGNP’s Gashaka sector represents one of the best chances for leopards to survive in Nigeria.

The question of how behavioural diversity in humans and other animals is shaped by the combined influence of demography, genetics, culture, and the environment receives much research attention. We take a macro-ecological approach to evaluate how chimpanzee ( Pan troglodytes ) behavioural diversity is spatially structured and associated with genetic diversity (i.e. heterozygosity as a proxy for effective population size) and contemporary and historic environmental context. We integrate the largest available chimpanzee behavioural and genomic datasets and apply spatially explicit Bayesian Generalised Linear Mixed Models to derive marginal effects for putative drivers and range wide spatial predictions of probability to observe behavioural traits. Contrary to expectations from neutral models of behavioural evolution, we observed a negative association of genetic diversity with behavioural diversity. This result suggests that behavioural traits may impact fitness. In contrast, we observed weaker associations of chimpanzee behavioural diversity with contemporary and historic environmental context. The very strong spatial structuring of behavioural traits is consistent with cultural transmission playing a major role in shaping chimpanzee behavioural diversity. Our analytical approach can be flexibly extended by additional candidate drivers of chimpanzee behavioural diversity, and offers a novel framework for testing competing ecological-evolutionary hypotheses across a wide variety of animal cultures.

Masturbation occurs throughout the animal kingdom. At first glance, however, the fitness benefits of this self-directed behaviour are unclear. Regardless, several drivers have been proposed. Non-functional hypotheses posit that masturbation is either a pathology, or a byproduct of high underlying sexual arousal, whereas functional hypotheses argue an adaptive benefit. The Postcopulatory Selection Hypothesis states that masturbation aids the chances of fertilization, while the Pathogen Avoidance Hypothesis states that masturbation helps reduce host infection by flushing pathogens from the genital tract. Here, we present comprehensive new data documenting masturbation across the primate order and use these, in conjunction with phylogenetic comparative methods, to reconstruct the evolutionary pathways and correlates of masturbation. We find that masturbation is an ancient trait within the primate order, becoming a more common aspect of the haplorrhine behavioural repertoire after the split from tarsiers. Our analyses provide support for both the Postcopulatory Selection and Pathogen Avoidance Hypotheses in male primates, suggesting that masturbation may be an adaptive trait, functioning at a macroevolutionary scale.