Biology subjects

Junker, J.

Publications and source records attributed to Junker, J..

11 recordsLinked to original sources

bioRxiv2026

Birds protected in Europe, overlooked in Africa: conservation synergies between African primates and wintering Afro-Palearctic migratory birds

Primates are frequent targets of international conservation efforts, due to their anthropological significance and function as biodiversity conservation flagship species. Afro-Palearctic migratory birds receive considerable conservation attention in their breeding habitats, but much less in their wintering areas. Good wintering habitat conditions are, however, crucial for long-term population viability. Integrating complementary conservation efforts for these taxa may provide substantial co-benefits. Here, we evaluate the spatial, ecological, and conservation congruence between 248 Afro-Palearctic migratory bird and 213 African primate species to identify potential synergies in intercontinental conservation efforts. The wintering areas of 218 migratory bird species overlap with primate ranges. Up to 125 Afro-Palearctic migratory bird species co-occur with at least one primate species locally and highest regional cross-taxon richness occurs in forest-savanna ecotones in West Africa and eastern DRC. Agriculture and hunting threaten both taxa (88-97% of primate and 59-70% of bird species). Several conservation interventions have demonstrated effectiveness for both taxa, particularly habitat protection and hunting reduction. We propose three policy priorities: strengthening cross-taxa monitoring within existing primate research infrastructure, improving the conservation evidence base in the African context, and creating financing synergies that allow conservation investments to simultaneously benefit both taxa.

ecology↗

bioRxiv2025

Temperature and predation alter metabolic scaling without changing size-based structure community in freshwater macroinvertebrates

Body size is a key trait that influences ecological processes such as metabolism, abundance, and species interactions. While the metabolic theory of ecology (MTE) proposes a universal scaling of metabolic rate with body mass, recent evidence shows that this relationship is not fixed. Environmental factors like temperature and predation can alter the metabolic scaling exponent, potentially reshaping size distribution. However, most research has examined these patterns within individual species, leaving open questions about how environmental drivers affect scaling at the community level. To address this, we performed a mesocosm experiment manipulating both temperature and fish predator presence in freshwater macroinvertebrate communities. We found that metabolic scaling at the community level is highly responsive to environmental context: warming steepened the scaling exponent in predator-free tanks but flattened it when predators were present. This suggests that larger individuals reduce their baseline metabolic rates under predation risk, especially at higher temperatures. Interestingly, the slope of the community size distribution remained stable across treatments, indicating that shifts in metabolic scaling occurred independently of changes in size structure. Together, these findings highlight the environmental sensitivity of metabolic scaling and suggest that links between metabolism scaling and size distribution may be more complex than MTE predicts.

ecology↗

bioRxiv2025

Admixture and environmental fluctuations shape the evolutionary history of a predator radiation in East Africa's Lake Tanganyika

Top predators have oversized influence on food webs and ecosystem dynamics, and introducing a novel predator to a naive environment can have dramatic consequences for endemic biodiversity. Using genomic data, we find that the colonization of Lake Tanganyika by Lates fishes--the top predators in this ancient lake--occurred more recently than other diverse clades within the lake. Diversification into four endemic Lates species occurred within the lake during a time of dramatic changes in lake levels driven by glacial-interglacial cycles, supporting the hypothesis that these fluctuations were a "species pump" for lacustrine taxa. These lake level fluctuations also likely contributed to multiple admixture events among Lates species during the Pleistocene ([~] 90-500 Kya). Together, our findings suggest a dynamic and environmentally-linked evolutionary history of this predator radiation, and that their colonization of the lake and subsequent diversification likely had dramatic ecosystem consequences for taxa already present in Lake Tanganyika.

evolutionary biology↗

bioRxiv2024

Local genetic adaptation to habitat in wild chimpanzees

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 SummaryChimpanzees show evidence of local genetic adaptation to habitat, particularly to pathogens, such as malaria, in forests.

evolutionary biology↗

bioRxiv2023

Threat of mining to African great apes

The rapid growth of clean energy technologies is driving a rising demand for critical minerals. In 2022 at the UN Biodiversity Conference (COP 15), seven major economies formed an alliance to enhance the sustainability of mining these essential decarbonization minerals. However, there is a scarcity of studies assessing the threat of mining to global biodiversity. By integrating a global mining dataset with ape density distribution estimates, we explored the potential negative impact of industrial mining on African great apes. Our findings reveal that up to one-third of Africas great ape population faces mining-related risks. This is especially pronounced in West Africa, where numerous mining areas overlap with fragmented ape habitats, often occurring in high-density ape regions. For 97% of mining areas, no ape survey data are available, underscoring the importance of increased accessibility to environmental data within the mining sector to facilitate research into the complex interactions between mining, climate, biodiversity and sustainability. TeaserMining for clean energy minerals could put one-third of Africas ape population at risk.

ecology↗

bioRxiv2023

Biodiversity monitoring in Europe: user and policy needs

To implement the goals of the 2030 Global Biodiversity Framework, the European Biodiversity Strategy and the EU Green Deal, biodiversity monitoring is a pivotal instrument to achieve accountability and progress in conservation. Monitoring efforts in Europe, however, suffer from gaps and biases in taxonomy, spatial coverage, and temporal resolution, resulting in fragmented and disconnected data which does not provide sufficient evidence for policy making. To assess user and policy needs in biodiversity monitoring, we employed with EuropaBON a four-step user-centred stakeholder engagement process, including an international public stakeholder workshop, a standardised online survey, semi-structured interviews, and an expert meeting with representatives of EU member states, the European Commission and the European Environment Agency. The resulting insights into national and European biodiversity monitoring schemes identify policy needs, current challenges and potential solutions. Based on this in-depth policy and science stakeholder assessment, we recommend the establishment of a European Biodiversity Observation Network through a permanent Biodiversity Monitoring and Coordinating Centre to optimise existing observation efforts, harmonise data, and enhance our ability to predict and respond to key challenges related to biodiversity loss in a changing climate in Europe.

ecology↗

bioRxiv2022

Pneumococcal Evasion of Antibiotics via Metabolic Adaptation During Infection

Streptococcus pneumoniae is a major human pathogen of global health concern, causing a range of mild to severe infections, including acute otitis media, pneumonia, sepsis, and meningitis. The rapid emergence of antibiotic resistance among S. pneumoniae isolates poses a serious public health problem worldwide. Resistant pneumococcal strains have rendered the mainstay treatment with beta-lactams, fluoroquinolones, and macrolides, ineffective. Antibiotic resistance in S. pneumoniae has spread globally via the emergence of de novo mutations and horizontal transfer of resistance. Fluoroquinolone resistance in S. pneumoniae is an intriguing case because the prevalence of fluoroquinolone resistance does not correlate with increasing usage, as is often the case with other classes of antibiotics. In this study, we demonstrated that deleterious fitness costs constrain the emergence of individual fluoroquinolone resistance mutations in either topoisomerase IV or gyrase A in S. pneumoniae. Generation of double point mutations in the target enzymes in topoisomerase IV and gyrase A conferred high-level fluoroquinolone resistance while restoring fitness comparable to the sensitive wild-type. During an in vivo model of antibiotic resistance evolution, S. pneumoniae was able to circumvent deleterious fitness costs imposed by resistance determinants through development of antibiotic tolerance through metabolic adaptation that reduced the production of reactive oxygen species, an effect that could be recapitulated pharmacologically. The metabolic mutants conferring tolerance resulted in a fitness benefit during infection following antibiotic treatment with fluroquinolones. These data suggest that emergence of fluoroquinolone resistance is tightly constrained in S. pneumoniae by host fitness tradeoffs and that mutational pathways involving metabolic networks to enable tolerance phenotypes may be an important contributor to the evasion of antibiotic mediated killing.

microbiology↗

bioRxiv2021

Isotopic signatures induced by upwelling tag regional fish populations in Lake Tanganyika

Lake Tanganyikas pelagic fish sustain the second largest inland fishery in Africa and are under pressure from heavy fishing and global warming related increases in stratification. Only little is known about whether basin-scale hydrodynamics - including a more stratified north and an upwelling-driven south - induce ecological and genetic differences among populations of highly mobile, pelagic fish inhabiting these different areas. Here, we examine whether the basin-scale dynamics leave distinct isotopic imprints in the pelagic fish of Lake Tanganyika, which may reveal differences in habitat, diet, or lipid content. We conducted two lake-wide campaigns during different seasons and collected physical, nutrient, chlorophyll, phytoplankton and zooplankton data. Additionally, we analyzed the pelagic fish - the clupeids Stolothrissa tanganicae, Limnothrissa miodon and four Lates species - for their isotopic and elemental carbon (C) and nitrogen (N) compositions. The {delta}13C values were significantly higher in the productive south after the upwelling/mixing period across all trophic levels, implying that the fish have regional foraging grounds, and thus record these latitudinal isotope gradients. By combining our isotope data with genetics, we demonstrate that the fish form regional populations on a seasonal to multiannual time scale. Based on {delta}15N and C:N ratios, we found no strong evidence for varying diets or lipid contents between those regional populations. Additional analyses revealed that isotopic variations between specimens from the same location are not linked to genetic differences. We suggest that the development of basinscale ecological differences in response to the prevailing hydrodynamic regimes may be inhibited by lake-wide gene flow on the long term. Our findings show that the pelagic fish species are genetically adapted to the whole lake, but they form regional populations on short time scales. This implies that sustainable management strategies may adopt basin-scale fishing quotas.

ecology↗

bioRxiv2021

The genetic population structure of Lake Tanganyika's Lates species flock, an endemic radiation of pelagic top predators

Understanding genetic connectivity plays a crucial role in species conservation decisions, and genetic connectivity is an important component of modern fisheries management. In this study, we investigated the population genetics of four endemic Lates species of Lake Tanganyika (Lates stappersii, L. microlepis, L. mariae and L. angustifrons) using reduced-representation genomic sequencing methods. We find the four species to be strongly differentiated from one another (mean interspecific FST = 0.665), with no evidence for contemporary admixture. We also find evidence for strong genetic structure within L. mariae, with the majority of individuals from the most southern sampling site forming a genetic group that is distinct from the individuals at other sampling sites. We find evidence for much weaker structure within the other three species (L. stappersii, L. microlepis, and L. angustifrons). Our ability to detect this weak structure despite small and unbalanced sample sizes and imprecise geographic sampling locations suggests the possibility for further structure undetected in our study. We call for further research into the origins of the genetic differentiation in these four species--particularly that of L. mariae--which may be important for conservation and management of this culturally and economically important clade of fish.

evolutionary biology↗

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↗

bioRxiv2019

Sex differentiation and a chromosomal inversion lead to cryptic diversity in Lake Tanganyika sardines

Identifying patterns in genetic structure and the genetic basis of ecological adaptation is a core goal of evolutionary biology and can inform the management and conservation of species that are vulnerable to population declines exacerbated by climate change. We used reduced representation genomic sequencing methods to gain a better understanding of genetic structure among and within populations of Lake Tanganyikas two sardine species, Limnothrissa miodon and Stolothrissa tanganicae. Samples of these ecologically and economically important species were collected across the length of Lake Tanganyika, as well as from nearby Lake Kivu, where L. miodon was introduced in 1959. Our results reveal unexpected differentiation within both S. tanganicae and L. miodon that is not explained by geography. Instead, this genetic differentiation is due to the presence of large sex-specific regions in the genomes of both species, but involving different polymorphic sites in each species. Our results therefore indicate rapidly evolving XY sex determination in the two species. Additionally, we found evidence of a large segregating inversion in L. miodon. We found all inversion karyotypes throughout Lake Tanganyika, but the frequencies vary along a north-south gradient, and differ substantially in the introduced Lake Kivu population. We do not find evidence for significant isolation-by-distance, even over the hundreds of kilometers covered by our sampling, but we do find shallow population structure.

evolutionary biology↗