Biology subjects

Masembe, C.

Publications and source records attributed to Masembe, C..

7 recordsLinked to original sources

bioRxiv2025

From deserts to forests: sequencing of the giant forest hog completes the genomic history of the African Suids

The giant forest hog (GFH, Hylochoerus meinertzhageni), the largest and most elusive wild pig, is found in a disjunct range across equatorial Africa, primarily inhabiting forests and woodlands. It is the only remaining African suid species without whole-genome data. The GFH is currently classified into three subspecies, differing in skull morphology and size. Here, we present the first whole-genome data of nine GFHs; one from Guinea and eight Uganda, representing the two geographically most distant subspecies. This genomic evidence allowed us to resolve the previously uncertain placement of the GFH among African suids as a sister group to the warthogs (Phacochoerus spp.). Also, we found a deep evolutionary split between the two GFH populations resulting in a level of genetic differentiation (FST > 0.75), which is similar to or higher than values observed among species of African wild pigs. The GFH likely diverged from warthogs around 4.6 Mya while the two study populations of GFH diverged at least 0.5 Mya and, subsequently, experienced very dissimilar demographic trajectories. The individual from Guinea had half of the heterozygosity level of the Uganda population, and lower value compared to all the African suids, probably as a result of the long term low Ne and isolation. Due to the close affinity of GFH with the African rainforest biotic zone, our findings have implications for understanding the history of habitat change in Africa. They also indicate a very deep and previously underappreciated evolutionary divergence within the GFH that may have implications for its conservation.

genomics↗

bioRxiv2024

Extensive population structure highlights an apparent paradox of stasis in the impala (Aepyceros melampus)

Impalas are unusual among bovids because they have remained morphologically similar over millions of years - a phenomenon referred to as evolutionary stasis. Here, we sequenced 119 whole genomes from the two extant subspecies of impala, the common (Aepyceros melampus melampus) and black-faced (A. m. petersi) impala. We investigated the evolutionary forces working within the species to explore how they might be associated with its evolutionary stasis as a taxon. Despite being one of the most abundant bovid species, we found low genetic diversity overall, and a phylogeographic signal of spatial expansion from southern to eastern Africa. Contrary to expectations under a scenario of evolutionary stasis, we found pronounced genetic structure between and within the two subspecies with indications of ancient, but not recent, gene flow. Black-faced impala and eastern African common impala populations had more runs of homozygosity than common impala in southern Africa, and, using a proxy for genetic load, we found that natural selection is working less efficiently in these populations compared to the southern African populations. Together with the fossil record, our results are consistent with a fixed-optimum model of evolutionary stasis, in which impalas in the southern African core of the range are able to stay near their evolutionary fitness optimum as a generalist ecotone species, whereas eastern African impalas may struggle to do so due to the effects of genetic drift and reduced adaptation to the local habitat, leading to recurrent local extinction in eastern Africa and re-colonization from the South.

evolutionary biology↗

bioRxiv2023

African bush pigs exhibit porous species boundaries and appeared in Madagascar concurrently with human arrival

Several African mammals exhibit a phylogeographic pattern where closely related taxa are split between West/Central and East/Southern Africa, but their evolutionary relationships and histories remain controversial. Bushpigs (Potamochoerus larvatus) and red river hogs (P. porcus) are recognised as separate species due to morphological distinctions, a perceived lack of interbreeding at contact, and putatively old divergence times, but historically, they were considered conspecific. Moreover, the presence of Malagasy bushpigs as the sole large terrestrial mammal shared with the African mainland raises intriguing questions about its origin and arrival in Madagascar. Analyses of 67 whole genomes revealed a genetic continuum between the two species, with putative signatures of historical gene flow, variable FST values, and a recent divergence time (<500,000 years). Thus, our study challenges key arguments for splitting Potamochoerus into two species and suggests their speciation might be incomplete. Our findings also indicate that Malagasy bushpigs diverged from southern African populations and underwent a limited bottleneck 1,000-5,000 years ago, concurrent with human arrival in Madagascar. These results shed new light on the evolutionary history of an iconic and widespread African genus and provide insight into the longstanding biogeographic puzzle surrounding the bushpigs presence in Madagascar.

evolutionary biology↗

bioRxiv2023

Ticks; a reservoir for virus emergence at the human-livestock interface in Uganda

BackgroundUganda is one of the most biodiverse regions on the planet and a hotspot for virus emergence. In particular, the warm-humid lowlands favour tick population growth with the associated risk of tick-borne disease. The prevalent tick species Rhipicephalus appendiculatus, R. evertsi evertsi and Amblyomma variegatum harbour a diverse range of viruses, from harmless to highly pathogenic. Notably, the orthonairoviruses cause human outbreaks of Crimean-Congo haemorrhagic fever (CCHF) regularly within the cattle corridor of Uganda, a region spanning from the south-west to the north-east of the country. MethodsIn the ArboViral Infection (AVI) study, the first to explore the virome of ticks in Uganda using next generation sequencing (NGS), we collected ticks from three geographically diverse areas and subjected these to target-enrichment (TE) NGS. Viral genomes were detected by de novo assembly, mapping and BLASTn. ResultsWe analyzed a total of 2,754 ticks collected from 31 livestock farms in the districts of Arua, Nakaseke and Lyantonde. These were combined into 219 pools by site of collection and tick species, including R. appendiculatus, R. evertsi evertsi, A. variegatum and Hyalomma rufipes. We detected partial or near-complete viral genomes in 163 tick pools; 110 (67%) of which were from Arua, 39 (24%) from Nakaseke and 12 (7%) from Lyantonde districts. 2 pools (2%) were from Arua/Lyantonde. These included 22 species of virus, representing 15 genera and 9 families, including the Nairoviridae, Retroviridae, Orthomyxoviridae, Chuviridae, Rhabdoviridae, Phenuiviridae, Parvoviridae, Poxviridae and Flaviviridae. There were 8 viral species known to be pathogens of humans or animals and 5 highly divergent genomes detected, representing novel virus species. A high abundance of orthonairoviruses was notable, including CCHFV, Dugbe virus and a novel Orthonairovirus species that we have named Macira virus. InterpretationTicks in Uganda are an important reservoir of diverse virus species, many of which remain uncharacterised and of unknown pathogenic potential. Author SummaryTicks are parasitic arachnids that may transmit a spectrum of viral diseases to humans and animals. Uganda is a hotspot for such tick-borne diseases. In this study, we sequenced ticks collected from three geographically diverse regions of Uganda using a semi-agnostic next- generation sequencing method in order to detect viruses from all known virus families. We collected and analyzed 2,754 ticks from 31 farms across the country. Within these ticks, we detected 22 species of virus from 15 genera and 9 viral families, including 8 animal or human pathogens and 5 new novel virus species. Notably, orthonairoviruses, including the highly pathogenic Crimean-Congo haemorrhagic fever virus, were highly prevalent in the ticks. The researchers suggest that ticks in Uganda serve as an important reservoir for diverse viruses, many of which have significant pathogenic potential. This information will inform public health efforts to prevent and control tick-borne diseases in Uganda and other similar regions.

microbiology↗

bioRxiv2022

Persistent gene flow suggests an absence of reproductive isolation in an African antelope speciation model

African antelope diversity is a globally unique vestige of a much richer world-wide Pleistocene megafauna. Despite this, the evolutionary processes leading to the prolific radiation of African antelopes are not well understood. Here, we sequenced 145 whole genomes from both subspecies of the waterbuck, an African antelope believed to be in the process of speciation. We investigated genetic structure and population divergence and found evidence of a mid-Pleistocene separation on either side of the eastern Great Rift Valley, consistent with vicariance caused by a rain shadow along the so-called Kingdons Line. However, we also found pervasive evidence of not only isolated and recent, but also widespread historical gene flow across the Rift Valley barrier. By inferring the genome-wide landscape of variation among subspecies, we found 14 genomic regions of elevated differentiation, including a locus that may be related to each subspecies distinctive coat pigmentation pattern. We investigated these regions as candidate speciation islands. However, we observed no significant reduction in gene flow in these regions, nor any indications of selection against hybrids. Altogether, these results suggest a pattern whereby climatically driven vicariance is the most important process driving the African antelope radiation, and suggest that reproductive isolation may not set in until very late in the divergence process.

evolutionary biology↗

bioRxiv2020

Increased resolution of African Swine Fever Virus genome patterns based on profile HMM protein domains

African Swine Fever Virus (ASFV) was originally described in Africa almost 100 years ago and is now spreading uncontrolled across Europe and Asia and threatening to destroy the domestic pork industry. Neither effective antiviral drugs nor a protective vaccine are currently available. Efforts to understand the basis for viral pathogenicity and the development of attenuated potential vaccine strains are complicated by the large and complex ASFV genome. We report here a novel method of documenting viral diversity based on profile Hidden Markov Model domains on a genome scale. The method can be used to infer genomic relationships independent of genome alignments and also reveal ASFV genome sequence differences that alter the presence of functional protein domains in the virus. We show that the method can quickly identify differences and shared patterns between virulent and attenuated ASFV strains and will be a useful tool for developing much-needed vaccines and antiviral agents to help control this virus. The tool is rapid to run and easy to implement, readily available as a simple Docker image.

genomics↗

bioRxiv2018

Combining landscape genomics and ecological modelling to investigate local adaptation of indigenous Ugandan cattle to East Coast fever

East Coast fever (ECF) is a fatal sickness affecting cattle populations of eastern, central, and southern Africa. The disease is transmitted by the tick Rhipicephalus appendiculatus, and caused by the protozoan Theileria parva parva, which invades host lymphocytes and promotes their clonal expansion. Importantly, indigenous cattle show tolerance to infection in ECF-endemically stable areas. Here, the putative genetic bases underlying ECF-tolerance were investigated using molecular data and epidemiological information from 823 indigenous cattle from Uganda. Vector distribution and host infection risk were estimated over the study area and subsequently tested as triggers of local adaptation by means of landscape genomics analysis. We identified 41 and seven candidate adaptive loci for tick resistance and infection tolerance, respectively. Among the genes associated with the candidate adaptive loci are PRKG1 and SLA2. PRKG1 was already described as associated with tick resistance in indigenous South African cattle, due to its role into inflammatory response. SLA2 is part of the regulatory pathways involved into lymphocytes proliferation. Additionally, local ancestry analysis suggested the zebuine origin of the genomic region candidate for tick resistance.\n\nAuthor summaryThe tick-borne parasite Theileria parva parva infects cattle populations of eastern, central and southern Africa, by causing a highly fatal pathology called \"East Coast fever\". The disease is especially severe for the exotic breeds imported to Africa, as well as outside the endemic areas of East Africa. In these regions, indigenous cattle populations can survive to infection, and this tolerance might result from unique adaptations evolved to fight the disease. We investigated this hypothesis by using a method named \"landscape genomics\", with which we compared the genetic characteristics of indigenous Ugandan cattle coming from areas at different infection risk, and located genomic sites potentially attributable to tolerance. In particular, the method pinpointed two genes, one (PRKG1) involved into inflammatory response and potentially affecting East Coast fever vector attachment, the other (SLA2) involved into lymphocytes proliferation, a process activated by T. parva parva infection. Our findings can orientate future research on the genetic basis of East Coast fever-tolerance, and derive from a general method that can be applied to investigate adaptation in analogous host-vector-parasite systems. Characterization of the genetic factors underlying East Coast-fever-tolerance represents an essential step towards enhancing sustainability and productivity of local agroecosystems.

evolutionary biology↗