Biology subjects

Martinkova, N.

Publications and source records attributed to Martinkova, N..

6 recordsLinked to original sources

bioRxiv2025

Eroding species barriers: hybridising canids remain distinct around centromeres

Species barriers are shaped by variation in recombination coupled with natural selection [1-3]. Canids lost the Prdm9 gene 40-60 million years ago [4-6], stabilising low recombination at the centromeric ends [7] of acrocentric autosomes despite overall high recombination rates [6]. We predict canid recombination architecture will tend to maintain barriers to gene flow at one end of autosomes while eroding them at the other. Polarization [8] of 31 million single nucleotide variants (SNVs) across 980 canid genomes reveals elevated barriers to gene flow at pericentromeric regions between grey wolves, coyotes and golden jackals. Highly diagnostic SNVs are six-fold enriched in pericentromeric regions. The exception is the barrier to gene flow between dogs and wolves, which accumulated divergence differently from other comparisons: genomes of domesticated dogs preserve ancient genetic diversity lost in contemporary grey wolf populations, positioning them as reservoirs of ancestral alleles. Our results show that genome architecture modulates permeability of barriers to gene flow, pointing to pericentromeric regions as targets for reinforcement selection that may maintain canid taxa.

zoology↗

bioRxiv2024

Large circulation of a novel vesiculovirus in bats in the Mediterranean region

Bats are the natural reservoirs of a variety of emerging or re-emerging viruses. Among them, rabies virus (genus Lyssavirus, family Rhabdoviridae) is of the first and most iconic described in these animals. Since its first description, various new bat lyssaviruses have been regularly described. Apart from lyssaviruses, other bat rhabdoviruses have been also identified, including members of the Vesiculovirus, Ledantevirus and more recently Alphanemrhavirus and Tupavirus genera. However, the family Rhabdoviridae is one of the most abundant and diverse viral families, with 318 officially recognized species divided into 3 subfamilies and 46 different genera. Thus, the number of bat- associated rhabdoviruses is probably higher. In this study, we first developed and validated a combined nested RT-qPCR technique (pan-rhabdo RT-nqPCR) dedicated to the broad detection of animal rhabdovirus. After validation, this technique was used for a large retrospective screening of archival bat samples (n = 1962), including blood (n = 816), brain (n = 723) and saliva (n = 423). These samples were collected from various bat species over a period of 12 years (2007-2019) in 9 different countries in Europe and Africa. A total of 23 samples (1.2%) from Miniopterus schreibersii, Rhinolophus euryale and Rhinolophus ferrumequinum bat species was found positive for rhabdovirus infection, including 17 (2.1%) blood and 6 (1.4%) saliva samples, all collected from bats originated from the Mediterranean region. The complete virus genome sequences were obtained by next-generation sequencing for most of the positive samples. Molecular and phylogenetic analysis of these sequences demonstrated that these virus isolates, named Mediterranean bat virus (MBV), were closely related, and represented a new species Vesiculovirus mediterranean within the Vesiculovirus genus. MBV was more specifically related to the other bat vesiculoviruses previously described in China and North America, together clustering into a distinct group of bat viruses within this genus. Interestingly, our results suggest that MBV is widely distributed, at least in the West part of the Mediterranean region, where it can act as an arbovirus infecting and circulating in multiple bat species. These findings expand the host range and the viral diversity of bat vesiculoviruses and pave the way for further investigations to determine the route of transmission and the dynamic of diffusion of these viruses into bat colonies, as well as to evaluate their potential hazard for public health.

microbiology↗

bioRxiv2022

High predation risk decimates survival duringthe reproduction season

O_LIPredators attack conspicuous prey phenotypes that are present in the environment. Male display behaviour of conspicuous nuptial colouration becomes risky in the presence of a predator, and adult males face higher predation risk. High predation risk in one sex will lead to low survival and sex ratio bias in adult cohorts, unless the increased predation risk is compensated by higher escape rate. C_LIO_LIHere, we tested the hypothesis that sand lizards (Lacerta agilis) have sex-specific predation risk and escape rate. We expected the differences to manifest in changes in sex ratio with age, differences in frequency of tail autotomy, and in sex-specific survival rate. C_LIO_LIWe developed a statistical model to estimate predation risk and escape rate, combining the observed sex ratio and frequency of tail autotomy with likelihood-based survival rate. Using Bayesian framework, we estimated the model parameters. We projected the date of the tail autotomy events from growth rates derived from capturerecapture data measurements. C_LIO_LIWe found statistically stable sex ratio in age groups, equal frequency of tail regenerates between sexes, and similar survival rate. Predation risk is similar between sexes, and escape rate increases survival by about 5%. We found low survival rate and a low number of tail autotomy events in females during months when sand lizards mate and lay eggs, indicating high predator pressure throughout reproduction. Our data show that gravid females fail to escape predation. C_LIO_LIThe risks of reproduction season in an ectotherm are a convolution of morphological changes (conspicuous colouration in males, body allometry changes in gravid females), behaviour (nuptial displays), and environmental conditions which challenge lizard thermal performance. Performance of endotherm predators in cold spring months endangers gravid females more than displaying males in bright nuptial colouration. C_LI

ecology↗

bioRxiv2022

diemr: Genome polarisation for detecting barriers to geneflow in R

O_LISemi-permeable barriers to geneflow in principle allow distantly related organisms to capture and exchange pre-adapted genes potentially speeding adaptation. However, describing barriers to geneflow on a genomic scale is non-trivial. C_LIO_LIWe extend classic diagnostic allele counting measures of geneflow across a barrier to the case of genome-scale data. Diagnostic index expectation maximisation (diem) polarises the labelling of bistate markers with respect to the sides of a barrier. An initial state of ignorance is enforced by starting with randomly generated marker polarisations. This means there is no prior on population or taxon membership of the genomes concerned. Using a deterministic data labelling, small numbers of classic diagnostic markers can be replaced by large numbers of markers, each with a diagnostic index. Individuals hybrid indices (genome admixture proportions) are then calculated genome wide conditioned on marker diagnosticity; within diploid, haplodiploid and/or haploid genome compartments; or indeed over any subset of markers, allowing classical cline width/barrier strength comparisons along genomes. Along-genome barrier strength hetero-geneity allows for barrier regions to be identified. Further, blocks of genetic material that have introgressed across a barrier are easily identified with high power. C_LIO_LIdiem indicates panmixis among Myotis myotis bat genomes, with a barrier separating low data quality outliers. In a Mus musculus domesticus/Mus spretus system, diem adds multiple introgressions of olfactory (and vomeronasal) gene clusters in one direction to previous demon-strations of a pesticide resistance gene introgressing in the opposite direction across a strong species barrier. C_LIO_LIdiem is a genomes analysis solution which scales over reduced representation genomics of thousands of markers to treatment of all variant sites in large genomes. While the method lends itself to visualisation, its output of markers with barrier-informative annotation will fuel research in population genetics, phylogenetics and association studies. diem can equip such downstream applications with millions of informative markers. C_LI

bioinformatics↗

bioRxiv2019

Quantifying colour difference in animals with variable patterning

Colour pattern influences behaviour and modifies survival of organisms through perception of light reflectance. Spectrophotometric methods used to study colour navigate between precision and accuracy of reflectance across wavelengths, while photographic methods are generally used to assess the complexity of colour patterns. Here, we compare how colours characterised using point measurements (simulating spectrophotometry) on the skin of a sand lizard (Lacerta agilis) differ from colours estimated by clustering pixels in a photograph of the lizards body. We found that point measurements adequately represented the dominant colour of the lizard; however, where colour patterning influenced measurement geometry, image analysis outper-formed point measurement as regards stability between technical replicates on the same animal. The greater colour variation established from point measurements increased further under controlled laboratory illumination. Both methods revealed lateral colour asymmetry in sand lizards. We conclude that studies assessing the impact of colour on animal ecology and behaviour should utilise hyperspectral imaging, followed by image analysis that encompasses the whole colour pattern.

ecology↗

bioRxiv2018

Modelling invasive pathogen load from non-destructive sampling data

Where microbes colonizing skin surface may help maintain organism homeostasis, those that invade living skin layers cause disease. In bats, white-nose syndrome is a fungal skin infection that affects animals during hibernation and may lead to mortality in severe cases. Here, we inferred the amount of fungus that had invaded skin tissue of diseased animals. We used simulations to estimate the unobserved disease severity in a non-lethal wing punch biopsy and to relate the simulated pathology to the measured fungal load in paired biopsies. We found that a single white-nose syndrome skin lesion packed with spores and hyphae of the causative agent, Pseudogymnoascus destructans, contains 48.93 pg of the pathogen DNA, which amounts to about 1560 P. destructans genomes in one skin lesion. Relating the information to the known UV fluorescence in Nearctic and Palearctic bats shows that Nearctic bats carry about 1.7 g of fungal DNA per cm2, whereas Palearctic bats have 0.04 g cm-2 of P. destructans DNA. With the information on the fungal load that had invaded the host skin, the researchers can now calculate disease severity as a function of invasive fungal growth using non-destructive UV light transillumination of each bat {square}s wing membranes. Our results will enable and promote thorough disease severity assessment in protected bat species without the need for extensive animal and laboratory labor sacrifices.

epidemiology↗