Biology subjects

Lougheed, S. C.

Publications and source records attributed to Lougheed, S. C..

9 recordsLinked to original sources

bioRxiv2025

Changes in sea ice alter genetic structure of an iconic Arctic apex predator in less than three decades

Climate change is having profound effects on biodiversity and species distributions worldwide. Nowhere are these effects potentially more pronounced than in the Arctic, where warming is almost two times the global average, and where year-round sea ice extent has significantly decreased, affecting many ice-dependent species. The polar bear (Ursus maritimus) is a circumpolar, apex Arctic predator, a sentinel of climate change, and a symbol of conservation. It is of immense cultural and spiritual importance to Inuit peoples and is hunted across the Arctic. Declines in sea ice have caused habitat fragmentation and loss, disrupting movement and prey access, potentially altering genetic structure and influencing polar bears potential to persist. Using samples collected from 1997 to 2020 by Inuit across much of the Canadian Arctic, 322 genome-wide autosomal DNA markers specifically designed to quantify polar bear genetic structure and a very stringent spatial-temporal method, we compare polar bear spatial genetic structure and landscape features between two periods across a consistent distribution:1997-2008 and 2009-2020. We observe marked changes in spatial genetic structure across the Arctic Archipelago over just two decades, shifting the boundaries between polar bear genetic clusters by [~]250 km. Landscape resistance models reveal the importance of sea ice and land cover type for each period, with spatial lag models showing that genetic change is best predicted by sea ice shifts between periods. Our study reveals rapid changes in genetic structure of polar bears in the Canadian Arctic, helps to inform conservation and management, and offers insight on future polar bear persistence across its immense, remote distribution.

genomics↗

bioRxiv2024

Insights on macrosynteny, 'rebel' genes, and a new sex-linked region in anurans from comparative genomics and a new chromosome-level genome for the western chorus frog

Amphibians have unique genome characteristics including slow karyotypic evolution and cytogenetically undifferentiated sex chromosomes. Yet our understanding of amphibian genomes has not kept pace with that of mammals and birds, partially due to scarce genomic resources and challenges associated with large genome sizes and high repetitiveness. We assembled and annotated a chromosome-level genome for the western chorus frog (Pseudacris triseriata), a species of conservation concern and importance in evolutionary research. Comparison of our new genome with other chromosome-level frog genomes reveals exceptionally conserved evolution of 13 chromosomal elements and gene orders across over 200 million years of anuran evolution. We uncovered rebel Benchmarking Universal Single-Copy Orthologs (BUSCO) genes that have been duplicated in almost all frog species, have been transposed, and showed lineage-specific synteny patterns - possibly relating to key traits such as frog advertisement calls and mitochondrial genome evolution. We also assembled a complete mitochondrial genome and found heteroplasmy of both point polymorphisms and length variation in the tandem repeat arrays in the control region. Double-digest restriction-site associated DNA sequencing analysis indicates that the western chorus frog has an XY sex system and the sex-linked region involved an [~]1Mb indel structural variant. Overall, our study provides important genomic resources for treefrogs and other anurans, documents highly conserved chromosomal evolution and gene orders in anurans, identifies rebel genes that might be important for frog evolution, and reveals a new sex-linked region with indel structural variants in anurans.

genomics↗

bioRxiv2024

Complete mitochondrial genomes of Eastern Massasauga (Sistrurus catenatus) and North American Racer (Coluber constrictor)

We report the complete mitochondrial genomes of two snake species of conservation concern, Eastern Massasauga (Sistrurus catenatus) and North American Racer (Coluber constrictor). The mitogenome length is 17,245bp for S. catenatus and 17,142bp for C. constrictor. Both mitogenomes include 13 protein-coding genes, 22 transfer RNA genes, two ribosomal RNA genes and two control regions. Gene arrangements are similar between two species, except that tRNA-Pro is located between tRNA-Ile and Control Region 2 in S. catenatus, but between tRNA-Thr and Control Region 1 in C. constrictor. Such gene arrangements are typical of their respective families, Viperidae and Colubridae. A phylogenetic tree with 21 additional snake species using concatenated 12 protein-coding genes (without ND6) supported current taxonomy of two reported species. We also found that North American racers in Ohio, Michigan (USA) and Pelee Island (Canada) were more closely allied to Pennsylvania individuals from the Eastern United States.

genomics↗

bioRxiv2023

How to barcode (almost all) freshwater biodiversity

Freshwater ecosystems are complex, diverse and face a variety of imminent threats that have led to changes in both ecosystem structure and function. It is urgent that we develop and standardize monitoring tools allowing for rapid and comprehensive assessment of freshwater communities to understand their changing dynamics and to inform conservation. Environmental DNA surveys offer a means to inventory and monitor aquatic diversity, yet most studies focus on one or a few taxonomic groups only. In this study, we sought to 1) identify thoroughly validated, cost-efficient primer pair combinations that maximize detection of broad swaths of freshwater diversity, and 2) facilitate future primer pair selection by creating a free online and user-friendly tool. We first evaluated the completeness of public reference sequence databases and the efficiency of 14 primer pairs using an in silico approach, and then performed eDNA surveys using five mock communities (mix of DNA from tissues), water samples from aquarium samples with known taxonomic composition, and finally water samples from freshwater systems in Eastern Canada. We highlight the power of eDNA-based metabarcoding for reconstructing freshwater communities, including prey, parasite, pathogen, invasive, and declining species. Our work reveals the importance of the marker choice on species resolution, as well as the importance of degenerate primers, the length of the target fragment and the filtering parameters on detection success in water eDNA samples. Our new online tool SNIPe revealed that 13 to 14 primer pairs are necessary to recover 100% of the species in water samples (aquarium and natural systems), but four primer pairs are sufficient to recover almost 75% of taxa with little overlap. These results highlight the usefulness of eDNA for freshwater monitoring and should prompt more studies on tools to survey all-inclusive communities.

ecology↗

bioRxiv2023

A new multiplexed magnetic-capture - droplet digital PCR (ddPCR) tool for monitoring wildlife population health and pathogen surveillance

Anthropogenic stressors are exacerbating the emergence and spread of pathogens worldwide. In regions like the Arctic where ecosystems are particularly susceptible, marked changes are predicted in regional diversity, intensity, and patterns of infectious diseases. To understand such rapidly changing host-pathogen dynamics and mitigate the impacts of novel pathogens, we need sensitive disease surveillance tools. We developed and validated a novel multiplexed, magnetic-capture and ddPCR tool for the surveillance of multiple pathogens in polar bears, a sentinel species that is considered susceptible to climate change and other stressors with a pan-Arctic distribution. Through sequence-specific magnetic capture, we concentrated five target template sequences from three zoonotic bacteria (Erysipelothrix rhusiopathiae, Francisella tularensis, and Mycobacterium tuberculosis complex) and two parasitic (Toxoplasma gondii and Trichinella spp.) pathogens from large quantities (< 100 g) of host tissue. We then designed and validated two multiplexed probe-based ddPCR assays for the amplification and detection of the low concentration target DNA. Validations used 48 polar bear tissues (muscle and liver). We detected 14, 1, 3, 4, and 22 tissue positives for E. rhusiopathiae, F. tularensis, Mycobacterium tuberculosis complex, T. gondii, and Trichinella spp., respectively. These multiplexed assays offer a rapid, specific tool for quantifying and monitoring the changing geographical and host distributions of pathogens relevant to human and animal health.

molecular biology↗

bioRxiv2022

Multi-omics analysis identifies symbionts and pathogens of blacklegged ticks (Ixodes scapularis) from a Lyme disease hotspot in southeastern Ontario, Canada

Ticks in the family Ixodidae are important vectors of zoonoses including Lyme disease (LD), which is caused by spirochete bacteria from the Borreliella (Borrelia) burgdorferi sensu lato (Bbsl) complex. The blacklegged tick (Ixodes scapularis) continues to expand across Canada, creating hotspots of elevated LD risk at the leading edge of its expansion range. Current efforts to understand the risk of pathogen transmission associated with I. scapularis in Canada focus primarily on targeted screens, while variation in the tick microbiome remains poorly understood. Using multi-omics consisting of 16S metabarcoding and ribosome-depleted, whole-shotgun RNA transcriptome sequencing, we examined the microbial communities associated with adult I. scapularis (N = 32), sampled from four tissue types (whole tick, salivary glands, midgut, and viscera) and three geographical locations within a LD hotspot near Kingston, Ontario, Canada. The communities consisted of both endosymbiotic and known or potentially pathogenic microbes, including RNA viruses, bacteria, and a Babesia sp. intracellular parasite. We show that {beta}-diversity is significantly higher between individual tick salivary gland and midgut bacterial communities, compared to whole ticks; while linear discriminant analysis (LDA) effect size (LEfSe) determined that the three potentially pathogenic bacteria detected by V4 16S rDNA sequencing also differed among dissected tissues only, including a Borrelia from the Bbsl complex, Borrelia miyamotoi, and Anaplasma phagocytophilum. Importantly, we find co-infection of I. scapularis by multiple microbes, in contrast to diagnostic protocols for LD, which typically focus on infection from a single pathogen of interest (B. burgdorferi sensu stricto). IMPORTANCEA vector of human health concern, blacklegged ticks, Ixodes scapularis, transmit pathogens that cause tick-borne diseases (TBDs), including Lyme disease (LD). Several hotspots of elevated LD risk have emerged across Canada as I. scapularis expands its range. Focusing on a hotspot in southeastern Ontario, we used high-throughput sequencing on whole ticks and dissected salivary glands and midguts. Compared to whole ticks, analysis of salivary glands and midguts revealed greater {beta}-diversity among microbiomes that are less dominated by Rickettsia endosymbiont bacteria and enriched for pathogenic bacteria including a Bbsl- associated Borrelia, Borrelia miyamotoi, and Anaplasma phagocytophilum. We also find evidence of co-infection of I. scapularis in this region by multiple microbes. Overall, our study highlights the challenges and opportunities associated with the surveillance of the microbiome of I. scapularis for pathogen detection using metabarcoding and metatranscriptome approaches.

microbiology↗

bioRxiv2020

Cytonuclear discordance in the crowned-sparrows, Zonotrichia atricapilla and Zonotrichia leucophrys: a mitochondrial selective sweep?

The golden-crowned (Zonotrichia atricapilla) and white-crowned (Z. leucophrys) sparrows have been presented as a compelling case for rapid speciation. They display divergence in song and plumage with overlap in their breeding ranges implying reproductive isolation, but have almost identical mitochondrial genomes. Previous research proposed hybridization and subsequent mitochondrial introgression as an alternate explanation, but lacked robust nuclear gene trees to distinguish between introgression and incomplete lineage sorting. We test for signatures of these processes between Z. atricapilla and Z. leucophrys, and investigate the relationships among Z. leucophrys subspecies, using mitochondrial sequencing and a reduced representation nuclear genomic dataset. Contrary to the paraphyly evident in mitochondrial gene trees, we confirmed the reciprocal monophyly of Z. atricapilla and Z. leucophrys using large panels of single nucleotide polymorphism (SNPs). The pattern of cytonuclear discordance is consistent with limited, historical hybridization and mitochondrial introgression, rather than a recent origin and incomplete lineage sorting between recent sister species. We found evidence of nuclear phylogeographic structure within Z. leucophrys with two distinct clades. Altogether, our results support the true species status of Z. atricapilla and Z. leucophrys, and indicate deeper divergences between the two species than inferred using mitochondrial markers. Our results demonstrate the limitations of relying solely on mitochondrial DNA for taxonomy, and raise questions about the possibility of selection on the mitochondrial genome during temperature oscillations (e.g. during the Pleistocene). Historical mitochondrial introgression facilitated by past environmental changes could cause erroneous dating of lineage splitting in other taxa when based on mitochondrial DNA alone.

evolutionary biology↗

bioRxiv2019

Phylogeography of two Andean frogs: Test of vicariance versus elevational gradient models of diversification

The tropical and subtropical Andes have among the highest levels of biodiversity in the world. Understanding the forces that underlie speciation and diversification in the Andes is a major focus of research. Here we tested two hypotheses of species origins in the Andes: 1. Vicariance mediated by orogenesis or shifting habitat distribution. 2. Parapatric diversification along elevational environmental gradients. We also sought insights on the factors that impacted the phylogeography of co-distributed taxa, and the influences of divergent species ecology on population genetic structure. We used phylogeographic and coalescent analyses of nuclear and mitochondrial DNA sequence data to compare genetic diversity and evolutionary history of two frog species: Pleurodema borellii (Family: Leiuperidae, 130 individuals; 20 sites), and Hypsiboas riojanus (Family: Hyllidae, 258 individuals; 23 sites) across their shared range in northwestern Argentina. The two showed concordant phylogeographic structuring, and our analyses support the vicariance model over the elevational gradient model. However, Pleurodema borellii exhibited markedly deeper temporal divergence ([≥]4 Ma) than H. riojanus (1-2 Ma). The three main mtDNA lineages of P. borellii were nearly allopatric and diverged between 4-10 Ma. At similar spatial scales, differentiation was less in the putatively more habitat-specialized H. riojanus than in the more generalist P. borellii. Similar allopatric distributions of major lineages for both species implies common causes of historical range fragmentation and vicariance. However, different divergence times among clades presumably reflect different demographic histories, permeability of different historical barriers at different times, and/or difference in life history attributes and sensitivities to historical environmental change. Our research enriches our understanding of the phylogeography of the Andes in northwestern Argentina.

evolutionary biology↗

bioRxiv2018

baRcodeR with PyTrackDat: Open-source labelling and tracking of biological samples for repeatable science

Repeatable experiments with accurate data collection and reproducible analyses are fundamental to the scientific method but may be difficult to achieve in practice. Several flexible, open-source tools developed for the R and Python coding environments aid the reproducibility of data wrangling and analysis in scientific research. In contrast, analogous tools are generally lacking for earlier stages, such as systematic labelling and processing of field samples with hierarchical structure (e.g. time points of individuals from multiple lines or populations) or curating heterogenous data collected by different researchers over several years. Such tools are critical for modern research given trends toward globally distributed collaborators using higher-throughput technologies. As a step toward improving repeatability of methods for the collection of biological samples, and curation of biological data, we introduce the R package baRcodeR and the PyTrackDat pipeline in Python. The baRcodeR package provides tools for generating biologically informative, hierarchical labels with digitally encoded 2D barcodes that can be printed and scanned using low-cost commercial hardware. The PyTrackDat pipeline integrates with baRcodeR output to build a web interface for sample management and tracking along with data collection and curation. We briefly describe the application of principles from baRcodeR and PyTrackDat in three large research projects, which demonstrate their value to (i) help document sampling methods, (ii) facilitate collaboration and (iii) reduce opportunities for human errors and omissions that could otherwise propagate through downstream data analysis to compromise biological inference.

bioinformatics↗