Biology subjects

Mason, R. T.

Publications and source records attributed to Mason, R. T..

5 recordsLinked to original sources

bioRxiv2026

Global slowdown in the rate of invasive alien species establishment

The number of species introduced outside of their historical ranges by human activity continues to rise. A subset of these species establishes, form self-sustaining populations, and some (invasive alien species) go on to cause substantial harm to biodiversity and ecosystems. Preventing new invasive alien species from establishing is the key focus of interventions, because post-establishment management is costly and often fails. However, it remains unclear how effective multilateral efforts have been in curbing the rise. Here we show that the emergence of new invasive alien species across countries is slowing, and trends are similarly negative across geographically diverse countries. Using data and modelling advances, we find a 35% reduction in the establishment of new invasive alien species over a policy-relevant 50-year time frame. The findings directly inform the assessment of progress for the invasive alien species target of the Kunming-Montreal Global Biodiversity Framework, and provide a global baseline for monitoring rates of invasive alien species establishment. Furthermore, the slowdown suggests that policy and investment over recent decades to prevent invasive alien species from entering and establishing in countries have had a positive effect.

ecology↗

bioRxiv2026

Cold, dark, and hungry: Dynamic transcriptional regulation across eight months of brumation

Long-term winter dormancy in ectotherms (brumation) defines the annual cycle of many temperate-zone reptiles, yet the transcriptional regulation that supports survival across months of cold and aphagy remains poorly understood. We generated time-resolved transcriptomic profiles of liver and testis from male red-sided garter snakes (Thamnophis sirtalis parietalis) at five timepoints spanning the eight-month brumation cycle: pre-brumation, early, mid-, and late brumation, and post-arousal under continued aphagy. Time-course negative-binomial regression (maSigPro) followed by gene-set enrichment analysis identified 3,715 transcripts in liver and 5,828 in testis with significant temporal expression structure organized into five overarching temporal patterns: sustained downregulation, downregulation with post-arousal recovery, sustained upregulation, brumation-specific upregulation and cyclic modulation. Liver showed coordinated upregulation of fatty acid mobilization enzymes (ATGL, FOXO1, PPAR, CPT1A) and gluconeogenic regulators (CREBBP, PCK1) coincident with sustained low temperatures. Additionally, low temperature transcriptional activity was suggestive of a shift toward hepatic lipid mobilization and alanine-supported gluconeogenesis. Testis showed sustained suppression of meiosis, reproduction, and DNA-metabolism gene sets that did not fully recover at arousal consistent with this species dissociated reproductive pattern. Both tissues showed coordinated upregulation of stress-response pathways involving heat-shock proteins, HIF1 and a glutathione-based antioxidant defense. Interestingly, three vitellogenin transcripts and 17{beta}-hydroxysteroid dehydrogenases associated with estradiol-favoring steroid metabolism were upregulated in male liver during late brumation, which is not expected during natural physiology in adult males. Together these data support a framework in which temperature- and starvation-associated transcriptional programs contribute to survival of one of the longest, coldest brumations documented in a squamate. Summary statementA time-resolved transcriptomic analysis of liver and testis spanning eight months of winter brumation in Thamnophis sirtalis parietalis reveals gene expression patterns consistent with a temperature-associated shift toward hepatic lipid mobilization, sustained reproductive suppression, and vitellogenin response in males.

physiology↗

bioRxiv2025

Trade-offs between surviving and thriving: A careful balance of physiological limitations and reproductive effort under thermal stress

Balancing survival and reproduction presents a fundamental evolutionary challenge, especially in extreme and unpredictable environments. Thermoregulatory behavior in particular imposes a costly trade-off, as time spent maintaining optimal body temperature precludes other essential activities and forces individuals to balance competing selective pressures. By combining field observations, behavioral assays, and gene expression profiling of red-sided garter snakes (Thamnophis sirtalis parietalis), we describe how an ectothermic vertebrate navigates this trade-off in an extreme thermal environment through a combination of finely tuned mechanisms of behavioral and physiological plasticity. Snakes demonstrated remarkably consistent critical thermal limits, with minimal individual variation, suggesting a hard physiological constraint. Importantly, behavioral temperature thresholds for voluntary withdrawal and courtship cessation occurred within 5 {degrees}C of lethal, demonstrating that males routinely operate perilously close to lethal body temperatures in order to maximize reproductive opportunities. Context-dependent plasticity allows males to prioritize mating opportunities over thermoregulation until survival becomes an immediate threat. Molecular analyses of multiple tissues revealed rapid, tissue-specific transcriptomic responses activated within one hour of thermal challenge, well before critical limits were reached. Heat shock proteins were universally upregulated across all tissues under both heat and cold stress, suggesting anticipatory protective mechanisms that support risky behavioral decisions rather than simply responding to thermal damage. Tissue-specific patterns of gene expression reflected functional priorities with liver showing extensive metabolic flexibility, heart maintaining conservative stability, while brain and testis appeared to balance critical functions with stress responses. These findings demonstrate precise thermal reaction norms that integrate behavioral and molecular plasticity to maximize reproductive effort without compromising survival. The narrow margin between behavioral thresholds and lethal limits suggests this system may already be approaching evolutionary constraints. While phenotypic plasticity currently buffers populations against extreme thermal variability, it may paradoxically limit long-term adaptive potential as increasing environmental temperatures further narrow safety margins. Precise thermal decision-making, rapid physiological responses, and context-dependent behavioral switching suggest an evolved solution to the problem of balancing competing selective pressures.

zoology↗

bioRxiv2025

Skin lipid chemistry influences host-microbiome-pathogen interactions in snake fungal disease (ophidiomycosis)

Within host-microbiome-pathogen systems, the host chemical microenvironment is often overlooked despite its inherent role in host physiology. We used a multifaceted experimental approach encompassing culture-dependent and independent methods, metagenomic and genomic data, and deep neural network modeling to assess the impact of host skin lipid chemistry and the bacterial microbiome on the growth of Ophidiomyces ophidiicola (ophidiomycosis, snake fungal disease). Results suggest that host skin lipid chemistry (e.g., oleic acid, squalene) and bacteria isolated from wild snake skins (e.g., Chryseobacterium sp. and Stenotrophomonas maltophilia) suppress O. ophidiicola growth. Notably, the O. ophidiicola genome contains biosynthetic gene clusters (BGCs) that encode metabolites that may suppress host lipid production, facilitating fungal pathogenicity. The contrastive deep neural network produced a near-perfect alignment of snake skin lipid and microbiome profiles for both individual snakes and disease states. BGCs from bacterial genomes isolated from snake skin overlap with metagenome profiles from wild snakes and correlate with disease state. We highlight antifungal activity found in the diverse lipid milieu of snake skin and bacterial-fungal interactions (BFIs) that structure the skin microbiome. Our results illustrate a strong relationship among a fungal pathogen, the microbiome, and host skin lipid chemistry.

microbiology↗

bioRxiv2023

Enhanced reproductive outcomes under worst-case climate change scenarios in Red-sided Garter snakes (Thamnophis sirtalis parietalis)

As global temperatures continue to increase, understanding the impacts of warming environments is increasingly relevant. Temperature is especially relevant for ectothermic organisms which depend upon consistent and predictable annual temperature cycles for reproduction and development. However, additional research is required in this area to elucidate the potential impacts of climate change on future generations. To understand how projected increases in environmental temperatures may impact reproductive outcomes within natural populations of ectothermic vertebrates, we manipulated minimum ambient temperatures during gestation in Red-sided garter snakes (Thamnophis sirtalis parietalis). Wild snakes were collected in the Interlake region of Manitoba, Canada during their spring mating season and allowed to mate in controlled conditions. For the duration of gestation, mated females were placed into one of two ambient thermal conditions: temperatures emulating those found in the species natural habitat or temperatures with a consistent 5 {degrees}C increase to match end-of-century climate change projections. We recorded observations for each litter and all neonates resulting from controlled mating trials. We observed no difference in litter sizes or birth rates between thermal conditions. However, we observed a significant reduction in gestation length and significant increase to neonate body mass and body condition associated with increased ambient temperatures. These results suggest that increased minimum temperatures during gestation may confer reproductive benefits for the northern populations of this species even under the most extreme current modeled warming predictions. We discuss the broader implications of this effect, including possible negative ecological outcomes.

ecology↗