Biology subjects

Cotter, S.

Publications and source records attributed to Cotter, S..

7 recordsLinked to original sources

bioRxiv2026

From individuals to ecosystems: carrion beetle responses to heatwaves impact nutrient cycling

Climate extremes, such as heatwaves, are becoming more frequent and severe, leading to significant disruptions in key ecosystem processes. The direct effects of heatwaves on these processes have thus received increasing attention, yet the indirect effects of heatwaves, as mediated through animal behavioural responses, are still unknown. Insects play a fundamental role in carrion decomposition by modifying carcasses and regulating nutrient transfer to soils. Understanding how insect responses to climate extremes scale up to ecosystem processes is therefore crucial. In this study, we used a widespread carrion beetle, the burying beetle Nicrophorus vespilloides, to experimentally investigate the direct and indirect effects of a simulated heatwave on carrion decomposition dynamics, and the consequences for soil nutrient cycling. We found that burying beetle presence increased carcass mass loss by 355% under ambient temperatures, and that this was accompanied by significant increases in dissolved organic carbon (+86%), ammonium (+71%), and nitrate (+47%) concentrations. However, the positive effects of burying beetle presence on carcass mass loss were severely diminished by heat stress. Path analyses revealed that this was related to marked reductions in certain beetle behaviours, such as carcass preparation, as well as a reduction in brood size. These behavioural and reproductive shifts were, in turn, linked to decreased soil nitrate concentrations and soil moisture. Together, these findings demonstrate that the indirect effects of heatwaves on decomposition processes, as mediated by shifts in the behaviour and traits of animal ecosystem engineers, can be as important as their direct effects. Such indirect effects must therefore be incorporated into our understanding of how key ecosystem processes respond to climate extremes.

ecology↗

bioRxiv2024

The decline of global pollinator biodiversity in the Anthropocene

Pollination underlies the functioning of ecosystems globally. Therefore, the endangerment and extinction of pollinator species are predicted to trigger cascade effects with the potential to alter the demographic collapse of complex ecological networks. However, although some studies have investigated the endangerment levels of pollinator species, the lack of global-scale analyses providing a universal overview of their extinction risks remains a major pending challenge in a world where climate change is rapidly decimating biodiversity. Here, we present the first truly global study of the endangerment level of vertebrate pollinators from across the tree of life. Based on a 1,666 species dataset, we investigate the macroecological patterns of species diversity and extinction risk of bird, mammal, and reptile pollinators of the world. We found higher extinction risk for mammal relative to bird and reptile pollinators. Globally, 1 in 3 mammal pollinators are currently threatened with extinction than 1 in 12 bird and 1 in 8 reptile pollinators. The hotspots of threatened bird pollinators mostly confined to Colombia and Hawaiian Islands, whereas the hotspots of threatened mammal and reptile pollinators are confined to Madagascar and various isolated islands. Notably, the endemic pollinators are more threatened than the widespread pollinators. The increasing decline of population will alter the status of threatened pollinators in future. While highlighting the quantity of threat and decline, we also show that the evolutionary predisposition along with habitat destruction for agriculture, and exploitation for bushmeat and pet trade are combinedly eroding the vertebrate pollinators biodiversity across the world at multiple scales. We suggest special environmental priorities such as controlled land-use, legislation on hunting, collaborative efforts between various stakeholders and community outreach programmes are essential for effective conservation of vertebrate pollinators.

ecology↗

bioRxiv2024

Combining in vivo and in vitro approaches to better understand host-pathogen interactions

Nutrition often shapes the outcome of host-parasite interactions, however understanding the mechanisms by which this occurs is confounded by the intimate nature of the association and by the fact that the host and parasite may compete for the same limiting nutrients. One way of disentangling this interaction is to combine in vivo and in vitro approaches. Here, we explore the role of host nutrition in determining the outcome of infections using a model insect-bacterium system: the cotton leafworm Spodoptera littoralis and the blood-borne bacterium Xenorhabdus nematophila. Spodoptera littoralis larvae were reared on one of a series of 20 chemically-defined diets ranging in their protein: carbohydrate (P:C) ratio and caloric density. They were then challenged with either a fixed dose of X. nematophila cells (live or dead) or were sham-injected. Survivorship of larvae challenged with live bacterial cells was strongly dependent on the protein levels of the diet, with mortality being highest on low-protein diets. This trend was reflected in the bacterial growth rate in vivo, which peaked in larvae fed low-protein diets. To determine whether in vivo bacterial growth rates were driven by blood nutrients, rather than an enhanced host immune response, we generated 20 synthetic haemolymphs ( nutribloods) that mimicked the nutritional content of host blood. Bacterial growth rate in the nutribloods was also negatively impacted by their protein content suggesting that nutrient availability and not host immunity was driving the interaction. By comparing standardized bacterial growth rates in vivo and in vitro, we conclude that the outcome of this host-parasite interaction is largely driven by bottom-up effects of nutrients on bacterial growth, rather than by top-down effects of nutrients on host-mediated immune responses. The outcome of host-parasite interactions is typically assumed to be strongly determined by the host immune response. The direct effects of nutrition have been underexplored and may have broad consequences for host-parasite interactions across taxa.

ecology↗

bioRxiv2024

Nutribloods: novel synthetic lepidopteran haemolymphs for understanding insect-microbe interactions in vitro

Understanding the role of nutrients in microbial population dynamics relies on a sound appreciation of their nutritional environment and how this may vary in different habitats. For microbial pathogens and commensals, this can be especially challenging because the microbe may share nutritional resources with its host. Here we design a series of 20 synthetic haemolymphs (nutribloods) that mimic haemolymph nutrient profiles of caterpillars fed on one of 20 chemically-defined diets, that vary in their protein:carbohydrate (P:C) ratio and caloric density. Using these, we are able to simulate the range of nutritional conditions that insect blood pathogens might face, providing a model system for understanding the role of nutrition in microbial growth. We tested this using the entomopathogen, Xenorhabdus nematophila, a gram-positive extracellular bacterium of insect hosts. This revealed that whilst bacterial fitness peaked in nutriblood nutrient space that was high in carbohydrates and low in proteins, levels of amino acids in the nutribloods also appear to be an important driving force for bacterial growth. Using synthetic haemolymphs that had average levels of all nutrients other than carbohydrate, protein or amino acids, we also established that bacterial growth is generally enhanced by carbohydrate and amino acids but reduced by proteins. Here, we have established a tractable model system for examining the role that nutrition plays in the growth of an entomopathogenic bacterium. In future work, this model host-pathogen system can be used to test a range of nutritionally-driven processes, including competition during co-infection and interactions with the host microbiome, as well as comparative studies of other entomopathogens.

physiology↗

bioRxiv2021

Judgement Bias During Pregnancy In Domestic Pigs

In humans and rats, changes in mood and affect are known to occur during pregnancy, however it is unknown how gestation may influence mood in other non-human mammals. This study assessed changes in pigs judgment bias as a measure of affective state throughout gestation. Pigs were trained to complete a spatial judgement bias task with reference to positive and negative locations. We tested gilts before mating, and during early and late pregnancy, by assessing their responses to ambiguous probe locations. Pigs responded increasingly negatively to ambiguous probes as pregnancy progressed and there were consistent inter-individual differences in baseline optimism. This suggests that the pigs affective state may be altered during gestation, although as a non-pregnant control group was not tested, an effect of learning cannot be ruled out. These results suggest that judgement bias is altered during pregnancy in domestic pigs, consequently raising novel welfare considerations for captive multiparous species.

animal behavior and cognition↗

bioRxiv2019

Parental care shapes evolution of aposematism and provides lifelong protection against predators

Social interactions within species can modulate the response to selection and determine the extent of evolutionary change. Yet relatively little work has determined whether the social environment can influence the evolution of traits that are selected by interactions with other species - a major source of natural selection. Here we show that the amount of parental care received as an offspring can influence the expression, and potential evolution, of warning displays deployed against predators in adulthood. In theory, warning displays by prey are selected by predators for uniformity and to reliably advertise the extent to which individuals are chemically defended. However, the correlated evolution of intensity of the visual display and strength of the chemical defense is only possible if there is a genetic correlation between them. Adult burying beetles Nicrophorus vespilloides bear bright orange elytral markings which advertise their chemical defenses. We experimentally manipulated the level of maternal care that individuals received when they were larvae and then measured the strength of the correlation between the component parts of the warning display when they reached adulthood. We found that under limited care individuals were smaller and produced less conspicuous warning displays. The underlying family (genetic) correlation between the visual display and the chemical defense was weaker in individuals that received little care as larvae. We conclude that parenting by burying beetles modulates the evolvability of aposematic defense, making correlated evolutionary change in signal intensity and chemical defense less likely when they restrict care to their young.\n\nSignificance StatementParental care can improve early offspring survival against predators. However, we have little knowledge of how its effects shape the evolution of predator-prey interactions later in the offsprings life. We tested this with carrion beetles who provide care for offspring and who carry warning coloration to advertise to predators that they are chemically defended. We show that more parental care resulted in larger, more brightly coloured and chemically defended adult beetles. Furthermore, when parents had provided little care for their young we found weaker genetic correlations between warning signal salience and chemical defense. Over time, this could result in untrustworthy warning signals, which could render them ineffective against predators.

evolutionary biology↗

bioRxiv2018

Macronutrients modulate resistance to infection and immunity in Drosophila

Immunity and nutrition are two essential modulators of individual fitness However, while the implications of immune function and nutrition on an individual s lifespan and reproduction are known, the interplay between feeding behaviour, infection, and immune function, remains poorly understood. In this study, we used the fruit fly, Drosophila melanogaster, to investigate how infection through septic injury modulates nutritional intake, and how macronutrient balance affects survival to infection by the pathogenic Gram-positive bacterium Micrococcus luteus. Our results show that infected flies maintain carbohydrate intake, but reduce protein intake, thereby shifting from a protein-to-carbohydrate (P:C) ratio of ~1:4 to ~1:10 relative to non-infected and sham-infected flies. Strikingly, we found that the proportion of flies dying after M. luteus infection was significantly lower when flies were fed a low-P high-C diet, revealing that flies shift their macronutrient intake as means of nutritional self-medication against bacterial infection. This is likely due to the effects of macronutrient balance on the regulation of the constitutive expression of innate immune genes, as a low-P high-C diet was linked to an up-regulation in the expression of key antimicrobial peptides. Together, our results reveal the intricate relationship between macronutrient intake and resistance to infection, and integrate the molecular cross-talk between metabolic and immune pathways into the framework of nutritional immunology.

physiology↗