Biology subjects

Fugere, V.

Publications and source records attributed to Fugere, V..

7 recordsLinked to original sources

bioRxiv2024

Pre-exposure to stress reduces loss of community and genetic diversity following severe environmental disturbance

Environmental stress caused by anthropogenic impacts is increasing worldwide. Understanding the ecological and evolutionary consequences for biodiversity will be crucial for our ability to respond effectively. Historical exposure to environmental stress is expected to select for resistant species, shifting community composition towards more stress-tolerant taxa. Concurrent with this species sorting process, genotypes within resistant taxa that have the highest relative fitness under severe stress are expected to increase in frequency, leading to evolutionary adaptation. However, empirical demonstrations of these dual ecological and evolutionary processes in natural communities are lacking. Here, we provide the first evidence for simultaneous species sorting and evolutionary adaptation across multiple species within a natural freshwater bacterial community. Using a two-phase stressor experimental design (acidification pre-exposure followed by severe acidification) in aquatic mesocosms, we show that pre-exposed communities were more resistant than naive communities to taxonomic loss when faced with severe acid stress. However, after sustained severe acidification, taxonomic richness of both pre-exposed and naive communities eventually converged. All communities experiencing severe acidification became dominated by an acidophilic bacterium, Acidiphilium rubrum, but this species retained greater genetic diversity and followed distinct evolutionary trajectories in pre-exposed relative to naive communities. These patterns were shared across other acidophilic species, providing repeated evidence for the impact of pre-exposure on evolutionary outcomes despite the convergence of community profiles. Our results underscore the need to consider both ecological and evolutionary processes to accurately predict the responses of natural communities to environmental change.

evolutionary biology↗

bioRxiv2021

A glyphosate-based herbicide cross-selects for antibiotic resistance genes in bacterioplankton communities

Agrochemicals often contaminate freshwater bodies, affecting microbial communities that underlie aquatic food webs. For example, Roundup, a widely-used glyphosate-based herbicide (GBH), has the potential to indirectly select for antibiotic resistant bacteria. Such cross-selection could occur, for example, if the same genes (e.g. encoding efflux pumps) confer resistance to both glyphosate and antibiotics. To test for cross-resistance in natural aquatic bacterial communities, we added Roundup to 1,000-L mesocosms filled with water from a pristine lake. Over 57 days, we tracked changes in bacterial communities with shotgun metagenomic sequencing, and annotated metagenome-assembled genomes (MAGs) for the presence of known antibiotic resistance genes (ARGs), plasmids, and resistance mutations in the enzyme targeted by glyphosate (enolpyruvyl-shikimate-3-phosphate synthase; EPSPS). We found that high doses of GBH significantly increased ARG frequency and selected for multidrug efflux pumps in particular. The relative abundance of MAGs after a high dose of GBH was predictable based on the number of ARGs encoded in their genomes (17% of variation explained) and, to a lesser extent, by resistance mutations in EPSPS. Together, these results indicate that GBHs have the potential to cross-select for antibiotic resistance in natural freshwater bacteria. IMPORTANCEGlyphosate-based herbicides (GBHs) such as Roundup may have the unintended consequence of selecting for antibiotic resistance genes (ARGs), as demonstrated in previous experiments. However, the effects of GBHs on ARGs remains unknown in natural aquatic communities, which are often contaminated with pesticides from agricultural runoff. Moreover, the resistance provided by ARGs compared to canonical mutations in the glyphosate target enzyme, EPSPS, remains unclear. Here we used freshwater mesocosm experiments to show that GBHs strongly select for ARGs, particularly multidrug efflux pumps. These selective effects are evident after just a few days, and at glyphosate concentrations that are high but still within short-term (1-4 day) regulatory limits. The ability of bacteria to survive and thrive after GBH stress was predictable by the number of ARGs in their genomes, and to a lesser extent by mutations in EPSPS. GBHs are therefore likely to select for higher ARG frequencies in natural streams, lakes, and ponds.

microbiology↗

bioRxiv2020

Widespread agrochemicals differentially affect zooplankton biomass and community structure

Anthropogenic environmental change is causing habitat deterioration at unprecedented rates in freshwater ecosystems. Despite increasing more rapidly than other agents of global change, synthetic chemical pollution -including agrochemicals such as pesticides- has received relatively little attention in freshwater biotic assessments. Determining the effects of multiple agrochemicals on complex community and ecosystem properties remains a major challenge, requiring a cross-field integration of ecology and ecotoxicology. Using a large-scale array of experimental ponds, we investigated the response of zooplankton community properties (biomass, composition, diversity metrics) to the individual and joint presence of three widespread agrochemicals: the herbicide glyphosate, the neonicotinoid insecticide imidacloprid, and fertilisers. We tracked temporal variation in community biomass and structure (i.e., composition, diversity metrics) along single and combined pesticide gradients (each spanning eight levels), under low (mesotrophic) and high (eutrophic) nutrient-enriched conditions, and quantified (i) agrochemical interactions, (ii) response threshold concentrations, and (iii) community resistance and recovery. We found that major zooplankton groups differed in their sensitivity to pesticides: [≥]3 {micro}g/L imidacloprid impaired copepods, rotifers collapsed at glyphosate levels [≥]0.3 mg/L, whereas some cladocerans were highly tolerant to pesticide contamination. Glyphosate was the most influential driver of community properties, with biomass and community structure responding rapidly but recovering unequally over time. Zooplankton biomass showed little resistance when first exposed to glyphosate, but rapidly recovered and even increased with glyphosate concentration; in contrast, richness declined in more contaminated ponds but failed to recover. Our results show that the biomass of tolerant taxa compensated for the loss of sensitive species, conferring greater resistance upon subsequent exposure; a rare example of pollution-induced community tolerance in freshwater metazoans. Overall, zooplankton biomass appears to be more resilient to agrochemical pollution than community structure, yet all community properties measured in this study were affected at glyphosate levels below common water quality guidelines in North America.

ecology↗

bioRxiv2020

Resistance, resilience, and functional redundancy of freshwater microbial communities facing multiple agricultural stressors in a mesocosm experiment

Agricultural pollution with fertilizers and pesticides is a common disturbance to freshwater biodiversity. Bacterioplankton communities are at the base of aquatic food webs, but their responses to these potentially interacting stressors are rarely explored. To test the extent of resistance and resilience in bacterioplankton communities faced with agricultural stressors, we exposed freshwater mesocosms to single and combined gradients of two commonly used pesticides: the herbicide glyphosate (0-15 mg/L) and the neonicotinoid insecticide imidacloprid (0-60 g/L), in high or low nutrient backgrounds. Over the 43-day experiment, we tracked variation in bacterial density with flow cytometry, carbon substrate use with Biolog EcoPlates, and taxonomic diversity and composition with environmental 16S rRNA gene amplicon sequencing. We show that only glyphosate (at the highest dose, 15 mg/L), but not imidacloprid, nutrients, or their interactions measurably changed community structure, favoring members of the Proteobacteria including the genus Agrobacterium. However, no change in carbon substrate use was detected throughout, suggesting functional redundancy despite taxonomic changes. We further show that communities are resilient at broad, but not fine taxonomic levels: 24 days after glyphosate application the precise amplicon sequence variants do not return, and tend to be replaced by phylogenetically close taxa. We conclude that high doses of glyphosate - but still within commonly acceptable regulatory guidelines - alter freshwater bacterioplankton by favoring a subset of higher taxonomic units (i.e. genus to phylum) that transiently thrive in the presence of glyphosate. Longer-term impacts of glyphosate at finer taxonomic resolution merit further investigation.

ecology↗

bioRxiv2020

Prior selection prevents the loss of an ecosystem cycle during acidification

Ecosystem processes vary temporally due to variation in environmental variables, such as when diurnal variation in sunlight causes diurnal cycles in net primary production. This variability can be characterized by its frequency and amplitude, used to define "normal" functioning of an ecosystem. Relatively little research has addressed how normal modes of variability, such as diurnal cycles, are lost or recovered, following anthropogenic stress. We conducted an aquatic mesocosm experiment to test whether prior application of environmental stress, in the form of moderate acidification, affected the diurnal cycle of dissolved oxygen when exposed to severe acidification. High-frequency data from sensor loggers deployed in 12 mesocosms showed that severe acidification caused a temporary loss of diurnal variation in dissolved oxygen concentration. However, pre-exposure to an acidic environment resulted in the persistence of the diurnal cycle. We hypothesize that pre-exposure shifted the community to acid tolerant genotypes and/or species of algae and other photosynthetic organisms. Our findings suggest that the stability of ecosystem cycles is intrinsically liked to the stress tolerance of the species assemblage.

ecology↗

bioRxiv2019

Worldwide impacts of human on animal genetic diversity

Human impacts on genetic diversity are poorly understood yet critical to understanding the evolutionary capacity of the worlds biodiversity. We used global maps of land use and human density to assess human impacts on the intraspecific genetic diversity of 15,946 species of birds, fishes, insects, and mammals over time and across four spatial scales worldwide. We analyzed 164,518 mitochondrial cytochrome c oxidase subunit I (COI) sequences to quantify changes in genetic diversity between 1980-2016. We found temporal change in genetic diversity, with both increasing and decreasing trends observed. The magnitude and sign of human impacts on genetic diversity depended on scale and taxon. In contrast, latitude was a strong predictor of diversity in fish, insects, and mammals. Our analyses provide a first worldwide picture of human impacts on animal genetic diversity. A global effort to systematically monitor genetic diversity is needed to fill the gaps in taxonomic and geographic coverage in this dataset.

evolutionary biology↗

bioRxiv2018

Community rescue in experimental phytoplankton communities facing severe herbicide pollution.

Evolutionary rescue occurs when adaptation prevents local extinction in deteriorating environments. Laboratory experiments with microorganisms have shown that the likelihood of evolutionary rescue is greatest in large populations that have previously experienced sublethal doses of stress. To assess this result in natural communities, we conducted a mesocosm experiment with semi-natural phytoplankton communities exposed to glyphosate, a widely used herbicide. We tested whether community biomass and pre-exposure to sublethal stress would facilitate community rescue after severe contamination. Exposure to sublethal stress, but not community biomass, facilitated rescue significantly-even though it led to biodiversity loss. Furthermore, glyphosate had modest effects on community composition, suggesting that community resistance to glyphosate was primarily driven by changes in resistance within taxa, not by community turnover. Our results expand the scope of community evolutionary rescue theory to complex ecosystems and confirm that prior stress exposure is a key predictor of rescue.

ecology↗