Inland water systems are regarded as a pathway and sink of plastic pollutants from the terrestrial environment.Aquatic ecosystems are globally contaminated with microplastics,but the spatiotemporal occurrence and dens...Inland water systems are regarded as a pathway and sink of plastic pollutants from the terrestrial environment.Aquatic ecosystems are globally contaminated with microplastics,but the spatiotemporal occurrence and density of microplastics in freshwater ecosystems remain poorly understood.The present study seasonally assessed differences in microplastic density in the sediments from two South African recreational reservoirs associated with low human activities(macadamia orchards)and high human activities(communal areas).Microplastics were recovered from all of the reservoirs assessed,indicating their extensive occurrence and densities.Microplastic numbers were significantly higher in reservoirs associated with high anthropogenic activities during the hot-dry season(140.6 particles kg^(-1)dwt)and lower in reservoirs associated with low anthropogenic activities during the hot-wet and cool-dry seasons,i.e.,22.60 particles kg^(-1)dwt and 16.13 particles kg^(-1)dwt,respectively.Overall,polypropylene(31%)and polystyrene(30%)were identified as the dominant types of microplastic polymer in both reservoir types.Moreover,no correlative relationships were observed for environmental parameters and microplastic densities across reservoirs and seasons,suggesting a widespread and largely context-independent pollution level.These results show that microplastics are not evenly distributed between waters associated with low human activities and high human activities.Future work should seek greater sample sizes and centre around observing microplastic contamination in the region by examining their sources,transport,and impacts to freshwater environments,whilst informing management strategies.展开更多
In nature,insects concurrently face multiple environmental stressors,a sce-nario likely increasing with climate change.Integrated stress resistance(ISR)thus often improves fitness and could drive invasiveness,but how ...In nature,insects concurrently face multiple environmental stressors,a sce-nario likely increasing with climate change.Integrated stress resistance(ISR)thus often improves fitness and could drive invasiveness,but how physiological mechanisms influ-ence invasion has lacked examination.Here,we investigated cross-tolerance to abiotic stress factors which may influence range limits in the South American tomato pinworm a global invader that is an ecologically and socially damaging crop pest.Specifically,we tested the effects of prior rapid cold-and heat-hardening(RCH and RHH),fasting,and desiccation on cold and heat tolerance traits,as well as starvation and desiccation sur-vivability between T.absoluta life stages.Acclimation effects on critical thermal minima(CT_(min))and maxima(CT_(max))were inconsistent,showing significantly deleterious effects of RCH on adult CT_(max) and CT_(min) and,conversely,beneficial acclimation effects of RCH on larval CT_(min).While no beneficial effects of desiccation acclimation were recorded for desiccation tolerance,fasted individuals had significantly higher survival in adults,whereas fasting negatively affected larval tolerances.Furthermore,fasted and desiccation acclimated adults had significantly higher starvation tolerance,showing strong evidence for cross-tolerance.Our results show context-dependent ISR traits that may promote T.absoluta fitness and competitiveness.Given the frequent overlapping occurrence of these divergent stressors,ISR reported here may thus partly elucidate the observed rapid global spread of T.absoluta into more stressful environments than expected.This information is vital in determining the underpinnings of multistressor responses,which are fundamental in forecasting species responses to changing environments and management responses.展开更多
Although reports have documented loss of species diversity and ecological services caused by stressful temperature changes that result from climate change,some species cope through behavioral compensation.As temperatu...Although reports have documented loss of species diversity and ecological services caused by stressful temperature changes that result from climate change,some species cope through behavioral compensation.As temperatures and magnitudes of temperature extremes increase,animals should compensate to maintain fitness(such as through temporary behavioral shifts in activity times).Appropriate timing of activity helps avoid competition across species.Although coprophagic dung beetles exhibit species-specific temporal activity times,it is unknown whether temperature drives evolution of these species-specific temporal activity times.Using nine dung beetle species(three each of diurnal,crepuscular,and nocturnal species),we explored differences in heat stress tolerance measured as critical thermal maxima(CTmax;the highest temperature allowing activity)and heat knockdown time(HKDT;survival time under acute heat stress)across these species,and examined the results using a phylogenetically informed approach.Our results showed that day-active species had significantly higher CTmax(diurnal>crepuscular=nocturnal species),whereas crepuscular species had higher HKDT(crepuscular>nocturnal>diurnal species).There was no correlation between heat tolerance and body size across species with distinct temporal activity,and no significant phylogenetic constraint for activity.Species with higher CTmax did not necessarily have higher HKDT,which indicates that species may respond differently to diverse heat tolerance metrics.Acute heat tolerance for diurnal beetles indicates that this trait may constrain activity time and,under high acute temperatures with climate change,species may shift activity times in more benign environments.These results contribute to elucidate the evolution of foraging behavior and management of coprophagic beetle ecosystem services under changing environments.展开更多
基金We greatly acknowledge the financial support of the University of Venda Niche Grant(UID:FSEA/21/GGES/02)National Research Foundation Grant(UID:138206)+2 种基金Thendo Mutshekwa,Ross N Cuthbert and Tatenda Dalu acknowledge funding from the NRF Postgraduate Bursary(UID:121348)Leverhulme Trust Early Career Fellowship(ECF-2021-001)Stellenbosch Institute for Advanced Study fellowship,respectively.
文摘Inland water systems are regarded as a pathway and sink of plastic pollutants from the terrestrial environment.Aquatic ecosystems are globally contaminated with microplastics,but the spatiotemporal occurrence and density of microplastics in freshwater ecosystems remain poorly understood.The present study seasonally assessed differences in microplastic density in the sediments from two South African recreational reservoirs associated with low human activities(macadamia orchards)and high human activities(communal areas).Microplastics were recovered from all of the reservoirs assessed,indicating their extensive occurrence and densities.Microplastic numbers were significantly higher in reservoirs associated with high anthropogenic activities during the hot-dry season(140.6 particles kg^(-1)dwt)and lower in reservoirs associated with low anthropogenic activities during the hot-wet and cool-dry seasons,i.e.,22.60 particles kg^(-1)dwt and 16.13 particles kg^(-1)dwt,respectively.Overall,polypropylene(31%)and polystyrene(30%)were identified as the dominant types of microplastic polymer in both reservoir types.Moreover,no correlative relationships were observed for environmental parameters and microplastic densities across reservoirs and seasons,suggesting a widespread and largely context-independent pollution level.These results show that microplastics are not evenly distributed between waters associated with low human activities and high human activities.Future work should seek greater sample sizes and centre around observing microplastic contamination in the region by examining their sources,transport,and impacts to freshwater environments,whilst informing management strategies.
文摘In nature,insects concurrently face multiple environmental stressors,a sce-nario likely increasing with climate change.Integrated stress resistance(ISR)thus often improves fitness and could drive invasiveness,but how physiological mechanisms influ-ence invasion has lacked examination.Here,we investigated cross-tolerance to abiotic stress factors which may influence range limits in the South American tomato pinworm a global invader that is an ecologically and socially damaging crop pest.Specifically,we tested the effects of prior rapid cold-and heat-hardening(RCH and RHH),fasting,and desiccation on cold and heat tolerance traits,as well as starvation and desiccation sur-vivability between T.absoluta life stages.Acclimation effects on critical thermal minima(CT_(min))and maxima(CT_(max))were inconsistent,showing significantly deleterious effects of RCH on adult CT_(max) and CT_(min) and,conversely,beneficial acclimation effects of RCH on larval CT_(min).While no beneficial effects of desiccation acclimation were recorded for desiccation tolerance,fasted individuals had significantly higher survival in adults,whereas fasting negatively affected larval tolerances.Furthermore,fasted and desiccation acclimated adults had significantly higher starvation tolerance,showing strong evidence for cross-tolerance.Our results show context-dependent ISR traits that may promote T.absoluta fitness and competitiveness.Given the frequent overlapping occurrence of these divergent stressors,ISR reported here may thus partly elucidate the observed rapid global spread of T.absoluta into more stressful environments than expected.This information is vital in determining the underpinnings of multistressor responses,which are fundamental in forecasting species responses to changing environments and management responses.
基金funding from the Alexander von Humboldt Foundation.
文摘Although reports have documented loss of species diversity and ecological services caused by stressful temperature changes that result from climate change,some species cope through behavioral compensation.As temperatures and magnitudes of temperature extremes increase,animals should compensate to maintain fitness(such as through temporary behavioral shifts in activity times).Appropriate timing of activity helps avoid competition across species.Although coprophagic dung beetles exhibit species-specific temporal activity times,it is unknown whether temperature drives evolution of these species-specific temporal activity times.Using nine dung beetle species(three each of diurnal,crepuscular,and nocturnal species),we explored differences in heat stress tolerance measured as critical thermal maxima(CTmax;the highest temperature allowing activity)and heat knockdown time(HKDT;survival time under acute heat stress)across these species,and examined the results using a phylogenetically informed approach.Our results showed that day-active species had significantly higher CTmax(diurnal>crepuscular=nocturnal species),whereas crepuscular species had higher HKDT(crepuscular>nocturnal>diurnal species).There was no correlation between heat tolerance and body size across species with distinct temporal activity,and no significant phylogenetic constraint for activity.Species with higher CTmax did not necessarily have higher HKDT,which indicates that species may respond differently to diverse heat tolerance metrics.Acute heat tolerance for diurnal beetles indicates that this trait may constrain activity time and,under high acute temperatures with climate change,species may shift activity times in more benign environments.These results contribute to elucidate the evolution of foraging behavior and management of coprophagic beetle ecosystem services under changing environments.
