Toxicity of clothianidin to common Eastern North American fireflies

Illuminating patterns of firefly abundance using citizen science data and machine learning models

As insect populations decline in many regions, conservation biologists are increasingly tasked with identifying factors that threaten insect species and developing effective strategies for their conservation. One insect group of global conservation concern are fireflies (Coleoptera: Lampyridae). Although quantitative data on firefly populations are lacking for most species, anecdotal reports suggest that some firefly populations have declined in recent decades. Researchers have hypothesized that North American firefly populations are most threatened by habitat loss, pesticide use, and light pollution, but the importance of these factors in shaping firefly populations has not been rigorously examined at broad spatial scales. Using data from >24,000 surveys (spanning 2008-16) from the citizen science program Firefly Watch, we trained machine learning models to evaluate the relative importance of a variety of factors on bioluminescent firefly populations: pesticides, artificial lights at night, land cover, soil/topography, short-term weather, and long-term climate. Our analyses revealed that firefly abundance was driven by complex interactions among soil conditions (e.g., percent sand composition), climate/weather (e.g., growing degree days), and land cover characteristics (e.g., percent agriculture and impervious cover). Given the significant impact that climactic and weather conditions have on firefly abundance, there is a strong likelihood that firefly populations will be influenced by climate change, with some regions becoming higher quality and supporting larger firefly populations, and others potentially losing populations altogether. Collectively, our results support hypotheses related to factors threatening firefly populations, especially habitat loss, and suggest that climate change may pose a greater threat than appreciated in previous assessments. Thus, future conservation of North American firefly populations will depend upon 1) consistent and continued monitoring of populations via programs like Firefly Watch, 2) efforts to mitigate the impacts of climate change, and 3) insect-friendly conservation practices.

Illuminating Firefly Diversity: Trends, Threats and Conservation Strategies

Fireflies are a diverse group of bioluminescent beetles belonging to the family Lampyridae. Recent research on their diversity, evolution, behavior and conservation has greatly advanced our scientific understanding of these charismatic insects. In this review, we first summarize new discoveries about their taxonomic and ecological diversity, then focus on recent endeavors to identify and protect threatened fireflies around the world. We outline the main threats linked to recent population declines (habitat loss and degradation, light pollution, pesticide overuse, climate change and tourism) and describe relevant risk factors that predict which species will be particularly vulnerable to these threats. Although global coordination of firefly conservation efforts has begun only recently, considerable progress has already been made. We describe work by the IUCN SSC Firefly Specialist Group to identify species currently facing elevated extinction risks and to devise conservation strategies to protect them. To date, IUCN Red List assessments have been completed for 150 firefly taxa, about 20% of which face heightened extinction risks. The conservation status for many species has yet to be determined due to insufficient information, although targeted surveys and community science projects have contributed valuable new data. Finally, we highlight some examples of successful firefly habitat protection and restoration efforts, and we use the framework of the IUCN SSC Species Conservation Cycle to point out high-priority actions for future firefly conservation efforts.

Predicting the potential suitable distribution area of Emeia pseudosauteri in Zhejiang Province based on the MaxEnt model

Human activities, including urbanization, industrialization, agricultural pollution, and land use, have contributed to the increased fragmentation of natural habitats and decreased biodiversity in Zhejiang Province as a result of socioeconomic development. Numerous studies have demonstrated that the protection of ecologically significant species can play a crucial role in restoring biodiversity. Emeia pseudosauteri is regarded as an excellent environmental indicator, umbrella and flagship species because of its unique ecological attributes and strong public appeal. Assessing and predicting the potential suitable distribution area of this species in Zhejiang Province can help in the widespread conservation of biodiversity. We used the MaxEnt ecological niche model to evaluate the habitat suitability of E. pseudosauteri in Zhejiang Province to understand the potential distribution pattern and environmental characteristics of suitable habitats for this species, and used the AUC (area under the receiver operating characteristic curve) and TSS (true skill statistics) to evaluate the model performance. The results showed that the mean AUC value was 0.985, the standard deviation was 0.011, the TSS average value was 0.81, and the model prediction results were excellent. Among the 11 environmental variables used for modeling, temperature seasonality (Bio_4), altitude (Alt) and distance to rivers (Riv_dis) were the key variables affecting the distribution area of E. pseudosauteri, with contributions of 33.5%, 30% and 15.9%, respectively. Its main suitable distribution area is in southern Zhejiang Province and near rivers, at an altitude of 50-300 m, with a seasonal variation in temperature of 7.7-8 °C. Examples include the Ou River, Nanxi River, Wuxi River, and their tributary watersheds. This study can provide a theoretical basis for determining the scope of E. pseudosauteri habitat protection, population restoration, resource management and industrial development in local areas.

Influence of temperature and soil moisture on the toxic potential of clothianidin to collembolan Folsomia candida in a tropical field soil

Climate change can alter the toxic effects of pesticides on soil invertebrates. However, the nature and magnitude of the influence of climatic factors on clothianidin impacts in tropical soils are still unknown. The influence of increasing atmospheric temperature and the reduction in soil moisture on the toxicity and risk of clothianidin (seed dressing formulation Inside FS^®) were assessed through chronic toxicity tests with collembolans Folsomia candida in a tropical field soil (Entisol). The risk of clothianidin for collembolans was estimated using the Toxicity-Exposure Ratio (TER) approach. Organisms were exposed to increasing clothianidin concentrations at 20, 25 and 27 °C in combination with two soil moisture conditions (30 and 60% of the maximum water holding capacity-WHC). The effect of temperature and soil moisture content on clothianidin toxicity was verified through the number of F. candida juveniles generated after 28 days of exposure to the spiked soil. The toxicities estimated at 25 °C (EC₅₀__30%WHC = 0.014 mg kg^-1; EC_{50_60%WHC} = 0.010 mg kg^-1) and 27 °C (EC_{50_30%WHC} = 0.006 mg kg^-1; EC_{50_60%WHC} = 0.007 mg kg^-1) were 2.9-3.0-fold (25 °C) and 4.3-6.7-fold (27 °C) higher than those found at 20 °C (EC_{50_30%WHC} = 0.040 mg kg^-1; EC_{50_60%WHC} = 0.030 mg kg^-1), indicating that clothianidin toxicity increases with temperature. No clear influence of soil moisture content on clothianidin toxicity could be observed once the EC₅₀ values estimated at 30% and 60% WHC, within the same temperature, did not significantly differ. A significant risk was detected in all temperatures and soil moisture scenarios studied, and the TER values indicate that the risk can increase with increasing temperatures. Our results revealed that temperature could overlap with soil moisture in regulating clothianidin toxicity and reinforce the importance of including climatic factors in the prospective risk assessment of pesticides.

Physiological Responses of the Firefly Pyrocoelia analis (Coleoptera: Lampyridae) to an Environmental Residue From Chemical Pesticide Imidacloprid

Imidacloprid, a neonicotinoid insecticide, is widely applied to control insect pests across a broad spectrum. Though the impact of residues from this chemical pesticide on non-target organisms in the field has been reported, it was not well characterized across a wide range of ecosystems, especially for some species considered as environmental indicators that live in forests. The effects of sublethal dose of imidacloprid on firefly, Pyrocoelia analis, were analyzed physiologically and biochemically in this study to better understand the impact of chemical pesticide application on environmental indicators such as fireflies. After imidacloprid treatment, the midgut tissues of the larva presented an abnormal morphology featured as atrophy of fat body cells, shrinking cells, and the destruction of a midgut structure. The activities of antioxidant enzymes, superoxide dismutase, catalase, and peroxidase were noticeably increased during early exposure to sublethal imidacloprid and then decreased at later stages. The malondialdehyde content significantly increased after 12 h of exposure to imidacloprid compared with the control. Similarly, the enzyme activities of polyphenol oxidase and acetylcholinesterase were increased after the imidacloprid treatment and then decreased at the later stage. In summary, a sublethal dose of imidacloprid caused destructive change in the tissue structure, and this damage was followed by an excessive reactive oxygen species that could not be eliminated by antioxidant enzymes. Our results indicated that the residues of imidacloprid might cause severe toxicity to non-target insects in the environment even far away from the agro-ecosystem where the chemicals were applied.