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Abstract Nutrient impacts on productivity in stream ecosystems can be obscured by light limitation imposed by canopy cover and water turbidity, thereby creating uncertainties in linking nutrient and productivity regimes. Evaluations of nutrient limitations are often based on a response ratio (RR) quantifying productivity stimulation above ambient levels given augmented nutrient supply. This metric neglects the primacy of light effects on productivity. We propose an alternative approach to quantify nutrient limitations using a “decline ratio” (DR), which quantifies the productivity decline from the maximum established by light availability. The DR treats light as the first‐order control and nutrient depletion as a disturbance causing productivity decline, allowing separation of nutrient and light influences. We used DR to assess nutrient diffusing substrate (NDS) experiments with three nutrients (nitrogen [N], phosphorus [P], iron [Fe]) from five Greenland streams during summer, where light is not limited due to the lack of canopy and low turbidity. We tested two hypotheses: (a) productivity maximum (i.e., highest chlorophyll‐aamong NDS treatments) is controlled by light and (b) DR depends on both light and nutrients. The productivity maximum was strongly predicted by light (R² = 0.60). The productivity decline induced by N limitation (i.e., DR_N) was best explained by light availability when parameterized with either dissolved inorganic nitrogen concentration (R² = 0.79) or N:Fe ratio (R² = 0.87). These predictions outperformed predictions of RR for which light was not a significant factor. Reversing the perspective on nutrient limitation from “stimulation above ambient” to “decline below maximum” provides insights into both light and nutrient impacts on stream productivity. 

ABSTRACT In Euthyneuran molluscs, the distribution and plethora of dopamine (DA) functions are likely coupled to the feeding ecology with a broad spectrum of modifications both in the central and peripheral neural systems. However, studies of benthic grazers currently dominate the analysis of DA‐mediated signaling, whereas adaptations to pelagic lifestyles and other feeding strategies are unknown. Here, we characterize the distribution of central and peripheral neurons in representatives of distinct ecological groups: the pelagic predatory pteropodClione limacina(Pteropoda, Gymnosomata) and its prey —Limacina helicina(Pteropoda, Thecosomata), as well as the plankton eaterMelibe leonina(Nudipleura, Nudibranchia). By using tyrosine hydroxylase immunoreactivity as a reporter, we mapped their dopaminergic systems. Across all studied species, despite their differences in ecology, small numbers of dopaminergic neurons in the central ganglia contrast to an incredible density of these neurons in the peripheral nervous system, primarily representing sensory‐like cells, which are predominantly concentrated in the chemotactic areas and project afferent axons to the central nervous system. Combined with tubulin immunoreactivity, this study illuminates the complexity of sensory signaling and peripheral neural systems in Euthyneuran molluscs with lineage‐specific adaptations across different taxonomical and ecological groups. 

ABSTRACT Alluaud's little yellow ant,Plagiolepis alluaudiEmery 1894, (Hymenoptera: Formicidae), is an emerging nuisance species in floriculture and residential areas around the globe. Originally described from Madagascar, it ranks among the smallest widespread formicine pests. To date, no evaluations of management protocols for this species have been reported. In ants, feeding preference is related to ant body size and viscosity and nutritional content of the food source. Optimizing these factors could lead to improved bait performance. To assess population management implications of various bait parameters on a small pest ant species, four commercial ant baits of varying viscosities, active ingredient (AI) group and concentration, and nutritional content were evaluated in laboratory and field assays againstP. alluaudi. All four products negatively affectedP. alluaudisurvival compared to the untreated control, and all products were associated with greater visitation compared to the control, suggesting all AIs tested are viable candidates forP. alluaudimanagement. However, their direct use for population management in the field may be limited, as feeding cessation was eventually observed on all four baits. When baits were diluted with water, viscosity was reduced and survival was initially higher compared to with undiluted baits. However, similarly low levels of survival were maintained over time. Most importantly, we found in a 2‐year observational field study involving sustained baiting within an infested structure that only the bait formulation with the lowest overall viscosity was able to alleviateP. alluaudinuisance indoors. Our results suggest that diluting baits may be a viable strategy for targeting very small pest ant species, and the greater time to lethality of diluted baits, resulting from reduced toxicant concentration, may be a reasonable trade‐off allowing smaller ant species to continue feeding for a sufficient duration on a bait formulation. 

Abstract We examined three descending positive leaders at distances of 5–11 km and three descending negative leaders at distances of 6–7 km, all simultaneously imaged by high‐speed framing cameras operating in the visible and UV ranges. UV images (290–370 nm) of the positive leaders each exhibited a strong embellishment at the lower channel end, which was not observed in the corresponding visible images (480–800 nm). In contrast, none of the negative leaders exhibited channel embellishment in the UV range and their morphology in UV was similar to that in the visible. Additionally, no embellishment was seen in four negative leaders imaged in UV only. The observed UV embellishment, which is likely to be the streamer zone at the positive‐leader tip, appeared to undergo expansion‐contraction cycles. We attributed the lack of detectable streamer‐zone emission in the UV range in negative leaders to a much lower streamer generation rate compared to positive leaders. 

Wildlife population monitoring over large geographic areas is increasingly feasible due to developments in aerial survey methods coupled with the use of computer vision models for identifying and classifying individual organisms. However, aerial surveys still occur infrequently, and there are often long delays between the acquisition of airborne imagery and its conversion into population monitoring data. Near real‐time monitoring is increasingly important for active management decisions and ecological forecasting. Accomplishing this over large scales requires a combination of airborne imagery, computer vision models to process imagery into information on individual organisms, and automated workflows to ensure that imagery is quickly processed into data following acquisition. Here we present our end‐to‐end workflow for conducting near real‐time monitoring of wading birds in the Everglades, Florida, USA. Imagery is acquired as frequently as weekly using uncrewed aircraft systems (aka drones), processed into orthomosaics (using Agisoft metashape), converted into individual‐level species data using a Retinanet‐50 object detector, post‐processed, archived, and presented on a web‐based visualization platform (using Shiny). The main components of the workflow are automated using Snakemake. The underlying computer vision model provides accurate object detection, species classification, and both total and species‐level counts for five out of six target species (White Ibis, Great Egret, Great Blue Heron, Wood Stork, and Roseate Spoonbill). The model performed poorly for Snowy Egrets due to the small number of labels and difficulty distinguishing them from White Ibis (the most abundant species). By automating the post‐survey processing, data on the populations of these species is available in near real‐time (<1 week from the date of the survey) providing information at the time scales needed for ecological forecasting and active management. 

Abstract Tropical elevation gradients support highly diverse assemblages, but competing hypotheses suggest either peak species richness in lowland rainforests or at mid‐elevations. We investigated scolytine beetles—phloem, ambrosia and seed‐feeding beetles—along a tropical elevational gradient in Papua New Guinea.Highly standardised sampling from 200 to 3700 m above sea level (asl) identified areas of highest and lowest species richness, abundance and other biodiversity variables.Using passive flight intercept traps at eight elevations from 200 to 3500 m asl, we collected over 9600 specimens representing 215 species. Despite extensive sampling, species accumulation curves suggest that diversity was not fully exhausted.Scolytine species richness followed a unimodal distribution, peaking between 700 and 1200 m asl, supporting prior findings of highest diversity at low‐to‐mid elevations.Alternative models, such as a monotonous decrease from lowlands to higher elevations and a mid‐elevation maximum, showed lesser fit to our data. Abundance is greatest at the lowest sites, driven by a few extremely abundant species. The turnover rate—beta diversity between elevation steps—is greatest between the highest elevations.Among dominant tribes—Dryocoetini, Xyleborini and Cryphalini—species richness peaked between 700 and 2200 m asl. Taxon‐specific analyses revealed distinct patterns:Euwallaceaspp. abundance uniformly declined with elevation, while other genera were driven by dominant species at different elevations.Coccotrypesand phloem‐feedingCryphalushave undergone evolutionary radiations in New Guinea, with many species still undescribed. Species not yet known to science are most likely to be found at lower and middle elevations, where overall diversity is highest. 

ABSTRACT Emerging aquatic insects can be an important resource subsidy for a variety of terrestrial consumers, including spiders, birds, bats and lizards. Emergence flux is influenced by a variety of abiotic and biotic variables, such as temperature, drying, and predators and these variables can also control the body size of emergent insects. Despite their importance, these variables can change rapidly during drought conditions as water temperatures rise, surface area decreases and predator densities increase.During 2018, the Konza Prairie Biological Station experienced a record drought: flow ceased in the lower reaches of Kings Creek for the first time in over 40 years of observation, leaving a series of isolated pools. We studied how the drought affected aquatic insect emergence in 12 of these pools via elevated temperatures, decreased surface area, and concentration of predators (e.g. fishes and crayfish) over a four‐week period. We returned in 2020 and sampled emergence in the same pools over 2 weeks under non‐drought conditions to compare emergence between drought and non‐drought conditions.We found three overall patterns: (1) rates of areal emergence abundance and biomass (number or mg DM m⁻²d⁻¹) did not differ between drought and non‐drought conditions. In contrast, pool‐scale emergence abundance, but not biomass (number or mg DM pool⁻¹d⁻¹), was lower during drought conditions; (2) average midge body size was larger during the drought relative to the non‐drought conditions; (3) environmental variables (e.g. temperature, pool surface area, predator biomass) were not predictive of emergence during drought and non‐drought conditions.Fewer, but larger emergent midges (as seen under drought conditions) may represent a higher quality resource for terrestrial consumers than many smaller midges due to increased per‐capita energy yield. However, due to the overall decrease in water availability throughout the stream network, the overall emergence flux was concentrated in reaches with remaining water during the drought, making pools emergence subsidy hotspots. Overall, these contrasting responses underscore the complex nature of community responses to shifting climatic conditions.