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1. Video surveillance reveals a community of largely nocturnal Danaus plexippus (L.) egg predators

   https://doi.org/10.1007/s10841-020-00248-w  

   Myers, Andrew T. ; Haan, Nathan L. ; Landis, Douglas A. ( May 2020 , Journal of Insect Conservation)

   Monarch butterfly (Danaus plexippus L.) declines in eastern North America have prompted milkweed host plant restoration efforts in non-agricultural grasslands. However, grasslands harbor predator communities that exert high predation pressure on monarch eggs and larvae. While diurnal monarch predators are relatively well known, no studies have investigated the contribution of nocturnal monarch predators. We used video cameras to monitor sentinel monarch eggs and fourth instars on milkweed in southern Michigan to identify predators and determine if nocturnally-active species impose significant predation pressure. We observed ten arthropod taxa consuming monarch eggs and larvae, with 74% of egg predation events occurring nocturnally. Taxa observed attacking monarch eggs included European earwigs (Forficula auricularia L.), tree crickets (Oecanthus sp.), lacewing larvae (Neuroptera), plant bugs (Miridae), small milkweed bugs (Lygaeus kalmii Stal), ants (Formicidae), spiders (Araneae: Salticidae and other spp.), harvestmen (Opiliones), and velvet mites (Trombidiformes: Trombidiidae). Larvae were attacked by ground beetles (Calleida sp.), jumping spiders (Araneae: Salticidae), and spined soldier bugs (Podisus maculiventris Say). Our findings provide important information about monarch predator-prey interactions that could be used to develop strategies to conserve monarchs through reducing predation on early life stages. 

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2. The nutritional geography of ants: Gradients of sodium and sugar limitation across North American grasslands

   https://doi.org/10.1111/1365-2656.13120  

   Kaspari, Michael ; Welti, Ellen A. R. ; de Beurs, Kirsten M. ; Dussutour, ed., Audrey ( November 2019 , Journal of Animal Ecology)

   Sugar and sodium are essential nutrients to above‐ and below‐ground consumers. Unlike other properties of ecological communities such as abundance and richness, we know relatively little about nutritional geography—the sources and supply rates of nutrients, and how and why they vary across communities and ecosystems.

   Towards a remedy, we present a suite of hypotheses for how sodium and sugary exudate availability should vary for a common omnivore—the ants—and test them using a survey of 53 North American grasslands.

   We do so by running transects of salt and sugar baits and inferring the magnitude of environmental supplies as the inverse of their use as exogenous baits. We then use estimates of potential drivers of the availability of salt and sugary exudates—plant and soil nutrients, and bioclimatic variables—to test the best predictors of sodium and salt use by ant communities.

   Beyond a baseline of ant activity, salt use increased as an inverse of the amount of sodium in an ecosystem's plant tissue, but not its soils. Plant sodium varied by two orders of magnitude in grasslands across 16° latitude. This suggests that plant exudates are an important source of sodium for grassland consumers. The three drivers that best predict exogenous sugar use by ants all point to factors constraining sugar production: net above‐ground productivity, how far the community is into that year's growing season (both reflecting the rates of photosynthesis) and, intriguingly, the potassium content of plant tissue, which is likely linked to exudate production via plant turgor.

   These data suggest that ants and other consumers across a range of grasslands and climate vary significantly in the demand and supply of sugar and salt. This nutritional geography ultimately arises from gradients of climate and biogeochemistry with implications for the geography of plant–consumer interactions.

    

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3. An aggressive nonconsumptive effect mediates pest control and multipredator interactions in a coffee agroecosystem

   https://doi.org/10.1002/eap.2653  

   Morris, Jonathan R. ; Perfecto, Ivette ( June 2022 , Ecological Applications)

   Natural pest control is an alternative to pesticide use in agriculture, and may help to curb insect declines and promote crop production. Nonconsumptive interactions in natural pest control that historically have received far less attention than consumptive interactions, may have distinct impacts on pest damage suppression and may also mediate positive multipredator interactions. Additionally, when nonconsumptive effects are driven by natural enemy aggression, variation in alternative resources for enemies may impact the strength of pest control. Here we study control of the coffee berry borer (CBB),Hypothenemus hampei, by a keystone arboreal ant species,Azteca sericeasur, which exhibits a nonconsumptive effect on CBB by throwing them off coffee plants. We conducted two experiments to investigate: (1) if the strength of this behavior is driven by spatial or temporal variability in scale insect density (an alternative resource thatAztecatends for honeydew), (2) if this behavior mediates positive interactions betweenAztecaand other ground‐foraging ants, and (3) the effect this behavior has on the overall suppression of CBB damage in multipredator scenarios. Our behavioral experiment showed that nearly all interactions betweenAztecaand CBB are nonconsumptive and that this behavior occurs more frequently in the dry season and with higher densities of scale insects on coffee branches. Our multipredator experiment revealed that borers thrown off coffee plants byAztecacan survive and potentially damage other nearby plants but may be suppressed by ground‐foraging ants. Although we found no non‐additive effects betweenAztecaand ground‐foraging ants on overall CBB damage, together, both species resulted in the lowest level of plant damage with the subsequent reduction in “spillover” damage caused by thrown CBB, indicating spatial complementarity between predators. These results present a unique case of natural pest control, in which damage suppression is driven almost exclusively by nonconsumptive natural enemy aggression, as opposed to consumption or prey behavioral changes. Furthermore, our results demonstrate the variability that may occur in nonconsumptive pest control interactions when natural enemy aggressive behavior is impacted by alternative resources, and also show how these nonconsumptive effects can mediate positive interactions between natural enemies to enhance overall crop damage reduction.

    

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4. Detection of prey odours underpins dietary specialization in a Neotropical top‐predator: How army ants find their ant prey

   https://doi.org/10.1111/1365-2656.13188  

   Manubay, John Aidan ; Powell, Scott ; Parr, ed., Catherine ( March 2020 , Journal of Animal Ecology)

   Deciphering the mechanisms that underpin dietary specialization and niche partitioning is crucial to understanding the maintenance of biodiversity. New world army ants live in species‐rich assemblages throughout the Neotropics and are voracious predators of other arthropods. They are therefore an important and potentially informative group for addressing how diverse predator assemblages partition available prey resources.

   New World army ants are largely specialist predators of other ants, with each species specializing on different ant genera. However, the mechanisms of prey choice are unknown. In this study, we addressed whether the army antEciton hamatum:(a) can detect potential prey odours, (b) can distinguish between odours of prey and non‐prey and (c) can differentiate between different types of odours associated with its prey.

   Using field experiments, we tested the response of army ants to the following four odour treatments: alarm odours, dead ants, live ants and nest material. Each treatment had a unique combination of odour sources and included some movement in two of the treatments (alarm and live ants). Odour treatments were tested for both prey and non‐prey ants. These data were used to determine the degree to whichE. hamatumare using specific prey stimuli to detect potential prey and direct their foraging.

   Army ants responded strongly to odours derived from prey ants, which triggered both increased localized recruitment and slowed advancement of the raid as they targeted the odour source. Odours from non‐prey ants were largely ignored. Additionally, the army ants had the strongest response to the nest material of their preferred prey, with progressively weaker responses across the live ant, dead ant and alarm odours treatments respectively.

   This study reveals that the detection of prey odours, and especially the most persistent odours related to the prey's nest, provides a mechanism for dietary specialization in army ants. If ubiquitous across the Neotropical army ants, then this olfaction‐based ecological specialization may facilitate patterns of resource partitioning and coexistence in these diverse predator communities.

    

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5. Red Imported Fire Ants Reduce Invertebrate Abundance, Richness, and Diversity in Gopher Tortoise Burrows

   https://doi.org/10.3390/d13010007  

   Epperson, Deborah M. ; Allen, Craig R. ; Hogan, Katharine F. ( January 2021 , Diversity)

   null (Ed.)

   Gopher Tortoise (Gopherus polyphemus) burrows support diverse commensal invertebrate communities that may be of special conservation interest. We investigated the impact of red imported fire ants (Solenopsis invicta) on the invertebrate burrow community at 10 study sites in southern Mississippi, sampling burrows (1998–2000) before and after bait treatments to reduce fire ant populations. We sampled invertebrates using an ant bait attractant for ants and burrow vacuums for the broader invertebrate community and calculated fire ant abundance, invertebrate abundance, species richness, and species diversity. Fire ant abundance in gopher tortoise burrows was reduced by >98% in treated sites. There was a positive treatment effect on invertebrate abundance, diversity, and species richness from burrow vacuum sampling which was not observed in ant sampling from burrow baits. Management of fire ants around burrows may benefit both threatened gopher tortoises by reducing potential fire ant predation on hatchlings, as well as the diverse burrow invertebrate community. Fire-ant management may also benefit other species utilizing tortoise burrows, such as the endangered Dusky Gopher Frog and Schaus swallowtail butterfly. This has implications for more effective biodiversity conservation via targeted control of the invasive fire ant at gopher tortoise burrows. 

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