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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.
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Arthropod rain in a lowland tropical forest
Abstract In lowland tropical forests, “arthropod rain” (i.e., arthropods falling from the canopy to the understory), represents a potentially important terrestrial nutrient flux.We investigated the composition, abundance, biomass and environmental drivers of arthropod rain on Barro Colorado Island, Panama. Pairs of traps (pan traps and pole traps) placed 1 m above the ground, respectively, collected fallen arthropods and arthropods potentially climbing to the canopy.Average (±SE) arthropod biomass in pan traps was dominated by Hymenoptera (primarily ants; 0.501 ± 0.023 mg dry mass m−2 day−1) and Lepidoptera larvae (0.228 ± 0.001 mg m−2 day−1). Total dry biomass in pan traps was 0.891 ± 0.033 mg m−2 day−1; thus, ca. 27 kg of arthropod biomass rains into the understory per km2per month during the wet season in this forest. This equates to ca. 3 million mid‐sized ants falling from the canopy per day on BCI as a whole.Arthropod abundance in pan traps, especially ants and spiders, increased marginally with the increasing number of high‐wind events. By contrast, arthropod biomass showed no relationship with wind or rain.Arthropod abundance was higher in pole traps than in pan traps and was dominated by Collembola and Acari. Compositional overlap between pan and pole trap contents suggests that some fallen arboreal arthropods regularly return to the canopy.These findings illustrate an understudied pathway linking canopy and understory food webs within tropical forests, and the complex interactions between environmental conditions and arthropod rain.
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- PAR ID:
- 10652142
- Publisher / Repository:
- Wiley
- Date Published:
- Journal Name:
- Insect Conservation and Diversity
- ISSN:
- 1752-458X
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1111/icad.70046
