Cross-Ecosystem Linkages: Transfer of Polyunsaturated Fatty Acids From Streams to Riparian Spiders via Emergent Insects

Kowarik, Carmen; Martin‐Creuzburg, Dominik; Robinson, Christopher T.

doi:10.3389/fevo.2021.707570

Cited by 17 publications

(29 citation statements)

References 76 publications

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“…Our finding that riparian and inland spider diets vary with distance from aquatic habitats generally echoes those of other recent studies on spider diets and PUFA sources at varying distances from streams (Chari et al, 2020;Kowarik et al, 2021) and lakes (Mathieu-Resuge et al, unpublished). Mathieu-Resuge et al (unpublished) reported that web-building spiders collected directly on emergence traps and those collected in terrestrial habitats at distances of 1-150 m from shore had different diet sources.…”

Section: Discussionsupporting

confidence: 90%

“…These ecosystem-based differences in fatty acid composition also persist at higher trophic levels: studies suggest that terrestrial insects contain little to no n-3 LC-PUFA, while emergent freshwater insects are rich in these compounds, especially EPA (Hixson et al, 2015;Martin-Creuzburg et al, 2017;Twining et al, 2019). Emergent aquatic insects from streams and lakes thus subsidize terrestrial predators not only with energy (e.g., Nakano and Murakami, 2001;Baxter et al, 2005;Kautza and Sullivan, 2016), but also with these physiologically important organic compounds (Martin-Creuzburg et al, 2017;Twining et al, 2019;Mathieu-Resuge et al, unpublished;Kowarik et al, 2021).…”

Section: Introductionmentioning

confidence: 99%

“…Within riparian zones, emergent insects from streams and lakes serve as key sources of n-3 LC-PUFA for terrestrial insectivores, such as spiders, bats, and birds (e.g., Lam et al, 2013;Fritz et al, 2017;Twining et al, 2019;Kowarik et al, 2021). A growing number of studies suggests that the higher n-3 LC-PUFA content of emergent aquatic insects compared to terrestrial insects makes them particularly valuable for riparian insectivores.…”

Section: Introductionmentioning

confidence: 99%

“…This is unsurprising because aerial insectivores include a diversity of flying insects from several different aquatic orders in their diet (Twining et al, 2018b), while feeding modes like bark-probing or ground-foraging preclude the capture of flying emergent insect prey (Schilke et al, 2020). In contrast, web-building spiders and predatory beetles (e.g., Staphylinidae) that live across both upland and riparian zones opportunistically consume aquatic resources in areas where emergent insects are readily available (Kato et al, 2004;Paetzold et al, 2005;Stenroth et al, 2015;Kautza and Sullivan, 2016;Chari et al, 2020;Kowarik et al, 2021), suggesting that their foraging modes allow them to capture a wider array of different prey. Riparian spiders have also been found to have elevated n-3 LC-PUFA content relative to upland spiders (Fritz et al, 2017;Chari et al, 2020;Kowarik et al, 2021).…”

Section: Introductionmentioning

confidence: 99%

“…In contrast, web-building spiders and predatory beetles (e.g., Staphylinidae) that live across both upland and riparian zones opportunistically consume aquatic resources in areas where emergent insects are readily available (Kato et al, 2004;Paetzold et al, 2005;Stenroth et al, 2015;Kautza and Sullivan, 2016;Chari et al, 2020;Kowarik et al, 2021), suggesting that their foraging modes allow them to capture a wider array of different prey. Riparian spiders have also been found to have elevated n-3 LC-PUFA content relative to upland spiders (Fritz et al, 2017;Chari et al, 2020;Kowarik et al, 2021).…”

Section: Introductionmentioning

confidence: 99%

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Use of Fatty Acids From Aquatic Prey Varies With Foraging Strategy

et al. 2021

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Across ecosystems, resources vary in their nutritional composition and thus their dietary value to consumers. Animals can either access organic compounds, such as fatty acids, directly from diet or through internal biosynthesis, and the extent to which they use these two alternatives likely varies based on the availability of such compounds across the nutritional landscape. Cross-ecosystem subsidies of important dietary nutrients, like omega-3 long-chain polyunsaturated fatty acids (n-3 LC-PUFA), may provide consumers with the opportunity to relax the demands of synthesis and rely upon dietary flexibility rather than internal metabolic processes. Here, we examined how dietary flexibility and distance from a lake influenced the degree to which generalist insectivores relied upon dietary n-3 LC-PUFA from emergent aquatic insects versus n-3 LC-PUFA synthesized from precursor compounds found in terrestrial insects. We used bulk and compound-specific stable isotope analyses to understand spider and insectivorous bird (Blue Tit; Cyanistes caeruleus) reliance on aquatic and terrestrial resources, including dietary PUFA sources, along a riparian to upland gradient from a lake. We simultaneously investigated n-3 LC-PUFA synthesis ability in nestlings using 13C fatty acid labeling. We found that riparian spiders took advantage of emergent aquatic insect subsidies, deriving their overall diet and their n-3 PUFA from aquatic resources whereas nestling birds at all distances and upland spiders relied upon terrestrial resources, including PUFA. Our 13C labeling experiment demonstrated that nestling tits were able to synthesize the n-3 LC-PUFA docosahexaenoic acid from the dietary precursor α-linolenic acid, suggesting that they are not limited by aquatic resources to satisfy their LC-PUFA requirements. Overall, this study suggests that habitat generalist insectivores vary in the degree to which they can shift diet to take advantage of high-quality aquatic resources depending upon both their foraging flexibility and internal synthesis capacity.

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Section: Discussionsupporting

confidence: 90%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Use of Fatty Acids From Aquatic Prey Varies With Foraging Strategy

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Trophic transfer of polyunsaturated fatty acids across the aquatic–terrestrial interface: An experimental tritrophic food chain approach

Ohler

Schreiner

Martin‐Creuzburg

et al. 2023

Ecology and Evolution

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Aquatic and their adjacent terrestrial ecosystems are linked via the flux of organic and inorganic matter. Emergent aquatic insects are recognized as high-quality food for terrestrial predators, because they provide more physiologically relevant long-chain polyunsaturated fatty acids (PUFA) than terrestrial insects. The effects of dietary PUFA on terrestrial predators have been explored mainly in feeding trials conducted under controlled laboratory conditions, hampering the assessment of the ecological relevance of dietary PUFA deficiencies under field conditions. We assessed the PUFA transfer across the aquatic-terrestrial interface and the consequences for terrestrial riparian predators in two outdoor microcosm experiments. We established simplified tritrophic food chains, consisting of one of four basic food sources, an intermediary collector gatherer (Chironomus riparius, Chironomidae), and a riparian web-building spider (Tetragnatha sp.). The four basic food sources (algae, conditioned leaves, oatmeal, and fish food) differed in PUFA profiles and were used to track the trophic transfer of single PUFA along the food chain and to assess their potential effects on spiders, that is, on fresh weight, body condition (size-controlled measurement of nutritional status), and immune response. The PUFA profiles of the basic food sources, C. riparius and spiders differed between treatments, except for spiders in the second experiment. The PUFA α-linolenic acid (ALA, 18:3n-3) and ɣ-linolenic acid (GLA, 18:3n-6) were major contributors to the differences between treatments. PUFA profiles of the basic food sources influenced the fresh weight and body condition of spiders in the first experiment, but not in the second experiment, and did not affect the immune response, growth rate, and dry weight in both experiments. Furthermore, our results indicate that the examined responses are dependent on temperature. Future studies including anthropogenic stressors would deepen our understanding of the transfer and role of PUFA in ecosystems.

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Interactions between temperature and predation impact insect emergence in alpine lakes

Owens,

Lee,

Grim

et al. 2023

Ecosphere

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While insect populations are simultaneously threatened by many local‐ and global‐scale stressors, the interacting effects of these factors remain poorly understood. These interactions between stressors, whether additive or antagonistic, may have profound effects on our assumptions about and predictions for any given system. Here we address this gap by exploring the interactive effects of introduced predators and elevated temperatures on emerging aquatic insects across alpine lakes. Using a crossed factorial field survey, we examine whether warmer temperatures either directly affect the magnitude or diversity of insect emergence, or mediate the impacts of predation via interactions with predator presence. Based on data from more than 11,000 insects collected across a two‐year period, we find a 71% reduction in insect emergence associated with an additional 3.6°C of water temperature in oligotrophic alpine lakes. While our work confirms prior findings that predator presence drives strong reductions in insect emergence, we find that the effects of predation are significantly weaker in warmer lakes (2% reduction in warmest lakes studied vs. 75% reduction in coldest). Combining our results with regional studies of predator communities to identify mechanisms suggests that the interaction effects between temperature and predator presence are likely due to changes in predator behavior across temperatures. Critically, to fully understand the multiple stressors that impact insect populations and predict their future effects, we must consider the interactions between stressors across spatial scales.

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Cross-Ecosystem Linkages: Transfer of Polyunsaturated Fatty Acids From Streams to Riparian Spiders via Emergent Insects

Cited by 17 publications

References 76 publications

Use of Fatty Acids From Aquatic Prey Varies With Foraging Strategy

Use of Fatty Acids From Aquatic Prey Varies With Foraging Strategy

Trophic transfer of polyunsaturated fatty acids across the aquatic–terrestrial interface: An experimental tritrophic food chain approach

Interactions between temperature and predation impact insect emergence in alpine lakes

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