Ecosystem engineering alters density‐dependent feedbacks in an aquatic insect population

Phillips, Joseph S.; McCormick, Amanda R.; Botsch, Jamieson C.; Ives, Anthony R.

doi:10.1002/ecy.3513

Cited by 4 publications

(9 citation statements)

References 28 publications

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“…In previous experiments, reducing per capita resource availability by increasing midge density resulted in fewer emerging T. gracilentus , higher mortality rates, and smaller larvae (Phillips et al 2021a, Wetzel et al 2021). Additionally, reductions in per capita algal growth rates via shading resulted in lower midge survival, growth, and emergence (Wetzel et al 2021, Phillips et al 2021b). Studies on other midge species that have manipulated food quantity have shown a similar response (Rasmussen 1985, Macchiusi and Baker 1992, Vos et al 2000, Péry et al 2002, Hooper et al 2003, Doi et al 2007); however, these studies generally used non‐growing food (e.g.…”

Section: Discussionmentioning

confidence: 99%

Aquatic insects balance growth with future supply of algal food resources

Botsch,

Book,

Phillips

et al. 2023

Oikos

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Many consumers depend on the contemporaneous growth of their food resources. For example, Tanytarsus gracilentus midges feed on algae, and because midge generation time is much longer than that of algae, individual midges benefit not just from the standing stock but also from the growth of algae during their lifespans. This implies that an intermediate consumption rate maximizes midge somatic growth: low consumption rates constrain midge growth because they do not fully utilize the available food, whereas high consumption rates suppress algal biomass growth and consequently limit future food availability. An experiment manipulating midge presence and initial algal abundance showed that midges can suppress algal growth, as measured by changes in algal gross primary production (GPP). We also found a positive relationship between GPP and midge growth. A consumer–resource model fit to the experimental data showed a hump‐shaped relationship between midge consumption rates and their somatic growth. In the model, predicted midge somatic growth rates were only positively associated with GPP when their consumption rate was below the value that optimized midge growth. Therefore, midges did not overexploit algae in the experiment. This work highlights the balance that consumers which depend on contemporaneous resource growth might have to strike between short‐term growth and future food availability, and the benefits for consumers when they ‘manage' their resources well.

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Section: Discussionmentioning

confidence: 99%

Aquatic insects balance growth with future supply of algal food resources

Botsch,

Book,

Phillips

et al. 2023

Oikos

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“…For example, low‐to‐moderate experimental densities of T. gracilentus larvae enhance benthic primary production by increasing substrate availability through their tube building (Phillips et al, 2019). However, the relationship between larval density and primary production is nonlinear and, at high larval densities, consumption of benthic algae may outweigh their substrate‐boosting effect (Phillips et al, 2021). Thus, it is likely that high T. gracilentus densities negatively affect primary production (Phillips et al, 2021), which is consistent with our results if δ 13 C is treated as a surrogate for benthic algal production.…”

Section: Discussionmentioning

confidence: 99%

“…However, the relationship between larval density and primary production is nonlinear and, at high larval densities, consumption of benthic algae may outweigh their substrate‐boosting effect (Phillips et al, 2021). Thus, it is likely that high T. gracilentus densities negatively affect primary production (Phillips et al, 2021), which is consistent with our results if δ 13 C is treated as a surrogate for benthic algal production. Moreover, in a paleoecology study at Mývatn, high concentrations of diatom pigments were associated with increased midge egg capsule abundance, and increased midge abundance was associated with declines in the diatom pigment (Einarsson et al, 2016), suggesting that midges reduce diatom biomass as their population grows.…”

Section: Discussionmentioning

confidence: 99%

Reconstructing midge consumer–resource dynamics using carbon stable isotope signatures of archived specimens

McCormick

Phillips

Botsch

et al. 2022

Ecology

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Population cycles can be caused by consumer-resource interactions. Confirming the role of consumer-resource interactions, however, can be challenging due to an absence of data for the resource candidate. For example, interactions between midge larvae and benthic algae likely govern the high-amplitude population fluctuations of Tanytarsus gracilentus in Lake Mývatn, Iceland, but there are no records of benthic resources concurrent with adult midge population counts. Here, we investigate consumer population dynamics using the carbon stable isotope signatures of archived T. gracilentus specimens collected from 1977 to 2015, under the assumption that midge δ 13 C values reflect those of resources they consumed as larvae. We used the time series for population abundance and δ 13 C to estimate interactions between midges and resources while accounting for measurement error and possible preservation effects on isotope values. Results were consistent with consumer-resource interactions: high δ 13 C values preceded peaks in the midge population, and δ 13 C values tended to decline after midges reached high abundance. One interpretation of this dynamic coupling is that midge isotope signatures reflect temporal variation in benthic algal δ 13 C values, which we expected to mirror primary production. Following from this explanation, high benthic production (enriched δ 13 C values) would contribute to increased midge abundance, and high midge abundance would result in declining benthic production (depleted δ 13 C values). An additional and related explanation is that midges deplete benthic algal abundance once they reach peak densities, causing midges to increase their relative reliance on other resources including detritus and associated microorganisms. Such a shift in resource use would be consistent with the subsequent decline in midge δ 13 C values. Our study adds evidence that midge-resource interactions drive T. gracilentus fluctuations and demonstrates a novel application of stable isotope time-series data to understand consumer population dynamics.

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“…We note that the light treatment microcosms were processed 1 day before the dark treatment ones, which could have resulted in inflated survival and depressed body size in the high light treatment; however, the effect of 1 day is likely modest relative to the full duration of the experiment. While phosphorous limitation of benthic algae has been demonstrated in many systems (Fairchild & Lowe, 1984; Fairchild et al ., 1985; Steinman et al ., 2016), it has not been observed as a limiting factor for benthic primary production in Mývatn (McCormick et al ., 2019; Phillips et al ., 2019), likely due to Mývatn's high phosphorous inputs and large pools in the sediment. These previous results suggest that phosphorous enrichment does not lead to elevated primary producer biomass in Mývatn, although it could lead to a reduction in C:P ratios.…”

Section: Discussionmentioning

confidence: 99%

“…The two light levels were achieved by covering half of the microcosms with two layers of 1 mm mosquito mesh (130 μmol‐photons m −2 s −1 ) and leaving the other half uncovered (230 μmol‐photons m −2 s −1 ). The darker treatment was close to mean benthic light levels in Mývatn (McCormick et al ., 2019), and both were within regularly experienced in situ benthic light levels (Phillips et al ., 2019). We based our concentrations for the nutrient treatments on previously measured interstitial concentrations of NH 4 (1000 μmol L −1 ) and PO 4 (65 μmol L −1 ) in Mývatn's sediment (Gíslason et al ., 2004).…”

Section: Methodsmentioning

confidence: 99%

Effects of light and nutrients on intraspecific competition among midges from a shallow eutrophic lake

Wetzel

McCormick

Phillips

et al. 2021

Ecological Entomology

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1. Intraspecific competition for food may affect the development, survival, and fecundity of organisms. However, environmental variation in abiotic conditions can influence resource quality and/or quantity, thereby modifying the strength of intraspecific competition.2. This study focuses on intraspecific competition among Tanytarsus gracilentus (Chironomidae: Diptera) larvae. In Lake Mývatn, Iceland, T. gracilentus undergoes large population fluctuations, and evidence suggests that these fluctuations are governed by consumer-resource interactions between the larvae and benthic diatoms. In two experiments, we studied (i) the effects of larval density on individual development and survival, and (ii) how light and nutrients (nitrogen and phosphorus) mediate the strength of intraspecific competition across a density gradient.3. Survival declined with increasing larval density in both experiments, although not significantly in the first experiment in which we manipulated only density. In the second experiment, enhancement of either light or phosphorus mitigated the negative effect of larval density on survival. In both experiments, density had a negative effect on individual development. In the first experiment, fewer larvae progressed to the final fourth instar at higher densities. In the second experiment, larvae were smaller in high density treatments, and this effect was most pronounced in the treatments without light or phosphorus supplementation.4. These results highlight the potential for environmental factors to influence the strength of density-dependent competition. Environmental variation that affects resource quantity or quality may influence the overall dynamics of our study organism and other populations whose dynamics are controlled by consumer-resource relationships.

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Ecosystem engineering alters density‐dependent feedbacks in an aquatic insect population

Cited by 4 publications

References 28 publications

Aquatic insects balance growth with future supply of algal food resources

Aquatic insects balance growth with future supply of algal food resources

Reconstructing midge consumer–resource dynamics using carbon stable isotope signatures of archived specimens

Effects of light and nutrients on intraspecific competition among midges from a shallow eutrophic lake

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