Macroinvertebrate size–mass relationships: how specific should they be?

Parasites can alter communities by reducing densities of keystone hosts, but few studies have examined how trait-mediated indirect effects of parasites can alter ecological communities. We test how trematode parasites (Microphallus spp.) that affect invasive crayfish (Orconectes rusticus) behavior alter how crayfish impact lake littoral communities. O. rusticus drive community composition in north temperate lakes, and predatory fish can reduce crayfish activity and feeding. In laboratory studies, Microphallus parasites also alter O. rusticus behavior: infected O. rusticus eat fewer macroinvertebrates and are bolder near predatory fish than uninfected individuals. We used a 2 x 2 factorial experiment to test how predatory fish and parasites affect O. rusticus impacts in large mesocosms over 4 weeks. We predicted (1) that when predators were absent, infected crayfish would have lower impacts than uninfected crayfish on macrophytes and macroinvertebrates (as well as reduced growth and higher mortality). However, (2) when predators were present but unable to consume crayfish, infected crayfish would have greater impacts (as well as greater growth and lower mortality) than uninfected crayfish because of increased boldness. Because of its effect on crayfish feeding behavior, we also predicted (3) that infection would alter macrophyte and macroinvertebrate community composition. In contrast to our first hypothesis, we found that infected and uninfected crayfish had similar impacts on lower trophic levels when predators were absent. Across all treatments, infected crayfish were more likely to be outside shelters and had greater growth than uninfected crayfish, suggesting that the reduced feeding observed in short-term experiments does not occur over longer timescales. However, in support of the second hypothesis, when predatory fish were present, infected crayfish ate more macroinvertebrates than did uninfected crayfish, likely due to increased boldness. We also observed a trend for greater macrophyte consumption associated with infection and a trend indicating infection might alter macroinvertebrate community composition. Our results suggest that parasites can alter aquatic communities in mesocosms merely by modifying host behavior.

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“…, Methot et al. ). We dried (60°C for 48 h) and weighed taxa for which there was no published equation.…”

Section: Methodsmentioning

confidence: 99%

Parasites alter freshwater communities in mesocosms by modifying invasive crayfish behavior

Reisinger

Lodge

2016

Ecology

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“…Aquatic invertebrates were identified to family or genus and counted. Dry weight of aquatic invertebrates in the diet were estimated with equations from Benke et al (1999) andM ethot et al (2012). Mean morphological measurements of aquatic invertebrates (body length, shell width) were calculated from subsamples of 20 individuals per taxon randomly selected from brown trout diets and used to estimate dry weight.…”

Section: Diet Analysismentioning

confidence: 99%

Winter feeding, growth and condition of brown troutSalmo truttain a groundwater-dominated stream

French

Vondracek

Ferrington

et al. 2013

Journal of Freshwater Ecology

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Winter can be a stressful period for stream-dwelling salmonid populations, often resulting in reduced growth and survival. Stream water temperatures have been identified as a primary mechanism driving reductions in fitness during winter. However, groundwater inputs can moderate water temperature and may reduce winter severity. Additionally, seasonal reductions in prey availability may contribute to decreased growth and survival, although few studies have examined food webs supporting salmonids under winter conditions. This study employed diet, stable isotope, and markrecapture techniques to examine winter (November through March) feeding, growth, and condition of brown trout Salmo trutta in a groundwater-dominated stream (Badger Creek, Minnesota, USA). Growth was greater for fish 150 mm (mean ¼ 4.1 mg g À1 day À1 ) than for those 151-276 mm (mean ¼ 1.0 mg g À1 day À1) during the winter season. Overall condition from early winter to late winter did not vary for fish 150 mm (mean relative weight (Wr) ¼ 89.5) and increased for those 151-276 mm (mean Wr ¼ 85.8 early and 89.4 late). Although composition varied both temporally and by individual, brown trout diets were dominated by aquatic invertebrates, primarily Amphipods, Dipterans, and Trichopterans. Stable isotope analysis supported the observations of the dominant prey taxa in stomach contents and indicated the winter food web was supported by a combination of allochthonous inputs and aquatic macrophytes. Brown trout in Badger Creek likely benefited from the thermal regime and increased prey abundance present in this groundwater-dominated stream during winter.

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“…Biomass estimated from head widths using size–mass relationships from Methot et al. . White shaded bars denote damselfly abundance in the absence of fish, gray shaded bars denote damselfly abundance in the presence of fish, and black bars denote chironomid abundance in the respective fish treatment.…”

Section: Resultsmentioning

confidence: 99%

“…We estimated biomass of larval damselflies and chironomidae from benthic samples by measuring head widths and using published size–mass relationships (Methot et al. ).…”

Section: Methodsmentioning

confidence: 99%

Fish presence and inter‐patch connectivity interactively alter the size of emergent insects in experimental enclosures

Pitcher

Soluk

2018

Ecosphere

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Citation: Pitcher, K. A., and D. A. Soluk. 2018. Fish presence and inter-patch connectivity interactively alter the size of emergent insects in experimental enclosures. Ecosphere 9(3):e02118. 10.1002/ecs2.2118Abstract. Structural habitat complexity (SHC) and functional habitat connectivity (FHC) are the basic components that make up the physical architecture of an ecosystem, and can have substantial impacts on predator-prey interactions. These structural components influence animal behaviors such as inter-patch movement, foraging, and competition, and can impact community structure/dynamics in terrestrial and aquatic ecosystems. The effects of SHC and FHC on predator-prey dynamics within an ecosystem may also have important cascading effects on neighboring ecosystems by altering the movement of individuals across ecosystem boundaries. For example, when aquatic insects emerge as adults, they enter terrestrial ecosystems where they become an important food resource for terrestrial predators. Using a multiple patch, predator enclosure design in ponds, we tested whether altering intra-patch plant stem densities (SHC) and inter-patch distances (FHC) would influence the impact a predatory fish has on the biomass, quality, and trophic composition of emergent insects. As expected, fish significantly reduced emergent insect biomass (33% AE 7.6, mean AE SE). Intra-patch stem densities (SHC) did not significantly alter fish effects; however, inter-patch distance (FHC) did significantly alter the impact of fish on the size of some emergent insects. Damselflies that emerged in treatments with fish present and shorter inter-patch distances were significantly larger, 4.1 AE 0.1 mg/m 2 compared to 3.3 mg/m 2 AE 0.1 in the long/fish treatments.In fish treatments, this effect on damselfly size resulted in greater reductions in total emergent insect biomass in long inter-patch distance treatments (47.3% AE 6.9) compared to short inter-patch distance treatments (20.5% AE 12.4). Our results suggest that physical components of a habitat, such as inter-patch distances, have important impacts on predator-prey dynamics within habitats. These altered predatorprey dynamics can then have cascading effects on adjacent habitats by influencing the abundance, trophic composition, and quality of exported trophic subsidies.

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Macroinvertebrate size–mass relationships: how specific should they be?

Cited by 51 publications

References 45 publications

Parasites alter freshwater communities in mesocosms by modifying invasive crayfish behavior

Parasites alter freshwater communities in mesocosms by modifying invasive crayfish behavior

Winter feeding, growth and condition of brown troutSalmo truttain a groundwater-dominated stream

Fish presence and inter‐patch connectivity interactively alter the size of emergent insects in experimental enclosures

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