Density‐ and trait‐mediated effects of a parasite and a predator in a tri‐trophic food web

Banerji, Aabir; Duncan, Alison B.; Griffin, Joanne S.; Humphries, Stuart; Petchey, Owen L.; Kaltz, Oliver

doi:10.1111/1365-2656.12317

Cited by 33 publications

(30 citation statements)

References 53 publications

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“…Indeed, recent experiments revealing cascading effects across trophic scales (e.g. parasites reducing availability of prey for predators; Banerji et al 2015) may represent a crucial frontier in functional ecology in which interactions or temporal synergies among resources, parasites and predators can be dissected across food webs. We keenly await more such work.…”

Section: Discussionmentioning

confidence: 99%

Bottom‐up regulation of malaria population dynamics in mice co‐infected with lung‐migratory nematodes

Griffiths¹,

Fairlie‐Clarke

Allen

et al. 2015

Ecology Letters

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When and how populations are regulated by bottom up vs. top down processes, and how those processes are affected by co‐occurring species, are poorly characterised across much of ecology. We are especially interested in the community ecology of parasites that must share a host. Here, we quantify how resources and immunity affect parasite propagation in experiments in near‐replicate ‘mesocosms’’ – i.e. mice infected with malaria (Plasmodium chabaudi) and nematodes (Nippostrongylus brasiliensis). Nematodes suppressed immune responses against malaria, and yet malaria populations were smaller in co‐infected hosts. Further analyses of within‐host epidemiology revealed that nematode co‐infection altered malaria propagation by suppressing target cell availability. This is the first demonstration that bottom‐up resource regulation may have earlier and stronger effects than top‐down immune mechanisms on within‐host community dynamics. Our findings demonstrate the potential power of experimental ecology to disentangle mechanisms of population regulation in complex communities.

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Section: Discussionmentioning

confidence: 99%

Bottom‐up regulation of malaria population dynamics in mice co‐infected with lung‐migratory nematodes

Griffiths¹,

Fairlie‐Clarke

Allen

et al. 2015

Ecology Letters

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“…Sloppy Didinium predators may increase infectious free living bacteria, when attacking infected Paramecium prey (Banerji et al 2015). Sloppy butterflyfish attack infected coral and enhance water-borne transmission of black-band disease (Aeby and Santavy 2006).…”

Section: Sloppy Predationmentioning

confidence: 99%

Habitat, predators, and hosts regulate disease in Daphnia through direct and indirect pathways

Strauss

Shocket

Civitello

et al. 2016

Ecological Monographs

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Community ecology can link habitat to disease via interactions among habitat, focal hosts, other hosts, their parasites, and predators. However, complicated food web interactions (i.e., trophic interactions among predators and their impacts on host density and diversity) often obscure the important pathways regulating disease. Here, we disentangle community drivers in a case study of planktonic disease, using a two-step approach. In step one, we tested univariate field patterns linking community interactions directly to two disease metrics. Density of focal hosts (Daphnia dentifera) was related to density but not prevalence of fungal (Metschnikowia bicuspidata) infections. Both disease metrics appeared to be driven by selective predators that cull infected hosts (fish, e.g., Lepomis macrochirus), sloppy predators that spread parasites while feeding (midges, Chaoborus punctipennis), and spore predators that reduce contact between focal hosts and parasites (other zooplankton, especially small-bodied Ceriodaphnia sp.). Host diversity also negatively correlated with disease, suggesting a dilution effect. However, several of these univariate patterns were initially misleading, due to confounding ecological links among habitat, predators, host density, and host diversity. In step two, path models uncovered and explained these misleading patterns, and grounded them in habitat structure (refuge size). First, rather than directly reducing infection prevalence, fish predation drove disease indirectly through changes in density of midges and frequency of small spore predators (which became more frequent in lakes with small refuges). Second, small spore predators drove the two disease metrics through fundamentally different pathways: they directly reduced infection prevalence, but indirectly reduced density of infected hosts by lowering density of focal hosts (likely via competition). Third, the univariate diversity-disease pattern (signaling a dilution effect) merely reflected the confounding direct effects of these small spore predators. Diversity per se had no effect on disease, after accounting for the links between small spore predators, diversity, and infection prevalence. In turn, these small spore predators were regulated by both size-selective fish predation and refuge size. Thus, path models not only explain each of these surprising results, but also trace their origins back to habitat structure.

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“…These intracellular bacteria are highly infectious nuclear symbionts with unique morphology and life cycle, and they have been considered to be a very promising model organism for investigations of symbiotic associations between eu- and prokaryotes [15]. Indeed, in the last years, several studies have been performed to facilitate their use as model organisms [16–19], and they have been extensively used in evolutionary ecology studies [20–22]. Up to now, the genus Holospora comprises ten species [13, 23], which have been described morphologically, but only for several of them molecular characterization is available [23–27].…”

Section: Introductionmentioning

confidence: 99%

Rare Freshwater Ciliate Paramecium chlorelligerum Kahl, 1935 and Its Macronuclear Symbiotic Bacterium “Candidatus Holospora parva”

et al. 2016

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Ciliated protists often form symbioses with many diverse microorganisms. In particular, symbiotic associations between ciliates and green algae, as well as between ciliates and intracellular bacteria, are rather wide-spread in nature. In this study, we describe the complex symbiotic system between a very rare ciliate, Paramecium chlorelligerum, unicellular algae inhabiting its cytoplasm, and novel bacteria colonizing the host macronucleus. Paramecium chlorelligerum, previously found only twice in Germany, was retrieved from a novel location in vicinity of St. Petersburg in Russia. Species identification was based on both classical morphological methods and analysis of the small subunit rDNA. Numerous algae occupying the cytoplasm of this ciliate were identified with ultrastructural and molecular methods as representatives of the Meyerella genus, which before was not considered among symbiotic algae. In the same locality at least fifteen other species of “green” ciliates were found, thus it is indeed a biodiversity hot-spot for such protists. A novel species of bacterial symbionts living in the macronucleus of Paramecium chlorelligerum cells was morphologically and ultrastructurally investigated in detail with the description of its life cycle and infection capabilities. The new endosymbiont was molecularly characterized following the full-cycle rRNA approach. Furthermore, phylogenetic analysis confirmed that the novel bacterium is a member of Holospora genus branching basally but sharing all characteristics of the genus except inducing connecting piece formation during the infected host nucleus division. We propose the name “Candidatus Holospora parva” for this newly described species. The described complex system raises new questions on how these microorganisms evolve and interact in symbiosis.

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Density‐ and trait‐mediated effects of a parasite and a predator in a tri‐trophic food web

Cited by 33 publications

References 53 publications

Bottom‐up regulation of malaria population dynamics in mice co‐infected with lung‐migratory nematodes

Bottom‐up regulation of malaria population dynamics in mice co‐infected with lung‐migratory nematodes

Habitat, predators, and hosts regulate disease in Daphnia through direct and indirect pathways

Rare Freshwater Ciliate Paramecium chlorelligerum Kahl, 1935 and Its Macronuclear Symbiotic Bacterium “Candidatus Holospora parva”

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