Dietary mixing in three generalist herbivores: nutrient complementation or toxin dilution?

Hägele, Bernd F.; Rowell‐Rahier, Martine

doi:10.1007/s004420050815

Cited by 109 publications

(106 citation statements)

References 52 publications

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“…Toxin dilution mechanisms may be a consequence of increasing excretion rates, enzymatic activity, and/or interference with other compounds. In such studies, estimates of fitness are often performed by measuring reduction in growth at juvenile stages (Pennings et al 1993, Bernays et al 1994, Hagele & Rowell-Rahier 1999. Although reduction in growth is assumed to have negative consequences on fitness, considered here as maintenance physiology, we showed that the effects of toxins on maintenance physiology can be different to those on reproductive physiology (a better estimate of fitness).…”

Section: Discussionmentioning

confidence: 78%

“…Feeding strategies to nullify the effects of toxic compounds have often been examined in invertebrates within the framework of the toxin-dilution and the non-additive hypotheses (Pennings et al 1993, Bernays et al 1994, Hagele & Rowell-Rahier 1999. Toxin dilution mechanisms may be a consequence of increasing excretion rates, enzymatic activity, and/or interference with other compounds.…”

Section: Discussionmentioning

confidence: 99%

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Feeding strategies of the copepod Acartia clausi on single and mixed diets of toxic and non-toxic strains of the dinoflagellate Alexandrium minutum

Barreiro¹,

Guisande²,

Frangópulos³

et al. 2006

Mar. Ecol. Prog. Ser.

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The role of mesozooplankton grazers in the development of monospecific algal blooms has often been examined in a scenario in which grazers, depending on their abilities of recognition, select against toxic species and increase grazing pressure on non-toxic species. Here, we present a different ecological scenario in which grazers may select between different strains (toxic and nontoxic) of the same species, which may coexist in similar densities in natural environments prior to bloom initiation. The calanoid copepod Acartia clausi was fed with single and mixed diets of 2 strains of the dinoflagellate Alexandrium minutum, a producer of paralytic shellfish poisoning (PSP) toxins. One strain produced high, and the other low, quantities of PSP toxins. We examined feeding strategies and estimated copepod responses based on their food selection abilities, toxic effects on maintenance physiology and fitness, and benefits produced by a toxin-dilution strategy in a mixed diet. Copepods were found to feed selectively on A. minutum strains. Diet composition had a strong effect on parameters such as food ingestion, mortality, egg hatching, and egg production. The effect on copepod mortality and egg production was greatly reduced when a mixed diet (toxic + non-toxic) was provided to the copepods. However, the negative effects on egg hatching were dose-dependent, and this parameter was not recovered by toxin-dilution mechanisms. We conclude that copepods did not effectively reject the toxic strain and that the effect of A. minutum on mortality and egg production, but not on egg hatching, is reduced by dilution mechanisms. Therefore, we suggest that feeding pressure by grazers does not appear to be an important mechanism that favors toxic over non-toxic strains prior to bloom initiation.

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Section: Discussionmentioning

confidence: 78%

Section: Discussionmentioning

confidence: 99%

Feeding strategies of the copepod Acartia clausi on single and mixed diets of toxic and non-toxic strains of the dinoflagellate Alexandrium minutum

Barreiro¹,

Guisande²,

Frangópulos³

et al. 2006

Mar. Ecol. Prog. Ser.

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“…Because of designs that incorporated both toxic and nontoxic species, the majority of studies included in our data set may not be the fairest test of the toxindilution hypothesis. Only two studies included all defended prey (Steinberg andvan Altena 1992, Ha¨gele andRowell-Rahier 1999), but the effect of diet mixing was still negative relative to the best single-species diet in these experiments. The strong and pervasive negative effects of diversity in experiments with defended prey presumably explain why prey defense was included in seven of the supported mixed models (Table 2).…”

Section: Discussionmentioning

confidence: 97%

Physiological effects of diet mixing on consumer fitness: a meta‐analysis

Lefcheck

Whalen

Davenport

et al. 2013

Ecology

136

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Abstract. The degree of dietary generalism among consumers has important consequences for population, community, and ecosystem processes, yet the effects on consumer fitness of mixing food types have not been examined comprehensively. We conducted a meta-analysis of 161 peer-reviewed studies reporting 493 experimental manipulations of prey diversity to test whether diet mixing enhances consumer fitness based on the intrinsic nutritional quality of foods and consumer physiology. Averaged across studies, mixed diets conferred significantly higher fitness than the average of single-species diets, but not the best single prey species. More than half of individual experiments, however, showed maximal growth and reproduction on mixed diets, consistent with the predicted benefits of a balanced diet. Mixed diets including chemically defended prey were no better than the average prey type, opposing the prediction that a diverse diet dilutes toxins. Finally, mixed-model analysis showed that the effect of diet mixing was stronger for herbivores than for higher trophic levels. The generally weak evidence for the nutritional benefits of diet mixing in these primarily laboratory experiments suggests that diet generalism is not strongly favored by the inherent physiological benefits of mixing food types, but is more likely driven by ecological and environmental influences on consumer foraging.

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“…Several insect species profit from mixed diets, suggesting that ovipositing in mixed host patches would be advantageous to them (e.g. Singer 1972, Barbosa et al 1986, Hägele and Rowell-Rahier 1999review in Waldbauer and Friedman 1991).…”

Section: Discussionmentioning

confidence: 99%

Spatial proximity between two host plant species influences oviposition and larval distribution in a leaf beetle

Ballabeni¹,

Conconi²,

Gateff³

et al. 2001

Oikos

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Everything else being equal, insect herbivores can be expected to oviposit on host plants that provide the qualitatively and quantitatively best food for larvae. However, the selection of a plant for oviposition may be influenced by such ecological factors as natural enemies, host distribution, host patch size or host patch density. We performed a field study to test whether spatial proximity between two host plant species influences the oviposition patterns and larval distribution of the alpine leaf beetle Oreina elongata. In the population studied, O. elongata oviposits and feeds on two host plants, that belong to the same family (Asteraceae): Adenostyles alliariae and Cirsium spinosissimum. The first species contains pyrrolizidine alkaloids that are sequestered by the beetle as a chemical defence, whereas the second plant does not contain any alkaloids but has hairy and spiny leaves that might give some mechanical protection to beetle larvae. During two consecutive summers, we quantified oviposition and larval distribution on randomly chosen C. spinosissimum that grew spatially isolated from A. alliariae, on C. spinosissimum that grew in leaf contact with A. alliariae and on A. alliariae that grew in leaf contact with C. spinosissimum (isolated A. alliariae was not considered, because it is rare in the study population). In both years, more eggs were laid on C. spinosissimum than on A. alliariae and more on those C. spinosissimum that were growing close to A. alliariae than on those growing isolated. Large numbers of larvae moved from C. spinosissimum to A. alliariae during the season. Patch size did not influence egg and larval numbers. Eggs survived better on C. spinosissimum than on A. alliariae in the field. The data suggest that C. spinosissimum may provide eggs with better protection against stormy weather. In a separate study of the same population, we found that larval performance was better on A. alliariae than on C. spinosissimum. Our present data suggest that O. elongata preferentially oviposits on plants of the species that maximizes egg survival and that grow in close proximity to plants of the species that provides better food and chemical defence.

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Dietary mixing in three generalist herbivores: nutrient complementation or toxin dilution?

Cited by 109 publications

References 52 publications

Feeding strategies of the copepod Acartia clausi on single and mixed diets of toxic and non-toxic strains of the dinoflagellate Alexandrium minutum

Feeding strategies of the copepod Acartia clausi on single and mixed diets of toxic and non-toxic strains of the dinoflagellate Alexandrium minutum

Physiological effects of diet mixing on consumer fitness: a meta‐analysis

Spatial proximity between two host plant species influences oviposition and larval distribution in a leaf beetle

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