Abstract
Abstract 1. Variables affecting species at the ends of trophic chains may modify the success of members with which they do not directly interact. The majority of such examples involve three trophic levels, but hyperparasitoids provide an excellent opportunity to examine four‐level relationships. 2. The gregarious hyperparasitoid Aprostocetus sp. (Hymenoptera: Eulophidae) commonly attacks the primary parasitoid Alabagrus texanus (Hymenoptera: Braconidae), by far the commonest parasitoid of the moth Herpetogramma theseusalis (Lepidoptera: Crambidae). 3. Larvae of this moth feed on ferns of two families, sensitive fern Onoclea sensibilis (Dryopteridaceae) and marsh fern Thelypteris palustris (Thelypteridaceae), in the study area, an old field in Maine, U.S.A. 4. I test the hypotheses that the ferns indirectly affect the reproductive success of the hyperparasitoids and that the ferns produce similar effects at intermediate links. 5. The moths experienced similar success on the two ferns, and the primary parasitoid performed similarly on moths reared from both ferns. The hyperparasitoid parasitized similar proportions of the primary parasitoid from moths that fed on sensitive fern and marsh fern. 6. However, hyperparasitoid broods on primary parasitoids from moths feeding on marsh fern contained approximately one‐third more offspring, whose individuals were significantly larger than those from sensitive fern, even though their hosts’ sizes did not differ significantly. 7. An indirect effect, related to the primary producers, thus strongly affected Trophic Level 4 in the absence of a significant effect at intermediate levels. To the best of my knowledge, this relationship has not been previously reported in a multi‐year or field‐based study of a natural system.
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Claims 7
Claim · model-written summary
Moths experienced similar success on sensitive fern and marsh fern.
- Taxon
- fernsPolypodiopsidae1
- Interactor
- mothse1herbivore
- Outcome
- successe1
- Direction
- similare1
Verbatim
e1“The moths experienced similar success on the two ferns”
Claim · model-written summary
The primary parasitoid performed similarly on moths reared from sensitive fern and marsh fern.
- Taxon
- fernsPolypodiopsidae2
- Interactor
- primary parasitoide2parasite
- Outcome
- performede2
- Direction
- similarlye2
Verbatim
e2“The primary parasitoid performed similarly on moths reared from both ferns”
Claim · model-written summary
The hyperparasitoid parasitized similar proportions of primary parasitoids from moths on sensitive fern and marsh fern.
- Taxon
- fernsPolypodiopsidae0
- Interactor
- hyperparasitoide3parasite
- Outcome
- proportionse3
- Direction
- similare3
Verbatim
e0“Larvae of this moth feed on ferns of two families, sensitive fern Onoclea sensibilis (Dryopteridaceae) and marsh fern Thelypteris palustris (Thelypteridaceae)”
e3“The hyperparasitoid parasitized similar proportions of the primary parasitoid from moths that fed on sensitive fern and marsh fern”
Claim · model-written summary
Hyperparasitoid broods on primary parasitoids from moths on marsh fern contained approximately one-third more offspring than on sensitive fern.
Verbatim
e0“Larvae of this moth feed on ferns of two families, sensitive fern Onoclea sensibilis (Dryopteridaceae) and marsh fern Thelypteris palustris (Thelypteridaceae)”
e4“hyperparasitoid broods on primary parasitoids from moths feeding on marsh fern contained approximately one‐third more offspring”
e5“whose individuals were significantly larger than those from sensitive fern”
Claim · model-written summary
Individuals of hyperparasitoid broods from marsh fern were significantly larger than those from sensitive fern.
- Taxon
- fernsPolypodiopsidae0
- Outcome
- individualse5
- Direction
- largere5
- Comparator
- sensitive ferne5
Verbatim
e0“Larvae of this moth feed on ferns of two families, sensitive fern Onoclea sensibilis (Dryopteridaceae) and marsh fern Thelypteris palustris (Thelypteridaceae)”
e5“whose individuals were significantly larger than those from sensitive fern”
Claim · model-written summary
Host sizes did not differ significantly between the two ferns.
- Taxon
- fernsPolypodiopsidae0
- Outcome
- sizese6
- Direction
- did not differe6
Verbatim
e0“Larvae of this moth feed on ferns of two families, sensitive fern Onoclea sensibilis (Dryopteridaceae) and marsh fern Thelypteris palustris (Thelypteridaceae)”
e6“even though their hosts’ sizes did not differ significantly”
Claim · model-written summary
An indirect effect related to the primary producers strongly affected Trophic Level 4 in the absence of a significant effect at intermediate levels.
- Taxon
- fernsPolypodiopsidae0
- Outcome
- Trophic Level 4e7
- Qualifier
- An indirect effect, related to the primary producerse7
Verbatim
e0“Larvae of this moth feed on ferns of two families, sensitive fern Onoclea sensibilis (Dryopteridaceae) and marsh fern Thelypteris palustris (Thelypteridaceae)”
e7“An indirect effect, related to the primary producers, thus strongly affected Trophic Level 4 in the absence of a significant effect at intermediate levels”