Abstract
Difficulties quantifying pathogen load and mutualist abundance limit our ability to connect disease dynamics to host community ecology. For example, specific predictions about how differential pathogen load is hypothesised to drive host competitive outcomes are rarely tested. Additionally, although infection is known to affect mutualists, we rarely measure the magnitude of pathogen effects on mutualist abundance across host competitive contexts. We tested for both mechanisms in a plant-rhizobia-nematode system. We paired the legume Medicago lupulina with intraspecific and interspecific plant competitors, with and without a generalist nematode parasite Meloidogyne sp. Relative change in plant biomass was used to determine how nematode inoculation affected plant competitive outcomes. We counted nematode galls to test for direct effects of parasitism on plant competition and rhizobia nodules to test for indirect effects of nematode presence on rhizobium abundance. Parasites were destabilising despite similar nematode load across competition treatments. During interspecific compared with intraspecific competition, nematode inoculation decreased nodulation on M. lupulina, increased nodulation on Trifolium repens and had no effect on nodulation on Chamaecrista fasciculata. We found no support for hypothesised direct effects of nematode load on competitive outcomes and strong but idiosyncratic indirect effects of nematode inoculation on rhizobium abundance.
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Claims 7
Claim · model-written summary
Nematode parasites destabilised plant competition.
- Taxon
- Medicago lupulina
Medicago lupulinae1 - Interactor
- Meloidogyne sp.
Meloidogynee2 - Outcome
- plant competitione3
- Direction
- destabilisinge0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.

_penetrates_a_tomato_root_-_USDA-ARS.jpg?width=500)
Verbatim
e0“Parasites were destabilising despite similar nematode load across competition treatments”
e1“Medicago lupulina”
e3“plant competition”
e2“Meloidogyne sp.”
Claim · model-written summary
Nematode load was similar across competition treatments.
- Taxon
- Medicago lupulina
Medicago lupulinae1 - Interactor
- Meloidogyne sp.
Meloidogynee2 - Outcome
- nematode loade0
- Direction
- similare0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.

_penetrates_a_tomato_root_-_USDA-ARS.jpg?width=500)
Verbatim
e0“similar nematode load across competition treatments”
e1“Medicago lupulina”
e2“Meloidogyne sp.”
Claim · model-written summary
Under interspecific versus intraspecific competition, nematode inoculation decreased Medicago lupulina nodulation.
- Taxon
- M. lupulina
Medicago lupulinae0 - Treatment
- nematode inoculatione0
- Outcome
- nodulatione0
- Direction
- decreasede0
- Qualifier
- interspecifice0
- Comparator
- intraspecific competitione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.

Verbatim
e0“During interspecific compared with intraspecific competition, nematode inoculation decreased nodulation on M. lupulina”
Claim · model-written summary
Under interspecific versus intraspecific competition, nematode inoculation increased Trifolium repens nodulation.
- Taxon
- Trifolium repens
Trifolium repense0 - Treatment
- nematode inoculatione0
- Outcome
- nodulatione0
- Direction
- increasede0
- Qualifier
- interspecifice0
- Comparator
- intraspecific competitione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.

Verbatim
e0“During interspecific compared with intraspecific competition, nematode inoculation decreased nodulation on M. lupulina, increased nodulation on Trifolium repens”
Claim · model-written summary
Under interspecific versus intraspecific competition, nematode inoculation had no effect on Chamaecrista fasciculata nodulation.
- Taxon
- Chamaecrista fasciculata
Chamaecrista fasciculatae0 - Treatment
- nematode inoculatione0
- Outcome
- nodulatione0
- Direction
- no effecte0
- Qualifier
- interspecifice0
- Comparator
- intraspecific competitione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.

Verbatim
e0“During interspecific compared with intraspecific competition, nematode inoculation decreased nodulation on M. lupulina, increased nodulation on Trifolium repens and had no effect on nodulation on Chamaecrista fasciculata”
Claim · model-written summary
The hypothesised direct effect of nematode load on competition was unsupported.
- Taxon
- Medicago lupulina
Medicago lupulinae1 - Interactor
- Meloidogyne sp.
Meloidogynee2 - Outcome
- competitive outcomese0
- Direction
- no supporte0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.

_penetrates_a_tomato_root_-_USDA-ARS.jpg?width=500)
Verbatim
e0“We found no support for hypothesised direct effects of nematode load on competitive outcomes”
e1“Medicago lupulina”
e2“Meloidogyne sp.”
Claim · model-written summary
Nematode inoculation had strong but host dependent indirect effects on rhizobium abundance.
- Taxon
- Medicago lupulina
Medicago lupulinae1 - Treatment
- nematode inoculatione0
- Outcome
- rhizobium abundancee0
- Direction
- strong but idiosyncratice0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.

Verbatim
e0“strong but idiosyncratic indirect effects of nematode inoculation on rhizobium abundance”
e1“Medicago lupulina”
The same questions in other papers
inoculation · symbiosis · Medicago lupulinaPositive and negative results
3 in the opposite direction
- positive
- positive
- positive
inoculation · symbiosis · Trifolium repens (white clover)Positive and negative results
8 papers in the same direction as this paper · 1 in the opposite direction
- no effect
- positive
- positive
6 papers more in this group
See all 10 papers →Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.