Abstract
Intra- and interspecific interactions can be broken down into facilitative and competitive components. The net interaction between two organisms is simply the sum of these counteracting elements. Disentangling the positive and negative components of species interactions is a critical step in advancing our understanding of how the interaction between organisms shift along physical and biotic gradients. We performed a manipulative field experiment to quantify the positive and negative components of the interactions between a perennial forb, Aster tenuifolius , and three dominant, matrix-forming grasses and rushes in a New England salt marsh. Specifically, we asked whether positive and negative interaction components: (1) are unique or redundant across three matrix-forming species (two grasses; Distichlis spicata and Spartina patens , and one rush; Juncus gerardi ), and (2) change across Aster life stages (seedling, juvenile, and adult). For adult Aster the strength of the facilitative component of the matrix-forb interaction was stronger than the competitive component for two of the three matrix species, leading to net positive interactions. There was no statistically significant variation among matrix species in their net or component effects. We found little difference in the effects of J. gerardi on Aster at later life-history stages; interaction component strengths did not differ between juveniles and adults. However, mortality of seedlings in neighbor removal plots was 100%, indicating a particularly strong and critical facilitative effect of matrix species on this forb during the earliest life stages. Overall, our results indicate that matrix forming grasses and rushes have important, yet largely redundant, positive net effects on Aster performance across its life cycle. Studies that untangle various components of interactions and their contingencies are critical to both expanding our basic understanding of community organization, and predicting how natural communities and their component parts will respond to environmental change.
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Claims 5
Claim · model-written summary
For adult Aster, facilitation exceeded competition for two of three matrix species, yielding net positive interactions.
- Taxon
- Aster tenuifolius
Symphyotrichum tenuifoliume1 - Organ / stage
- adult Astere0
- Outcome
- net positive interactionse0
- Qualifier
- two of the three matrix speciese0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“For adult Aster the strength of the facilitative component of the matrix-forb interaction was stronger than the competitive component for two of the three matrix species, leading to net positive interactions.”
e1“a perennial forb, Aster tenuifolius”
Claim · model-written summary
Net and component effects did not vary significantly among matrix species.
- Taxon
- Aster tenuifoliusSymphyotrichum tenuifoliume1
- Outcome
- net or component effectse0
- Direction
- no statistically significant variatione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“There was no statistically significant variation among matrix species in their net or component effects.”
e1“a perennial forb, Aster tenuifolius”
Claim · model-written summary
Juncus gerardi interaction component strengths did not differ between juvenile and adult Aster.
- Taxon
- Aster tenuifoliusSymphyotrichum tenuifoliume1
- Organ / stage
- juveniles and adultse0
- Interactor
- J. gerardi
Juncus gerardiie0other - Outcome
- interaction component strengthse0
- Direction
- did not differe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“We found little difference in the effects of J. gerardi on Aster at later life-history stages; interaction component strengths did not differ between juveniles and adults.”
e1“a perennial forb, Aster tenuifolius”
Claim · model-written summary
Seedling mortality reached 100% when neighbors were removed.
- Taxon
- Aster tenuifoliusSymphyotrichum tenuifoliume1
- Organ / stage
- seedlingse0
- Treatment
- neighbor removale0
- Outcome
- mortality of seedlingse0
- Value
- 100%e0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“mortality of seedlings in neighbor removal plots was 100%”
e1“a perennial forb, Aster tenuifolius”
Claim · model-written summary
Matrix grasses and rushes had largely redundant positive net effects on Aster performance across its life cycle.
- Taxon
- Aster tenuifoliusSymphyotrichum tenuifoliume1
- Interactor
- grasses and rushese0other
- Outcome
- positive net effects on Aster performancee0
- Direction
- positivee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“matrix forming grasses and rushes have important, yet largely redundant, positive net effects on Aster performance across its life cycle”
e1“a perennial forb, Aster tenuifolius”