Abstract
Xanthium is represented in Europe by three species complexes: X. strumarium L., X. orientale L., and X. spinosum L. The former two complexes are similar, in both morphology and ecological requirements. Xanthium strumarium is native to the Old World, whereas X. orientale originates from America and was accidentally introduced into Europe about two centuries ago. Since then, it has colonized the whole continent, while the native congener has become increasingly rare.Over two years, we conducted competition experiments to assess the impact of the introduced X. orientale on the fitness of the native X. strumarium. Germination time, dry biomass, number of burs (pistillate flower heads) and bur biomass were measured as proxies of fitness. Xanthium strumarium was grown alone (control), together with conspecifics (intraspecific competition) or with X. orientale plants (interspecific competition). We also evaluated the allelopathic effect of X. orientale over X. strumarium, by watering Xanthium seedlings with exudate of X. orientale dry leaves.Growth and reproductive traits of X. strumarium were significantly lower in individuals growing in proximity of X. orientale compared to the control, whereas intraspecific competition has a lower but still significant effect. Xanthium orientale, although, germinates and grows faster than the Old-World congener, and under interspecific competition regime, X. strumarium produces significantly lower biomass, number of burs and bur biomass. Watering with exudates negatively influences the germination and the growth of the two species. We therefore believe that interspecific competition of the introduced congener may be one of the causes explaining the drastic decline of X. strumarium populations in Europe in the past century.
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Claims 5
Claim · model-written summary
Growth and reproductive traits of X. strumarium were significantly lower when growing in proximity of X. orientale than in the control.
- Taxon
- X. strumarium
Xanthium strumariume0 - Treatment
- growing in proximity of X. orientalee0
- Interactor
- X. orientale
Xanthium orientalee0other - Outcome
- Growth and reproductive traitse0
- Direction
- lowere0
- Comparator
- the controle0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Growth and reproductive traits of X. strumarium were significantly lower in individuals growing in proximity of X. orientale compared to the control”
Claim · model-written summary
Intraspecific competition also lowered growth and reproductive traits of X. strumarium relative to the control, but less than interspecific competition, and the effect remained significant.
- Taxon
- X. strumariumXanthium strumariume0
- Treatment
- intraspecific competitione1
- Outcome
- Growth and reproductive traitse0
- Direction
- lowere1
- Comparator
- the controle0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Growth and reproductive traits of X. strumarium were significantly lower in individuals growing in proximity of X. orientale compared to the control”
e1“intraspecific competition has a lower but still significant effect”
Claim · model-written summary
X. orientale germinates and grows faster than the Old-World congener X. strumarium.
- Taxon
- Xanthium orientaleXanthium orientalee0
- Outcome
- germinates and growse0
- Direction
- fastere0
- Comparator
- the Old-World congenere0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Xanthium orientale, although, germinates and grows faster than the Old-World congener”
Claim · model-written summary
Watering Xanthium seedlings with exudate of X. orientale dry leaves negatively influenced germination and growth of the two species.
- Treatment
- Watering with exudatese1
- Interactor
- X. orientaleXanthium orientalee0other
- Outcome
- germination and the growthe1
- Direction
- negatively influencese1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“watering Xanthium seedlings with exudate of X. orientale dry leaves”
e1“Watering with exudates negatively influences the germination and the growth of the two species”
Claim · model-written summary
The authors believe interspecific competition from introduced X. orientale may be one cause of the decline of X. strumarium populations in Europe.
- Taxon
- X. strumariumXanthium strumariume0
- Treatment
- interspecific competition of the introduced congenere0
- Outcome
- drastic decline of X. strumarium populationse0
- Setting
- Europee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“interspecific competition of the introduced congener may be one of the causes explaining the drastic decline of X. strumarium populations in Europe in the past century”
The same questions in other papers
competition · growth · Xanthium strumarium (cocklebur)Results agree
1 paper in the same direction as this paper
- negative
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.