The biology of Canadian weeds. 110. Tragopogon dubius Scop., Tragopogon pratensis L., and Tragopogon porrifolius L.

Clements, David R.; Upadhyaya, Mahesh K.; Bos, Shelley J.

doi:10.4141/p98-007

Cited by 24 publications

(23 citation statements)

References 45 publications

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“…For example, the biennial forb T. dubius is widespread within our system and across North America (Clements et al. ), but we found no significant impacts of this species. Interestingly, recent research suggests that the local abundance of this species is greatly suppressed by native generalist consumers (Pearson et al.…”

Section: Discussioncontrasting

confidence: 52%

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Quantifying “apparent” impact and distinguishing impact from invasiveness in multispecies plant invasions

Pearson

Ortega

Eren

et al. 2016

Ecological Applications

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The quantification of invader impacts remains a major hurdle to understanding and managing invasions. Here, we demonstrate a method for quantifying the community-level impact of multiple plant invaders by applying Parker et al.'s (1999) equation (impact = range x local abundance x per capita effect or per unit effect) using data from 620 survey plots from 31 grasslands across west-central Montana, USA. In testing for interactive effects of multiple invaders on native plant abundance (percent cover), we found no evidence for invasional meltdown or synergistic interactions for the 25 exotics tested. While much concern exists regarding impact thresholds, we also found little evidence for nonlinear relationships between invader abundance and impacts. These results suggest that management actions that reduce invader abundance should reduce invader impacts monotonically in this system. Eleven of 25 invaders had significant per unit impacts (negative local-scale relationships between invader and native cover). In decomposing the components of impact, we found that local invader abundance had a significant influence on the likelihood of impact, but range (number of plots occupied) did not. This analysis helped to differentiate measures of invasiveness (local abundance and range) from impact to distinguish high-impact invaders from invaders that exhibit negligible impacts, even when widespread. Distinguishing between high- and low-impact invaders should help refine trait-based prediction of problem species. Despite the unique information derived from evaluation of per unit effects of invaders, invasiveness 'scores based on range and local abundance produced similar rankings to impact scores that incorporated estimates of per unit effects. Hence, information on range and local abundance alone was sufficient to identify problematic plant invaders at the regional scale. In comparing empirical data on invader impacts to the state noxious weed list, we found that the noxious weed list captured 45% of the high impact invaders but missed 55% and assigned the lowest risk category to the highest-impact invader. While such subjective weed lists help to guide invasive species management, empirical data are needed to develop more comprehensive rankings of ecological impacts. Using weed lists to classify invaders for testing invasion theory is not well supported.

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Section: Discussioncontrasting

confidence: 52%

“…For example, T. dubius has a windborne seed that effectively disperses over great distances (Clements et al. ), presumably contributing to its invasion success, but this same seed is also highly palatable to rodents, a trait linked to its limited local abundance (Pearson et al. ).…”

Section: Discussionmentioning

confidence: 99%

Quantifying “apparent” impact and distinguishing impact from invasiveness in multispecies plant invasions

Pearson

Ortega

Eren

et al. 2016

Ecological Applications

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“…Invading plant species may not necessarily be a random sample from the total species pool. In our selection of native species from the Dutch flora, we choose species that themselves have become invaders in other regions of the world (Clements et al . 1999; Cody et al .…”

Section: Methodsmentioning

confidence: 99%

Reduced plant–soil feedback of plant species expanding their range as compared to natives

et al. 2007

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Summary 1.As a result of global warming, species may spread into previously cool regions. Species that disperse faster than their natural enemies may become released from top-down control. We investigated whether plants originating from southern Europe and recently established in north-western Europe experience less soil pathogen effects than native species. 2. We selected three plant species originating from southern Europe that have immigrated into the Netherlands and three similar native Dutch species. All six plant species were grown in sterilized soils with a soil inoculum collected from the rhizospheres of field populations. As a control we grew a series of all six plant species with a sterilized rhizosphere inoculum. 3. We harvested the plants, added the conditioned soil to sterilized soil and grew a second generation of all six plant species in order to test for each plant pair feedback effects from the conditioned soil communities to conspecifics and heterospecifics. 4. The effect of the soil community is dependent on plant species, and is dependent on soil fertility in only one of the three pairs. 5. Soil conditioning caused less biomass reduction to exotic plant species than to native species, suggesting that exotic immigrants are less exposed to soil pathogens than similar native plant species. 6. Our results suggest that plant species that expand their range as a result of climate change may become released from soil pathogenic activity. Whether the exotics are released from soil pathogens, or whether they experience enhanced benefit from mutualistic symbionts remains to be studied. We conclude that range expansion may result in enemy release patterns that are similar to artificially introduced invasive exotic plant species. 7. The escape from enemies through range shifts changes key biotic interactions and complicates predictions of future distribution and dominance.

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“…It usually occupies disturbed sites in slightly moist habitats, although once established, plants can withstand drought (Clements et al 1999). This species produces a rosette of long narrow grasslike leaves.…”

Section: The Speciesmentioning

confidence: 99%

“…Tragopogon porrifolius L. (Asteraceae), or common salsify, is a monocarpic perennial herb (Qi et al 1996;Clements et al 1999) native to Eurasia. It usually occupies disturbed sites in slightly moist habitats, although once established, plants can withstand drought (Clements et al 1999).…”

Section: The Speciesmentioning

confidence: 99%

Fruit size decline from the margin to the center of capitula is the result of resource competition and architectural constraints

Torices

Méndez

2010

Oecologia

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Plants produce repeated structures, such as leaves, flowers, and fruits, which differ in size and shape. One example of this is fruit size, which is commonly observed to decrease from proximal to distal positions within an inflorescence. The resource limitation hypothesis proposes that because proximal fruits usually develop first, they have temporal priority on access to resources over distal fruits. The non-mutually exclusive architectural effects hypothesis suggests that these position effects in fruit size may also be due to inherent architectural variation along infructescence axes. We separated out the effects of resource competition and inflorescence architecture by removing the outer or the inner flowers within capitula of Tragopogon porrifolius. We also studied if fruit position influenced germination and seedling performance in order to assess fitness consequences of position effects. Inner fruits were significantly heavier when outer flowers were removed. However, outer fruits did not significantly increase when inner flowers were removed, suggesting later fruits were limited by the development of early fruits. Our findings also suggest that architectural constraints restricted the size of inner fruits in comparison with outer ones. We found that both resource competition and inflorescence architecture affected the fruit size of T. porrifolius, even though this species does not have linear, indeterminate inflorescences. We advance the hypothesis that, when such effects on fitness occur, resource competition-mediated position effects could turn, in evolutionary time, into architectural position effects.

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The biology of Canadian weeds. 110. Tragopogon dubius Scop., Tragopogon pratensis L., and Tragopogon porrifolius L.

Cited by 24 publications

References 45 publications

Quantifying “apparent” impact and distinguishing impact from invasiveness in multispecies plant invasions

Quantifying “apparent” impact and distinguishing impact from invasiveness in multispecies plant invasions

Reduced plant–soil feedback of plant species expanding their range as compared to natives

Fruit size decline from the margin to the center of capitula is the result of resource competition and architectural constraints

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