scholarly journals Phenology of competitive interactions and implications for management of the invasive wetland plant Alternanthera philoxeroides

2021 ◽  
Author(s):  
Nathan Harms ◽  
James Cronin
Keyword(s):  
Resource Availability ◽  
Technical Note ◽  
Priority Effects ◽  
Competitive Interactions ◽  
Alternanthera Philoxeroides ◽  
Field Observations ◽  
Wetland Plant ◽  
Resident Species ◽  
Early Season ◽  
Emergent Species

Phenological differences between invading plants and members of recipient communities may increase the success of invaders because of priority effects. Thus, the application of management when the invader has a phenological advantage (for example, early in the year) can benefit other species by increasing resource availability. This technical note summarizes results from a combination of field observations and a mesocosm experiment to explore whether phenological differences between the invasive wetland plant, alligatorweed (Alternanthera philoxeroides [Mart.] Grseb.), and resident species contribute to alligatorweed success. We documented over two years the early-season growth of alligatorweed and other species at 12 sites in Louisiana, USA. We then conducted a subsequent mesocosm competition experiment between alligatorweed and a common wetland emergent species, spotted lady’s thumb (Persicaria maculosa [L.] Small), over a full year to detect differences in timing of growth and competitive interactions under two fertilizer levels.

scholarly journals Technical Note: Preliminary estimation of rockfall runout zones

2011 ◽  
Vol 11 (3) ◽  
pp. 819-828 ◽  
Author(s):  
M. Jaboyedoff ◽  
V. Labiouse
Keyword(s):  
Slope Angle ◽  
Digital Terrain Model ◽  
Grid Cell ◽  
Technical Note ◽  
Field Observations ◽  
Source Areas ◽  
Terrain Model ◽  
Digital Terrain ◽  
Energy Line ◽  
Potential Source

Abstract. Rockfall propagation areas can be determined using a simple geometric rule known as shadow angle or energy line method based on a simple Coulomb frictional model implemented in the CONEFALL computer program. Runout zones are estimated from a digital terrain model (DTM) and a grid file containing the cells representing rockfall potential source areas. The cells of the DTM that are lowest in altitude and located within a cone centered on a rockfall source cell belong to the potential propagation area associated with that grid cell. In addition, the CONEFALL method allows estimation of mean and maximum velocities and energies of blocks in the rockfall propagation areas. Previous studies indicate that the slope angle cone ranges from 27° to 37° depending on the assumptions made, i.e. slope morphology, probability of reaching a point, maximum run-out, field observations. Different solutions based on previous work and an example of an actual rockfall event are presented here.

scholarly journals Metabolic Symbiosis Facilitates Species Coexistence and Generates Light-Dependent Priority Effects

2021 ◽  
Vol 8 ◽  
Author(s):  
Veronica Hsu ◽  
Holly V. Moeller
Keyword(s):  
Carbon Source ◽  
Community Composition ◽  
Green Algae ◽  
Species Interactions ◽  
Species Coexistence ◽  
Priority Effects ◽  
Competitive Interactions ◽  
Paramecium Bursaria ◽  
Mutual Benefit ◽  
Cascading Effects

Metabolic symbiosis is a form of symbiosis in which organisms exchange metabolites, typically for mutual benefit. For example, acquired phototrophs like Paramecium bursaria obtain photosynthate from endosymbiotic green algae called Chlorella. In addition to facilitating the persistence of P. bursaria by providing a carbon source that supplements P. bursaria’s heterotrophic digestion of bacteria, symbiotic Chlorella may impact competitive interactions between P. bursaria and other bacterivores, with cascading effects on community composition and overall diversity. Here, we tested the effects of metabolic symbiosis on coexistence by assessing the impacts of acquired phototrophy on priority effects, or the effect of species arrival order on species interactions, between P. bursaria and its competitor Colpidium. Our results suggest light-dependent priority effects. The acquired phototroph benefited from metabolic symbiosis during sequential arrival of each organism in competition, and led to increased growth of late-arriving Colpidium. These findings demonstrate that understanding the consequences of priority effects for species coexistence requires consideration of metabolic symbiosis.

scholarly journals Applying modern coexistence theory to priority effects

2019 ◽  
Vol 116 (13) ◽  
pp. 6205-6210 ◽  
Author(s):  
Tess Nahanni Grainger ◽  
Andrew D. Letten ◽  
Benjamin Gilbert ◽  
Tadashi Fukami
Keyword(s):  
Growth Rates ◽  
Competitive Exclusion ◽  
Abiotic Factors ◽  
Priority Effects ◽  
Competitive Interactions ◽  
Competing Species ◽  
Coexistence Theory ◽  
Dependent Growth ◽  
Established Population ◽  
Positive Frequency

Modern coexistence theory is increasingly used to explain how differences between competing species lead to coexistence versus competitive exclusion. Although research testing this theory has focused on deterministic cases of competitive exclusion, in which the same species always wins, mounting evidence suggests that competitive exclusion is often historically contingent, such that whichever species happens to arrive first excludes the other. Coexistence theory predicts that historically contingent exclusion, known as priority effects, will occur when large destabilizing differences (positive frequency-dependent growth rates of competitors), combined with small fitness differences (differences in competitors’ intrinsic growth rates and sensitivity to competition), create conditions under which neither species can invade an established population of its competitor. Here we extend the empirical application of modern coexistence theory to determine the conditions that promote priority effects. We conducted pairwise invasion tests with four strains of nectar-colonizing yeasts to determine how the destabilizing and fitness differences that drive priority effects are altered by two abiotic factors characterizing the nectar environment: sugar concentration and pH. We found that higher sugar concentrations increased the likelihood of priority effects by reducing fitness differences between competing species. In contrast, higher pH did not change the likelihood of priority effects, but instead made competition more neutral by bringing both fitness differences and destabilizing differences closer to zero. This study demonstrates how the empirical partitioning of priority effects into fitness and destabilizing components can elucidate the pathways through which environmental conditions shape competitive interactions.

MATING BEHAVIOR OF RHAGOLETIS POMONELLA (DIPTERA: TEPHRITIDAE) VI. SITE OF EARLY-SEASON ENCOUNTERS

1980 ◽  
Vol 112 (6) ◽  
pp. 585-590 ◽  
Author(s):  
D. Courtney Smith ◽  
Ronald J. Prokopy
Keyword(s):  
Mating Behavior ◽  
Oviposition Behavior ◽  
Rhagoletis Pomonella ◽  
Field Observations ◽  
Early Season

AbstractField observations of Rhagoletis pomonella (Walsh) adults on apple and hawthorn trees revealed that mating encounters occur on leaves in early-season and shift to fruit with the onset of oviposition. Most matings on leaves are initiated from a male frontal approach to the female and most of those on fruit from a rear approach while the female is engaged in some phase of oviposition behavior. This suggests that matings on fruit may be forced matings with unreceptive females.

scholarly journals Resource availability modulates biodiversity‐invasion relationships by altering competitive interactions

2017 ◽  
Vol 19 (8) ◽  
pp. 2984-2991 ◽  
Author(s):  
Tianjie Yang ◽  
Zhong Wei ◽  
Ville‐Petri Friman ◽  
Yangchun Xu ◽  
Qirong Shen ◽  
...  
Keyword(s):  
Resource Availability ◽  
Competitive Interactions

scholarly journals Resource stoichiometry shapes community invasion resistance via productivity-mediated species identity effects

2018 ◽  
Vol 285 (1893) ◽  
pp. 20182035 ◽  
Author(s):  
Tianjie Yang ◽  
Gang Han ◽  
Qingjun Yang ◽  
Ville-Petri Friman ◽  
Shaohua Gu ◽  
...  
Keyword(s):  
Resource Availability ◽  
Relative Concentration ◽  
Microbial Community Composition ◽  
Community Diversity ◽  
Invasion Resistance ◽  
Resident Species ◽  
Negative Effects ◽  
Species Identity ◽  
Community Resistance ◽  
The Mean

Diversity–invasion resistance relationships are often variable and sensitive to environmental conditions such as resource availability. Resource stoichiometry, the relative concentration of different elements in the environment, has been shown to have strong effects on the physiology and interactions between different species. Yet, its role for diversity–invasion resistance relationships is still poorly understood. Here, we explored how the ratio of nitrogen (N) and phosphorus affects the productivity and invasion resistance of constructed microbial communities by a plant pathogenic bacterium, Ralstonia solanacearum . We found that resource stoichiometry and species identity effects affected the invasion resistance of communities. Both high N concentration and resident community diversity constrained invasions, and two resident species, in particular, had strong negative effects on the relative density of the invader and the resident community productivity. While resource stoichiometry did not affect the mean productivity of the resident community, it favoured the growth of two species that strongly constrained invasions turning the slope of productivity–invasion resistance relationship more negative. Together our findings suggest that alterations in resource stoichiometry can change the community resistance to invasions by having disproportionate effects on species growth, potentially explaining changes in microbial community composition under eutrophication.

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