Density and biotic interactions modify the combined effects of global and local stressors

Paul R. Brooks; Tasman P. Crowe

doi:10.1111/oik.04459

Biotic interactions experienced by a new invader: effects of its close relatives at the community scale

Botany ◽

10.1139/b11-084 ◽

2012 ◽

Vol 90 (1) ◽

pp. 35-42 ◽

Cited By ~ 6

Author(s):

Steven B. Hill ◽

Peter M. Kotanen

Keyword(s):

Shoot Growth ◽

Biotic Interactions ◽

Soil Biota ◽

Community Type ◽

Combined Effects ◽

Old Field ◽

Soil Sterilization ◽

Vegetation Removal ◽

Solidago Virgaurea ◽

Close Relatives

The success of nonindigenous species may be influenced by biotic interactions during the initial stages of invasion. Here, we investigated whether a potential invader, Solidago virgaurea L., would experience more damage by natural enemies in communities dominated by close relatives than those without them; interactions with mutualistic mycorrhizae might partially counteract these effects. We monitored damage experienced by S. virgaurea planted into communities with native congeners and without close relatives. Community type was crossed with a vegetation removal treatment to assess the combined effects of herbivory and competition on survival. We also evaluated growth of S. virgaurea in a greenhouse experiment where seedlings were exposed to soil biota sampled from these communities and compared with sterile controls. Overall, community type did not affect levels of herbivory or plant survival. Removal of surrounding vegetation resulted in reduced damage and increased survival; these effects were largest in grass-dominated communities. Soil sterilization reduced root growth and tended to reduce shoot growth, especially when compared with plants inoculated with biota collected near congeners. Overall, our results suggest that the presence of close relatives is unlikely to make old-field communities more resistant to invasion by S. virgaurea; instead, soil biota might facilitate growth in communities dominated by close relatives.

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Combined effects of climate and biotic interactions on the elevational range of a phytophagous insect

Journal of Animal Ecology ◽

10.1111/j.1365-2656.2007.01303.x ◽

2008 ◽

Vol 77 (1) ◽

pp. 145-155 ◽

Cited By ~ 97

Author(s):

Richard M. Merrill ◽

David Gutiérrez ◽

Owen T. Lewis ◽

Javier Gutiérrez ◽

Sonia B. Díez ◽

...

Keyword(s):

Biotic Interactions ◽

Combined Effects ◽

Phytophagous Insect ◽

Elevational Range

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Combined Impacts of Predation, Mutualism and Dispersal on the Dynamics of a Four-Species Ecological System

Pertanika Journal of Science and Technology ◽

10.47836/pjst.29.1.13 ◽

2021 ◽

Vol 29 (1) ◽

Author(s):

Murtala Bello Aliyu ◽

Mohd Hafiz Mohd

Keyword(s):

Hopf Bifurcation ◽

Species Interactions ◽

Species Coexistence ◽

Biotic Interactions ◽

Ecological System ◽

Stable Limit ◽

Combined Effects ◽

Coexistence Mechanisms ◽

Multiple Species ◽

The Stability

Multi-species and ecosystem models have provided ecologist with an excellent opportunity to study the effects of multiple biotic interactions in an ecological system. Predation and mutualism are among the most prevalent biotic interactions in the multi-species system. Several ecological studies exist, but they are based on one-or two-species interactions, and in real life, multiple interactions are natural characteristics of a multi-species community. Here, we use a system of partial differential equations to study the combined effects of predation, mutualism and dispersal on the multi-species coexistence and community stability in the ecological system. Our results show that predation provided a defensive mechanism against the negative consequences of the multiple species interactions by reducing the net effect of competition. Predation is critical in the stability and coexistence of the multi-species community. The combined effects of predation and dispersal enhance the multiple species coexistence and persistence. Dispersal exerts a positive effect on the system by supporting multiple species coexistence and stability of community structures. Dispersal process also reduces the adverse effects associated with multiple species interactions. Additionally, mutualism induces oscillatory behaviour on the system through Hopf bifurcation. The roles of mutualism also support multiple species coexistence mechanisms (for some threshold values) by increasing the stable coexistence and the stable limit cycle regions. We discover that the stability and coexistence mechanisms are controlled by the transcritical and Hopf bifurcation that occurs in this system. Most importantly, our results show the important influences of predation, mutualism and dispersal in the stability and coexistence of the multi-species communities

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Sunspot Groups as Tracers of Sub-Surface Processes

International Astronomical Union Colloquium ◽

10.1017/s0252921100064393 ◽

2000 ◽

Vol 179 ◽

pp. 155-160

Author(s):

M. H. Gokhale

Keyword(s):

Magnetic Flux ◽

Indian Institute ◽

Surface Processes ◽

The Sun ◽

Global And Local ◽

Sunspot Groups

AbstractData on sunspot groups have been quite useful for obtaining clues to several processes on global and local scales within the sun which lead to emergence of toroidal magnetic flux above the sun’s surface. I present here a report on such studies carried out at Indian Institute of Astrophysics during the last decade or so.

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Effects of Retinoic Acid and 1,25-Dihydroxyvitamin D3 on IFN-gamma Secretion by Mononuclear Leukocytes from Nulliparous and Postparturient Dairy Cattle

International Journal for Vitamin and Nutrition Research ◽

10.1024/0300-9831.70.3.92 ◽

2000 ◽

Vol 70 (3) ◽

pp. 92-101 ◽

Cited By ~ 14

Author(s):

Burim Ametaj ◽

Brian Nonnecke ◽

Ronald Horst ◽

Donald Beitz

Keyword(s):

Retinoic Acid ◽

Dairy Cattle ◽

Dairy Cows ◽

Dairy Cow ◽

Pokeweed Mitogen ◽

Mononuclear Leukocytes ◽

Combined Effects ◽

Ifn Gamma ◽

Dihydroxyvitamin D ◽

1,25 Dihydroxyvitamin D

Individual and combined effects of several isomers of retinoic acid (RA) and 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3) on interferon-gamma (IFN-gamma) secretion by blood mononuclear leukocytes (MNL) from nulliparous and postparturient Holstein cattle were evaluated in vitro. In the first experiment, effects on incubation period (24 to 72 hours) and time of supplementation (0 to 32 hours) with all-trans, 9-cis, 13-cis-, and 9,13-dicis-RAs (0 to 100 nM) on IFN-gamma secretion by pokeweed mitogen (PWM)-stimulated (0 and 10 mug/ml) MNL from nulliparous cattle were evaluated. In the second experiment, MNL from postparturient cows (bled at 0, 2, 4, and 16 days postpartum) were stimulated with PWM (0 and 10 mug/ml) in the presence of RA isomers (9-cis- or 9,13-dicis-RA; 0 to 100 nM), 1,25-(OH)2D3 (0 to 100 nM), or with combinations of these metabolites. The results show that individual isomers of RA had no effect on IFN-gamma secretion by PWM-stimulated MNL from nulliparous or postparturient cows. Furthermore 1,25-dihydroxyvitamin D3 inhibited IFN-gamma secretion by MNL from nulliparous and postparturient dairy cows; however, the degree of inhibition was greater when 9-cis- and 9,13-dicis-RA were also present in the cultures. Finally mononuclear leukocytes from postparturient dairy cows produced substantially less IFN-gamma than did MNL from nulliparous cattle. It is concluded that retinoic acids individually did not affect the capacity of leukocytes from dairy cattle to secrete IFN-gamma. This result is in marked contrast to studies in monogastric species indicating that RAs inhibit IFN-gamma secretion by peripheral blood T cells. Inhibition of IFN-gamma secretion by 1,25-(OH)2D3 was potentiated by 9-cis- and 9,13-di-cis-retinoics acids, suggesting that an excess of dietary vitamins A and D may compromise further the naturally immunosuppressed postparturient dairy cow. Additional research is necessary to determine if the combined effects of these metabolites on IFN-gamma secretion represent an increased susceptibility of the dairy cow to infectious diseases during the periparturient period. Lower secretion of IFN-gamma by MNL from postpartutient dairy cows, relative to nulliparous cattle, suggests that recently-calved cows are naturally immunosuppressed.

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