scholarly journals The effect of positive interactions on community structure in a multi-species metacommunity model along an environmental gradient

2010 ◽  
Vol 221 (6) ◽  
pp. 885-894 ◽  
Author(s):  
Elise Filotas ◽  
Martin Grant ◽  
Lael Parrott ◽  
Per Arne Rikvold
Keyword(s):  
Community Structure ◽  
Environmental Gradient ◽  
Positive Interactions

Competitive and facilitative interactions within and between two species of coastal dune perennials

2003 ◽  
Vol 81 (4) ◽  
pp. 330-337 ◽  
Author(s):  
Steven J Franks
Keyword(s):  
Environmental Gradient ◽  
Coastal Dune ◽  
Positive Interactions ◽  
Substantial Evidence ◽  
Species Identity ◽  
Uniola Paniculata ◽  
Disturbed Zone ◽  
As Stress ◽  
Facilitative Interactions ◽  
Target Plant

While there is substantial evidence for facilitation, the effects of such factors as stress and species identity on positive interactions remain controversial. At two coastal dune sites, I tested the hypotheses that facilitative interactions increase with increasing stress and disturbance along an environmental gradient and that facilitative interactions are stronger among heterospecific than among conspecific individuals. I transplanted Uniola paniculata and Iva imbricata plants into plots along with four conspecific neighbors, four heterospecific neighbors, or no neighbors across an environmental gradient. Neighbors increased target plant survival, suggesting facilitation, but biomass of targets was reduced by the presence of neighbors, suggesting competition. Unexpectedly, competition was greatest in the purportedly most stressful and disturbed zone. In this study, the outcome of neighbor interactions differed for biomass and survival and depended on position along the environmental gradient, but was independent of neighbor identity.Key words: competition, disturbance, facilitation, Iva imbricata, stress, Uniola paniculata.

Broad-scale environmental gradients among estuarine benthic macrofaunal assemblages of south-eastern Australia: implications for monitoring estuaries

2004 ◽  
Vol 55 (1) ◽  
pp. 79 ◽  
Author(s):  
Alastair J. Hirst
Keyword(s):  
Community Structure ◽  
Spatial Scale ◽  
Environmental Gradient ◽  
Physical Parameters ◽  
South Eastern ◽  
Eastern Australia ◽  
Macrofaunal Community ◽  
Broad Spatial Scale ◽  
Broad Scale ◽  
South Eastern Australia

The importance of abiotic factors in explaining patterns of estuarine benthic macrofaunal community structure was examined on a broad spatial scale across south-eastern Australia. Macrofaunal communities were surveyed using an Ekman grab and a modified epibenthic sled (dredge) at each sampling site: data for 24 environmental variables were also collected. Twenty-eight estuaries were sampled on a single occasion during late summer at three stratified locations within each estuary (upper, mid and lower). Macrofaunal community composition was best explained by a common environmental gradient summarising variation in both salinity and longitude. Hence, although the distribution of macrofaunal taxa can be clearly linked to changes in salinity, the geographical position of the sites along an east–west axis, rather than a generalised down-stream gradient, appears to best explain the data. This association was primarily linked to broad-scale changes in estuarine morphology across the geographical range of this survey. A sediment-based environmental gradient among grab samples, but not dredge samples, reflected the largely infaunal nature of the grab samples. In general, the present survey did not support the classification of estuarine assemblages on the basis of a range of physical parameters but, instead, emphasised the continuity of estuarine benthic macrofaunal community structure on a broad spatial scale.

The structure of the community of strongyloid nematodes of domestic equids

1996 ◽  
Vol 70 (3) ◽  
pp. 185-192 ◽  
Author(s):  
D. Bucknell ◽  
H. Hoste ◽  
R.B. Gasser ◽  
I. Beveridge
Keyword(s):  
Community Structure ◽  
Multivariate Analyses ◽  
Positive Interactions ◽  
Prominent Feature ◽  
Using Data ◽  
Satellite Species ◽  
Stable Community ◽  
Negative Interactions

AbstractThe community structure exhibited by strongyloid nematodes from the large intestines of horses was examined using data from autopsies of 150 horses. Thirty-one species of nematodes were encountered, but they were not clearly divisible into core and satellite species. Multiple congeneric, consubfamilial and confamilial species were a prominent feature of the community and were more common than singleton infections. Multivariate analyses provided evidence of a stable community of helminths dominated by positive interactions but with few negative interactions, suggesting the absence of competition within the community.

scholarly journals Comparative co-occurrence network analyses of the cichlid fish gut microbiota: community conservation and diet-associated shifts

2020 ◽  
Author(s):  
Joan Lluís Riera ◽  
Laura Baldo
Keyword(s):  
Community Structure ◽  
Gut Microbiota ◽  
Positive Interactions ◽  
Fish Family ◽  
Comparative Analyses ◽  
Cichlid Fishes ◽  
Network Analyses ◽  
Primary Model ◽  
Microbial Associations ◽  
Microbiota Structure

AbstractCo-occurrence networks of bacteria associations are a powerful approach to explore ecologically relevant aspects of the gut microbiota structure, beyond community composition alone. Here we exploit the remarkable diversity of cichlid fishes and their multiple lake assemblages to investigate a) network features and patterns of microbial associations that were robust to major phylogeographical variables, and b) community structure changes along cichlid dietary shifts. We tackled these objectives using the large gut microbiota sequencing dataset available (nine lakes from Africa and America), building geographical and diet-specific networks and performing comparative analyses. Major findings indicated that lake and continental networks were highly resembling in global topology and node taxonomic composition, suggesting important constraints in the cichlid gut community assembling. A small fraction of the observed co-occurrence pairwises was conserved across all lake assemblages; while the origin and ecological relevance of these core associations remains unclear, their persistence suggests a potential functional role in the cichlid gut. Comparison of carnivores and herbivores-specific networks as well as mapping of diet-specific values on the African Lake Tanganyika network revealed a clear community shift as a function of diet, with an increase in complexity and node taxonomic diversity from carnivores-omnivores-plantkivores to herbivores. More importantly, diet-associated nodes in herbivores formed complex modules of positive interactions. By intersecting results from association patterns and experimental trials, future studies will be directed to test the strength of these microbial associations and predict the outcome of community alterations driven by diet.ImportanceThe gut microbiota is a complex community of interacting bacteria. Predicting patterns of co-occurrence among microbes can help understanding key ecological aspects driving community structure, maintenance and dynamics. Here we showed a powerful application of co-occurrence networks to explore gut bacteria interactions in a primary model system to study animal diversification, the cichlid fishes. Taking advantage of the large scale of phylogeographical and ecological diversity of this fish family, we built gut microbiota networks from distinct lake and continental fish assemblages and performed extensive comparative analyses to retrieve conserved and trait-specific patterns of bacteria associations. Our results identified network features that were independent from the fish biogeography and that indicated an important host selection effect on gut community assembling. Focusing on a single lake assemblage, and therefore excluding the major geographical effect, we observed that the gut microbiota structure dramatically shifted from carnivore to herbivore fishes, with a substantial increase in the number and complexity of microbial interactions.

Impacts of trails on cliff-edge forest structure

1995 ◽  
Vol 73 (6) ◽  
pp. 943-953 ◽  
Author(s):  
Pampang Parikesit ◽  
Douglas W. Larson ◽  
Uta Matthes-Sears
Keyword(s):  
Species Richness ◽  
Community Structure ◽  
Soil Properties ◽  
Plant Community ◽  
Forest Structure ◽  
Environmental Gradient ◽  
Soil Characteristics ◽  
Anthropogenic Factors ◽  
Plant Community Structure ◽  
Niagara Escarpment

Plant community structure and soil characteristics were quantitatively studied along forested cliff edges of the Niagara Escarpment in southern Ontario, Canada. The objective of the study was to try to differentiate between the effects of two gradients on vegetation structure: the environmental gradient between the cliff edge and dense forest, and an anthropogenic gradient, generated by the presence of major hiking trails parallel to the cliff edges. Species frequencies were determined along 69 transects distributed over eight sites with different amounts of past and present trampling disturbance. The data were analyzed using cluster and ordination analysis as well as analyses of variance. The results showed that soil characteristics were the major influence organizing the vegetation of cliff-edge forests and that soil properties and plant community structure were more strongly influenced by anthropogenic factors than by the environmental gradient between cliff edge and forest. Trampled plots had some properties in common with cliff-edge plots. Species richness was highest at intermediate trail-use levels; abandonment of heavily disturbed trails resulted in the restoration of species richness, but most new colonizing plants were disturbance-tolerant ruderals. Soil properties did not completely recover even after 10 years of trail abandonment. The results suggest that the current use of cliff edges along the Niagara Escarpment is nonsustainable, and reversing its effects on cliff-edge forest structure may take a considerable amount of time. Key words: Niagara Escarpment, plant community ecology, disturbance, trampling, cluster analysis, ordination.

scholarly journals Positive interactions and the emergence of community structure in metacommunities

2010 ◽  
Vol 266 (3) ◽  
pp. 419-429 ◽  
Author(s):  
Elise Filotas ◽  
Martin Grant ◽  
Lael Parrott ◽  
Per Arne Rikvold
Keyword(s):  
Community Structure ◽  
Positive Interactions

scholarly journals Dynamics of Free-Living and Attached Bacterial Assemblages in Skeletonema sp. Diatom Cultures at Elevated Temperatures

2021 ◽  
Vol 8 ◽  
Author(s):  
Zichao Deng ◽  
Shouchang Chen ◽  
Ping Zhang ◽  
Xu Zhang ◽  
Jonathan M. Adams ◽  
...  
Keyword(s):  
Community Structure ◽  
Elevated Temperature ◽  
Bacterial Communities ◽  
Elevated Temperatures ◽  
Bacterial Species ◽  
Positive Interactions ◽  
Growth Stages ◽  
Free Living ◽  
Attached Bacteria ◽  
Living Bacteria

In the context of global warming, changes in phytoplankton-associated bacterial communities have the potential to change biogeochemical cycling and food webs in marine ecosystems. Skeletonema is a cosmopolitan diatom genus in coastal waters worldwide. Here, we grew a Skeletonema strain with its native bacterial assemblage at different temperatures and examined cell concentrations of Skeletonema sp. and free-living bacteria, dissolved organic carbon (DOC) concentrations of cultures, and the community structure of both free-living and attached bacteria at different culture stages. The results showed that elevated temperature increased the specific growth rates of both Skeletonema and free-living bacteria. Different growth stages had a more pronounced effect on community structure compared with temperatures and different physical states of bacteria. The effects of temperature on the structure of the free-living bacterial community were more pronounced compared with diatom-attached bacteria. Carbon metabolism genes and those for some specific amino acid pathways were found to be positively correlated with elevated temperature, which may have profound implications on the oceanic carbon cycle and the marine microbial loop. Network analysis revealed evidence of enhanced cooperation with an increase in positive interactions among different bacteria at elevated temperature. This may help the whole community to overcome the stress of elevated temperature. We speculate that different bacterial species may build more integrated networks with a modified functional profile of the whole community to cope with elevated temperature. This study contributes to an improved understanding of the response of diatom-associated bacterial communities to elevated temperature.

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