scholarly journals Biotic resistance or invasional meltdown? Diversity reduces invasibility but not exotic dominance in southern California epibenthic communities

2021 ◽  
Author(s):  
Ryan Amir Beshai ◽  
Danny Truong ◽  
Amy Henry ◽  
Cascade Sorte
Keyword(s):  
Community Development ◽  
Exotic Species ◽  
Community Assembly ◽  
Southern California ◽  
Biotic Resistance ◽  
Community Diversity ◽  
Fouling Communities ◽  
Invasional Meltdown ◽  
Facilitative Interactions ◽  
Over Time

Abstract High community diversity may either prevent or promote the establishment of exotic species. The biotic resistance hypothesis holds that species-rich communities are more resistant to invasion than species-poor communities due to greater interspecific competition. Conversely, the invasional meltdown hypothesis proposes that greater exotic diversity increases invasibility via facilitative interactions between exotic species. To evaluate the degree to which biotic resistance or invasional meltdown influences marine community structure during the assembly period, we studied the development of marine epibenthic “fouling” communities at two southern California harbors. We found that fewer exotic species established as total and exotic richness increased during community assembly and that this effect remained after accounting for space availability. We also found that changes in exotic abundance decreased over time. Throughout the assembly period, gains in exotic abundance were greatest when space was abundant and richness was low. Altogether, we found greater support for biotic resistance than invasional meltdown, suggesting that both native and exotic species contribute to biotic resistance during early community development. However, this resistance may not reduce the total dominance of exotic species.

Facilitative interactions among aquatic invaders: is an "invasional meltdown" occurring in the Great Lakes?

2001 ◽  
Vol 58 (12) ◽  
pp. 2513-2525 ◽  
Author(s):  
Anthony Ricciardi
Keyword(s):  
Great Lakes ◽  
Introduced Species ◽  
Biotic Resistance ◽  
Past Century ◽  
Theoretical Argument ◽  
Cumulative Number ◽  
Invasional Meltdown ◽  
Species Introductions ◽  
Facilitative Interactions ◽  
The Impact

A widely cited hypothesis in ecology is that species-rich communities are less vulnerable to invasion than species-poor ones, owing to competition for limiting resources (the "biotic resistance" model). However, evidence for biotic resistance in aquatic ecosystems is equivocal. Contrary to the view that communities become more resistant to invasion as they accumulate species, the rate of invasion has increased over the past century in areas that have received frequent shipping traffic. Furthermore, introduced species may facilitate, rather than compete with, one another. A review of invasions in the Great Lakes indicates that direct positive (mutualistic and commensal) interactions among introduced species are more common than purely negative (competitive and amensal) interactions. In addition, many exploitative (e.g., predator–prey) interactions appear to be strongly asymmetric in benefiting one invading species at a negligible cost to another. These observations, combined with an increasing invasion rate in the Great Lakes, tentatively support the Simberloff – Von Holle "invasional meltdown" model. The model posits that ecosystems become more easily invaded as the cumulative number of species introductions increases, and that facilitative interactions can exacerbate the impact of invaders. It provides a theoretical argument for substantially reducing the rate of species introductions to the Great Lakes.

scholarly journals Climate and plant community diversity in space and time

2020 ◽  
Vol 117 (9) ◽  
pp. 4464-4470 ◽  
Author(s):  
Susan Harrison ◽  
Marko J. Spasojevic ◽  
Daijiang Li
Keyword(s):  
Plant Community ◽  
Plant Diversity ◽  
Phylogenetic Diversity ◽  
Spatial Scales ◽  
Community Diversity ◽  
Niche Conservatism ◽  
Space And Time ◽  
Drying Trend ◽  
Functional And Phylogenetic Diversity ◽  
Over Time

Climate strongly shapes plant diversity over large spatial scales, with relatively warm and wet (benign, productive) regions supporting greater numbers of species. Unresolved aspects of this relationship include what causes it, whether it permeates to community diversity at smaller spatial scales, whether it is accompanied by patterns in functional and phylogenetic diversity as some hypotheses predict, and whether it is paralleled by climate-driven changes in diversity over time. Here, studies of Californian plants are reviewed and new analyses are conducted to synthesize climate–diversity relationships in space and time. Across spatial scales and organizational levels, plant diversity is maximized in more productive (wetter) climates, and these consistent spatial relationships are mirrored in losses of taxonomic, functional, and phylogenetic diversity over time during a recent climatic drying trend. These results support the tolerance and climatic niche conservatism hypotheses for climate–diversity relationships, and suggest there is some predictability to future changes in diversity in water-limited climates.

scholarly journals Phyllosphere community assembly and response to drought stress on common tropical and temperate forage grasses

2021 ◽  
Author(s):  
Emily K. Bechtold ◽  
Stephanie Ryan ◽  
Sarah E. Moughan ◽  
Ravi Ranjan ◽  
Klaus Nüsslein
Keyword(s):  
Microbial Community ◽  
Drought Stress ◽  
Bacterial Community ◽  
Community Assembly ◽  
Community Diversity ◽  
Grass Species ◽  
Severe Drought ◽  
Hormone Production ◽  
Plant Host ◽  
Bacterial Community Diversity

Grasslands represent a critical ecosystem important for global food production, soil carbon storage, and water regulation. Current intensification and expansion practices add to the degradation of grasslands and dramatically increase greenhouse gas emissions and pollution. Thus, new ways to sustain and improve their productivity are needed. Research efforts focus on the plant-leaf microbiome, or phyllosphere, because its microbial members impact ecosystem function by influencing pathogen resistance, plant hormone production, and nutrient availability through processes including nitrogen fixation. However, little is known about grassland phyllospheres and their response to environmental stress. In this study, globally dominant temperate and tropical forage grass species were grown in a greenhouse under current climate conditions and drought conditions that mimic future climate predictions to understand if (i) plant host taxa influence microbial community assembly, (ii) microbial communities respond to drought stress, and (iii) phyllosphere community changes correlate to changes in plant host traits and stress-response strategies. Community analysis using high resolution sequencing revealed Gammaproteobacteria as the dominant bacterial class, which increased under severe drought stress on both temperate and tropical grasses while overall bacterial community diversity declined. Bacterial community diversity, structure, and response to drought were significantly different between grass species. This community dependence on plant host species correlated with differences in grass species traits, which became more defined under drought stress conditions, suggesting symbiotic evolutionary relationships between plant hosts and their associated microbial community. Further understanding these strategies and the functions microbes provide to plants will help us utilize microbes to promote agricultural and ecosystem productivity in the future.

scholarly journals An exotic species alters patterns of marine community development

2017 ◽  
Vol 88 (1) ◽  
pp. 92-108 ◽  
Author(s):  
Kathrynlynn W. Theuerkauf ◽  
David B. Eggleston ◽  
Seth J. Theuerkauf
Keyword(s):  
Community Development ◽  
Exotic Species ◽  
Marine Community

Two unusual keyhole limpets (Mollusca: Gastropoda: Fissurellidae) from southern California

The Festivus ◽  
2020 ◽  
Vol 52 (3) ◽  
pp. 233-237
Author(s):  
Charles Powell ◽  
Cheryl Millard
Keyword(s):  
South Africa ◽  
New Species ◽  
Exotic Species ◽  
Intertidal Zone ◽  
Southern California ◽  
Orange County ◽  
Senior Author ◽  
Small Specimen ◽  
A New Species

Two small keyhole limpets (Mollusca: Gastropoda: Fissurellidae) were collected live by the senior author and his father (Charles Powell) in the winters of 1967 and 1968 from the side/bottom of moderately flat rocks in the low intertidal zone at Doheny Beach State Park, Dana Point, Orange County, southern California. The larger specimen was collected in the winter of 1968 and the small specimen was collected in winter of 1967. These specimens resemble the genus Lucapinella yet do not quite match any of the known species. The shells are also somewhat similar to Dendrofissurella scutellum from South Africa and two species of Amblychilepas from Australia, however neither of the Dohney Beach specimens can be attributed to those species. This possible new species is assigned to the genus Lucapinella and remains unnamed until additional specimens can be located to determine if they are a new species, a rare exotic species, or a very unusual, miniature L. callomarginata.

How direct and indirect non-native interactions can promote plant invasions, lead to invasional meltdown and inform management decisions.

2020 ◽  
pp. 153-176
Author(s):  
Sara E. Kuebbing
Keyword(s):  
Native Species ◽  
Native Plants ◽  
Full Range ◽  
Invasion Biology ◽  
Apparent Competition ◽  
Indirect Interactions ◽  
Competitive Interactions ◽  
Invasional Meltdown ◽  
Soil Microbial ◽  
Facilitative Interactions

Abstract In 1999, Daniel Simberloff and Betsy Von Holle introduced the term 'invasional meltdown'. The term and the concept have been embraced and critiqued but have taken a firm hold within the invasion biology canon. The original formulation of the concept argued two key points: first, biologists rarely study how non-natives interact with one another. Second, nearly all the conceptual models about the success and impact of invasive species are predicated on the importance of competitive interactions and an implicit assumption that non-natives should interfere with establishment, spread and impact of other non-natives. In response, Simberloff and Von Holle called for more research on invader interactions and proposed an alternative consequence of non-native species interactions - invasional meltdown - where facilitative interactions among non-natives could increase the invasion rate or ecological impacts in invaded systems. This chapter outlines the primary pathways in which direct and indirect interactions among non-natives could lead to invasional meltdown. It provides examples of how different types of interactions among non-natives could lead to net positive effects on the invasion success of non-native plants or the impact of non-native plants on invaded ecosystems. Direct effects are by far the most commonly explored form of non-native- non- native interaction, primarily focusing on plant mutualisms with pollinators, seed dispersers or soil microbial mutualists. There are, however, also examples of non-native plants that benefit from commensal and even herbivorous interactions with other non-natives. Indirect interactions among non-natives are very infrequently studied. Although examples are scarce, non-natives may indirectly benefit other non-native plants through trophic cascades, apparent competition and indirect mutualisms. It remains unclear whether indirect effects are important pathways to invasional meltdown. More work is needed on studying ecosystems that are invaded by multiple non-native species and we need to consider the full range of interactions among non-natives that could either stymie or promote their spread, population growth and impact. Only then can we address how common facilitative interactions are relative to competitive interactions among non-natives or provide robust suggestions on how to manage ecosystems.

scholarly journals A quantitative framework reveals ecological drivers of grassland microbial community assembly in response to warming

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Daliang Ning ◽  
Mengting Yuan ◽  
Linwei Wu ◽  
Ya Zhang ◽  
Xue Guo ◽  
...  
Keyword(s):  
Animal Ecology ◽  
Microbial Community ◽  
Community Assembly ◽  
Null Model ◽  
High Accuracy ◽  
Relative Importance ◽  
Experimental Warming ◽  
Community Based ◽  
Microbial Community Assembly ◽  
Over Time

Abstract Unraveling the drivers controlling community assembly is a central issue in ecology. Although it is generally accepted that selection, dispersal, diversification and drift are major community assembly processes, defining their relative importance is very challenging. Here, we present a framework to quantitatively infer community assembly mechanisms by phylogenetic bin-based null model analysis (iCAMP). iCAMP shows high accuracy (0.93–0.99), precision (0.80–0.94), sensitivity (0.82–0.94), and specificity (0.95–0.98) on simulated communities, which are 10–160% higher than those from the entire community-based approach. Application of iCAMP to grassland microbial communities in response to experimental warming reveals dominant roles of homogeneous selection (38%) and ‘drift’ (59%). Interestingly, warming decreases ‘drift’ over time, and enhances homogeneous selection which is primarily imposed on Bacillales. In addition, homogeneous selection has higher correlations with drought and plant productivity under warming than control. iCAMP provides an effective and robust tool to quantify microbial assembly processes, and should also be useful for plant and animal ecology.

scholarly journals Plant Community Assembly in Invaded Recipient Californian Grasslands and Putative Donor Grasslands in Spain

Diversity ◽  
2020 ◽  
Vol 12 (5) ◽  
pp. 193
Author(s):  
Javier Galán Díaz ◽  
Enrique de la Riva ◽  
Ingrid Parker ◽  
María Leiva ◽  
Rubén Bernardo-Madrid ◽  
...  
Keyword(s):  
Community Structure ◽  
Exotic Species ◽  
Community Assembly ◽  
Model System ◽  
Context Dependency ◽  
Novel Ecosystems ◽  
Pest Species ◽  
Mediterranean Regions ◽  
Global And Local ◽  
Plant Community Assembly

The introduction of exotic species to new regions offers opportunities to test fundamental questions in ecology, such as the context-dependency of community structure and assembly. Annual grasslands provide a model system of a major unidirectional introduction of plant species from Europe to North America. We compared the community structure of grasslands in two Mediterranean regions by surveying plots in Spain and in California with similar environmental and management conditions. All species found in Spanish grasslands were native to Spain, and over half of them (74 of 139 species) are known to have colonized California. In contrast, in California, over half of the species (52 of 95 species) were exotic species, all of them native to Spain. Nineteen species were found in multiple plots in both regions (i.e., shared species). The abundance of shared species in California was either similar to (13 species) or greater than (6 species) in Spain. In California, plants considered pests were more likely than non-pest species to have higher abundance. Co-occurring shared species tended to maintain their relative abundance in native and introduced communities, which indicates that pools of exotic species might assemble similarly at home and away. These findings provide interesting insights into community assembly in novel ecosystems. They also highlight an example of startling global and local floristic homogenization.

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