scholarly journals Predictions of biodiversity are improved by integrating trait-based competition with abiotic filtering

2021 ◽  
Author(s):  
Loïc Chalmandrier ◽  
Daniel B Stouffer ◽  
Adam S. T. Purcell ◽  
William G. Lee ◽  
Andrew J Tanentzap ◽  
...  
Keyword(s):  
Community Assembly ◽  
Resource Competition ◽  
Local Environment ◽  
Competitive Interactions ◽  
Combined Approach ◽  
Model Species ◽  
Abiotic Tolerance ◽  
Species Abundances ◽  
Explained Variance ◽  
Competitive Phenotypes

All organisms must simultaneously tolerate the environment and access limiting resources if they are to persist. Otherwise they go extinct. Approaches to understanding environmental tolerance and resource competition have generally been developed independently. Consequently, integrating the factors that determine abiotic tolerance with those that affect competitive interactions to model species abundances and community structure remains an unresolved challenge. This is likely the reason why current models of community assembly do not accurately predict species abundances and dynamics. Here, we introduce a new synthetic framework that models both abiotic tolerance and biotic competition by using functional traits, which are phenotypic attributes that influence organism fitness. First, our framework estimates species carrying capacities that vary along abiotic gradients based on whether the phenotype tolerates the local environment. Second, it estimates pairwise competitive interactions as a function of multidimensional trait differences between species and determines which trait combinations produce the most competitive phenotypes. We demonstrate that our combined approach more than doubles the explained variance of species covers in a wetland community compared to the model of abiotic tolerances alone. Trait-based integration of competitive interactions and abiotic filtering improves our ability to predict species abundances across space, bringing us closer to more accurate predictions of biodiversity structure in a changing world.

scholarly journals Spatio-temporal modeling of the crowding conditions and metabolic variability in microbial communities

2021 ◽  
Vol 17 (7) ◽  
pp. e1009140
Author(s):  
Liliana Angeles-Martinez ◽  
Vassily Hatzimanikatis
Keyword(s):  
Microbial Communities ◽  
Extracellular Polymeric Substances ◽  
Resource Competition ◽  
Local Environment ◽  
Microbial Interactions ◽  
Relative Fitness ◽  
Flux Analysis ◽  
Scaled Particle Theory ◽  
Spatio Temporal ◽  
The Impact

The metabolic capabilities of the species and the local environment shape the microbial interactions in a community either through the exchange of metabolic products or the competition for the resources. Cells are often arranged in close proximity to each other, creating a crowded environment that unevenly reduce the diffusion of nutrients. Herein, we investigated how the crowding conditions and metabolic variability among cells shape the dynamics of microbial communities. For this, we developed CROMICS, a spatio-temporal framework that combines techniques such as individual-based modeling, scaled particle theory, and thermodynamic flux analysis to explicitly incorporate the cell metabolism and the impact of the presence of macromolecular components on the nutrients diffusion. This framework was used to study two archetypical microbial communities (i) Escherichia coli and Salmonella enterica that cooperate with each other by exchanging metabolites, and (ii) two E. coli with different production level of extracellular polymeric substances (EPS) that compete for the same nutrients. In the mutualistic community, our results demonstrate that crowding enhanced the fitness of cooperative mutants by reducing the leakage of metabolites from the region where they are produced, avoiding the resource competition with non-cooperative cells. Moreover, we also show that E. coli EPS-secreting mutants won the competition against the non-secreting cells by creating less dense structures (i.e. increasing the spacing among the cells) that allow mutants to expand and reach regions closer to the nutrient supply point. A modest enhancement of the relative fitness of EPS-secreting cells over the non-secreting ones were found when the crowding effect was taken into account in the simulations. The emergence of cell-cell interactions and the intracellular conflicts arising from the trade-off between growth and the secretion of metabolites or EPS could provide a local competitive advantage to one species, either by supplying more cross-feeding metabolites or by creating a less dense neighborhood.

scholarly journals Local Victory: Assessing Interspecific Competition in Seagrass From a Trait-Based Perspective

2021 ◽  
Vol 12 ◽  
Author(s):  
Agustín Moreira-Saporiti ◽  
Sonia Bejarano ◽  
Inés G. Viana ◽  
Elizabeth Fay Belshe ◽  
Matern S. P. Mtolera ◽  
...  
Keyword(s):  
Resource Competition ◽  
Plant Size ◽  
Maximum Length ◽  
Competitive Interactions ◽  
Size Difference ◽  
Seagrass Species ◽  
Thalassia Hemprichii ◽  
Functional Strategy ◽  
Seagrass Meadows ◽  
Halophila Ovalis

Tropical seagrass meadows are formed by an array of seagrass species that share the same space. Species sharing the same plot are competing for resources, namely light and inorganic nutrients, which results in the capacity of some species to preempt space from others. However, the drivers behind seagrass species competition are not completely understood. In this work, we studied the competitive interactions among tropical seagrass species of Unguja Island (Zanzibar, Tanzania) using a trait-based approach. We quantified the abundance of eight seagrass species under different trophic states, and selected nine traits related to light and inorganic nutrient preemption to characterize the functional strategy of the species (leaf maximum length and width, leaves per shoot, leaf mass area, vertical rhizome length, shoots per meter of ramet, rhizome diameter, roots per meter of ramet, and root maximum length). From the seagrass abundance we calculated the probability of space preemption between pairs of seagrass species and for each individual seagrass species under the different trophic states. Species had different probabilities of space preemption, with the climax species Thalassodendron ciliatum, Enhalus acoroides, Thalassia hemprichii, and the opportunistic Cymodocea serrulata having the highest probability of preemption, while the pioneer and opportunistic species Halophila ovalis, Syringodium isoetifolium, Halodule uninervis, and Cymodocea rotundata had the lowest. Traits determining the functional strategy showed that there was a size gradient across species. For two co-occurring seagrass species, probability of preemption was the highest for the larger species, it increased as the size difference between species increased and was unaffected by the trophic state. Competitive interactions among seagrass species were asymmetrical, i.e., negative effects were not reciprocal, and the driver behind space preemption was determined by plant size. Seagrass space preemption is a consequence of resource competition, and the probability of a species to exert preemption can be calculated using a trait-based approach.

scholarly journals Can functional traits explain phylogenetic signal in the composition of a plant community?

2015 ◽  
Author(s):  
Daijiang Li ◽  
Anthoy R Ives ◽  
Donald M Waller
Keyword(s):  
Functional Traits ◽  
Community Assembly ◽  
Phylogenetic Signal ◽  
Species Traits ◽  
Functional Trait ◽  
Phylogenetic Information ◽  
Ecological Processes ◽  
Forest Sites ◽  
Species Abundances ◽  
Understory Plant

Phylogeny-based and functional trait-based analyses are two principle ways to study community assembly and underlying ecological processes. In principle, knowing all information about species traits would make phylogenetic information redundant, at least that component of phylogenetic signal in the distribution of species among communities that is caused by phylogenetically related species sharing similar traits. In reality, phylogenies may contain more information than a set of singular, discretely measured traits because we cannot measure all species traits and may misjudge which are most important. The extent to which functional trait information makes phylogenetic information redundant, however, has not been explicitly studied with empirical data in community ecology. Here, we use phylogenetic linear mixed models to analyze community assembly of 55 understory plant species in 30 forest sites in central Wisconsin. These communities show strong phylogenetic attraction, yet variation among sites in 20 environmental variables could not account for this pattern. Most of the 15 functional traits we measured had strong phylogenetic signal, but only three varied strongly among sites in ways that affected species' abundances. These three traits explained only 19% of variation in phylogenetic patterns of species co-occurrence. Thus, phylogenies appear to provide considerably more information about community assembly than the functional traits measured in this study, demonstrating the value of phylogeny in studying of community assembly processes even with abundant functional traits.

scholarly journals Biomass explains the intensity of facilitative – not competitive – interactions: three intraspecific tests with annuals

Web Ecology ◽  
2012 ◽  
Vol 12 (1) ◽  
pp. 49-55 ◽  
Author(s):  
C. Ariza ◽  
K. Tielbörger
Keyword(s):  
Size Dependence ◽  
Resource Competition ◽  
Theoretical Models ◽  
Plant Size ◽  
Competitive Interactions ◽  
Positive Interactions ◽  
Plant Interactions ◽  
Belowground Competition ◽  
Size Dependent ◽  
Negative Effect

Abstract. Despite efforts to discern the role of plant size in resource competition, the circumstances under which size-dependent plant-plant interactions occur are still unclear. The traditional assumption is that competition intensifies with increasing neighbour size. However, recent studies suggest that the size (biomass) dependence of competitive interactions is strongest at very low biomass levels and becomes negligible after a certain threshold neighbour biomass has been reached. We searched for the generality of such patterns for three common annual plant species in Israel. We monitored target and neighbour biomass along their entire lifecycle using an even-aged, intraspecific and intrapopulation competition screenhouse experiment under water-limited conditions. For all focal species, neighbour presence had a net negative effect on vegetative biomass at harvest. However, this was not explained by increasing neighbour biomass over time, as a consistent pattern of size-dependent facilitative, rather than competitive, interactions was observed at all life stages. We explain these observations in terms of co-occurring aboveground facilitation and dominant belowground competition for water. Since our findings are the first of their kind and contradict theoretical predictions of biomass dependence of net negative interactions, we advocate further experiments addressing size dependence in interactions among plants. In particular, theoretical models addressing size dependence of positive interactions must be developed.

scholarly journals Constraints on the distribution of species abundances indicate universal mechanisms of community assembly

2020 ◽  
Vol 35 (2) ◽  
pp. 362-371 ◽  
Author(s):  
Werner Ulrich ◽  
Thomas J. Matthews ◽  
Yasuhiro Kubota
Keyword(s):  
Community Assembly ◽  
Species Abundances

scholarly journals Niche partitioning among dead wood-dependent beetles

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Jakub Horák
Keyword(s):  
Dead Wood ◽  
Resource Competition ◽  
Niche Partitioning ◽  
Species Abundance ◽  
Landscape Scale ◽  
Habitat Requirements ◽  
Wood Material ◽  
Neutral Drift ◽  
Species Abundances

AbstractNiche partitioning among species with virtually the same requirements is a fundamental concept in ecology. Nevertheless, some authors suggest that niches have little involvement in structuring communities. This study was done in the Pardubice Region (Czech Republic) on saproxylic beetles with morphologically similar larvae and very specific requirements, which are related to their obligatory dependence on dead wood material: Cucujus cinnaberinus, Pyrochroa coccinea, and Schizotus pectinicornis. This work was performed on 232 dead wood pieces at the landscape scale over six years. Based on the factors studied, the relationships among these species indicated that their co-occurrence based on species presence and absence was low, which indicated niche partitioning. However, based on analyses of habitat requirements and species composition using observed species abundances, there was no strong evidence for niche partitioning at either studied habitat levels, the tree and the microhabitat. The most likely reasons for the lack of strong niche partitioning were that dead wood is a rich resource and co-occurrence of saproxylic community was not driven by resource competition. This might be consistent with the theory that biodiversity could be controlled by the neutral drift of species abundance. Nevertheless, niche partitioning could be ongoing, meaning that the expanding C. cinnaberinus may have an advantage over the pyrochroids and could dominate in the long term.

scholarly journals Exploring the niche concept in a simple metaorganism

2019 ◽  
Author(s):  
Peter Deines ◽  
Katrin Hammerschmidt ◽  
Thomas CG Bosch
Keyword(s):  
Community Assembly ◽  
Bacterial Species ◽  
Realized Niche ◽  
Darwinian Fitness ◽  
Host Health ◽  
Species Abundances ◽  
Metabolic Interactions ◽  
Niche Concept ◽  
The Individual ◽  
Microbial Community Assembly

AbstractOrganisms and their resident microbial communities - the microbiome - form a complex and mostly stable ecosystem. It is known that the composition of the microbiome and bacterial species abundances can have a major impact on host health and Darwinian fitness, but the processes that lead to these microbial patterns have not yet been identified. We here apply the niche concept and trait-based approaches as a first step in understanding the patterns underlying microbial community assembly and structure in the simple metaorganism Hydra. We find that the carrying capacities in single associations do not reflect microbiota densities as part of the community, indicating a discrepancy between the fundamental and realized niche. Whereas in most cases, the realized niche is smaller than the fundamental one, as predicted by theory, the opposite is observed for Hydra’s two main bacterial colonizers. Both, Curvibacter sp. and Duganella sp. benefit from association with the other members of the microbiome and reach higher fractions as compared to when they are the only colonizer. This cannot be linked to any particular trait that is relevant for interacting with the host or by the utilization of specific nutrients but is most likely determined by metabolic interactions between the individual microbiome members.

scholarly journals Nutritional ecology provides insights into competitive interactions between closely-related marten species

2019 ◽  
Author(s):  
Andrea Gazzola ◽  
Alessandro Balestrieri
Keyword(s):  
Interspecific Competition ◽  
Food Item ◽  
Resource Competition ◽  
Feeding Habits ◽  
Nutritional Ecology ◽  
Metabolizable Energy ◽  
Competitive Interactions ◽  
Stone Marten ◽  
Pine Marten ◽  
Nutrient Profiles

AbstractFor generalist, closely-related predators as those belonging to the genusMartes, it is a hard task to differentiate the effects on feeding habits of variation in food availability from those of resource competition. To overcome this obstacle, we reviewed dietary studies that assessed the relative bulk of each food item, as either percent biomass or percent mean volume, in the diet of both the pine-(M. martes) and stone-(M. foina) marten, and calculated the nutrient profiles (intakes of protein, lipids and carbohydrates, expressed as percentages of total metabolizable energy) of each diet. Both martens’ diets tightly clustered (average values: 47% protein-, 39% lipid- and 14% carbohydrate energy), but, most interestingly, in allopatry the nutritional niches of the two species did not differ, while the stone marten ate more carbohydrates and less protein when sympatric with the pine marten. Our data suggest that stone marten frugivory is the result of interspecific competition.

scholarly journals Coupling spatiotemporal community assembly processes to changes in microbial metabolism

2016 ◽  
Author(s):  
Emily Graham ◽  
Alex R. Crump ◽  
Charles T Resch ◽  
Sarah Fansler ◽  
Evan Arntzen ◽  
...  
Keyword(s):  
Conceptual Model ◽  
Community Assembly ◽  
Microbial Community Composition ◽  
Microbial Metabolism ◽  
Habitat Types ◽  
Selective Pressures ◽  
Ecological Selection ◽  
Species Abundances ◽  
Ecosystem Level ◽  
Microbial Systems

Community assembly processes generate shifts in species abundances that influence ecosystem cycling of carbon and nutrients, yet our understanding of assembly remains largely separate from ecosystem-level functioning. Here, we investigate relationships between assembly and changes in microbial metabolism across space and time in hyporheic microbial communities. We pair sampling of two habitat types (i.e., attached and planktonic) through seasonal and sub-hourly hydrologic fluctuation with null modeling and temporally-explicit multivariate statistics. We demonstrate that multiple selective pressures—imposed by sediment and porewater physicochemistry—integrate to generate changes in microbial community composition at distinct timescales among habitat types. These changes in composition are reflective of contrasting associations of Betaproteobacteria and Thaumarchaeota with ecological selection and with seasonal changes in microbial metabolism. We present a conceptual model based on our results in which metabolism increases when oscillating selective pressures oppose temporally-stable selective pressures. Our conceptual model is pertinent to both macrobial and microbial systems experiencing multiple selective pressures and presents an avenue for assimilating community assembly processes into predictions of ecosystem-level functioning.

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