Species diversity rises exponentially with the number of available resources in a multi-trait competition model

Theoretical studies of ecosystem models have generally concluded that large numbers of species will not stably coexist if the species are all competing for the same limited set of resources. Here, we describe a simple multi-trait model of competition where the presence of N resources will lead to the stable coexistence of up to 2 N species. Our model also predicts that the long-term dynamics of the population will lie on a neutral attractor hyperplane. When the population shifts within the hyperplane, its dynamics will behave neutrally, while shifts which occur perpendicular to the hyperplane will be subject to restoring forces. This provides a potential explanation of why complex ecosystems might exhibit both niche-like and neutral responses to perturbations. Like the neutral theory of biodiversity, our model generates good fits to species abundance distributions in several datasets but does so without needing to evoke inter-generational stochastic effects, continuous species creation or immigration dynamics. Additionally, our model is able to explain species abundance correlations between independent but similar ecosystems separated by more than 1400 km inside the Amazonian forests.

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Towards a unification of niche and neutral models of community ecology

10.1101/273664 ◽

2018 ◽

Author(s):

Andres Laan ◽

Gonzalo G. de Polavieja

Keyword(s):

Population Dynamics ◽

Large Scale ◽

Community Dynamics ◽

Neutral Theory ◽

Species Abundance ◽

Theory Model ◽

Niche Theory ◽

Species Abundance Distributions ◽

Restoring Forces ◽

Neutral Models

AbstractEcological models of community dynamics fall into two main categories. The neutral theory of biodiversity correctly predicts various large-scale ecosystem characteristics such as the species abundance distributions. On a smaller scale, the niche theory of species competition explains population dynamics and interactions between two to a dozen species. Despite the successes of the two theories, they rely on two contradictory assumptions. In the neutral theory each species is competitively equivalent while in the niche theory every species is specialized to exploit a specific part of its environment. Here we propose a resolution to this contradiction using a game theory model of competition with an attractor hyperplane as its equilibrium solution. When the population dynamics shifts within the hyperplane, it is selectively neutral. However, any movement perpendicular to the hyperplane is subject to restoring forces similar to what is predicted by the niche theory. We show that this model correctly reproduces empirical species abundance distributions and is also compatible with species removal experiments.

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The commonness of rarity: Global and future distribution of rarity across land plants

10.32942/osf.io/qfpa9 ◽

2019 ◽

Author(s):

Brian Joseph Enquist ◽

Xiao Feng ◽

Bradley Boyle ◽

Brian Maitner ◽

Erica A. Newman ◽

...

Keyword(s):

Plant Species ◽

Rare Species ◽

Large Fraction ◽

Neutral Theory ◽

Species Abundance ◽

Land Plant ◽

Observation Data ◽

Heavy Tailed Distributions ◽

Species Abundance Distributions ◽

Heavy Tailed

A key feature of life’s diversity is that some species are common but many more are rare. Nonetheless, at global scales, we do not know what fraction of biodiversity consists of rare species. Here, we present the largest compilation of global plant species observation data in order to quantify the fraction of Earth’s extant land plant biodiversity that is common versus rare. Tests of different hypotheses for the origin of species commonness and rarity indicates that sampling biases and prominent models such as niche theory and neutral theory cannot account for the observed prevalence of rare species. Instead, the distribution of commonness is best approximated by heavy-tailed distributions like the Pareto or Poisson-lognormal distributions. As a result, a large fraction, ~36.5% of an estimated ~435k total plant species, are exceedingly rare. We also show that rare species tend to cluster in a small number of ‘hotspots’ mainly characterized by being in tropical and subtropical mountains and areas that have experienced greater climate stability. Our results indicate that (i) non-neutral processes, likely associated with reduced risk of extinction, have maintained a large fraction of Earth’s plant species but that (ii) climate change and human impact appear to now and will disproportionately impact rare species. Together, these results point to a large fraction of Earth’s plant species are faced with increased chances of extinction. Our results indicate that global species abundance distributions have important implications for conservation planning in this era of rapid global change.

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The commonness of rarity: Global and future distribution of rarity across land plants

Science Advances ◽

10.1126/sciadv.aaz0414 ◽

2019 ◽

Vol 5 (11) ◽

pp. eaaz0414 ◽

Cited By ~ 37

Author(s):

Brian J. Enquist ◽

Xiao Feng ◽

Brad Boyle ◽

Brian Maitner ◽

Erica A. Newman ◽

...

Keyword(s):

Plant Species ◽

Conservation Planning ◽

Rare Species ◽

Extinction Risk ◽

Large Fraction ◽

Neutral Theory ◽

Species Abundance ◽

Risk Assessments ◽

Human Land Use ◽

Species Abundance Distributions

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Predicting community structure in snakes on Eastern Nearctic islands using ecological neutral theory and phylogenetic methods

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2015.1700 ◽

2015 ◽

Vol 282 (1819) ◽

pp. 20151700 ◽

Cited By ~ 10

Author(s):

Frank T. Burbrink ◽

Alexander D. McKelvy ◽

R. Alexander Pyron ◽

Edward A. Myers

Keyword(s):

Community Structure ◽

Island Biogeography ◽

Neutral Theory ◽

Species Abundance ◽

Phylogenetic Methods ◽

Island Communities ◽

Theory Of Island Biogeography ◽

Neutral Theory Of Biodiversity ◽

Neutral Models ◽

Better Than

Predicting species presence and richness on islands is important for understanding the origins of communities and how likely it is that species will disperse and resist extinction. The equilibrium theory of island biogeography (ETIB) and, as a simple model of sampling abundances, the unified neutral theory of biodiversity (UNTB), predict that in situations where mainland to island migration is high, species-abundance relationships explain the presence of taxa on islands. Thus, more abundant mainland species should have a higher probability of occurring on adjacent islands. In contrast to UNTB, if certain groups have traits that permit them to disperse to islands better than other taxa, then phylogeny may be more predictive of which taxa will occur on islands. Taking surveys of 54 island snake communities in the Eastern Nearctic along with mainland communities that have abundance data for each species, we use phylogenetic assembly methods and UNTB estimates to predict island communities. Species richness is predicted by island area, whereas turnover from the mainland to island communities is random with respect to phylogeny. Community structure appears to be ecologically neutral and abundance on the mainland is the best predictor of presence on islands. With regard to young and proximate islands, where allopatric or cladogenetic speciation is not a factor, we find that simple neutral models following UNTB and ETIB predict the structure of island communities.

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The Dynamic Hypercube as a Niche Community Model

Frontiers in Ecology and Evolution ◽

10.3389/fevo.2021.686403 ◽

2021 ◽

Vol 9 ◽

Author(s):

John M. Halley ◽

Stuart L. Pimm

Keyword(s):

Community Dynamics ◽

Neutral Theory ◽

Species Abundance ◽

Ecological Communities ◽

Evolutionary Time ◽

Community Model ◽

Theory Of Island Biogeography ◽

Species Abundance Distributions ◽

Hypercube Model ◽

Zero Sum

Different models of community dynamics, such as the MacArthur–Wilson theory of island biogeography and Hubbell’s neutral theory, have given us useful insights into the workings of ecological communities. Here, we develop the niche-hypervolume concept of the community into a powerful model of community dynamics. We describe the community’s size through the volume of the hypercube and the dynamics of the populations in it through the fluctuations of the axes of the niche hypercube on different timescales. While the community’s size remains constant, the relative volumes of the niches within it change continuously, thus allowing the populations of different species to rise and fall in a zero-sum fashion. This dynamic hypercube model reproduces several key patterns in communities: lognormal species abundance distributions, 1/f-noise population abundance, multiscale patterns of extinction debt and logarithmic species-time curves. It also provides a powerful framework to explore significant ideas in ecology, such as the drift of ecological communities into evolutionary time.

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Understanding how biodiversity unfolds through time under neutral theory

Philosophical Transactions of the Royal Society B Biological Sciences ◽

10.1098/rstb.2015.0226 ◽

2016 ◽

Vol 371 (1691) ◽

pp. 20150226 ◽

Cited By ~ 17

Author(s):

Olivier Missa ◽

Calvin Dytham ◽

Hélène Morlon

Keyword(s):

Species Richness ◽

Dynamic Equilibrium ◽

Neutral Theory ◽

Species Abundance ◽

Ecological Systems ◽

Biodiversity Patterns ◽

Species Abundance Distributions ◽

Species Area ◽

The Difference ◽

Time Required

Theoretical predictions for biodiversity patterns are typically derived under the assumption that ecological systems have reached a dynamic equilibrium. Yet, there is increasing evidence that various aspects of ecological systems, including (but not limited to) species richness, are not at equilibrium. Here, we use simulations to analyse how biodiversity patterns unfold through time. In particular, we focus on the relative time required for various biodiversity patterns (macroecological or phylogenetic) to reach equilibrium. We simulate spatially explicit metacommunities according to the Neutral Theory of Biodiversity (NTB) under three modes of speciation, which differ in how evenly a parent species is split between its two daughter species. We find that species richness stabilizes first, followed by species area relationships (SAR) and finally species abundance distributions (SAD). The difference in timing of equilibrium between these different macroecological patterns is the largest when the split of individuals between sibling species at speciation is the most uneven. Phylogenetic patterns of biodiversity take even longer to stabilize (tens to hundreds of times longer than species richness) so that equilibrium predictions from neutral theory for these patterns are unlikely to be relevant. Our results suggest that it may be unwise to assume that biodiversity patterns are at equilibrium and provide a first step in studying how these patterns unfold through time.

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Emergent neutrality in consumer-resource dynamics

10.1101/710541 ◽

2019 ◽

Cited By ~ 2

Author(s):

Rafael D’Andrea ◽

Theo Gibbs ◽

James P. O’Dwyer

Keyword(s):

Community Dynamics ◽

Neutral Theory ◽

Species Abundance ◽

Natural World ◽

Biodiversity Patterns ◽

Interspecific Differences ◽

Community Turnover ◽

Species Abundance Distributions ◽

Resource Dynamics ◽

Taxonomic Groups

AbstractNeutral theory assumes all species and individuals in a community are ecologically equivalent. This controversial hypothesis has been tested across many taxonomic groups and environmental contexts, and successfully predicts species abundance distributions across multiple high-diversity communities. However, it has been critiqued for its failure to predict a broader range of community properties, particularly regarding community dynamics from generational to geological timescales. Moreover, it is unclear whether neutrality can ever be a true description of a community given the ubiquity of interspecific differences, which presumably lead to ecological inequivalences. Here we derive analytical predictions for when and why non-neutral communities of consumers and resources may present neutral-like outcomes, which we verify using numerical simulations. Our results, which span both static and dynamical community properties, demonstrate the limitations of summarizing distributions to detect non-neutrality, and provide a potential explanation for the successes of neutral theory as a description of macroecological pattern.Author SummaryThe neutral theory of biodiversity assumes that species are ecologically equivalent. Given the natural history observation of ubiquitous phenotypic differences between species, it is surprising that neutral theory has successfully predicted a broad range of biodiversity patterns, and simultaneously unsurprising that these results have not convinced ecologists that the natural world is neutral. However, we have lacked a description of how neutrality can emerge in a natural way from ecological mechanisms and species differences. Our study sheds light on this question, providing a theoretical backdrop for the success of neutral theory as a description of macroecological pattern. We derive a prediction for the degree to which consumers must differ in preferences for different resources before the resulting biodiversity patterns become distinguishable from neutrality. These predictions, which we confirm using simulations, show that neutral-like outcomes are possible even when resource requirements across consumers are very far from neutral. Our results can be tested in experimental microbial communities, where, equipped with an inferred consumption network, our analysis can yield predictions for biodiversity patterns and community turnover at different taxonomic levels.

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Macroscale estimates of species abundance reveal evolutionary drivers of biodiversity

10.1101/426379 ◽

2018 ◽

Author(s):

Keiichi Fukaya ◽

Buntarou Kusumoto ◽

Takayuki Shiono ◽

Junichi Fujinuma ◽

Yasuhiro Kubota

Keyword(s):

Point Mutation ◽

Neutral Theory ◽

Species Abundance ◽

Species Abundance Distribution ◽

Absolute Size ◽

Evolutionary Diversification ◽

Ecological Patterns ◽

Neutral Theory Of Biodiversity ◽

Number Of Individuals

AbstractEvolutionary processes underpin the biodiversity on the planet. Theories advocate that the form of the species abundance distribution (SAD), presented by the number of individuals for each species within an ecological community, is intimately linked to speciation modes such as point mutation and random fission. This prediction has rarely been, however, verified empirically; the fact that species abundance data can be obtained only from local communities critically limits our ability to infer the role of macroevolution in shaping ecological patterns. Here, we developed a novel statistical model to estimate macroscale SADs, the hidden macroecological property, by integrating spatially replicated multispecies detection-nondetection observations and the data on species geographic distributions. We determined abundance of 1,248 woody plant species at a 10 km grid square resolution over East Asian islands across subtropical to temperate biomes, which produced a metacommunity (i.e. species pool) SAD in four insular ecoregions along with its absolute size. The metacommunity SADs indicated lognormal-like distributions, which were well explained by the unified neutral theory of biodiversity and biogeography (UNTB) with protracted speciation, a mode of speciation intermediate between point mutation and random fission. Furthermore, the analyses yielded an estimate of speciation rate in each region that highlighted the importance of geographic characteristics in macroevolutionary processes and predicted the average species lifetime that was congruent with previous estimates. The estimation of macroscale SADs plays a remarkable role in revealing evolutionary diversification of regional species pools.

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The Shape of Species Abundance Distributions Across Spatial Scales

Frontiers in Ecology and Evolution ◽

10.3389/fevo.2021.626730 ◽

2021 ◽

Vol 9 ◽

Author(s):

Laura H. Antão ◽

Anne E. Magurran ◽

Maria Dornelas

Keyword(s):

Large Scale ◽

Spatial Scales ◽

Neutral Theory ◽

Species Abundance ◽

Taxonomic Diversity ◽

Spatial Aggregation ◽

Systematic Effect ◽

Multiple Modes ◽

Wide Range ◽

Species Abundance Distributions

Species abundance distributions (SADs) describe community structure and are a key component of biodiversity theory and research. Although different distributions have been proposed to represent SADs at different scales, a systematic empirical assessment of how SAD shape varies across wide scale gradients is lacking. Here, we examined 11 empirical large-scale datasets for a wide range of taxa and used maximum likelihood methods to compare the fit of the logseries, lognormal, and multimodal (i.e., with multiple modes of abundance) models to SADs across a scale gradient spanning several orders of magnitude. Overall, there was a higher prevalence of multimodality for larger spatial extents, whereas the logseries was exclusively selected as best fit for smaller areas. For many communities the shape of the SAD at the largest spatial extent (either lognormal or multimodal) was conserved across the scale gradient, despite steep declines in area and taxonomic diversity sampled. Additionally, SAD shape was affected by species richness, but we did not detect a systematic effect of the total number of individuals. Our results reveal clear departures from the predictions of two major macroecological theories of biodiversity for SAD shape. Specifically, neither the Neutral Theory of Biodiversity (NTB) nor the Maximum Entropy Theory of Ecology (METE) are able to accommodate the variability in SAD shape we encountered. This is highlighted by the inadequacy of the logseries distribution at larger scales, contrary to predictions of the NTB, and by departures from METE expectation across scales. Importantly, neither theory accounts for multiple modes in SADs. We suggest our results are underpinned by both inter- and intraspecific spatial aggregation patterns, highlighting the importance of spatial distributions as determinants of biodiversity patterns. Critical developments for macroecological biodiversity theories remain in incorporating the effect of spatial scale, ecological heterogeneity and spatial aggregation patterns in determining SAD shape.

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Computer Analyses in Preventive Health Research

Methods of Information in Medicine ◽

10.1055/s-0038-1636287 ◽

1967 ◽

Vol 06 (01) ◽

pp. 8-14 ◽

Cited By ~ 11

Author(s):

M. F. Collen

Keyword(s):

Medical Research ◽

Preventive Medicine ◽

Health Research ◽

Large Scale ◽

Preventive Health ◽

New Era ◽

Large Numbers ◽

Normal Test ◽

Computer Analyses

The utilization of an automated multitest laboratory as a data acquisition center and of a computer for trie data processing and analysis permits large scale preventive medical research previously not feasible. Normal test values are easily generated for the particular population studied. Long-term epidemiological research on large numbers of persons becomes practical. It is our belief that the advent of automation and computers has introduced a new era of preventive medicine.

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