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Scaling issues of neutral theory reveal violations of ecological equivalence for dominant Amazonian tree species.

ABSTRACT: Neutral models are often used as null models, testing the relative importance of niche versus neutral processes in shaping diversity. Most versions, however, focus only on regional scale predictions and neglect local level contributions. Recently, a new formulation of spatial neutral theory was published showing an incompatibility between regional and local scale fits where especially the number of rare species was dramatically under-predicted. Using a forward in time semi-spatially explicit neutral model and a unique large-scale Amazonian tree inventory data set, we show that neutral theory not only underestimates the number of rare species but also fails in predicting the excessive dominance of species on both regional and local levels. We show that although there are clear relationships between species composition, spatial and environmental distances, there is also a clear differentiation between species able to attain dominance with and without restriction to specific habitats. We conclude therefore that the apparent dominance of these species is real, and that their excessive abundance can be attributed to fitness differences in different ways, a clear violation of the ecological equivalence assumption of neutral theory.

SUBMITTER: Pos E

PROVIDER: S-EPMC6849817 | biostudies-literature | 2019 Jul

REPOSITORIES: biostudies-literature

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Scaling issues of neutral theory reveal violations of ecological equivalence for dominant Amazonian tree species.

Pos Edwin E Guevara Juan Ernesto JE Molino Jean-François JF Sabatier Daniel D Bánki Olaf S OS Pitman Nigel C A NCA Mogollón Hugo F HF García-Villacorta Roosevelt R Neill David D Phillips Oliver L OL Cerón Carlos C Ríos Paredes Marcos M Núñez Vargas Percy P Dávila Nállarett N Fiore Anthony Di AD Rivas-Torres Gonzalo G Thomas-Caesar Raquel R Vriesendorp Corine C Young Kenneth R KR Tirado Milton M Wang Ophelia O Sierra Rodrigo R Mesones Italo I Zagt Roderick R Vasquez Rodolfo R Ahuite Reategui Manuel A MA Palacios Cuenca Walter W Valderrama Sandoval Elvis H EH Ter Steege Hans H

Ecology letters 20190402 7

Neutral models are often used as null models, testing the relative importance of niche versus neutral processes in shaping diversity. Most versions, however, focus only on regional scale predictions and neglect local level contributions. Recently, a new formulation of spatial neutral theory was published showing an incompatibility between regional and local scale fits where especially the number of rare species was dramatically under-predicted. Using a forward in time semi-spatially explicit neu ...[more]

PMID: 30938488

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Project description:BackgroundHubbell's 2001 neutral theory unifies biodiversity and biogeography by modelling steady-state distributions of species richness and abundances across spatio-temporal scales. Accurate predictions have issued from its core premise that all species have identical vital rates. Yet no ecologist believes that species are identical in reality. Here I explain this paradox in terms of the ecological equivalence that species must achieve at their coexistence equilibrium, defined by zero net fitness for all regardless of intrinsic differences between them. I show that the distinction of realised from intrinsic vital rates is crucial to evaluating community resilience.Principal findingsAn analysis of competitive interactions reveals how zero-sum patterns of abundance emerge for species with contrasting life-history traits as for identical species. I develop a stochastic model to simulate community assembly from a random drift of invasions sustaining the dynamics of recruitment following deaths and extinctions. Species are allocated identical intrinsic vital rates for neutral dynamics, or random intrinsic vital rates and competitive abilities for niche dynamics either on a continuous scale or between dominant-fugitive extremes. Resulting communities have steady-state distributions of the same type for more or less extremely differentiated species as for identical species. All produce negatively skewed log-normal distributions of species abundance, zero-sum relationships of total abundance to area, and Arrhenius relationships of species to area. Intrinsically identical species nevertheless support fewer total individuals, because their densities impact as strongly on each other as on themselves. Truly neutral communities have measurably lower abundance/area and higher species/abundance ratios.ConclusionsNeutral scenarios can be parameterized as null hypotheses for testing competitive release, which is a sure signal of niche dynamics. Ignoring the true strength of interactions between and within species risks a substantial misrepresentation of community resilience to habitat loss.

Dataset Information

Scaling issues of neutral theory reveal violations of ecological equivalence for dominant Amazonian tree species.

Publications

Scaling issues of neutral theory reveal violations of ecological equivalence for dominant Amazonian tree species.

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