Zero Sum, the Niche, and Metacommunities: Long‐Term Dynamics of Community Assembly

Ernest, S. K. Morgan; Brown, James H.; Thibault, Katherine M.; White, Ethan; Goheen, Jacob R.

doi:10.1086/592402

Cited by 106 publications

(109 citation statements)

References 123 publications

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“…The literature on the temporal dynamics of energy flow and functional compensation is limited to modern-day ecological studies spanning at most several decades (3,4,6,20), with only one historical snapshot comparison extending back to a century (5). This is despite the urgent need to understand natural variability and establish baselines against which to evaluate ecosystem function in today's rapidly changing world (21).…”

Section: Discussionmentioning

confidence: 99%

“…This limits direct comparison with modern ecological studies, but nonetheless provides insight into the compensatory dynamics of community functional structure and the contribution of individual and species body size distributions to sample-standardized energy flow. The consideration of metabolic theory, a century-scale resurvey of small mammals in a Great Basin mountain range (5), and decadal-scale studies of granivorous rodents at the Portal long-term ecological research site in Arizona (20) offers hypotheses for the mechanisms controlling the functional compensation and energetic stability exhibited by Homestead Cave's small mammals across the terminal Pleistocene environmental transition. It also suggests mechanisms for the recent breakdown of this compensation.…”

Section: Discussionmentioning

confidence: 99%

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Energy flow and functional compensation in Great Basin small mammals under natural and anthropogenic environmental change

Terry

Rowe

2015

Proc. Natl. Acad. Sci. U.S.A.

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Research on the ecological impacts of environmental change has primarily focused at the species level, leaving the responses of ecosystem-level properties like energy flow poorly understood. This is especially so over millennial timescales inaccessible to direct observation. Here we examine how energy flow within a Great Basin small mammal community responded to climate-driven environmental change during the past 12,800 y, and use this baseline to evaluate responses observed during the past century. Our analyses reveal marked stability in energy flow during rapid climatic warming at the terminal Pleistocene despite dramatic turnover in the distribution of mammalian body sizes and habitat-associated functional groups. Functional group turnover was strongly correlated with climatedriven changes in regional vegetation, with climate and vegetation change preceding energetic shifts in the small mammal community. In contrast, the past century has witnessed a substantial reduction in energy flow caused by an increase in energetic dominance of smallbodied species with an affinity for closed grass habitats. This suggests that modern changes in land cover caused by anthropogenic activities-particularly the spread of nonnative annual grasslandshas led to a breakdown in the compensatory dynamics of energy flow. Human activities are thus modifying the small mammal community in ways that differ from climate-driven expectations, resulting in an energetically novel ecosystem. Our study illustrates the need to integrate across ecological and temporal scales to provide robust insights for long-term conservation and management.paleoecology | Quaternary | desert rodents | body size | invasive grass T he chronic and cumulative anthropogenic impacts of the past century have spurred considerable shifts in climates and habitats over local to global scales. Efforts to understand ecological responses to these changes have largely been focused at the species level (e.g., range shifts) over annual to decadal timescales. However, climate and habitat change impact biotas across all levels of ecological organization, from individuals to entire ecosystems. Furthermore, many ecological processes unfold over timescales inaccessible to direct observation or experimentation (1). Evaluating the response of higher-level aggregate properties (e.g., energy flow) to environmental change across centennial to millennial timescales can thus provide the temporal context needed to assess whether modern systems now fall within or outside their natural range of variability.Emphasis on species-level responses to environmental change is rooted in the paradigm that populations are highly dynamic while the aggregate properties of a community remain relatively stable and are thus more robust to perturbation. Aggregate properties have been shown to reflect resource availability (2, 3), and their stability has often been attributed to compensatory dynamics among individual species or functional groups (4). However, recent work has shown that marked change in aggrega...

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Energy flow and functional compensation in Great Basin small mammals under natural and anthropogenic environmental change

Terry

Rowe

2015

Proc. Natl. Acad. Sci. U.S.A.

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“…The energetic zero-sum dynamics hypothesis, (Ernest et al, 2008(Ernest et al, , 2009, was tested by correlation (Spearman's rank method, r s ) of geometric mean individual polychaete energy use rate with polychaete total density, D tot (hypothesis B). Similarly, the correlation between the total energy use rate and total density was also computed.…”

Section: Analyses Of Potential Mechanisms Of Changementioning

confidence: 99%

“…Note that species level compensatory dynamics may occur with or without community level compensation (Gonzalez and Loreau, 2009). Ernest et al (2008) suggested that energetic demand may be a more suitable currency than density to address the occurrence of compensatory dynamics. Further they suggest that under a metabolism-based zero-sum framework there could be a direct trade-off between population density and mean individual energy use rate (see also Ernest et al, 2009), Hypothesis B: under zero-sum dynamics, there will be a significant negative relationship between density and mean individual energy use.…”

Section: Introductionmentioning

confidence: 99%

Inter-annual species-level variations in an abyssal polychaete assemblage (Sta. M, NE Pacific, 4000 m)

Laguionie‐Marchais

Paterson

Bett

et al. 2016

Progress in Oceanography

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Please cite this article as: Laguionie-Marchais, C., Paterson, G.L.J., Bett, B.J., Smith, K.L. Jr., Ruhl, H.A., Interannual species-level variations in an abyssal polychaete assemblage (Sta. M, NE Pacific, 4000 m), Progress in Oceanography (2015), doi: http://dx.doi.org/10.1016/j.pocean. 2015.10.006 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Changes in several species were also lagged to changes in POC flux by 4 to 10 months. The polychaete fauna exhibited a significant positive relationship between total density and total energy use rate, suggesting population-level tracking of a common resource (e.g. POC flux food supply). Neither compensatory nor energetic zero-sum dynamics were detected among the polychaete assemblage, but the results suggest that the latter occur in the macrofaunal community as a whole. The results do indicate (a) potential control of species composition, and the density of individual key species, by food supply, when the time-series prior to the sampling location was analysed separately, and (b) generally sensitive detection of environmental change by species-level analysis of the abyssal polychaete assemblage.

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“…Such location specific changes in the environment could have important effects on co‐occurring animal assemblages. For example, changes in precipitation levels can lead to shifts in vegetation structure and resulting changes in rodent community composition (Ernest, Brown, Thibault, White, & Goheen, 2008). The wetter marshes of Studland may have similarly affected local invertebrate and mammal assemblages, and we have shown that hierarchical modeling is better suited to uncover such effects when using EIVs.…”

Section: Discussionmentioning

confidence: 99%

Improving estimates of environmental change using multilevel regression models of Ellenberg indicator values

Carroll

Gillingham

Stafford

et al. 2018

Ecology and Evolution

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Ellenberg indicator values (EIVs) are a widely used metric in plant ecology comprising a semi‐quantitative description of species’ ecological requirements. Typically, point estimates of mean EIV scores are compared over space or time to infer differences in the environmental conditions structuring plant communities—particularly in resurvey studies where no historical environmental data are available. However, the use of point estimates as a basis for inference does not take into account variance among species EIVs within sampled plots and gives equal weighting to means calculated from plots with differing numbers of species. Traditional methods are also vulnerable to inaccurate estimates where only incomplete species lists are available.We present a set of multilevel (hierarchical) models—fitted with and without group‐level predictors (e.g., habitat type)—to improve precision and accuracy of plot mean EIV scores and to provide more reliable inference on changing environmental conditions over spatial and temporal gradients in resurvey studies. We compare multilevel model performance to GLMMs fitted to point estimates of mean EIVs. We also test the reliability of this method to improve inferences with incomplete species lists in some or all sample plots. Hierarchical modeling led to more accurate and precise estimates of plot‐level differences in mean EIV scores between time‐periods, particularly for datasets with incomplete records of species occurrence. Furthermore, hierarchical models revealed directional environmental change within ecological habitat types, which less precise estimates from GLMMs of raw mean EIVs were inadequate to detect. The ability to compute separate residual variance and adjusted R 2 parameters for plot mean EIVs and temporal differences in plot mean EIVs in multilevel models also allowed us to uncover a prominent role of hydrological differences as a driver of community compositional change in our case study, which traditional use of EIVs would fail to reveal. Assessing environmental change underlying ecological communities is a vital issue in the face of accelerating anthropogenic change. We have demonstrated that multilevel modeling of EIVs allows for a nuanced estimation of such from plant assemblage data changes at local scales and beyond, leading to a better understanding of temporal dynamics of ecosystems. Further, the ability of these methods to perform well with missing data should increase the total set of historical data which can be used to this end.

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Zero Sum, the Niche, and Metacommunities: Long‐Term Dynamics of Community Assembly

Cited by 106 publications

References 123 publications

Energy flow and functional compensation in Great Basin small mammals under natural and anthropogenic environmental change

Energy flow and functional compensation in Great Basin small mammals under natural and anthropogenic environmental change

Inter-annual species-level variations in an abyssal polychaete assemblage (Sta. M, NE Pacific, 4000 m)

Improving estimates of environmental change using multilevel regression models of Ellenberg indicator values

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