Dataset Information

Community inertia of Quaternary small mammal assemblages in North America.

ABSTRACT: One of the longest running debates in ecology is whether chance or determinism structures biotic communities, and this question is often studied by looking for the presence or absence of community inertia (lack of change) over time or space. Results have been equivocal. We adopted three tactics for a fresh approach: (i) allowing the answer to vary with the geographic, temporal, and taxonomic scale of study, (ii) using appropriate reference points for the amount of inertia in random biological systems, and (iii) using a robust approach for measurement of inertia. We examined fossil assemblages of mammalian communities across almost 1,000,000 years and at sites spanning approximately 3,500 km. We showed that in general there is good evidence for inertia but that the results change in a quantifiable fashion with taxonomic, spatial, and temporal scales. By using neutral theory we place a reference point on the degree of inertia and demonstrate that empirical mammalian communities show greater inertia than neutral communities over time scales >3,000 year. Although our results do not specifically reveal mechanism, they emphasize that deterministic forces are at work in structuring communities over millennia.

SUBMITTER: McGill BJ

PROVIDER: S-EPMC1283796 | biostudies-literature | 2005 Nov

REPOSITORIES: biostudies-literature

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Community inertia of Quaternary small mammal assemblages in North America.

McGill Brian J BJ Hadly Elizabeth A EA Maurer Brian A BA

Proceedings of the National Academy of Sciences of the United States of America 20051031 46

One of the longest running debates in ecology is whether chance or determinism structures biotic communities, and this question is often studied by looking for the presence or absence of community inertia (lack of change) over time or space. Results have been equivocal. We adopted three tactics for a fresh approach: (i) allowing the answer to vary with the geographic, temporal, and taxonomic scale of study, (ii) using appropriate reference points for the amount of inertia in random biological sy ...[more]

PMID: 16260748

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Project description:BACKGROUND: Although arctic lakes have responded sensitively to 20(th)-century climate change, it remains uncertain how these ecological transformations compare with alpine and montane-boreal counterparts over the same interval. Furthermore, it is unclear to what degree other forcings, including atmospheric deposition of anthropogenic reactive nitrogen (Nr), have participated in recent regime shifts. Diatom-based paleolimnological syntheses offer an effective tool for retrospective assessments of past and ongoing changes in remote lake ecosystems. METHODOLOGY/PRINCIPAL FINDINGS: We synthesized 52 dated sediment diatom records from lakes in western North America and west Greenland, spanning broad latitudinal and altitudinal gradients, and representing alpine (n = 15), arctic (n = 20), and forested boreal-montane (n = 17) ecosystems. Diatom compositional turnover (beta-diversity) during the 20(th) century was estimated using Detrended Canonical Correspondence Analysis (DCCA) for each site and compared, for cores with sufficiently robust chronologies, to both the 19(th) century and the prior approximately 250 years (Little Ice Age). For both arctic and alpine lakes, beta-diversity during the 20(th) century is significantly greater than the previous 350 years, and increases with both latitude and altitude. Because no correlation is apparent between 20(th)-century diatom beta-diversity and any single physical or limnological parameter (including lake and catchment area, maximum depth, pH, conductivity, [NO(3)(-)], modeled Nr deposition, ambient summer and winter air temperatures, and modeled temperature trends 1948-2008), we used Principal Components Analysis (PCA) to summarize the amplitude of recent changes in relationship to lake pH, lake:catchment area ratio, modeled Nr deposition, and recent temperature trends. CONCLUSIONS/SIGNIFICANCE: The ecological responses of remote lakes to post-industrial environmental changes are complex. However, two regions reveal concentrations of sites with elevated 20(th)-century diatom beta-diversity: the Arctic where temperatures are increasing most rapidly, and mid-latitude alpine lakes impacted by high Nr deposition rates. We predict that remote lakes will continue to shift towards new ecological states in the Anthropocene, particularly in regions where these two forcings begin to intersect geographically.

Dataset Information

Community inertia of Quaternary small mammal assemblages in North America.

Publications

Community inertia of Quaternary small mammal assemblages in North America.

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