On the prevalence and dynamics of inverted trophic pyramids and otherwise top-heavy communities

Douglas J. McCauley, Gabriel Gellner, Neo D. Martinez, Richard J. Williams, Stuart A. Sandin, Fiorenza Micheli, Peter J. Mumby, Kevin S. McCann

Research output: Contribution to journalReview articlepeer-review

36 Scopus citations

Abstract

Classically, biomass partitioning across trophic levels was thought to add up to a pyramidal distribution. Numerous exceptions have, however, been noted including complete pyramidal inversions. Elevated levels of biomass top-heaviness (i.e. high consumer/resource biomass ratios) have been reported from Arctic tundra communities to Brazilian phytotelmata, and in species assemblages as diverse as those dominated by sharks and ants. We highlight two major pathways for creating top-heaviness, via: (1) endogenous channels that enhance energy transfer across trophic boundaries within a community and (2) exogenous pathways that transfer energy into communities from across spatial and temporal boundaries. Consumer–resource models and allometric trophic network models combined with niche models reveal the nature of core mechanisms for promoting top-heaviness. Outputs from these models suggest that top-heavy communities can be stable, but they also reveal sources of instability. Humans are both increasing and decreasing top-heaviness in nature with ecological consequences. Current and future research on the drivers of top-heaviness can help elucidate fundamental mechanisms that shape the architecture of ecological communities and govern energy flux within and between communities. Questions emerging from the study of top-heaviness also usefully draw attention to the incompleteness and inconsistency by which ecologists often establish definitional boundaries for communities.

Original languageEnglish (US)
Pages (from-to)439-454
Number of pages16
JournalEcology letters
Volume21
Issue number3
DOIs
StatePublished - Mar 2018

Keywords

  • Allometric trophic network
  • biomass
  • boundary
  • community
  • consumer
  • inverted pyramid
  • resource
  • stability
  • top-heavy
  • trophic

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics

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