Compensatory dynamics are rare in naturalecological communities

TitleCompensatory dynamics are rare in naturalecological communities
Publication TypeJournal Article
Year of Publication2007
AuthorsHoulahan, JE, Currie, DJ, Cottenie, K, Cumming, GS, Ernest, SKM, Findlay, CS, Fuhlendorf, SD, Gaedke, U, Legendre, P, Magnuson, JJ, McArdle, BH, Muldavin, EH, Noble, D, Russell, R, Stevens, RD, Willis, TJ, Woiwod, IP, Wondzell, SM
JournalProceedings of the National Academy of Sciences
Pagination3273 -3277
Accession NumberKNZ001090
Keywordsbiological interactions, Community dynamics, negative covariance, neutral models, zero-sum

In population ecology, there has been a fundamental controversy about the relative importance of competition-driven (density-dependent) population regulation vs. abiotic influences such as temperature and precipitation. The same issue arises at the community level; are population sizes driven primarily by changes in the abundances of cooccurring competitors (i.e., compensatory dynamics), or do most species have a common response to environmental factors? Competitive interactions have had a central place in ecological theory, dating back to Gleason, Volterra, Hutchison and MacArthur, and, more recently, Hubbell's influential unified neutral theory of biodiversity and biogeography. If competitive interactions are important in driving year-to-year fluctuations in abundance, then changes in the abundance of one species should generally be accompanied by compensatory changes in the abundances of others. Thus, one necessary consequence of strong compensatory forces is that, on average, species within communities will covary negatively. Here we use measures of community covariance to assess the prevalence of negative covariance in 41 natural communities comprising different taxa at a range of spatial scales. We found that species in natural communities tended to covary positively rather than negatively, the opposite of what would be expected if compensatory dynamics were important. These findings suggest that abiotic factors such as temperature and precipitation are more important than competitive interactions in driving year-to-year fluctuations in species abundance within communities.