Title: DEMOGRAPHIC STOCHASTICITY AND THE VARIANCE REDUCTION EFFECT
Abstract: EcologyVolume 83, Issue 7 p. 1928-1934 Article DEMOGRAPHIC STOCHASTICITY AND THE VARIANCE REDUCTION EFFECT Gordon A. Fox, Gordon A. Fox Department of Biology (SCA 110), University of South Florida, 4202 E. Fowler Ave., Tampa, Florida 33620-2000 USA E-mail: [email protected]Search for more papers by this authorBruce E. Kendall, Bruce E. Kendall Donald Bren School of Environmental Science and Management, University of California, Santa Barbara, California 93106 USASearch for more papers by this author Gordon A. Fox, Gordon A. Fox Department of Biology (SCA 110), University of South Florida, 4202 E. Fowler Ave., Tampa, Florida 33620-2000 USA E-mail: [email protected]Search for more papers by this authorBruce E. Kendall, Bruce E. Kendall Donald Bren School of Environmental Science and Management, University of California, Santa Barbara, California 93106 USASearch for more papers by this author First published: 01 July 2002 https://doi.org/10.1890/0012-9658(2002)083[1928:DSATVR]2.0.CO;2Citations: 74 Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinkedInRedditWechat Abstract Demographic stochasticity is almost universally modeled as sampling variance in a homogeneous population, although it is defined as arising from random variation among individuals. This can lead to serious misestimation of the extinction risk in small populations. Here, we derive analytical expressions showing that the misestimation for each demographic parameter is exactly (in the case of survival) or approximately (in the case of fecundity) proportional to the among-individual variance in that parameter. We also show why this misestimation depends on systematic variation among individuals, rather than random variation. These results indicate that correctly assessing the importance of demographic stochasticity requires (1) an estimate of the variance in each demographic parameter; (2) information on the qualitative shape (convex or concave) of the mean–variance relationship; and (3) information on the mechanisms generating among-individual variation. An important consequence is that almost all population viability analyses (PVAs) overestimate the importance of demographic stochasticity and, therefore, the risk of extinction. Supporting Information Filename Description https://dx.doi.org/10.6084/m9.figshare.c.3297617 Research data pertaining to this article is located at figshare.com: Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article. Literature Cited Allison, P. D. 1995. Survival analysis using the SAS system. SAS Institute, Cary, North Carolina, USA. Google Scholar Beissinger, S. R., and M. I. Westphal . 1998. On the use of demographic models of population viability in endangered species management. Journal of Wildlife Management 62: 821–841. 10.2307/3802534 PubMedWeb of Science®Google Scholar Belovsky, G. E., C. Mellison, C. Larson, and P. A. Van Zandt . 1999. Experimental studies of extinction dynamics. Science 286: 1175–1177. 10.1126/science.286.5442.1175 CASPubMedWeb of Science®Google Scholar Benton, T. G., and A. 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