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PRODUCTIVITY ALTERS THE SCALE DEPENDENCE OF THE DIVERSITY–INVASIBILITY RELATIONSHIP
Author(s) -
Davies Kendi F.,
Harrison Susan,
Safford Hugh D.,
Viers Joshua H.
Publication year - 2007
Publication title -
ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.144
H-Index - 294
eISSN - 1939-9170
pISSN - 0012-9658
DOI - 10.1890/06-1907.1
Subject(s) - ecology , introduced species , productivity , invasive species , range (aeronautics) , diversity (politics) , competition (biology) , spatial ecology , biology , species diversity , biodiversity , scale (ratio) , geography , materials science , sociology , anthropology , economics , composite material , macroeconomics , cartography
At small scales, areas with high native diversity are often resistant to invasion, while at large scales, areas with more native species harbor more exotic species, suggesting that different processes control the relationship between native and exotic species diversity at different spatial scales. Although the small‐scale negative relationship between native and exotic diversity has a satisfactory explanation, we lack a mechanistic explanation for the change in relationship to positive at large scales. We investigated the native–exotic diversity relationship at three scales (range: 1–4000 km 2 ) in California serpentine, a system with a wide range in the productivity of sites from harsh to lush. Native and exotic diversity were positively correlated at all three scales; it is rarer to detect a positive relationship at the small scales within which interactions between individuals occur. However, although positively correlated on average, the small‐scale relationship between native and exotic diversity was positive at low‐productivity sites and negative at high‐productivity sites. Thus, the change in the relationship between native and exotic diversity does not depend on spatial scale per se, but occurs whenever environmental conditions change to promote species coexistence rather than competitive exclusion. This occurred within a single spatial scale when the environment shifted from being locally unproductive to productive.