02234nas a2200253   4500008004100000245008800041210006900129300001300198490000800211520144800219100001601667700001401683700002001697700001501717700001801732700001801750700001901768700001601787700001801803700001801821700001601839700001201855856011301867       2006                        eng d00aA comparison of the species-timerelationship across ecosystems and taxonomic groups0 acomparison of the speciestimerelationship across ecosystems and   a185 -1950 v1123 aThe species–time relationship (STR) describes how the species richness of a community increases with the time span over which the community is observed. This pattern has numerous implications for both theory and conservation in much the same way as the species–area relationship (SAR). However, the STR has received much less attention and to date only a handful of papers have been published on the pattern. Here we gather together 984 community time-series, representing 15 study areas and nine taxonomic groups, and evaluate their STRs in order to assess the generality of the STR, its consistency across ecosystems and taxonomic groups, its functional form, and its relationship to local species richness. In general, STRs were surprisingly similar across major taxonomic groups and ecosystem types. STRs tended to be well fit by both power and logarithmic functions, and power function exponents typically ranged between 0.2 and 0.4. Communities with high richness tended to have lower STR exponents, suggesting that factors increasing richness may simultaneously decrease turnover in ecological systems. Our results suggest that the STR is as fundamental an ecological pattern as the SAR, and raise questions about the general processes underlying this pattern. They also highlight the dynamic nature of most species assemblages, and the need to incorporate time scale in both basic and applied research on species richness patterns.1 aWhite, E.P.1 aAdler, P.1 aLauenroth, W.K.1 aGill, R.A.1 aGreenberg, D.1 aKaufman, D.M.1 aRassweiler, A.1 aRusak, J.A.1 aSmith, M., A.1 aSteinbeck, J.1 aWaide, R.B.1 aYao, J.  uhttp://lter.konza.ksu.edu/content/comparison-species-timerelationship-across-ecosystems-and-taxonomic-groups