Abstract
Patterns of species associations have been commonly used to infer interactions among species. If species positively co‐occur, they may form predominantly neutral assemblages, and such patterns suggest a relatively weak role for compensatory dynamics. The main objective of this study was to test this prediction on temporal samples of bird assemblages (n = 19, 10–57 years) by the presence/absence and quantitative null models on assemblage and guild levels. These null model outcomes were further analyzed to evaluate the effects of various data set characteristics on the outcomes of the null models. The analysis of two binary null models in combination with three association indices revealed 20% with significant aggregations, 61% with random associations, and only 19% with significant segregations (n = 95 simulations). The results of the quantitative null model simulations detected more none‐random associations: 61% aggregations, 6% random associations, and 33% segregations (n = 114 simulations). Similarly, quantitative analyses on guild levels showed 58% aggregations, 20% segregations, and 22% random associations (n = 450 simulations). Bayesian GLMs detected that the outcomes of the binary and quantitative null models applied to the assemblage analyses were significantly related to census plot size, whereas the outcomes of the quantitative analyses were also related to the mean population densities of species in the data matrices. In guild‐level analyses, only 9% of the GLMs showed a significant influence of matrix properties (plot size, matrix size, species richness, and mean species population densities) on the null model outcomes. The results did not show the prevalence of negative associations that would have supported compensatory dynamics. Instead, we assume that a similar response of the majority of species to climate‐driven and stochastic factors may be responsible for the revealed predominance of positive associations.
Highlights
Compensatory dynamics are believed to play an important role in community organization and functioning especially under environmental stress (Gonzalez & Loreau, 2009)
The theory of compensatory dynamics assumes that if competi‐ tive interactions are important in driving year‐to‐year fluctuations in abundance, changes in the abundance of one species should be generally accompanied by compensatory changes in the abundances of other members of community (Houlahan et al, 2007)
Based on meta‐analyses of 41 data matrices from various taxonomic groups except birds, Houlahan et al (2007) concluded that compen‐ satory dynamics are rare in natural ecological communities
Summary
Compensatory dynamics are believed to play an important role in community organization and functioning especially under environmental stress (Gonzalez & Loreau, 2009). Korňan and Svitok (2018) tested this concept on 19 long‐term data sets of bird assemblages, and their pairwise null model analyses led to similar conclusions. In our previous study using pairwise null model analysis of species association on 19 long‐term data sets (>10 years) of bird assemblages, we detected the overall very low frequency of sig‐ nificant species pairs with a strong predominance of positive as‐ sociations (Korňan & Svitok, 2018). Having conducted analyses of three basic levels of community or‐ ganization (species pairs, guilds, and whole assemblage), we can develop much stronger interferences about the general applica‐ bility of the compensatory dynamic concept for bird assemblages This is the first such study testing species associations in temporal bird data sets. | 8543 the relationships between various data set characteristics (such as matrix size, duration of study, and proportion of zero in a matrix) and the outcomes of the null model simulations
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