Matrix population models capture how variation among life stages in responses to biotic and abiotic environmental factors translates to population dynamics.  Many of these analyses rely on an assumption that populations have reached their stable stage distribution (SSD), where the proportion of individuals in each life stage remains constant.  Yet a population may be moved away from this equilibrium when life stages respond uniquely to environmental cues and perturbations.  While this statement may seem self-evident, in light of recent work demonstrating the potential for transient population dynamics to be dramatically different from asymptotic, the material question is how often natural populations are actually far from their SSD.  We analyzed published matrix models from 51 studies to examine the variability in distance between observed and stable stage distributions and the associated consequences for near-term transient population dynamics. 

Results/Conclusions

In the majority of studies, populations were near their expected stable structure, and the asymptotic population growth rate matched near-term growth.  In a few cases, however, deviations from SSD caused important (up to 16-fold) differences between asymptotic and transient predictions of population size.  Larger deviations from SSD were positively correlated with longer generation times and matrix size, although not statistically significant, but the equilibrium population growth rate had no influence.  Thus, measuring the current stage structure can determine whether asymptotic measures of population growth will be reliable, and we argue that this is an important step to take in studies where precise population metrics are necessary for guiding conservation and management.