The collapse indicators of the dominant species outperform community-level critical slowing down indicators

Abstract

We studied similarities of collapses and concluded that dominant species have a universal effect on the pattern of collapses. We used open paleoecological and modern data to detect early warning signals of collapses. We tested and ranked collapse indicators at the community level (abundance, species richness, constancy, dominance, Shannons H, standard deviation, variance, lag-1 autocorrelation of community abundance, lag-1 autocorrelation of Shannons H) and at the level of the dominant species (total changes of pre-collapse and collapse dominant species, lag-1 autocorrelation of pre-collapse and collapse dominant species) based on their performances. We distinguished between small-scale signals (sharp drops and peaks) and large-scale signals (trend changes). Small-scale signals and large-scale signals can be at the same time, however, small-scale signals can also precede large-scale signals. Small-scale signals indicate environmental events. Large-scale trend changes refer to the decline and eventually the collapse of the community. Our results show that the collapse indicators of the dominant species outperform community-level critical slowing down indicators, which suggests that the dominant species probably have an important role in community-level collapses triggered by environmental events. We also concluded that unusual environmental events might be the number one cause of collapses therefore small-scale signals should be involved in analyses.