Exploring the proportion of rarity in tropical insects: evaluating hypotheses and variables

Abstract

ABSTRACT Theoretical models suggest that rare species in a community should be few, but empirical evidence indicates the opposite in insect communities. We reviewed 1170 articles for suitable datasets and selected 100 publications with 140 datasets for our rarity analysis. The objective was to estimate the rarity percentage among insects and whether this value is related to positional, methodological, environmental, or variables intrinsic to the communities. Information was found for eight insect orders, of which Hymenoptera and Coleoptera were the most studied. The authors of 70% of the articles did not discuss hypotheses explaining the observed percentage of rare species. In the remaining, the most discussed hypotheses were undersampling (10%), distribution range (15%), study group phenology (4%), and diffusive rarity (1%). Only two studies tested hypotheses of rarity. In 66 datasets, the proportion of rare species was between 11% and 30%; in 70 datasets, this proportion was higher. The greatest effects on species rarity were sample coverage, abundance, and richness. The study of rarity remains a critical problem in community ecology; this study shows that the issues are not solely based on methodological limitations like undersampling but need deeper conceptual and empirical approaches.