Conclusions
There are limits to the generalities that can be made about the causes of rarity. Species are rare due to unique combinations of factors, including traits, trait–environment interactions, biotic interactions, geographical contingencies, and historical contingencies. That said, there is value to using a conceptual framework to structure and guide our explorations of the phenomenon of rarity , as evidenced by the widespread use of the Rabinowitz framework. We have created a framework that can be used to infer potential causes of rarity depending on the type of rarity exhibited by a species. The generalities provided by the framework can be combined with empirical observations and natural history knowledge to more precisely determine the causes of rarity in particular species. Our hope is that this work will spur further explorations into the causes of rarity, stimulate the development of hypotheses about focal rare taxa, guide the selection of focal traits for future trait–rarity studies, and identify effective, targeted conservation measures for rare species.