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.