Geographic range size and rarity of epiphytic flowering plants

For over a century, epiphytes have been considered to have larger geographic ranges than terrestrial plants, yet this assumption is based on studies at restricted geographic and taxonomic scales and is contradicted by recent research. Misunderstanding the ranges of epiphytes may distort perceptions of their extinction risk. To address this, here we analysed global data on 330,087 angiosperm species, including 27,184 epiphytes, comparing range size and rarity between epiphytes and terrestrial plants. We calculated three range metrics, tested for differences across angiosperms and within epiphyte-rich families and used phylogenetic regressions to explore the role of epiphytism on species ranges. On average, epiphytes have larger ranges than closely related terrestrial species, supporting hypotheses that epiphytism promotes dispersal. However, small ranges are prevalent in epiphyte-rich families regardless of lifeform. Notably, about half of epiphyte species are rare, indicating greater vulnerability than terrestrials. Epiphyte rarity is attributable to evolutionary history and shared traits rather than epiphytism itself.