The geographic range size and vulnerability to extinction of angiosperm epiphytes in the Atlantic Forest of Brazil

Abstract

AimAngiosperm epiphytes have long been reported to have larger geographic ranges than terrestrial species, despite evidence of their outstanding diversity and endemism. This apparent contradiction calls for further investigation of epiphytes' poorly understood range size patterns. Here, we address the question of whether epiphytes have larger geographic ranges and different vulnerability to extinction than terrestrial species.LocationThe Atlantic Forest of Brazil, a global centre of tropical epiphyte diversity with relatively well‐known flora, where we can estimate the geographic ranges of a large number of species with reasonable confidence.Time periodOccurrence records from the 17th century to the year 2021.Major taxa studiedFlowering plants (angiosperms).MethodsWe downloaded, processed and cleaned all occurrence records for the angiosperm species native to the Atlantic Forest of Brazil available in the speciesLink network and the Global Biodiversity Information Facility. We estimated the extent of occurrence and area of occupancy of 12,679 native flowering plants, including 1251 epiphytic species. We compared the geographic ranges of epiphytes and other life forms at broad (e.g. Angiosperms, Monocots) and more restricted taxonomic scales (e.g. individual families), assuming species are independent entities and also when accounting for species phylogenetic dependence.ResultsWe found that epiphytes have among the smallest geographic ranges of flowering plants. We found no consistent evidence that epiphytism leads to differences in geographic ranges between close relatives. However, both epiphytes and non‐epiphytes in epiphyte‐rich lineages have small ranges and likely a high vulnerability to extinction.Main ConclusionsOur findings contrast with the long‐held hypothesis that epiphytes have larger geographic ranges than terrestrial species. Epiphytes and their close relatives share many diversification mechanisms and ecological adaptations (‘epiphyte‐like traits’), which probably explain why both sets of species have small range sizes and high vulnerability to extinction.

Extinction risk predictions for the world’s flowering plants to support their conservation

“…We found support for known spatial hotspots of extinction risk such as Madagascar and Hawaii. We found that epiphytes are highly threatened, with an elevated extinction risk of 53.9% (95% CI 52 – 56%, compared to the current Red List 49%), which is consistent with findings that 45% of epiphytes have a high proportion of species with ‘vulnerably small ranges’ compared to other life forms (Leão et al ., 2023). For large families (>= 3,000 species) the estimations of percentage threatened are broadly similar for the Red List and our predictions (Figure 1).…”

Extinction risk predictions for the world's flowering plants to support their conservation

“…We found support for known spatial hotspots of extinction risk such as Madagascar and Hawaii. We found that epiphytes are highly threatened, with an elevated extinction risk of 53.9% (95% CI 52–56%, compared to the current Red List 49%), which is consistent with findings that epiphytes have a high proportion of species with ‘vulnerably small ranges’ (Leão et al ., 2023; Svahnström et al ., 2023). For large families (≥ 3000 species), the estimations of percentage threatened are broadly similar for the Red List and our predictions (Fig.…”