Abstract
The high species richness of tropical forests has long been recognized, yet there remains substantial uncertainty regarding the actual number of tropical tree species. Using a pantropical tree inventory database from closed canopy forests, consisting of 657,630 trees belonging to 11,371 species, we use a fitted value of Fisher's alpha and an approximate pantropical stem total to estimate the minimum number of tropical forest tree species to fall between ∼ 40,000 and ∼ 53,000, i.e., at the high end of previous estimates. Contrary to common assumption, the Indo-Pacific region was found to be as species-rich as the Neotropics, with both regions having a minimum of ∼ 19,000-25,000 tree species. Continental Africa is relatively depauperate with a minimum of ∼ 4,500-6,000 tree species. Very few species are shared among the African, American, and the Indo-Pacific regions. We provide a methodological framework for estimating species richness in trees that may help refine species richness estimates of tree-dependent taxa.
Highlights
The high species richness of tropical forests has long been recognized, yet there remains substantial uncertainty regarding the actual number of tropical tree species
People are fascinated by the amazing diversity of tropical forests and will be surprised to learn that robust estimates of the number of tropical tree species are lacking
Almost all tropical tree species are restricted to their respective continents, and the Indo-Pacific region appears to be as species-rich as tropical America, with each of these two regions being almost five times as rich in tree species as African tropical forests
Summary
Griffithww, James Groganxx, Nimal Gunatillekeyy, David Harriszz, Rhett Harrisonaaa,bbb, Andy Hectorccc, Jürgen Homeierbb, Nobuo Imaiddd, Akira Itoheee, Patrick A. Suganumabbbb, Douglas Sheilooo,zzzz, Eduardo da Silva Pinheiroaaaaa, Plinio Sistbbbbb, Tariq Stevartccccc, Raman Sukumardd, I.-Fang Sunddddd, Terry Sunderlandooo, H. Zahawiggggg, Rahmad Zakariauuu, Runguo Zangttt, Rafael L. de Assismm,zzzz, Bruno Garcia Luizemm, and Eduardo M. The Indo-Pacific region was found to be as species-rich as the Neotropics, with both regions having a minimum of ∼19,000–25,000 tree species. This article contains supporting information online at www.pnas.org/lookup/suppl/doi:.
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