Local and regional diversity of frog communities along an extensive rainforest elevation gradient in Papua New Guinea

Rainforests on high tropical mountains are globally important species diversity hotspots. We studied amphibians along an extensive rainforest elevation gradient on Mt. Wilhelm (4,509 m) in Papua New Guinea. We established eight sites at 500 m elevation increments between 200 and 3,700 m a.s.l. and related their community composition to the known species pool of New Guinea island. We recorded 3,390 frogs from 55 species, which is three times more species than at any local community along the elevation gradient. Species diversity peaked at 1,700 m a.s.l. for Mt. Wilhelm communities, and at 500–1,100 m a.s.l. in the broader New Guinea fauna, probably reflecting increasing speciation and decreasing dispersal rates with increasing elevation. The beta diversity between frog communities was high and increased with increasing elevation. The change in frog community composition across 500 m elevation corresponded to the change over 200 km distance within lowland forests. A majority of frog species were distributed over narrow <500 m elevational ranges, at Mt Wilhelm and the New Guinea fauna more broadly. We did not detect Rapoport's pattern of wider elevation range for species at higher elevations than for lowland species, for Mt. Wilhelm communities or the New Guinea fauna. The high beta diversity patterns along elevation gradients generated by rapid species turnover with narrow elevation ranges make frog communities vulnerable to change in the environment, including climate change.