The grasshopper (Orthoptera : Acridoidea, Eumastacoidea and Tettigonioidea) fauna of Kakadu National Park in the Australian seasonal tropics: biogeography, habitat associations and functional groups

Abstract

Grasshoppers are a diverse and functionally important group of insects, but assemblages of Australian grasshoppers are extremely poorly known. This study of the grasshoppers (Orthoptera : Acrididae, Eumastacidae, Pyrgomorphidae, Tridactylidae, Tetrigidae and Tettigoniidae) of Kakadu National Park in the seasonal tropics of the Northern Territory is the first comprehensive description of any regional grasshopper fauna in Australia. We list all known species, describe their biogeography, habitat associations and abundance, and propose a functional group classification for Australian grasshoppers as a framework for future ecological and biogeographical studies. In all, 161 grasshopper species from 90 genera are known from Kakadu. The dominant family is Acrididae (64% of all genera, 63% of all species), within which the subfamily Catantopinae (44% of all grasshopper genera, 47% species) is particularly important, as is typical for Australia. The Tettigoniidae is also relatively diverse, with 35 species from 16 genera. A large proportion of the fauna – 81 species (50%) and 15 genera (17%) – is undescribed. In total, 86% of Kakadu’s species and 73% of genera are endemic to Australia. Many (42%) of the species are endemic to the northern half of the Northern Territory, and most of the others (36% of total species) have their Australian distributions restricted to the tropics. The major functional groups in terms of species are Grass-eating Acrididae and Pyrgomorphidae (33% total species), Broadleaf-eating Acrididae and Pyrgomorphidae (19%) and Open-ground Acrididae and Pyrgomorphidae (12%). There is a widespread macroecological tendency for locally abundant species to have wide geographic ranges, but there was no consistent trend for locally abundant species in Kakadu to have widespread distributions.