Assemblages of orthopteroid insects along environmental gradients in central and southern Madagascar

Abstract

Madagascar is one of the world hotspots for endemics, and its rapidly changing habitats accelerate the need for their study and conservation. Orthopterans, mantids, phasmids, and cockroaches were sampled in five main habitats (savanna and shrubland, semiarid spiny forest, rainforest, mountain grass- and shrubland, and cultivated habitats) in central and southern Madagascar (41 sites, 0–2250 m a.s.l.) with the aim of getting the first data on their diversity and distribution along environmental gradients shortly after the rainy period. Samples were collected primarily by sweeping herb and shrub vegetation along transects 100 m long and 1–2 m wide (5–8 transects/site) and supplemented using other techniques. Altogether 117 species of orthopteroid insects were found (94 Orthoptera, 7 Mantodea, 4 Phasmida, and 12 Blattodea), among them two katydid species which had been recently described as new to science (Mimoscudderia longicaudata Heller & Krištín, 2019, Parapyrrhicia leuca Hemp & Heller, 2019). High species diversity was documented: altogether 63 species (53.8%) were present at only one site, 14 (12%) at two sites, and 5 species (4.2%) at three sites. Nonmetric multidimensional scaling analysis on species composition did not clearly separate the assemblages of the sampled sites. Species assemblages from four habitats overlapped due to their similarity. Only assemblages from the rainforest sites were partially separated from the other sites. Cultivated habitats were characterized by the most frequent (F > 50%) and abundant grasshopper species, such as Acorypha decisa, Aiolopus thalassinus rodericensis, Oedaleus virgula, Gelastorrhinus edax, Gymnobothrus spp,. and Acrotylus spp. We found a significant association between habitat management and species rareness, where the number of rare species was higher in natural/unmanaged habitats. However, we found no association between habitat management and the number of endemic species. For several species we provide the first detailed data on their localities and habitat.