Orthoptera Tettigoniidae as indicators of biodiversity hotspots in the Guinean Forests of Central and West Tropical Africa.

Abstract

The present paper has two aims: 1) to present the results of the study of selected species of Orthoptera Tettigoniidae collected in the Guinean forests of West Africa and in the important hotspot of Dzanga-Ndoki National Park (Central African Republic); 2) to carry out a check-list of six subfamilies of Tettigoniidae (Pseudophyllinae, Conocephalinae, Hexacentrinae, Phaneropterinae, Mecopodinae and Hetrodinae) living in Central-West tropical Africa, in particular in two main tropical forests, in the subregion of upper Guinea, and in the subregion Nigeria-Cameroon plus the biodiversity hotspots of Central African Republic and Gabon. Many new records are reported and the following new species are described: Plangia astylata n. sp. from Central African Republic and Gabon, Plangia chopardi n. sp. from Côte d'Ivoire, and Catoptropteryx lineata n. sp. from Liberia. In addition the male of Plangia karschi Chopard, 1954 is described and some taxonomical notes on the recently described Arantia marginata Massa, 2021 are discussed. The new name Pseudorhynchus raggei is proposed for Pseudorhynchus robustus Ragge, 1969, junior primary homonym of Pseudorhynchus robustus Willemse, 1953. Then, the author lists all the Tettigoniidae of the above listed subfamilies presently known in central-west tropical Africa (Guinean forests). This wide tropical area holds important biodiversity hotspots that the author highlights through the study of katydids. Many groups of species tend to isolate and speciate probably more than other groups of insects. Overall, the total number amounts to 332 species, of which 242 live in Cameroon-Nigeria subregion plus Central African Republic and Gabon, 216 in the Upper Guinea subregion. The occurrence of endemic taxa is 35.9 and 40.3%, respectively; this resulted a very high percentage compared to that known for plants and animals in the area. Starting from the list of Tettigoniidae three remarkable biodiversity hotspots were examined, Dzanga-Ndoki National Park (Central African Republic), Mt. Tonkoui and Taï National Park (both in Côte d'Ivoire); overall they hold 134, 81 and 88 species, respectively. It seems that in tropical Africa there is a specific richness gradient with an East-West impoverishment, but also a possible increase of endemism occurrence. However, presently this richness suffers a high decline risk, due to deforestation and environmental degradation, in turn dependent on the inequality between human populations, wars and political instability in some tropical areas.