Endemism of Arachnida (Amblypygi, Scorpiones and Solifugae) in the highlands and escarpments of Angola and Namibia: current knowledge and future directions

Authors

  • L Prendini Division of Invertebrate Zoology, American Museum of Natural History, New York, New York, USA; Research Associate, National Museum of Namibia, Windhoek, Namibia
  • TL Bird Research Associate, National Museum of Namibia, Windhoek, Namibia; Department of General Entomology, Ditsong National Museum of Natural History, Pretoria, South Africa; Department of Zoology and Entomology, University of Pretoria, Hatfield, Pretoria, South Africa

Keywords:

Amblypygi, Angola, Arachnida, endemism, escarpments, highlands, Namibia, Scorpiones, Solifugae

Abstract

The arachnid fauna of Angola and Namibia is diverse and includes high levels of endemism, much of which is associated with the arid zone, especially the Namib Desert. The endemic arachnid fauna of the highlands and escarpments, including mountain ranges, plateaus and inselbergs, has received less attention. The study presented here is the first to compile existing distributional data for three arachnid orders – whip spiders (Amblypygi Thorell, 1883), scorpions (Scorpiones C.L. Koch, 1837) and solifuges (Solifugae Sundevall, 1833) – occurring in the highlands and escarpments of Angola and Namibia from published literature, online databases and natural history collections. Distribution maps were used, together with available data or expert knowledge of taxon habitat requirements, to prepare a list of described arachnid taxa considered endemic or near-endemic to the western highlands and escarpments of these two countries. In addition, arachnid endemism was assessed more broadly by scoring the presence of described and potential undescribed endemics in relevant highlands and escarpments, tallying the scores for each order, and ranking the highlands and escarpments based on the sum of all three ordinal tallies. These scores provide a rough index of the relative importance of highlands and escarpments in Angola and Namibia for prioritising decisions regarding conservation as well as further survey and inventory from the arachnid perspective. Although the highlands and escarpments of Angola and Namibia probably serve as refugia for taxa requiring cooler, more humid habitats than are available in the surrounding arid lowlands, including palaeoendemics, they appear to contain fewer endemic arachnid taxa than the lowlands. This may be because: (1) the highlands and escarpments of Angola and Namibia are relatively low, on average, providing few opportunities for insular speciation; (2) much arachnid endemism in the arid lowlands is associated with unique substrates that are absent in the highlands, including sand dunes, gravel plains and clays associated with drainage systems, all of which facilitate burrowing to escape the arid conditions and promote diversification; and (3) much of the taxonomy of the arachnids of both countries remains unresolved, and the distributions poorly understood, especially in Angola. More intensive surveys, with an emphasis on collecting genetic samples from disjunct populations across the distributions of each putative species, are needed to better understand arachnid diversity and endemism in the region.

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Published

2023-12-16