Effects of aspect and altitude on scorpion diversity along an environmental gradient in the Soutpansberg, South Africa

• We present the first quantitative survey of scorpion diversity across a mountain range.
• Richness was greater on the arid northern slope, and greater at lower altitudes.
• Turnover decreased with altitude, endemic taxa were restricted to upper northern slope.
• Local patterns in the Soutpansberg mimic continental patterns of diversity.
• Conservation of arid northern slopes and foothills should be prioritized.

Landforms with steep environmental gradients provide natural laboratories for studying regional dynamics of diversity. The Soutpansberg range in South Africa presents contrasting habitats and climatic conditions on its northern and southern slopes. Scorpions are well adapted to arid environments, with greatest diversity in temperate deserts, but few studies have investigated the effects of aspect and altitude on scorpion diversity. We surveyed scorpion diversity along an altitudinal transect across the Soutpansberg by actively searching for scorpions during the night and day. Patterns of scorpion diversity along the transect were compared to those of ants and woody plants. Unlike these taxa, scorpions exhibited a significant difference in species richness between slopes; higher on the arid northern slope, and greater at lower than higher altitudes. Endemic taxa were restricted to mid-to higher altitudes of the northern slope. Species turnover decreased at higher altitudes and assemblage structure was influenced by slope, altitude and rock cover. The Soutpansberg appears to be a hotspot of scorpion richness and mimics patterns of diversity in southern Africa. The richness and endemism of the scorpion fauna of the arid northern slopes and foothills of the Soutpansberg emphasizes the need to prioritize the conservation of these areas.

Heatmap of scorpion species distributions along an altitudinal transect across the Soutpansberg range, Limpopo Province, South Africa. Colours represent faunal elements from which species are derived: widespread (red); endemic (black); Kalahari (orange); Afromontane/grassland (green); Bushveld (grey). Intensity of shading represents relative abundance.Figure optionsDownload as PowerPoint slide