Abstract:
We investigate biogeographical, regional and sub-regional scale responses of scarabaeine dung beetles to late
Cenozoic changes in edaphic and climatic character that created a Savanna / Karoo transition zone in the
Northern Cape, South Africa. Across a 50,200 km2 study area, the Northern Cape species pool comprised six
biogeographical groups defined from distribution across Southern Africa. These species groups contributed in
different proportions to five regional assemblages defined from structural differences across the transition zone.
Towards transition zone peripheries, regional assemblage structure was more strongly correlated to sandiness
dating from Miocene to Pliocene deposition (Kalahari), aridity dating from Pliocene to Pleistocene climatic
change (Bushmanland Karoo), or cooler temperatures dating from Miocene to Pliocene uplift (Upper Karoo).
Correlates of sub-regional assemblages trended to intensification of dominant drivers towards regional
peripheries. Drivers of central transition zone, regional assemblages ("Gariep Karoo", "Gariep Stony Karoo")
showed no dominance. Biogeographically, endemism dominates the Northern Cape transition zone: southwest
arid groups in Nama Karoo regions; Kalahari plus northeast savanna groups in the Kalahari. Regionally,
transition drives assemblage structure: unique variance, 60% in the Kalahari, 21-30% in four Nama Karoo
regions; shared variance (overlap), 25-65% between Kalahari and warmer Karoo regions, 11-71% between
mainly cooler Karoo regions.
