Exploring co-extinction correlates: the effects of habitat, biogeography and anthropogenic factors on ground squirrels–dung beetles associations

Co-extinction is a recurring topic in conservation biology. Quantification of co-extinction has been generally restricted to parasite–host, predator–prey and herbivore–host plant interactions. The loss of detritivorous insects upon the depletion of herbivore mammals has been poorly explored. Here, we used rarefaction curves to predict co-decline involving the decrease in scarab dung beetles diversity due to a reduction in the number of dens of the Asia minor ground squirrel in the Turkish steppe biome. We also evaluated the potential benefits provided by livestock in mitigating the decline of scarab beetle communities. Rarefaction curves estimated that a 50% reduction in the number of sample units where squirrel faecal pellets are the only available food resource accounts for a reduction of 28% of all the scarab species, and of 24% of the squirrel-linked species. The current decline of ground squirrels, mainly due to intensification of agriculture, may represent a threat for biodiversity in steppic environments because it may affect the specialized insects, and may produce a cascade effect also on their predators, i.e., saker falcon, buzzards, eagles and mustelids. We also showed that the conservation of ground squirrels and their affiliate scarab species may be ensured by a moderate livestock grazing, owing to the higher ecological success of these rodents in the presence of large herbivores keeping low the grass cover.