Use of Quercus Acorns and Leaf Litter by North African Thorectes Species (Coleoptera: Scarabaeoidea: Geotrupidae)

Abstract

Acorn burial and consumption by geotrupid dung beetles is an interesting trophic interaction recently reported for Iberian Thorectes and North American Mycotrupes species. In Iberian Thorectes species, this interaction provides not only ecophysiological and reproductive advantages to the beetles but also more effective dispersal for Quercus acorns. The genus Thorectes is particularly diverse in the Iberian Peninsula and North Africa, where most species of the genus occur. Due to the high diversity of Thorectes in North Africa, especially in Morocco, where Quercus forests are widely distributed, we investigated whether acorn burial and consumption by Thorectes beetles also occurred in this region. For this, field sampling was conducted in northern Morocco by searching for beetles buried and consuming acorns within 1 m2 quadrats in areas where Thorectes species and Quercus forests occur jointly. Three beetle species (T. distinctus, T. laevigatus and T. trituberculatus) were found consuming buried acorns of Q. suber in the field. Most of the beetles were found feeding on acorns, while only 20% were found in dung-provisioned burrows. These results suggest that acorns constitute the staple food of some North African Thorectes species. In addition, we found T. trituberculatus and T. distinctus burrows and nests provisioned with oak leaf litter. Burrows and nests provisioned with Quercus litter also suggest a tighter interaction of Thorectes beetles with oaks. Feeding and nesting with relatively predictable and abundant resources in oak forests, such as acorns and leaf litter, may be especially important to explain the diversification and success of flightless Thorectes species in Mediterranean ecosystems such as those of the Iberian Peninsula and North Africa.