The diversity of associated fauna and ecological interactions in mud-dauber wasp ( Sceliphron ) nests: a first study from Spain

Sceliphron mud-dauber wasps (Hymenoptera: Sphecidae) are common inhabitants of anthropized areas, where they engage in complex interactions with other taxa that either exploit their nests (inquilines [INQ]) or their nest contents (parasitoids, cleptoparasites, predators and scavengers [NES]). This study investigates such interactions at wasp genus-level in two agricultural and one urban localities of Spain, a region previously unstudied from this point of view. Using data from 118 nests, we recorded higher rates of cell reoccupation by INQ and higher mortality due to NES in the two agricultural habitats compared to the urban one (cell ratio with INQ: 13.03% and 6.18% in agricultural and urban habitats, respectively; cell ratio with NES: 29.15% and 12.12% in agricultural and urban habitats, respectively). A total of seven INQ taxa and 15 NES taxa were identified, with solitary megachilid bees (INQ) and dermestid beetles (NES) (known as primarily scavengers in hymenopteran nests) being the most frequent. Alpha diversity of Sceliphron-associated fauna was positively correlated with nest size and significantly higher in agricultural habitats. Community composition differed among habitats. For example, chrysidid wasps, braconid wasps and tachinid flies (all NES: e.g. tachinid flies, braconid and chrysidid wasps) exhibited their lowest abundance in the urban nests. However, network topology showed similar structure across habitats. Our preliminary comparison across the two habitat types suggests their potential role as bioindicators of different types of human-impacted habitats.